Browsing by Person "Lewandowski, Iris"

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Agricultural diversification of biogas crop cultivation
(2018) von Cossel, Moritz; Lewandowski, Iris
For all types of agricultural land-use, more diverse cropping systems are required, with respect to the maintenance of ecosystem values such as biodiversity conservation and climate change adaptation. This need for greater agricultural diversity is clearly illustrated by biogas crop cultivation. In Germany, maize currently dominates biogas crop cultivation due to its outstanding methane yield performance. However, the ecosystem value of maize cultivation decreases if good agricultural practices are ignored. Additionally, the poor aesthetical value of maize has led to biogas production gaining a negative reputation in society. To increase the diversity of biogas crop cultivation, alternative biogas crops such as amaranth and wild plant mixtures need to be investigated with respect to both yield performance and biogas substrate quality. The research objective of this study was the development of strategies for agricultural diversification of biogas crop cultivation. For this purpose, the following research questions were formulated: 1. How does amaranth perform as a biogas crop compared to maize and what are the major opportunities for and obstacles to the large-scale implementation of amaranth cultivation? 2. How does the spatial diversification ‘legume intercropping’ perform in amaranth compared to maize and what are the major opportunities for and obstacles to its practical implementation? 3. How do perennial wild plant mixtures perform in biomass production with respect to yield, quality and species diversity in the long term and what are the relevant agronomic factors? 4. How do available models perform in the prediction of specific methane yield of different crops based on their lignocellulosic biomass composition and how could they be improved? To address research questions 1 and 2, field trials with amaranth and maize were conducted in southwest Germany in the years 2014 and 2015. Amaranth established well in both years. Its dark red inflorescences attracted many insects such as honeybees, wild bees and bumble bees. Therefore, a systematic implementation of amaranth into biogas crop rotations could significantly improve their socio-ecological value in terms of biodiversity conservation and landscape beauty. However, amaranth showed significantly lower dry matter yields (DMY) and specific methane yields (SMY), together resulting in lower methane yields than maize in both years. Therefore, breeding and an optimization of agricultural practices such as sowing density, planting geometry and fertilization management are required to make amaranth more competitive in comparison to maize. To address research question 2, the amaranth field trials mentioned above also included treatments of legume intercropping with runner bean (RB, Phaseolus vulgaris L.) and white clover (WC, Trifolium repens, L.). The RB and WC developed equally well in amaranth and maize each year. For both amaranth and maize, the RB share of total DMY was low (5-10%) and did not significantly affect the total DMY. By contrast, WC had a significant negative effect on the DMY. Overall, the spatial diversification ‘legume intercropping’ could considerably improve the socio-ecological value of amaranth cultivation in terms of biodiversity conservation, greenhouse gas (GHG) mitigation and soil protection. For research question 3, two different wild plant mixtures (WPM) were cultivated on three sites in southwest Germany from the years 2011 to 2015. At each location, the WPM showed great potential for both biodiversity conservation and ecosystem resilience. Numerous insect species were observed in the WPM stands each year, indicating WPM as a relevant cropping system for habitat networking. Furthermore, the aesthetic appearance of the WPM stands over the years demonstrated the potential positive effect WPM cultivation could have on the public perception of biogas production. The DMY of the WPM varied strongly depending on (i) the initial composition of species sown, (ii) the establishment procedure, (iii) the environmental conditions, (iv) the pre-crop, and (v) the number of predominant species. WPM were found to have low demands for fertilization and crop protection. Thus, WPM appear a promising low-input cropping system for the promotion of biodiversity conservation, habitat networking, soil and water protection, GHG mitigation and climate change adaptation. However, high DMY gaps remain a challenge for the practical inclusion of WPM in existing biogas cropping systems. With respect to research question 4, a meta-analysis revealed that available models proved to be much less precise than expected. Although outperforming all available models, the correlation of the new models was still low (up to r = 0.66). It was also found that non-linear terms are of less importance than crop-specific regressors including the intercept. This indicates that across-crop models including crop-specific configurations could help to improve the identification of alternative crops and cropping systems for a more diverse biogas crop cultivation in the future.
Agrivoltaics mitigate drought effects in winter wheat
(2023) Pataczek, Lisa; Weselek, Axel; Bauerle, Andrea; Högy, Petra; Lewandowski, Iris; Zikeli, Sabine; Schweiger, Andreas
Climate change is expected to decrease water availability in many agricultural production areas around the globe. At the same time renewable energy concepts such as agrivoltaics (AV) are necessary to manage the energy transition. Several studies showed that evapotranspiration can be reduced in AV systems, resulting in increased water availability for crops. However, effects on crop performance and productivity remain unclear to date. Carbon‐13 isotopic composition (δ13C and discrimination against carbon‐13) can be used as a proxy for the effects of water availability on plant performance, integrating crop responses over the entire growing season. The aim of this study was to assess these effects via carbon isotopic composition in grains, as well as grain yield of winter wheat in an AV system in southwest Germany. Crops were cultivated over four seasons from 2016–2020 in the AV system and on an unshaded adjacent reference (REF) site. Across all seasons, average grain yield did not significantly differ between AV and REF (4.7 vs 5.2 t ha−1), with higher interannual yield stability in the AV system. However, δ13C as well as carbon‐13 isotope discrimination differed significantly across the seasons by 1‰ (AV: −29.0‰ vs REF: −28.0‰ and AV: 21.6‰ vs REF: 20.6‰) between the AV system and the REF site. These drought mitigation effects as indicated by the results of this study will become crucial for the resilience of agricultural production in the near future when drought events will become significantly more frequent and severe.
Agrivoltaics: The environmental impacts of combining food crop cultivation and solar energy generation
(2023) Wagner, Moritz; Lask, Jan; Kiesel, Andreas; Lewandowski, Iris; Weselek, Axel; Högy, Petra; Trommsdorff, Max; Schnaiker, Marc-André; Bauerle, Andrea
The demand for food and renewable energy is increasing significantly, whereas the availability of land for agricultural use is declining. Agrivoltaic systems (AVS), which combine agricultural production with solar energy generation on the same area, are a promising opportunity with the potential to satisfy this demand while avoiding land-use conflicts. In the current study, a Consequential Life-Cycle Assessment (CLCA) was conducted to holistically assess the environmental consequences arising from a shift from single-use agriculture to AVS in Germany. The results of the study show that the environmental consequences of the installation of overhead AVS on agricultural land are positive and reduce the impacts in 15 of the 16 analysed impact categories especially for climate change, eutrophication and fossil resource use, as well as in the single score assessment, mainly due to the substitution of the marginal energy mix. It was demonstrated that, under certain conditions, AVS can contribute to the extension of renewable energy production resources without reducing food production resources. These include maintaining the agricultural yields underneath the photovoltaic (PV) modules, seeking synergies between solar energy generation and crop production and minimising the loss of good agricultural land.
Approaches to improve the implementation and expansion of Miscanthus production
(2016) Xue, Shuai; Lewandowski, Iris
Several species within the miscanthus genus (Miscanthus spp.) are characterized by high biomass yields and low production input requirements. This raised increasing interests in their applications for bioenergy. However, to date, only small areas of Miscanthus × giganteus (approximately 40,000 ha) are commercially grown and used for generating electricity and heat in Europe, where miscanthus has been developed as bioenergy crop for more than decade. Reviewing state-of-the-art revealed four main factors limiting the implementation of miscanthus production. These are inefficient and expensive propagation techniques, land use dilemma (i.e. lack of land available for growing miscanthus), lack of varieties/genotypes adapted to various and especially to stressful environmental conditions and lack of efficient agronomic practices for miscanthus establishment. Against these limiting factors, this thesis aims to (1) evaluate the different propagation systems with regard to technologies and costs, and improve the preferred rhizome propagation techniques; (2) address the land use dilemma through exploring marginal land (i.e. non-arable land with ability to grow plants with tolerance to environmental stresses) for miscathus production; (3) and screen optimal genotypes and effective practices for establishing and managing miscanthus on marginal land in a case study on grassland. To achieve the first objective, a review, our own field trials and farmer surveys were performed. Direct seed sowing was found to be the cheapest propagation method (1,508.5 € ha-1 overall establishment costs) and micro-propagation the most expensive (6,320.8 € ha-1). Direct rhizome planting is the farmers’ most preferred and most applied establishment method and has moderate establishment cost of 1,904-3,375.7 € ha-1. However, it goes along with the lowest propagation efficiency (1:10) and consequently restricts the availability of propagation material for large-scale plantations. However, the multiplication ratio can be increased by reducing the rhizome size. Field trial results showed that 6-cm length is close to the minimum size of rhizome that can germinate after directly planting into field. Compared to the traditionally used macro-rhizome, the multiplication ratio of the improved rhizome propagation (using 6-cm rhizomes) is tripled. In addition, the multiplication ratio can also be increased by transplanting rhizome- or stem-derived plantlets. However, due to higher labour and energy inputs required for the pre-growing of plantlets, their establishment cost reduction potential is limited, with estimated costs of 4,240.8-4,400.8 € ha-1. Direct seed sowing as the cheapest method is presently only possible for Miscanthus sinensis and not yet practical under German conditions. In addition, the seed-setting rate of M. sinensis is very low (0.0-28.7%) under the climatic conditions of south-west Germany, making commercial seeds production difficult. For all the propagation methods considered, more research efforts are still required to reduce the material production costs and simultaneously increase the multiplication ratio. For the second objective, the production potential of miscanthus on marginal land in China was assessed. Because China has limited agricultural land resources and its non-food bioenergy policy (it is only allowed to grow energy crops on marginal land) is adamant, there is a desideration for exploiting its marginal land potential. In this study, Geographic Information System (GIS) techniques, model simulation were adopted to identify the productive marginal areas for miscanthus and to estimate their biomass and bioenergy production potentials. The results show that in China there are large marginal land areas of 17,163.54 × 104 ha available for growing miscanthus. However, due to limitation by low winter temperatures and low precipitation levels in some areas, the total marginal area suitable for growing miscanthus is only 769.37 × 104 ha. The Monteith radiation yield model was used to determine the potential miscanthus yield in Chinese climatic conditions. The simulation gave the actual harvestable yield levels on arable land of 18.1-44.2 odt ha-1 yr-1. Taking the environmental stresses of marginal conditions into account an achievable miscanthus yield potential on marginal land of 2.1-32.4 odt ha-1 yr-1 was calculated (varying between different marginal land types). Based on these achievable yield levels, the total miscanthus production potential on the entire suitable marginal land areas is 13,521.7 × 104 odt yr-1; the corresponding bio-electricity generation and total greenhouse gas saving potentials are 183.9 TW h yr-1 and 21,242.4 × 104 t CO2 eq. yr-1, respectively. The spatial distribution of the suitable marginal areas shows that they are mainly concentrated in the central part of Northeast China and the Loess Plateau. Both regions are recommended as priority development zones for the Chinese miscanthus-based bioenergy industry. However, implementation of this huge marginal land potential is currently constrained by many barriers, e.g. concerns on potential ecological effects, competition for marginal land from other uses, lack of high yield varieties in marginal conditions. Lack of varieties with suitability to marginal conditions and efficient agronomic practices for the establishment on marginal land are the main barriers that limit using marginal land for miscanthus production. Therefore, stress tolerant varieties need to be selected and methods of effective establishment of miscanthus on marginal land need to be developed. Worldwide, grassland is the most important marginal land type because it has the largest terrestrial area and mild environmental stresses for growing energy crops (including miscanthus). However, it is undesirable or even legally prohibited to convert grassland into bioenergy cropland to avoid biodiversity loss and soil carbon being reduced by tilling practices. Hence, no-till establishment practices for miscanthus establishment and maintenance on grassland are investigated here under the third objectives. Our study demonstrates that miscanthus can be successfully cultivated on both good (nutrient-rich) and marginal (nutrient-poor) grassland using the proposed agronomic practices and an increased grassland productivity may be achieved through the establishment of suitable miscanthus genotypes. The recommended agronomic practices are summarized as following. Miscanthus genotypes with tall, thick shoots perform better than those with short, thin shoots. Better establishment is achieved when rhizome-derived plantlets are transplanted into pre-disturbed grassland. The grassland pre-disturbance of low vegetation cutting (5 cm) and herbicide spraying in narrow stripes is recommended for its beneficial effect on miscanthus establishment without significant negative effects on grassland productivity. Two harvests, one in late spring and one in late autumn, are optimal to achieve a high grassland yield. In this thesis, the limitation of the inefficient propagation technique was mitigated through minimizing the rhizome size and exploring the seeds propagation potential. The land-use dilemma was alleviated by exploring the marginal land production potential. Additionally, constrains of lack of genotypes and agronomic practices for the miscanthus establishment on marginal land were improved by field trials on grassland (the most important marginal land type with a huge potential).These results can improve the implementation and expansion of miscanthus production. However, in addition to constrains improved in this thesis, the miscanthus production is currently constrained by many other technical, economic and financial, social and political, environmental issues. It is unlikely that the implementation and expansion will achieve without mitigating these constrains. Further research and support should address these barriers in an integrate manner.
Assessing social aspects of biobased value chains
(2024) Marting Vidaurre, Nirvana Angela; Lewandowski, Iris
Achieving human well-being for all humanity, reducing inequality, and eradicating poverty while preserving the environment are the aims of sustainable development. The bioeconomy offers alternative ways of utilising biomass and other biogenic resources with the objective of addressing global challenges relevant for sustainable development such as resource scarcity, climate change and food security. Lignocellulosic perennial crops like miscanthus, have been investigated as a sustainable source for energy and materials. While various studies assessing the environmental performance of lignocellulosic crops have been published, the analysis of the social dimension of such systems has been little explored. Existing frameworks to perform social assessments are general in their coverage of social aspects and provide long lists of social impact categories, for which adaptation and prioritization is needed according to the specific case being analysed. Furthermore, existing methodologies for social life cycle assessment (S-LCA) leave the practitioner to choose between pursuing a context-specific analysis or a general (country or sector specific) analysis considering the value chain. To date there is no methodology to perform a S-LCA in an integrated manner for both the foreground and background systems of a biobased value chain, which takes into account the different requirements for analysing these systems. The foreground system is composed by the core processes being analysed, while the background system is constituted by the processes needed to supply inputs required for the foreground system. This doctoral thesis aims to develop an integrated methodology to assess the foreground and the background systems of biobased value chains, which combines techniques for performing a context-specific assessment of the foreground system and a generic assessment of the background system. The overall question that this study aims to answer is how to proceed in assessing the social aspects of a biobased value chain covering both the foreground and the background systems of a production process considering the study is an ex-ante analysis? The specific objectives to answer this question are i) to identify which social aspects are relevant for the assessment of biobased value chains, ii) to identify which aspects are to be considered when assessing the potential social impacts of agricultural production processes on the stakeholder “farmer” and iii) to develop a social risk assessment approach that is regionalized in order to assess the potential social impacts within biobased value chains. To achieve the first objective a literature review of empirical studies covering social impacts of agricultural and forestry value chains was performed. This helped in the identification of social aspects that are often assessed and reported. Then the Methodological Sheets for Subcategories in S-LCA were used as a reference to allocate the social aspects reported and evaluated by empirical literature and review studies to those impact subcategories proposed by the sheets. This enabled the identification of social aspects often assessed and those potentially overlooked in the sheets. To achieve the second objective a survey among farmers in a region of Croatia was conducted. Additionally, the study aimed to assess the feasibility of cultivating miscanthus in the region, taking into account potential challenges and opportunities, as well as farmers' willingness to adopt the crop miscanthus. The third objective of performing a regionalized social risk assessment of a biobased value chain was achieved by following the SOCA approach in combination with EXIOBASE 3 as a source of regional information on the origin of inputs and for the estimation of worker hours. This analysis used a case study based on the production of advanced biofuels in Croatia to assess the shortcomings of the methodology. The results showed that the Methodological Sheets for Subcategories in S-LCA provide good coverage of social topics relevant for biobased value chains, but that the stakeholders “smallholder” and “family farm” are not adequately addressed. Drawing on the empirical literature reviewed, the study emphasizes the relevance of these stakeholders in the analysis of biobased value chains, and proposes criteria for consideration in the assessment of these stakeholders. Furthermore, the interviews with farmers revealed that the aspects most valued by them were health and safety, access to water, land consolidation and rights, income and local employment, and food security. Responses to the question of whether they would adopt the crop miscanthus highlight the importance of an established market, good trading conditions and profitability of cultivation. The farmers regarded the provision of subsidies as one of the main factors that make a crop attractive. Opportunities for the adoption of the miscanthus cultivation are related to high yields and low input requirements. Barriers include land conflicts and land availability. Results also showed that mainly harvesting operations were identified as hotspots in the local agricultural operations due to the amount of worker hours required for these processes in comparison to the rest of the agricultural operations. The main contribution of this study is the development of an integrated approach that provides guidance for assessing comprehensively the foreground and background systems of biobased value chains. This consists of a local perspective and a value chain perspective of not yet established value chains. The methodology and framework developed serve for the early identification of potential social impacts in biobased value chains, specifically agricultural value chains. In the current literature, this methodology could be part of what is called materiality assessment. The theoretical framework developed serves for the analysis of the stakeholders “smallholder” and “family farm” and recommends the subsequent involvement of this stakeholder in the selection of context-relevant impact categories. The participation of these stakeholders is important to acquire local knowledge and to select impact categories that reflect their interests, merging a top-down with a bottom-up approach. The social risk assessment to analyse the background system should be applied when the value chain suppliers are not known and when a rapid assessment of the social risk of the value chain is required. The ultimate goal of S-LCA is to provide quality information about potential social impacts in production systems to decision makers, which will take action to reduce inequalities in the different regions of the world and thus contributing to achieve a more sustainable economy.
Biomass quality of miscanthus genotypes for different bioconversion routes
(2017) Iqbal, Yasir; Lewandowski, Iris
Currently, a wide range of biomass based resources (wood, agricultural residues, municipal waste, perennial dedicated energy crops) are being tested for different bioconversion routes such as combustion and ethanol production. In Europe, combustion is the most prevalent bioconversion route being adopted to produce heat and electricity. By 2020, in Europe out of 139 Mtoe biomass based energy production, 110.4 Mtoe will be heat and electricity. Along with combustion, EU (European Union) focuses on increasing the share of biofuels production to achieve the EU 2020 target to reach 10% share of renewables in the transportation sector. For both aforementioned bioconversion routes, large amount of feedstocks, produced in a sustainable way, are required. Miscanthus, being a perennial dedicated energy crop has the potential to deliver high yields by using the soil resources efficiently. However, the per unit energy yield depends not only on biomass yield but also quality of biomass relevant for a specific end use. For miscanthus based combustion, high lignin contents increase the energy yield of the biomass. The main challenges are high emissions (e.g. NOx) and combustion relevant problems such as corrosion, fouling and low ash melting temperature. Other than for combustion, the high lignin content is the main problem during miscanthus based ethanol production. Presently, M. x giganteus is the only commercially grown genotype, however a wide range of genotypes are being tested under the European conditions to select the most promising ones for both combustion and ethanol production. Therefore, the focus of this study is to evaluate the biomass quality of different miscanthus genotypes for combustion and ethanol production and relevant measures for each bioconversion route to optimize biomass quality at field level to fit the user demand. To realise the aim of this study, two different field trials were used: 1) long term field trial with 15 miscanthus genotypes (four M. x giganteus, one M. sacchariflorus, five M. sinensis hybrids and five M. sinensis genotypes) was established as randomized block design with three replications; 2) field trial with M. x giganteus and switchgrass was established as a randomized split plot design with different crops as main plots, divided into three subplots with different N levels (0, 40, and 80 kg N ha-1a-1). The biomass samples collected from these field trials were processed and analysed in laboratory to test the biomass quality parameters for combustion (mineral analysis, silicon, chloride, ash, moisture and ash melting behaviour) and ethanol production (fiber analysis, acid/base based pre-treatment). The outcomes of this study show that at biomass production level, crop management practices such as selection of appropriate genotypes, fertilization and time of harvesting determine the yield, biomass quality, overall cost of production and environmental performance of the crop for a specific bioconversion route (combustion, ethanol production). The ash melting behavior during combustion process can be improved through appropriate genotype selection from an ash deformation temperature of 800 °C up to 1100 °C. For ethanol production, fiber composition can be improved up to 16% through appropriate genotype selection by decreasing the lignin content and improving the cellulose content. This improvement will not be completely translated to increase in ethanol yield. However, it can improve the overall efficiency of conversion process by decreased the lignin content and subsequently lowering the energy and chemical inputs required for pre-treatment. In this study, no quantification is made about improvement in final ethanol yield. In fertilization, N fertilization is very important because it constituted up to 72% of the emissions in the conducted LCA described in chapter-1. Therefore, in case of high N fertilization, it not only affects the biomass quality but also increases the cost of biomass production and decreases the environmental performance of the crop. Based on the outcomes of this study, it can be concluded that at this location 40 kg N ha-1a-1 fertilization is sufficient to achieve good yield and quality biomass under late harvest regimes (March). At 40 kg N ha-1a-1 fertilization, the N content in the harvested biomass was still well below the threshold level set (0.3-1%) for biomass by the ENplus wood pellets. The other important factor which offers opportunity to optimize biomass quality is time of harvesting. Through appropriate harvesting time, biomass combustion quality can be improved up to 30% through decreasing the mineral, chloride and ash content whereas for ethanol production, fiber composition can be improved up to 12% by decreasing the lignin content. In practical terms, the delay in harvest will help to meet the set quality standards and counter the relevant challenges for each bioconversion route. In current study, none of the biomasses harvested from the different miscanthus genotypes, except for M. sinensis, could meet the ENplus-B wood pellet standards. For combustion, early ripening thin stemmed genotypes such as M. sinensis are recommended under late harvest regime (March). However, the low yield of these genotypes is a major concern because low biomass quantity decreases the final energy yield. Considering the high dry matter yield, cellulose and hemicellulose content, M. x giganteus and M. sacchariflorus are recommended for ethanol production under early harvest regimes (September-October). However, the high lignin content of M. x giganteus and M. sacchariflorus reduces the efficiency of overall process. Therefore, in this study recommendations were given to breeders about development of new genotypes for combustion by combining interesting traits such as high yield and lignin content of M. x giganteus, low ash content of M. sacchariflorus, low mineral content especially K and Cl of M. sinensis, whereas for ethanol production low lignin content of M. sinensis can be combined with high yield of M. x giganteus. This study suggests that optimization of biomass quality for a specific end use can be achieved through adoption of appropriate crop management practices such as selection of appropriate genotype and time of harvesting. This is the most cost-effective way with least environmental implications.
Changing botanical composition of species-rich meadows through variation of management
(2022) Boob, Meike; Lewandowski, Iris
Species-rich hay meadows are threatened habitats for many plant and animal species. The biomass of these meadows has traditionally been used as forage for extensively kept ruminants. During the last decades, their habitat quality and area have been declining. On the one hand, the decline of species-rich hay meadows could be caused by increased fertiliser use as well as earlier and more frequent cutting. On the other hand, a reduction or abandonment of agricultural usage reduces their floristic diversity. This reduces important ecosystem services provided by these habitats, e.g. pollination. Therefore, benchmarking data on botanical composition and biomass is needed to estimate effects of different fertilisation and cutting regimes. This thesis aims at developing recommendations on how to manage species-rich hay meadows in order to conserve habitat functions and to enable agronomic usage at the same time. More specifically, management effects on botanical composition, biomass quantity and quality were investigated in a field trial running from 2013-2018. In this field trial, twelve different treatments were tested in a randomised block design at two sites in southern Germany. The different treatments consisted of a combination of three fertilisation levels (none, PK and NPK) and four different dates of first cut. The cutting date variants were chosen according to the phenology of dominant grasses before, at the beginning and at the end of flowering as well as a late cut at the seed-ripening stage. Both sites were species-rich hay meadows and each plot was fertilised annually and cut twice a year during the six-year field trial. The first study investigates changes in botanical composition. The number of vascular plant species did not significantly change after four years of fertilisation or cutting-date treatments, but botanical composition was affected significantly. The proportion of grasses was promoted by NPK fertilisation at both sites and by early cutting dates at one site only. Forbs were replaced by grasses because this site was dominated by the annual species Rhinanthus alectorolophus, a hemiparasite relying on generative reproduction. The second study addresses the question if living conditions of small plant species are affected by changed management. It was shown that shading reduced the proportion of small plant species due to the increased dry matter yield (DMY) caused by NPK fertilisation. It was concluded that annual NPK fertilisation containing 35 kg N ha-1 impairs the habitat function of species-rich hay meadows and, in the long term, excessive fertilisation could lead to reduced species numbers. Results of the third study revealed that although the date of first cut plays an important role in determining chemical composition of biomass, there is flexibility of choice at later cutting dates. Between the flowering and the seed-ripening stage, there were no significant differences in forage quality. However, late-cut hay is suitable as exclusive feed for horses only. Therefore, an early cut is recommended for use as biogas substrate and to be included into rations for extensively kept ruminants. In conclusion, general patterns of management effects were detected: Annual NPK fertilisation decreases the habitat quality of species-rich hay meadows. Based on the three studies presented in this thesis, the date of first cut in perennial plant communities should be handled more flexibly. This would benefit farmers, because higher forage qualities can be achieved. However, it was shown that there are site-specific effects. Plant communities containing annuals can be severely affected by advanced cutting dates, and the phenology at the date of first cut is crucial for the survival of these species. Interacting negative effects of fertilisation and cutting date on habitat quality suggest that the combination of late cutting date and NPK fertilisation should be avoided. Therefore, the best management at whole-farm scale appears to be a rotational cut and an extensive fertilisation of single meadows.
How can miscanthus be integrated most efficiently into agricultural production systems?
(2019) Mangold, Anja; Lewandowski, Iris
The demand for biomass is increasing steadily, as fossil resources are gradually being replaced by biomass within the context of a developing bioeconomy. Plant-based feedstocks currently used for this replacement virtually all come from annual crops. However, perennial crops such as miscanthus are expected to be more environmentally benign due to their generally low-input requirements and high yield potential. Despite these advantages, the current cultivation area of miscanthus in Europe is quite low. One reason for this is that the cultivation and utilization of miscanthus faces several challenges. For example, the most common propagation method via rhizomes is very labour-intensive and thus expensive, leading to high establishment costs. Seed propagation is a promising option to reduce costs, but is not suitable for sterile genotypes. Another challenge to be overcome is the problem of re-integrating former miscanthus fields into crop rotations. The crop following miscanthus needs to be highly competitive in order not to be impaired by resprouting miscanthus shoots and thus able to achieve high yields. Additionally, there is only little information available on the effect of miscanthus cultivation and its subsequent removal on soil N content. This information is however crucial, for example to avoid environmental problems being caused by a potential nitrogen leaching after a miscanthus removal. If miscanthus is to be utilized as a biogas substrate, there are further challenges to be overcome. Firstly, the optimal harvest date needs to be defined with regard to the methane hectare yield and resilience of the crop to green cutting. Secondly, as a continuous supply of biomass throughout the year is necessary, ensiling will become a relevant topic. However, information is still required on the optimal harvest date to achieve a sufficient silage quality and the effects of ensiling on methane hectare yield. Finally, the suitability of miscanthus for biogas production is also influenced by biomass quality such as the proportions of leaf and stem. This has already been established for miscanthus utilization in combustion but has not yet been sufficiently investigated for anaerobic digestion. In summary, there are a number of uncertainties involved in miscanthus establishment, removal and utilization, which currently hamper its integration into agricultural production systems. From a bioeconomic point of view, this integration needs to be conducted as efficiently as possible in terms of nutrient-use, environmental and land-use efficiency. The aim of this study was to contribute to the filling of these knowledge gaps. To answer these knowledge gaps, several miscanthus field trials and laboratory experiments were conducted: a novel propagation method was tested; the re-integration of miscanthus fields into a crop rotation was analysed; and the effect of genotype, harvest date and ensiling on the digestibility and methane hectare yield was investigated. The results illustrate some possibilities of improving the nutrient-use, environmental and land-use efficiency of miscanthus biomass production along its supply chain: It was shown that miscanthus propagation via collars is feasible and a promising alternative to rhizome propagation, as the multiplication rate of collars is comparable to that of rhizome propagation. As the harvesting of collars is likely to be less labour-intensive and is less destructive for the mother field than rhizome propagation, this method is more favourable for both economic and ecological reasons. The re-integration of miscanthus into crop rotations revealed maize to be a suitable crop after miscanthus, as it coped with the prevailing soil conditions and suppressed resprouting miscanthus efficiently, resulting in satisfactory yields. The soil mineral nitrogen (Nmin) content was found to increase during the vegetation period following a miscanthus removal, but was generally on a low level (average: 17.3 kg Nmin ha-1). Additionally, it was found that, in Germany, miscanthus should be harvested in mid-October to maximize methane yields and nutrient recycling but minimize yield reduction. In addition, silage quality was best when miscanthus was harvested on this date. As leaf proportion correlated positively with substrate-specific methane yield (SMY) and thus genotypes with a higher leaf proportion were found to have a higher SMY, methane hectare yields could be increased even further by using genotypes with a high leaf proportion. In summary, the approaches developed in this study allow to considerably improve the ecological and economic performance of miscanthus production by increasing nutrient-use,environmental impact and land-use, and thus simplifying implementation into practice.
Integrated rural and urban agricultural systems for the sustainability transition towards the bioeconomy
(2021) Winkler, Bastian; Lewandowski, Iris
The goal of the bioeconomy is a fundamental transition of both the economy and society towards sustainability. Replacing fossil resources by biomass for the provision of food, feed, fibre and fuel/energy (the 4F’s) will result in a substantial increase in demand for agricultural products. The consequent intensification of agricultural production, however, needs to be achieved while alleviating the societal challenges of the 21st century. The bioeconomy provides a knowledge-based, cross-sectoral and systemic pathway to increase agricultural production that involves all relevant stakeholders in the sustainability transition. This interdisciplinary thesis investigated the contribution that three selected bioeconomic approaches can make to the sustainable intensification of agricultural production, encompassing the growing urban population on the demand side and the numerous smallholder family farmers in countries of the global South on the supply side. The first study develops the ‘Integrated Renewable Energy Potential Assessment’ (IREPA) approach that involves smallholder farmers in planning and selection of renewable energy (RE) technologies for implementation into their agricultural systems. The bottom-up potential assessment, participatory learning and action research and multi-criteria decision analysis supported the smallholders in two case studies in rural South Africa and India in the identification of locally appropriate RE technologies. The second study uses IREPA to explore smallholders’ perception of agricultural RE production. Social, environmental, technical, institutional and economic factors are analysed to identify drivers of and barriers to RE implementation into smallholder agricultural systems. Mainly environmental factors, in particular climate change impacts, motivate smallholders to produce RE, while social factors (social cohesion, gender aspects, well-being, food and water security) determine the actual change. The barrier of high upfront investment costs can be eliminated by falling RET prices, the development of novel rural RE business models and institutional support. In addition, growing smartphone penetration rates in rural areas and open-access online information enables do-it-yourself RET operation and maintenance. Integrated approaches and such insights are crucial for the targeted formulation of agricultural development policies and stakeholder involvement in the sustainability transition towards a bioeconomy. The third study investigates the characteristics of urban gardening in Germany and its potential to encourage sustainable consumer behaviour, based on a review of 657 urban gardening project websites and an online survey involving 380 project participants. The results reveal multiple social, environmental and economic benefits of urban gardens for sustainable city development. The diverse gardener communities actively promote sustainable consumer behaviour by (unintentionally) applying several methods known to encourage pro-environmental behaviour. Hence, urban gardens are transformative spaces that involve the growing urban population in the societal transition towards a bioeconomy. In the context of sustainable intensification of biomass production in rural areas, the fourth study investigates the contribution of environmental service assessment and monetization in agricultural systems, using the example of the perennial biomass crop miscanthus for biofuel production. The valorisation makes environmental services - such as soil fertility improvement, carbon sequestration, water and air purification – tangible. This can incentivise payments to farmers for the provision of these public goods. Enhancing and utilising environmental services through nature-based solutions is a promising pathway to sustainable intensification, providing a shift from input-based towards process-based agricultural production. Finally, it can be concluded that integrated approaches which connect different production systems, disciplines and stakeholders are central for the development of the bioeconomy: - The integration of sustainable technologies, such as RE, into agricultural systems requires case-based research and participation of local stakeholders in project planning, decision making and targeted policy formulation. - The integration of the growing urban population in the sustainability transition can be supported by urban gardening because it promotes sustainable consumer behaviour. - The integration of nature-based solutions into agricultural systems enhances environmental service provision and supports the shift from input-based towards process-based agricultural systems. The approaches discussed in this thesis can support the sustainable intensification of agriculture, serve to re-connect the perspectives of rural producers and urban consumers, and enable the involvement of large portions of society in the sustainability transition towards the bioeconomy.
Integrating perennial biomass crops into crop rotations: How to remove miscanthus and switchgrass without glyphosate
(2023) Lewin, Eva; Kiesel, Andreas; Magenau, Elena; Lewandowski, Iris
Perennial energy grasses have gained attention in recent years as a promising resource for the bioeconomy because of their benign environmental profile, high stress tolerance, high biomass yields and low input requirements. Currently, strong breeding efforts are being made to extend the range of commercially available miscanthus and switchgrass genotypes. In order to foster farmers' acceptance of these crops, and especially of novel hybrids, more information is required about how they can be efficiently integrated into cropping rotations, how they can be removed at the end of their productive lifespan, and what effect they have on subsequently grown crops. Farmers in Europe are meanwhile increasingly constrained in the methods available to them to remove these crops, and there is a risk that the herbicide glyphosate, which has been used in many studies to remove them, will be banned in coming years. This study looks at the removal of seven‐year‐old stands of miscanthus and switchgrass over 1 year at an experimental site in Southern‐Germany. Three novel miscanthus genotypes were studied, alongside one variety of switchgrass, and the impact of each crop's removal on the yield of maize grown as a follow‐on crop was examined. A combination of soil tillage and grass herbicides for maize cultivation was successful in controlling miscanthus regrowth, such that yields of maize grown after miscanthus did not differ significantly from yields of maize grown in monoculture rotation (18.1 t dry biomass ha−1). Yields of maize grown after switchgrass (14.4 t dry biomass ha−1) were significantly lower than maize in monoculture rotation caused by insufficient control of switchgrass regrowth by the applied maize herbicide. Although some regrowth of miscanthus and switchgrass was observed in the follow‐on crop maize, complete eradication of both crops was achieved by subsequent winter wheat cultivation.
Introducing new miscanthus hybrids into the European bioeconomy : the effect of environment and management on biomass quantity and quality
(2023) Magenau, Elena; Lewandowski, Iris
Miscanthus has been identified as a promising lignocellulosic perennial biomass crop for temperate climates and different (marginal) soils in terms of yield and ecological benefits. The cultivation of miscanthus brings numerous ecological advantages, such as a reduction in soil erosion, protection of aquatic ecosystems from alteration through eutrophication, and increasing heterogeneity in annual arable landscapes leading to increased biodiversity compared to annual crops. Reasons for this are its perenniality, the long period of time it stands on the field, and its low fertiliser and plant protection demands. Nevertheless, the area under cultivation in Europe is limited. The reasons are that the scientific yield levels are not reached commercially, and the only commercially cultivated hybrid Miscanthus × giganteus (M×g) is sterile. Miscanthus is therefore currently propagated and established via rhizomes, which limits upscaling. However, the seed-based hybrids tested so far do not reach the potential of M×g in terms of yield, quality, and ecological impact under a wide range of climatic conditions. To improve the integration of miscanthus as a biomass crop in the growing European bioeconomy, it is required to reach high and stable yields over several years (security of biomass supply) and a low ecological impact by low nutrient offtakes under different European climates. Therefore, it is essential to gain agronomic knowledge on how genetic (G), location-specific environment (E), and management (M) factors and the interactions between them affect the security of biomass supply and ecosystem services of novel seed-based hybrids. Against this background, the research objectives of this study are: 1) to investigate the effect of the onset of the growing season on biomass supply security and how it is affected by late spring frosts, 2) to assess G × E interaction effects on miscanthus biomass security, and 3) to assess G × E × M interaction effects on nutrient offtake, yield and quality of miscanthus biomass. For this purpose, new seed- and rhizome-based miscanthus hybrids were compared with the commercially grown M×g and evaluated for biomass yield, quality, and nutrient offtakes (a key parameter defining the ecological impact) under different European conditions to determine biomass supply security and ecological effects. The effect of the management parameters cutting height and harvest time was also analysed. The results show that to reach a high biomass supply security, avoiding damage by late spring frosts is essential. An effective mechanism is a low frost sensitiveness of the emerging shoots and to produce new shoots over the whole growth period, as observed for the seed-based M. sinensis × sinensis (M sin×sin). By contrast, a late emergence and producing fewer, thicker but frost-susceptible shoots at the beginning of the growing season, as observed for rhizome-based M×g and rhizome- and seed-based M. sacchariflorus × sinensis (M sac×sin), endangers the biomass supply security in case of frost after emerging. Over the first three years, the establishment process of miscanthus depended on location and hybrid. The M sin×sin hybrids flowered and senesced earlier than the taller M sac×sin hybrids. Active senescence, probably initiated by flowering, increases biomass quality by reducing the moisture and nutrient content. Following the third growing season, the highest yields were recorded at the low-altitude site in northern Italy and the lowest on a industrially damaged marginal land site in northern France. Moisture contents at spring harvest were lowest in Croatia and highest in Wales, United Kingdom. A lower moisture content is highly desirable for transport, storage and most end-use applications. Overall, lower moisture contents at harvest were found in M sin×sin hybrids than in M sac×sin. As expected, delaying the harvest until spring reduced yield and nutrient contents. At lower latitudes, the late-ripening M sac×sin combined high yields with low nutrient contents when harvested in spring. At the most elevated latitude location (Wales), the early-ripening M sin×sin combined high biomass yields with low nutrient offtakes. The M×g clone with intermediate flowering and senescence showed similarly low nutrient contents at all locations. An increased cutting height at spring harvest decreased yields by 270 kg ha-1 (0.83%) with each 1-cm increase in cutting height up to 40 cm. Although whole shoot mineral concentrations were significantly influenced by both hybrid and year interactions, total nutrient contents did not differ significantly from those in the lower basal sections. In years with wet conditions before harvest, an increase in cutting height of 10 cm decreased moisture content by up to 8%, whereas the effect during dry conditions was marginal. To achieve high biomass supply security and increased ecological benefits in miscanthus cultivation, the results of this study lead to the recommendation to cultivate M sin×sin hybrids at locations with a high risk of late spring frosts, as observed in northern European sites, and M sac×sin hybrids at locations where the risk is low, as observed in southern Europe. In southern Europe, M sac×sin hybrids achieved high yields with low nutrient and moisture contents as they made use of the long vegetation period. In general, M sin×sin has a shorter growth period than M sac×sin hybrids, making it the perfect hybrid for northern Europe, where the vegetation period is short. To ensure biomass supply in regions with extreme minimum winter temperatures and late spring frosts, miscanthus should be harvested in spring due to the thicker mulch layer, which functions as insulation. To ensure biomass supply security, a successful establishment is essential. Therefore, during the establishment phase, harvest should generally take place in spring, as the establishment period is crucial for securing biomass yield throughout the cultivation period. Weakening or even loss of plants during this period will lead to higher weed pressure and lower than optimal yields. The harvest cutting height should be as low as possible to achieve a higher yield without an over-proportional increase in nutrient offtake. However, cutting height needs to be adapted according to local conditions by finding an optimum between biomass loss and the risk of damage to harvest machinery and contamination of the biomass by soil. Should the moisture content of the biomass be too high for safe storage due to wet conditions during harvest, the cutting height can be increased to avoid costly post-harvest drying procedures. This study recommends hybrids for specific locations in Europe, provides important data for determining harvest timing and height, and key data on the ecological impact. It shows that the cultivation of miscanthus in Europe, taking into account the G × E × M interactions, has the potential to secure the biomass supply for the growing bioeconomy while positively influencing the provision of ecosystem services. Furthermore, integrating miscanthus into the agricultural system increases its resilience by diversifying the crops grown, the structure of the agricultural landscape and farmers income.
Life cycle assessment of perennial cultivation systems : advancing applicability and comprehensiveness
(2021) Lask, Jan; Lewandowski, Iris
Resource-efficient perennial cultivation systems are considered promising sources of sustainably produced biomass to meet the growing demand of a future European bioeconomy. They require fewer agricultural procedures than annual systems, contribute to an increase in soil carbon sequestration and can be productive on marginal land. In Europe, the C4 grass miscanthus is the most prominent and best researched perennial crop for lignocellulosic biomass production. Recently, wild plant mixtures (WPM) have been suggested as a more diverse alternative system. Perennial cultivation systems have already been the subject of multiple sustainability assessments, with life cycle assessment (LCA) being the method most commonly used. This method aims to provide a holistic depiction of the environmental performance of a system. However, two challenges are usually encountered. First, results of agricultural LCAs very much depend on site- and management-specific characteristics. Parameters such as biomass yield, quantity of fertiliser applied and carbon sequestered can vary considerably, impairing the applicability of the method. Second, most of these studies focus on greenhouse gas emissions only. Land use impacts on biodiversity are commonly neglected, casting doubt on the comprehensiveness that LCA is trying to achieve. This thesis aims to advance the applicability and comprehensiveness of LCA of perennial cultivation systems. For this purpose, it focuses on three aspects relevant to the assessment of such systems, each of which was addressed by a dedicated research question: 1) How can the conducting and application of LCAs of perennial cultivations systems be simplified? 2) Which methodological approaches are best suited for the consideration of carbon sequestration and storage in LCAs of perennial cultivation systems? 3) How can land use impacts of perennial cultivation systems on biodiversity best be incorporated into the LCA framework? These questions were answered by applying the LCA method to perennial cultivation systems in three case studies, using specific approaches for the inclusion of sensitivity analysis and the evaluation of carbon sequestration and storage. In addition, information on the biodiversity impacts of perennial crop cultivation was collated by means of a meta-analysis which compared species richness and abundance in annual and perennial crop cultivation systems. Due to the variability of agricultural systems, the life cycle inventory phase can be quite intricate. Thus, the conducting of an LCA can be substantially simplified by focusing on a few relevant inputs and outputs only. In this thesis a global sensitivity analysis was used to identify the most important inventory parameters in the greenhouse gas assessment of miscanthus cultivation: carbon sequestration, biomass yield, length of the cultivation period, nitrogen and potassium fertiliser application, and the distance over which the harvested biomass is transported. Focusing on these inventory parameters, a simplified model was developed. It allows farmers and SME active in miscanthus-based value chains easy access to customised LCA results. This thesis includes a detailed analysis of the relevance of carbon sequestration and storage in the sustainability assessment of perennial cultivation systems. It was found that the quantity and in particular the permanence of carbon sequestered through the cultivation of perennial crops are critical for their favourability in terms of global warming impacts. Two alternative methodological approaches for the quantification of carbon sequestered were tested within two of the case studies – a simple carbon model and an allometric approach. In addition, the handling of the uncertain permanence of the carbon storage was reflected upon. The approaches were compared with regard to their suitability for use by typical LCA practitioners. It was concluded that allometric models should be used for the quantification of carbon sequestered and the corresponding amount accounted for as delayed emissions. This combination provides a manageable approach for the accounting of benefits from carbon sequestration and storage, and also prevents their overestimation. Established impact assessment methods such as ReCiPe2016 suggest characterisation factors for the incorporation of land use impacts on biodiversity into LCA. These factors use relative species richness as an indicator and assume a higher species richness in perennial than annual cultivation systems. This thesis includes a critical review of these characterisation factors, drawing on the results of the meta-analysis comparison of species richness in annual arable crops and perennial rhizomatous grasses. The meta-study did not confirm a higher number of species in perennial rhizomatous grasses than in annual arable crops. It was concluded that LCA studies on perennial cultivation systems need to be cautious in their application of the land use characterisation factors suggested in present-day impact assessment methods. Criticisms of the approach include the application of one single characterisation factor for diverse perennial cultivation systems such as WPM and miscanthus and the sole focus on species richness. In future, LCA research should focus on context-specific adjustment options for land use characterisation factors to ensure an adequate representation of biodiversity impacts in agricultural LCAs. Finally, the current focus on species richness in biodiversity impact assessment needs to be reassessed.
Methodological approaches for assessing the environmental performance of perennial crop-based value chains
(2017) Wagner, Moritz; Lewandowski, Iris
In a developing bioeconomy, the demand for biomass for industrial purposes is expected to increase significantly. This demand needs to be met in a sustainable way and without compromising food security. With this goal in mind, resource-efficient lignocellulosic crops, such as perennial energy grasses, are often cited as a biomass source with low negative impacts on the environment. Under European conditions, miscanthus is the leading perennial energy grass because of its high biomass and energy yield potential. It is a C4 plant, which achieves dry matter biomass yields of up to 20 Mg ha−1 yr−1 when harvested in later winter, and up to 30 Mg ha−1 yr−1 when harvested green in October. Currently the main utilization route of miscanthus is direct combustion for heat generation, but the biomass can also be used for various other applications, such as biofuels and insulation material. Several studies have analysed the environmental performance of perennial crop-based value chains, but most of these only assessed the Global Warming Potential (GWP). However, the GWP alone is not an adequate indicator for the holistic assessment of the environmental performance of such value chains. In addition, these studies often used generic data and applied varying assumptions, which makes a comparison of different value chains difficult. The main goal of this thesis is to draw up recommendations for future assessments of the environmental performance of perennial crop-based value chains. For this purpose, five research objectives were formulated: 1) to identify the key parameters influencing the environmental performance of perennial crop-based value chains; 2) to analyse which impact categories are most relevant when assessing the environmental performance; 3) to assess the differences between various perennial-crop based value chains; 4) to assess the environmental performance of the utilization of marginal land to grow perennial crops for industrial purposes; and 5) to analyse and compare the environmental performance of annual and perennial crops in the example value chain ‘biogas production’. To achieve these research objectives, the environmental performance of several perennial crop-based value chains was analysed in various impact categories applying the same underlying assumptions and using field data obtained under ceteris paribus conditions. The analysis was carried out using the globally recognised Life Cycle Assessment (LCA) methodology, which is standardized by two ISO norms (14040/44). The results revealed that biomass yield is one of the most important parameters influencing the environmental performance of perennial crop-based value chains. An increase in yield of 50%, for instance, leads to an increase in carbon mitigation potential in a comparable range (46%). Furthermore, the marked influence on the environmental impact mitigation potential of both fertilizer-induced emissions and selection of the reference system was demonstrated. For example, if the reference system is changed from light fuel oil to natural gas, the substituting by heat generated from the combustion of miscanthus biomass increases the net impact in the category ‘particulate matter formation’ by 220%. The relevance of different impact categories was analysed for various perennial crop-based value chains using a normalisation approach. The results clearly indicated that a holistic assessment of the environmental performance of perennial crop-based value chains should at least include the impact categories ‘marine ecotoxicity’, ‘human toxicity’, ‘agricultural land occupation’, ‘freshwater eutrophication’ and ‘freshwater ecotoxicity’. In future assessments, it is recommended to include the impacts of land-use on both biodiversity (using species richness as an indicator) and soil quality (using SOM as an indicator). The comparison of the environmental performance of different perennial crop-based value chains revealed clear environmental advantages of the cascade use of biomass. An example is the production of miscanthus-based insulation material, which is first used as a building material and then incinerated to generate heat and electricity. The results also demonstrate that, despite low biomass yield on marginal land, miscanthus-based value chains have a substantial environmental impact mitigation potential when substituting a fossil-based reference system. Furthermore, the comparison of annual and perennials crops as biogas substrates showed that perennial crops, and in particular miscanthus, have a considerably better environmental performance in the impact categories ‘climate change’ (up to -73%), ‘fossil fuel depletion’ (up to -79%), ‘freshwater eutrophication’ (up to -69%), ‘marine eutrophication’ (up to -67%), and ‘terrestrial acidification’ (up to -26%). In all four studies included in this thesis, it was observed that the data used for the biomass cultivation in particular, such as yield and fertilizer-induced emissions, have a considerable influence on the environmental performance. This data is highly site- and crop-specific and is strongly dependent on the agricultural management system applied. Based on the results of this thesis, the common practice of using generic data in assessments of the environmental performance of perennial crop-based value chains should be rejected. In order to obtain realistic results, the use of site- and crop-specific data is highly recommended.
Perennial biomass cropping and use: Shaping the policy ecosystem in European countries
(2023) Clifton‐Brown, John; Hastings, Astley; von Cossel, Moritz; Murphy‐Bokern, Donal; McCalmont, Jon; Whitaker, Jeanette; Alexopoulou, Efi; Amaducci, Stefano; Andronic, Larisa; Ashman, Christopher; Awty‐Carroll, Danny; Bhatia, Rakesh; Breuer, Lutz; Cosentino, Salvatore; Cracroft‐Eley, William; Donnison, Iain; Elbersen, Berien; Ferrarini, Andrea; Ford, Judith; Greef, Jörg; Ingram, Julie; Lewandowski, Iris; Magenau, Elena; Mos, Michal; Petrick, Martin; Pogrzeba, Marta; Robson, Paul; Rowe, Rebecca L.; Sandu, Anatolii; Schwarz, Kai‐Uwe; Scordia, Danilo; Scurlock, Jonathan; Shepherd, Anita; Thornton, Judith; Trindade, Luisa M.; Vetter, Sylvia; Wagner, Moritz; Wu, Pei‐Chen; Yamada, Toshihiko; Kiesel, Andreas
Demand for sustainably produced biomass is expected to increase with the need to provide renewable commodities, improve resource security and reduce greenhouse gas emissions in line with COP26 commitments. Studies have demonstrated additional environmental benefits of using perennial biomass crops (PBCs), when produced appropriately, as a feedstock for the growing bioeconomy, including utilisation for bioenergy (with or without carbon capture and storage). PBCs can potentially contribute to Common Agricultural Policy (CAP) (2023–27) objectives provided they are carefully integrated into farming systems and landscapes. Despite significant research and development (R&D) investment over decades in herbaceous and coppiced woody PBCs, deployment has largely stagnated due to social, economic and policy uncertainties. This paper identifies the challenges in creating policies that are acceptable to all actors. Development will need to be informed by measurement, reporting and verification (MRV) of greenhouse gas emissions reductions and other environmental, economic and social metrics. It discusses interlinked issues that must be considered in the expansion of PBC production: (i) available land; (ii) yield potential; (iii) integration into farming systems; (iv) R&D requirements; (v) utilisation options; and (vi) market systems and the socio‐economic environment. It makes policy recommendations that would enable greater PBC deployment: (1) incentivise farmers and land managers through specific policy measures, including carbon pricing, to allocate their less productive and less profitable land for uses which deliver demonstrable greenhouse gas reductions; (2) enable greenhouse gas mitigation markets to develop and offer secure contracts for commercial developers of verifiable low‐carbon bioenergy and bioproducts; (3) support innovation in biomass utilisation value chains; and (4) continue long‐term, strategic R&D and education for positive environmental, economic and social sustainability impacts.
Site impacts nutrient translocation efficiency in intraspecies and interspecies miscanthus hybrids on marginal lands
(2022) Magenau, Elena; Clifton‐Brown, John; Awty‐Carroll, Danny; Ashman, Chris; Ferrarini, Andrea; Kontek, Mislav; Martani, Enrico; Roderick, Kevin; Amaducci, Stefano; Davey, Chris; Jurišić, Vanja; Kam, Jason; Trindade, Luisa M.; Lewandowski, Iris; Kiesel, Andreas
Miscanthus, a C4 perennial rhizomatous grass, is capable of growing in varied climates and soil types in Europe, including on marginal lands. It can produce high yields with low nutrient inputs when harvested after complete senescence. Senescence induction and rate depend on complex genetic, environmental, and management interactions. To explore these interactions, we analysed four miscanthus hybrids (two novel seed‐based hybrids, GRC 3 [Miscanthus sinensis × sinensis] and GRC 14 [M. sacchariflorus × sinensis]; GRC 15, a novel M. sacchariflorus × sinensis clone; and GRC 9, a standard Miscanthus × giganteus clone) in Italy, Croatia, Germany and the UK. Over all trial locations and hybrids, the average aboveground biomass of the 3‐year‐old stands in August 2020 was 15 t DM ha−1 with nutrient contents of 7.6 mg N g−1 and 14.6 mg K g−1. As expected, delaying the harvest until spring reduced overall yield and nutrient contents (12 t DM ha−1, 3.3 mg N g−1, and 5.5 mg K g−1). At lower latitudes, the late‐ripening M. sacchariflorus × sinensis GRC 14 and GRC 15 combined high yields with low nutrient contents. At the most elevated latitude location (UK), the early‐ripening M. sinensis × sinensis combined high biomass yields with low nutrient offtakes. The clonal Miscanthus × giganteus with intermediate flowering and senescence attained similar low nutrient contents by spring harvest at all four locations. Seasonal changes in yield and nutrient levels analysed in this study provide: (1) a first step towards recommending hybrids for specific locations and end uses in Europe; (2) crucial data for determination of harvest time and practical steps in the valorization of biomass; and (3) key sustainability data for life cycle assessments. Identification of trade‐offs resulting from genetic × environment × management interactions is critical for increasing sustainable biomass supply from miscanthus grown on marginal lands.
Social assessment of miscanthus cultivation in Croatia: Assessing farmers' preferences and willingness to cultivate the crop
(2023) Marting Vidaurre, Nirvana A.; Jurišić, Vanja; Bieling, Claudia; Magenau, Elena; Wagner, Moritz; Kiesel, Andreas; Lewandowski, Iris
Social aspects of miscanthus cultivation have been investigated in a limited way in the scientific literature. Adopting existing frameworks for social life‐cycle assessment enables assessments to include numerous social aspects; however, the relevance of these aspects depends on the local context. This study aims to identify the most relevant social aspects from the farmers' perspective using a previously proposed framework for the assessment of the stakeholder ‘farmer’. It is based on a case study for miscanthus production in Sisak Moslavina in Croatia. The existence of abandoned lands in Croatia presents an opportunity for the cultivation of miscanthus as a potential source of biomass for the production of bio‐based materials and fuels. The study seeks to assess the feasibility of cultivating miscanthus in the region, taking into account potential challenges and opportunities, as well as farmers' willingness to adopt the crop, and to understand the reasons behind land abandonment. We conducted a survey among 44 farmers in the region and used a scoring method to identify the most relevant social aspects. The aspects most valued by the farmers were health and safety, access to water, land consolidation and rights, income and local employment, and food security. Responses to the question of whether they would adopt the crop highlight the importance of an established market, good trading conditions and profitability of cultivation. The survey also enabled an understanding of farmers' preferences with respect to the production conditions of crops. The farmers regarded the provision of subsidies as one of the main factors that render a crop attractive. Opportunities for the adoption of the miscanthus cultivation include high yields and low input requirements. Barriers include land conflicts and land availability. Despite the opportunities for miscanthus development in the region, there are important challenges to consider for successful implementation of the crop.
Spring emergence and canopy development strategies in miscanthus hybrids in Mediterranean, continental and maritime European climates
(2023) Magenau, Elena; Clifton‐Brown, John; Parry, Catherine; Ashman, Chris; Awty‐Carroll, Danny; Ferrarini, Andrea; Kontek, Mislav; Martani, Enrico; Amaducci, Stefano; Davey, Chris; Dolstra, Oene; Jurišić, Vanja; Kam, Jason; Trindade, Luisa M.; Lewandowski, Iris; Kiesel, Andreas
Due to its versatility and storability, biomass is an important resource for renewable materials and energy. Miscanthus hybrids combine high yield potential, low input demand, tolerance of certain marginal land types and several ecosystem benefits. To date, miscanthus breeding has focussed on increasing yield potential by maximising radiation interception through: (1) selection for early emergence, (2) increasing the growth rate to reach canopy closure as fast as possible, and (3) delayed flowering and senescence. The objective of this study is to compare early season re‐growth in miscanthus hybrids cultivated across Europe. Determination of differences in early canopy development on end‐of‐year yield traits is required to provide information for breeding decisions to improve future crop performance. For this purpose, a trial was planted with four miscanthus hybrids (two novel seed‐based hybrids M. sinensis × sinensis [M sin × sin] and M. sacchariflorus × sinensis [M sac × sin], a novel rhizome‐based M sac × sin and a standard Miscanthus × giganteus [M × g] clone) in the UK, Germany, Croatia and Italy, and was monitored in the third and fourth growing season. We determined differences between the hybrids in base temperature, frost sensitivity and emergence strategy. M × g and M sac × sin mainly emerged from belowground plant organs, producing fewer but thicker shoots at the beginning of the growing season but these shoots were susceptible to air frosts (determined by recording 0°C 2 m above ground surface). By contrast, M sin × sin emerged 10 days earlier, avoiding damage by late spring frosts and producing a high number of thinner shoots from aboveground shoots. Therefore, we recommend cultivating M sac × sin at locations with low risk and M sin × sin at locations with higher risk of late spring frosts. Selecting miscanthus hybrids that produce shoots throughout the vegetation period is an effective strategy to limit the risk of late frost damage and avoid reduction in yield from a shortened growing season.
Suitability of recycled organic residues from animal husbandry and bioenergy production for use as fertilizers
(2021) Bauerle, Andrea; Lewandowski, Iris
In recent years, agriculture has been increasingly faced with the acute need to find a more sustainable practice for dealing with nutrient-rich organic side streams. For ecological and economic reasons, pressure is mounting every day to implement an improved utilisation and to close nutrient loops in agriculture to the maximum possible. Pig manure and biogas digestates are suitable as organic fertilisers because they contain essential plant nutrients. They also provide organic matter that contributes to the maintenance of soil fertility. However, their current use is often insufficient. Both residues can be used as fertilisers either directly or following treatment. This can be as simple as solid-liquid separation. A more advanced approach is the precipitation of phosphorus for conversion into phosphate fertilisers ("P-Salts"). The fertilising effect of such innovative P-Salts needs to be investigated in an agronomic context. The same applies for the integration of separated biogas digestates as organic fertilisers into different biomass production systems. The primary objective of this thesis is to establish whether recycled fertilisers from organic residues are comparable to mineral fertilisers and can serve as a suitable substitution. For this purpose, five specific objectives were defined: (1) to determine whether separated biogas digestates can complement or substitute mineral fertilisers and whether/how they affect long-term yield performance in different biomass cropping systems; (2) to ascertain which type of separated biogas digestate is suitable for which biomass production system; (3) to test the effect of two recycled P-Salts on yield and quality of different crops compared to triple superphosphate (TSP); (4) to examine whether the combination of recycled P-Salts with biochar and dried solid digestates results in interaction effects; and (5) to assess whether there are differences in the uptake efficiency of recycled and mineral fertilisers between different crop types. Thus, several experiments were carried out. The fertilising effect of separated biogas digestates on three biomass production systems (perennial grassland, intercropping of triticale and clover grass, silage maize) was investigated in multi-year field experiments in south-west Germany. P-Salt and biochar from pig manure were tested in a greenhouse study with spring barley and faba bean. In a second greenhouse study with ornamentals, the P-Salt from manure, a P-Salt from biogas digestate, and dried solid digestates were assessed. The long-term yield stability of biomass cropping systems fertilised with separated biogas digestates was clearly demonstrated under field conditions. Separated biogas digestates can substitute mineral fertiliser in perennial and intercropping systems. Solid digestates were most suitable for cropping systems with soil tillage where their incorporation into soil is possible. The intercropping of triticale and clover grass was found to be the most stable system, with constantly high biomass yields being maintained using only digestates. For maize, a combined application of digestates and mineral fertiliser proved to be the best option. The P-Salt from manure had the same or even better effects than TSP on spring barley and faba bean. In the experiment with ornamentals, the two P-Salts from manure and digestate had more or less the same effect as TSP on biomass production. These results suggest that both P-Salts have an equivalent fertilisation effect to TSP and can thus replace it as mineral fertiliser. In this thesis, it was possible to achieve competitive yield results with the tested fertilisers, provided that they are integrated in a suitable fertilising strategy. The next step is for the recycled fertilisers to be actually used in agricultural practice - a prerequisite for which being that their implementation has agronomic, practical, ecological and economic advantages. The enhanced use efficiency of N and P already available on farms is challenging but necessary to reduce dependency on both synthesised N fertilisers and imported P fertilisers. This thesis significantly contributes by providing knowledge on the fertilising effect of selected recycled fertilisers necessary for their future implementation in agriculture. Optimised nutrient management and residue treatment using advanced technologies can contribute to the further closing of nutrient cycles. The highest environmental benefits can be realised on farms with excess residues and limited agricultural land. It is therefore highly recommended that these farms improve their current practice by prioritising the implementation of appropriate measures. Sound residue management necessitates strategic planning and capital investments from farmers and companies, but is a crucial step towards the sustainable intensification of cropping systems and resilient future agriculture.
The impact of agrivoltaics on crop production
(2022) Weselek, Axel; Lewandowski, Iris
Facing the consequences of global warming and climate change, the reduction of greenhouse gas emissions is one of the most prior tasks of todays society and policymakers. To achieve this, energy generation is currently transformed towards a reduced utilization of fossil fuels and its replacement through an increased expansion of renewable energy sources. In this context, one challenge will be to spare land resources and diminish potential land use conflicts, in particular between food and energy production. An approach to accomplish this, can be the utilization of production-integrated technologies such as agrivoltaic systems (AV). Agrivoltaic systems are photovoltaic systems specifically adapted for its application in combination with agricultural production. For this, AV systems are installed above or on agricultural fields with certain technical adaptions, enabling agricultural production to be continued. First described in 1981, this approach was taken up in the early 2000s with first AV pilot systems being developed. In first experiments in South-France it has been shown, that through the combined utilization of agricultural land for food and energy production, AV can contribute to an increment of total land productivity. While electrical yields can be increased with an increasing density of the photovoltaic modules mounted above, the proportion of light available for the plants grown underneath and consequently also agricultural yields are reduced. The aim of the present work was to examine, whether the results from these first experiments on crop production under AV can also be transferred to conditions in more moderate climates and also account for crops other than the so far investigated ones. The following four research objectives were defined: 1.) To what extent is plant-available radiation reduced by the solar panels of the AV system? 2.) How does this effect parameters of aerial and soil climate? 3.) How do the cultivated crops respond to the altered cropping conditions with regard to plant growth and development? 4.) Which consequences does this have regarding the yields and the chemical composition of the investigated crop-species? In order to examine these research objectives, a field experiment has been established underneath an experimental AV pilot facility in Southwest-Germany, near Lake Constance. Four different types of crops (grass clover, potatoes, celery and winter wheat) have been selected and cultivated underneath the AV system and on an adjacent reference area for comparison within a two-year experiment. Various microclimatic parameters were recorded in a high-resolution monitoring including all investigated crops on both sites. Crop growth and development was monitored in regular intervals during vegetation period. The harvestable yields of both experimental sites, including crop-specific yield components, were recorded and partially supplemented with an analysis of chemical compounds. The results show, that crop production under an APV system is affected in several ways. Under the given climatic conditions, losses in harvestable yields as a consequence of a reduction of crop-available radiation are most likely. Exceptional years such as 2018 suggest however, that cultivation under AV can have advantages for crop production, in particular under dry and hot climatic conditions. In order to fully exploit this potential, the application of the APV thus seems to be most suitable for more dry climatic regions, whereby innovations and developments in AV technology as well as an improved water management can facilitate a further optimization. Regardless of this, potential conflicts of interest with regard to land use cannot be ruled out and require the integration of agrivoltaics in the existing legislation.
The potential of miscanthus as biogas feedstock
(2020) Kiesel, Andreas; Lewandowski, Iris
Of all renewable energy forms, biomass accounts for the by far largest proportion of gross inland energy consumption in Europe. As the biogas sector in particular can provide demand-driven electricity generation, energy storage and flexible utilization options including biofuels, it is likely to play an important role in future energy systems in future. In Germany, the largest biogas market in Europe, energy crops provide the highest proportion of biogas input substrates, with maize being the most dominant. The environmental impact of biogas production is mainly attributed to energy crop production, with the risks of maize cultivation being particularly criticized. Perennial biomass crops have the potential to reduce the environmental impact of the biogas sector and miscanthus is an especially promising candidate crop due to its high yields. However, preliminary observations have indicated that the green harvest of miscanthus necessary for biogas production leads to a strong yield depression in the subsequent year. The aim of this thesis was to determine and understand the mechanisms influencing the green-cut tolerance of miscanthus and to assess the potential of different green-harvest regimes for biogas production. Here, ‘green-cut tolerance’ is defined as the crop’s ability to regrow in the year after the green harvest is performed without yield depression. A further aim of this thesis was to investigate the environmental performance of miscanthus-based biogas production and to determine its energy efficiency compared to other utilization options. Field trials were conducted to assess the potential of miscanthus hybrids for biogas production, the green-cut tolerance of Miscanthus x giganteus (Mxg), and how both are influenced by management practices (harvest regime x nitrogen fertilization). A Life-Cycle Assessment was performed to evaluate the environmental impact of biogas production from perennial C4 grasses, including miscanthus, and to assess the optimization potential compared to the standard biogas crop maize. The suitability of miscanthus biomass was investigated for the utilization options bioethanol, biogas and combustion, and the energy efficiency of these was compared based on their net energy yield. The results revealed that Mxg harvested in October showed the highest average biomass yield, the highest methane yield (approx. 6000 m3 methane ha-1) of all harvest regimes, and a higher substrate-specific methane (SMY) yield than for biomass harvested after winter. An earlier green harvest (July, August) improved the SMY, but led to a sharp biomass and thus methane yield decline in the second year and was identified as unsuitable for Mxg. As increased nitrogen fertilization showed no effect on the yield in any of the harvest regimes, it can be disregarded as a management practice for improving green-cut tolerance. Instead, harvest date was found to have a strong influence on green-cut tolerance and sufficient time for relocation of carbohydrates needs to be allowed before a green cut is performed. This finding is crucial for the utilization of miscanthus biomass harvested green and also for the breeding of new varieties with improved green-cut tolerance. Breeding targets for optimized biogas varieties should include to increase the SMY and biomass yield and to widen the possible harvest window. Selecting genotypes that relocate carbohydrates to the rhizomes earlier would allow an earlier green harvest without yield decline the following year, but this may involve a trade-off with the SMY. The suitability of miscanthus for the utilization options assessed was found to be influenced by biomass composition, which in turn was affected by genotype and harvest date. Lignin content had a negative effect on biomass quality for biogas and bioethanol production and increased with later harvest dates. Hemicellulose had a positive effect on biomass quality for bioethanol production through the improvement of the saccharification potential. Low ash, potassium and chloride content enhanced biomass quality for combustion by increasing the ash melting temperatures and decreased with a delay in harvest to after winter. For the biogas and bioethanol utilization pathways, novel miscanthus varieties with low lignin content need to be developed, whereas for combustion varieties with a high lignin content are more favourable. The Life Cycle Assessment revealed that the use of miscanthus has a high potential to reduce the environmental impacts of biogas crop production and thus the biogas sector. Miscanthus had a more favourable performance than the annual biogas crop maize in each impact category considered and the highest reduction potential compared to the fossil reference in the impact categories climate change, fossil fuel depletion and marine eutrophication. The choice of biomass utilization pathway had a considerable effect on the energy yield per unit area, with combustion showing the overall highest energy yield potential for electricity production. However, for the combustion pathway, miscanthus is generally harvested after winter and this is accompanied by biomass yield losses of 35% compared to peak yield. In the biogas pathway, miscanthus can be harvested close to peak yield, leading to an only 10% lower energy yield than that of combustion. When considering the use of miscanthus for biofuel production, the highest area efficiency was found for the direct use of biomethane, followed by battery electric vehicles fuelled by electricity from biomass combustion, and the lowest for the direct use of bioethanol. However, the low conversion efficiency of bioethanol production did not consider energy generation from by-products. In this thesis it was determined that the green-cut tolerance of miscanthus is influenced by the carbohydrate relocation to the rhizomes and thus by harvest date. Miscanthus harvested in October shows a high potential as feedstock for biogas production due to its high yield and sufficient digestibility, can help improve the biogas sector’s environmental performance and contribute to an increase in greenhouse gas mitigation. The digestibility of miscanthus biomass for biogas production could be improved by breeding and selecting genotypes with low lignin contents and by applying suitable pretreatment methods. Increased digestibility could also help to overcome potential trade-offs between early carbohydrate relocation and SMY. The efficiency of biomass utilization greatly depends on the utilization option, with a high efficiency being identified for biomethane as a transportation fuel and for peak-load power generation. It was shown that miscanthus is a suitable crop for the provision of sustainably produced biomass as a feedstock for the growing European bioeconomy that provides additional ecosystem services, e.g. groundwater and surface water protection.