Browsing by Subject "Recycling"

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An integrated computable general equilibrium model including multiple types and uses of water
(2015) Luckmann, Jonas Jens; Grethe, Harald
Water is a scarce resource in many regions of the world and competition for water is an increasing problem. To countervail this trend policies are needed regulating supply and demand for water. As water is used in many economic activities, water related management decisions usually have complex implications. Economic simulation models have been proven useful to ex-ante assess the consequences of policy changes. Specifically, Computable General Equilibrium (CGE) models are very suitable to analyze the consequences of water-related management decisions, as they consider the interlinkages between different sectors and economic agents within an economy. However, so far there is no CGE model which provides a holistic picture of the water sector including all aspects of provision, demand and management. Against this background, in this thesis a CGE model (STAGE_W) is developed which is especially focused on the water sector and provides a generic, integrated and flexible framework to incorporate various water sources from which several water activities produce water commodities of differing quality. These are consumed by other activities or by households. The applications presented in this thesis are to the best knowledge of the author the first CGE approaches to depict the recycling of wastewater and the provision of brackish groundwater as independent activities. Another novelty of the model is that it is capable to depict cascading water use. Furthermore, the inclusion of several water specific taxation instruments allows for a wide range of water policy simulations. To demonstrate the capabilities of the model, STAGE_W is applied to a Social Accounting Matrix for Israel. Based on this database several case studies are conducted which are presented in three scientific articles. Israel provides an ideal example as the country is strongly affected by water scarcity and is also among the world leaders regarding the development of new water sources and technologies. In the first article, a literature review on previously existing approaches of water depiction in CGE models is provided along with a detailed description of the specifics of STAGE_W. The model is applied to simulate a reduction of freshwater resources. The effects of this shock are analyzed with and without further increasing the desalination capacity. The results show that the economic effects are slightly negative under both scenarios. Counterintuitively, the provision of additional potable water through desalination does not substantively reduce the negative outcomes. This is mainly due to the high costs of desalination, which are currently subsidized in Israel. The second article simulates an abolishment of the discriminatory water pricing system currently established in Israel. Instead, two alternative schemes are introduced: price liberalization, which unifies the prices for all potable water consumers at cost recovery rates, and marginal pricing, lifting the potable water price to the cost of desalination. It is found that both schemes yield a double dividend by simultaneously saving water and increasing economic growth. Thereby, marginal pricing allows for larger water savings while price liberalization results in higher economic growth. In the third article, the model is further refined: the quantity of sewage available for reclamation is linked to the water consumption of economic entities connected to a sewer system. This allows to depict cascading water use and to endogenously estimate the marginal value of unpurified sewage. It is shown that a consideration of this link is crucial, if a high share of potable water is reclaimed and used. In this case, reducing the potable water consumption of municipalities also negatively affects the availability of reclaimed wastewater and thereby reduces its potential as a substitute for potable water. These case studies provide evidence of the validity of the model developed. The model results cannot necessarily be anticipated, as they are the outcome of complex interrelations within the model and none of the previous models has the capacity to capture all the relevant aspects of the water sector which influence these outcomes. Therefore, it is concluded that STAGE_W constitutes a helpful tool to implement a more sustainable management of water resources, allowing policy makers to ex-ante estimate the economy-wide effects of water related decisions. As the whole economy is depicted, a more holistic picture of effects resulting from changes in the water sector can be drawn in comparison to single sector models or cost-benefit analyzes.
Phosphorus bioavailability of fertilizers recycled from sewage sludge and their suitability for organic crop production
(2020) Wollmann, Iris; Möller, Kurt
Phosphorus (P) nutrition of plants is a key production factor in agriculture. In an approach to recycle P from urban areas back to agriculture, technologies have been developed to produce mineral P fertilizers out of municipal sewage sludge. In this study, different P fertilizers recycled from sewage sludge have been investigated in pot and field experiments for their bioavailability to maize and several plant species of a crop rotation. It was also investigated, if bioavailability of recycled P fertilizers can be enhanced either by a soil inoculation with different bacteria strains that are efficient in P solubilizing, or by a cultivation of red clover in the crop rotation. As there is a lack of bioavailable P fertilizers in organic cropping systems, P fertilizers recycled from sewage sludge were evaluated for their suitability to be used in organic crop production. It has been shown that most of the investigated fertilizers recycled from sewage sludge have a higher P bioavailability than Phosphate Rock (PR). Fertilizer efficacy seems very dependent from specific production conditions which are decisive for the final product. Among the tested fertilizers, struvite (MgNH4PO4 . 6 H2O) was most efficient in increasing plant P offtake of maize (+ 27.5% in the field, and more than sixfold in a pot experiment, compared to the unfertilized control). Struvite and calcined sewage sludge ash (SSA) are efficient fertilizers at both acidic and neutral soil pH. Other fertilizers (e.g. untreated incineration ashes) have low solubility at soil with pH > 6, and thus, might be used on acidic soil only, or as raw material for fertilizer production. In the field experiment, the overall response to P fertilizer input was low, which probably can be attributed to a sufficient inherent P supply on the used site. An immobilization of fertilizer P over time could be shown in all experiments. Thus, recycled P fertilizers should be applied to responsive crops in the rotation. An improved P supply of maize could be shown when grown after red clover in the crop rotation. This might be attributed to a combination of different factors, such as a solubilization of sparingly soluble P forms in recycled fertilizers, following a drop in soil pH due to biological N2 fixation of clover. A recycling of P to maize via decomposed clover roots might in addition have contributed to an increased P supply of the subsequent maize. Despite this promising effect, P mobilization by clover cultivation was not sufficient to cover the entire P demand of maize. Thus, additional fertilizer P inputs to maize might still be necessary to ensure optimal plant growth on P deficient soils. With one exception, an application of different bacteria strains generally did not affect P supply of the plants. Applied bacteria seem very dependent on the environmental conditions. It is conceivable, that especially in organic systems, a soil application with external bacteria does not enhance the beneficial effects of a high microbial abundance and activity which often is already present in organic cropping systems. From an agronomic point of view, P fertilizers recycled from sewage sludge are better alternatives for organic crop production than PR. A recycling of nutrients generally fits well with basic organic principles. By introducing those fertilizers, the organic system could make a decisive contribution to the ongoing effort of closing the P cycle, and, once more, develop towards a farming system of the future.
Towards a sustainable nutrient management in organic farming : closing the nutrient gap with recycled fertilizers from urban waste
(2022) Reimer, Marie; Möller, Kurt
Nutrient scarcity is one of the main challenges in arable organic farming. Yet, little is known about the current supply and need of nutrients on organic farms and even less about the nutrient sources utilized by organic farmers. However, most stakeholders within the organic sector agree that additional nutrients, preferably from recycled sources, such as urban waste materials, are needed. In this thesis, the current need and use of nutrients (N, P, K, Mg, S) in the organic farming systems was investigated by performing a meta-analysis of previous studies and two farm gate nutrient budget studies across Europe. Further, the effect of recycled fertilizers from urban waste, such as compost from household and green waste, human urine and sewage sludge on crop yield, nutrient balances, soil fertility, and risk of contamination with potentially toxic elements (PTEs) were examined. To this end, three long-term field trials using different recycled fertilizers were investigated and combined with results of a simulation using the soil-plant-atmosphere model DAISY. The results of this thesis show that the organic cropping system within Europe operates under nutrient limited conditions, which limits the yield potential and can cause soil nutrient depletion, especially of P. Farms that relied to a high extend (>60%) on biological nitrogen fixation for their N supply were particularly prone to the risk of soil P and K depletion. Further, 17% of external N inputs derived from the conventional livestock system, which is often considered contentious. Omitting these would further increase the nutrient gap. Therefore, changes to the contemporary practice are needed to ensure sustainability in the organic nutrient management. First, a better distribution of nutrients within the organic sector is needed. In particular, to avoid nutrient surpluses in one farm type (e.g., livestock or vegetable farms), while other farm types (e.g., arable farms) experience nutrient deficits. Further, due to N losses during processing the nutrient composition of organic fertilizers does not match the crops’ nutrient offtake. Digestates from biogas plant show the closest resemblance. However, to avoid nutrient imbalances an adequate use of external inputs that is tailored to the specific farm’s nutrient demands and reliance on biological N fixation is necessary. Increased awareness of tools like nutrient budgeting among farmers and advisors could facilitate achieving a more balanced nutrient management. Still, additional nutrients are needed to close the current nutrient gap and to substitute animal manures from conventional origin. Recycled fertilizers from urban waste represent a suitable nutrient source to this end. Sewage sludge and human urine performed similarly to cattle slurry with N recovery rates of about 0.5 – 0.6 and household waste compost had similar values to straw-rich animal manures with recovery rate of about 0.3. Nitrogen losses after field application ranged between 34-55% of the applied N amount, with nitrate leaching being the main loss pathway. Total N losses were slightly smaller for compost and cattle manure and were accompanied by a higher soil N accumulation of about 25% of applied N. Similar to the accumulation of soil N, compost also resulted in the highest soil C sequestration. Using cattle manures and sewage sludge showed a smaller effect, while cattle slurry did not cause a soil C increase. Most concerns related to the use of recycled fertilizers derive from the risk of contaminants, such as potentially toxic elements (PTEs). Compost and sewage sludge fertilization can lead to a higher amount of PTEs in the soil. However, significant changes in crop PTE uptake were rare due to low PTE bioavailability. The risk to human health and soil environment associated with PTEs through recycled fertilizer application is therefore neglectable. Urban waste can also be refined by incineration or precipitation processes to ensure less contamination, yet this results in nutrient (e.g., N) and organic matter loss. An argument can therefore be made for the use of raw materials if they lie within the contamination threshold values. In conclusion, the organic nutrient management in Europe requires more external nutrient inputs. Recycled fertilizers from urban wastes are an adequate source in terms of yield effect and soil fertility to close the nutrient gap and to substitute animal manures from conventional origin. However, the infrastructure and availability of recycled fertilizers need to be improved and suitable policy making is needed to fulfil the whole potential of these nutrient sources by for example permitting fertilizers derived from human excreta or the strategical placement of biogas plants which recycle urban wastes.
Wasted! Resource recovery and waste management in Cuba
(2018) Trastl, Heike; Ahlheim, Michael; Becker, Maike; Allegue Losada, Yeniley
The collection of solid waste and the recovery of recyclable material from waste belong to the many challenges Cuba has been facing over the past years. In this paper, we give a short account of the actual waste situation and analyze the causes of the obvious deficiencies of the waste sector. We conducted a small survey in Havana city in order to assess peoples awareness of the garbage problem, their appraisal of the actual situation and their willingness to contribute personally to an improvement of the waste situation. Based on the insights gained from this survey and from our theoretical analysis of the Cuban waste management we develop suggestions for an improvement of the waste situation in Cuba. These suggestions take into account that the financial means available for a reform of the waste management system in Cuba are severely restricted. Therefore, our suggestions are more focused on organizational and motivational changes than on the introduction of high technology.