Browsing by Subject "Circular economy"

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Characterisation of biogas digestate as raw material for fibre composites
(2022) Gebhardt, Marion; Lemmer, Andreas
Various synthetic fibres and natural fibres are used as reinforcing fibres in the fibre composite industry. Efforts towards sustainable products and the avoidance of land-use competition are increasingly driving the search for alternatives. Biorefineries are one possible solution. Biogas plants process structurally rich plant-based biomass. The resulting digestates have already been partially degraded. Natural reinforcement fibres are extracted chemically or biologically from plants, the use of digestates is obvious. This paper deals with the question whether biogas digestate can be used as a fibre raw material for composite materials. Digestates from four different commercially operated biogas plants in Germany are considered. Besides three biogas plants that utilize an average mix of animal excrement and plants one plant is operating solely plant-based. The solid portions of the fermentation residues were first examined regarding fibre quality. For this purpose, the fibre dimensions (fibre length and degree of slenderness) and the density of the fermentation residues were determined. Utilizing a feed analysis according to van Soest, the proportions of cell wall components were examined. The results of the investigations were compared with common fibres such as flax and wood. In addition to the properties, the possible fibre yield from the various fermentation residues was also considered. In this study, the influence of the starting substrates was considered in detail. For this purpose, the distribution of different size classes was first determined utilizing wet sieve analysis. These results were combined with the dry matter content. Digestates from a plant using exclusively plants as substrates, with a high proportion of hop vines, are considered separately. It is considered whether the additional washing of the fermentation residues brings an advantage for the fibre quality. To prove this thesis, the most common fibre properties are also examined and compared with wood fibres. These digestates from this biogas plant are used for the following investigations. Composite materials are often produced with a textile as reinforcement. Therefore, the digestate is first processed into a nonwoven. The wet laying technology is used, as it is suitable for various types of fibres. Only cellulose is used as a binding material so that the nonwoven is completely bio-based. The hot-press technology with a thermoset matrix is used to produce the composites. The matrix used is a partially bio-based epoxy resin system. The most suitable process parameters are determined with two test scenarios. In the first run, the proportion of added matrix is varied at constant pressure. In the second run, the pressure is varied at constant matrix content. Destructive and non-destructive material tests are carried out to check the material properties. To make a statement about a suitable application, the mechanical properties and the water absorption are of particular importance. In addition, the behaviour towards chemicals is examined to be able to assess the resistance of the material. For this purpose, the composite material is produced with the previously determined process parameters and immersed in various chemicals. Finally, the durability of the composite materials is examined. For this purpose, the composite material is also produced with the previously determined process parameters. An epoxy resin with a higher bio-based content is used as the matrix. The material is exposed to UV radiation and humid air for three months. Afterwards, the mechanical properties and water absorption are examined again. The main finding of the presented study is that the solid components of digestate can be processed into composite materials. The properties of the digestate fibres are similar to those of wood fibres. For the yield of digestate fibres, it is advantageous if only a small proportion of animal excrements is used as substrate in the biogas plant. Additional processing after fermentation leads to an increase in fibre quality. The hot-press-technology has proven to be a suitable process, as fully impregnated composites with reproducible properties can be produced. The process parameters determined are a pressure of at least 4:5MPa and a matrix addition of 60%, which corresponds to an excess of about 10%. The properties of the composites are comparable to Wood Plastic Composites. Therefore, they can be considered adequate. The durability is shown to be inadequate due to the strong reduction in mechanical properties after artificial weathering and chemical storage. The durability is mainly dependent on the matrix. Based on the results described, an application for the digestate composites as furniture material is recommended.
Characteristics and anaerobic co-digestion of press water from wood fuel preparation and digested sewage sludge
(2022) Sailer, Gregor; Empl, Florian; Kuptz, Daniel; Silberhorn, Martin; Ludewig, Darwin; Lesche, Simon; Pelz, Stefan; Müller, Joachim
Technical drying of harvested wood fuels is heat and energy consuming, while natural pre-drying in the forest, e.g., in stacks or storage piles, is accompanied by energy losses through natural degradation processes. Dewatering of energy wood by mechanical pressing is an innovative method to reduce the moisture content prior to thermal drying while producing press waters (PW, also referred to as wood juice) as a by-product. To date, the characteristics and utilization potentials of PW are largely unknown. In this study, three different spruce- and poplar-based PW were analyzed for their characteristics such as dry matter (DM), organic dry matter (oDM) concentration, pH-value, element concentration or chemical compounds. Additionally, they were used for anaerobic digestion (AD) experiments with digested sewage sludge (DSS) serving as inoculum. The fresh matter-based DM concentrations of the PW were between 0.4 and 3.2%, while oDM concentrations were between 87 and 89%DM. The spruce-based PW were characterized by lower pH-values of approx. 4.4, while the poplar-based PW was measured at pH 8. In the AD experiments, DSS alone (blank variant) achieved a specific methane yield of 95 ± 26 mL/goDM, while the mixture of spruce-based PW and DSS achieved up to 160 ± 12 mL/goDM, respectively. With further research, PW from wood fuel preparation offer the potential to be a suitable co-substrate or supplement for AD processes.
Kunststoffabfallmanagement und Strategien für eine Kreislaufwirtschaft in der Lebensmittelindustrie
(2025) Mielinger, Ellen; Weinrich, Ramona
The increasing global volume of waste poses a threat to the environment and the climate. Limiting the amount of waste and transforming the prevailing linear systems into a circular economy is an important task of our time. Packaging waste and especially plastic food packaging, account for a large proportion of waste due to their strong frequency and short lifespan. Avoiding waste from the outset and reducing food packaging is a top priority. At the same time, however, packaging increases the shelf life and transportability of foods, which is why it is often necessary to package food. Besides the threat to the earth’s health caused by plastic waste, food waste is also a major problem. To relieve the burden on ecosystems and achieve sustainability at all levels, it is therefore fundamental to prevent food waste and increase the recycling rates for packaging waste. In addition to technical innovations and the upgrading of recycling plants, consumer behaviour and the behaviour of the food industry play a decisive role. Through correct sorting behaviour at the household level and separately collected waste higher recycling rates can be achieved. On the other hand, which packaging and packaging materials are placed on the market by the food industry is crucial for a functioning circular economy. Against this background, the dissertation Plastic waste management and strategies for a circular economy in the food industry was authored. The first part of this dissertation analyses the introduction of sustainable food packaging from a social science perspective. Cross-national expert interviews provide information on what influences decision-making in companies in the food industry concerning sustainable packaging and what role consumers play from the experts' point of view. Although packaging sustainability is important, the economic aspect prevails when trade-offs between environmental compatibility and (additional) costs occur. According to the experts, consumers do not have sufficient knowledge and interest in packaging, leading to poor purchase decisions. This hinders the establishment of sustainable packaging. Moreover, the establishment of sustainable packaging is impeded by a certain disempowerment the interviewed experts feel exposed to. As a result, the experts dismiss the responsibility for more sustainable packaging solutions and shift it onto the state and food retailers. In line with a circular economy, in addition to the design and utilisation of environmentally friendly product packaging, the handling of the packaging after the consumption of the product is also of essential importance. Therefore, the second part of this thesis deals with the waste disposal behaviour of consumers. Influencing factors of waste separation behaviour at the private household level, preferred ways of information transmission concerning recycling rules and an extended deposit system as an approach to promoting the circular economy are analysed. Apart from packaging factors such as labels, internal factors that can be directly linked back to consumers can influence plastic packaging sorting behaviour. Focus group discussions reveal that uncertainty and confusion regarding the type of material often stand in the way of correct sorting behaviour. The internet and social media in particular are preferred for the information transmission of waste separation practices. Also, external factors, such as financial incentives or the prevalent waste disposal system, can influence consumers' sorting behaviour. One type of financial incentive is, for example, a deposit paid on single-use plastic packaging. This deposit is refunded as soon as the packaging is returned. This ensures a clean material flow, which can lead to higher recycling rates. Such a deposit refund system (DRS) already exists in Germany, including single-use beverage packages. Expert interviews with various stakeholders in the German waste management industry suggest that the success of the system in use and consumers' familiarity with it speaks for extending it also onto other single-use plastic food packages. However, this would require various different legal adjustments and the cooperation of all stakeholders involved in the process. There are also a number of organisational, economic and technical challenges that might stand in the way of an extension. In addition to the ecological optimisation of food packaging and resulting packaging waste, avoiding food waste at the private household level is an important sustainability goal. Therefore, in the digression of this work, a smartphone application aiming at reducing food waste is presented. The presented prototype can help consumers to better assess the shelf life of food and reduce uncertainty. Limitations concerning the results of the work arise primarily from the qualitative, explorative research approaches. Qualitative research is used to gain detailed and in-depth insights. Due to smaller sample sizes, it is not possible to derive generalisable results.
New sustainable banana value chain: Waste valuation toward a circular bioeconomy
(2023) Krungkaew, Samatcha; Hülsemann, Benedikt; Kingphadung, Kanokwan; Mahayothee, Busarakorn; Oechsner, Hans; Müller, Joachim
According to the needs of sustainability, a new sustainable banana chip value chain, which is a combination of the traditional banana chip value chain and the banana waste value chain, was designed. Scenarios were created assuming that an anaerobic digester would be implemented to produce biogas—which can act as a substitute for liquefied petroleum gas (LPG) used in banana processing—from banana wastes. The values of banana residues throughout the value chain were determined depending on farm gate tree price, transportation cost, and the final value of LPG substitution. The value chain was optimized using two objective functions: total chain profit maximization and factory profit maximization. The tree price at the farm gate was determined and assumed to be between USD 0.067 and USD 0.093 per tree, and the transportation cost of tree transportation was assumed to be between USD 0.31 and USD 0.39 per km. Different tree prices and transportation costs affected the profits of all stakeholders throughout the chain. The scenarios that maximized total chain profits showed superior environmental performance compared to the scenarios that maximized factory profits. The proposed sustainable value chain will lead to an increase in farmers’ profits of 15.5–17.0%, while the profits gained by collectors and factory will increase between 3.5 and 8.9% when compared to business as usual.
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.
The role of consumers in business model innovations for a sustainable circular bioeconomy
(2023) Lang, Stephanie; Minnucci, Giulia; Mueller, Matthias; Schlaile, Michael P.
Over the last decade, various governments and supranational bodies have promoted the development of a circular bioeconomy (CBE) as a response to sustainability challenges. The transition towards a CBE requires the collaboration of different actors in the innovation (eco)system. With this conceptual paper, we apply a circular business model lens to address the research question: “What are the archetypical roles of consumers in business model innovations for a sustainable CBE?” We use a combination of complementary theories from the circular economy and bioeconomy literature, evolutionary innovation economics, sustainability transitions research, the business model literature, and the work on active consumers. Considering consumers’ agency as a continuum between the manufacturer-active paradigm and the consumer-active paradigm, we propose: (i) consumers in the manufacturer-active paradigm can actively influence circular business models with their purchase decision; (ii) consumers can act as lobbyists and influencers for circular business model innovation; (iii) in their different roles as customer, user, repairer, and reseller, consumers can incentivize organizations to adapt their business models to their needs; (iv) consumers can become key partners in the process of defining the normative orientation of the innovation paradigm for a CBE; (v) consumers can actively co-create value by means of co-ownership (e.g., through platform cooperatives).