02 Fakultät Bau- und Umweltingenieurwissenschaften
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/3
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Item Open Access Enhanced composting as a way to a climate-friendly management of coffee by-products(2020) San Martin Ruiz, Macarena; Reiser, Martin; Kranert, MartinThis study investigated the performance of aerobic windrow systems by using coffee by-products and green waste to reduce gaseous emissions. Thereafter, a comparison with the current treatment and gaseous emissions at a Coffee Mill in Costa Rica was made. Two different studies where performed in Germany (pile I and II) and one study in a Coffee Mill in Costa Rica (pile III). Temperature, water content, and pH were the key parameters controlled over 35 days in all the systems. Moreover, CH4 emission rates were quantified by a FTIR and by a portable gas detector device where the emissions reached values 100 times higher when coffee by-products as a unique material for the composting process was used. Results show that highest emission rates during the composting process for pile I was 0.007 g(m2)-1 h-1, for pile II 0.006 g(m2)-1 h-1, and for pile III 3.1 g(m2)-1 h-1. It was found that CH4 emissions could be avoided if the mixture and the formation of the windrow piles were performed following the key parameter for composting, and the usage of additional material is used. With this, the reduction of CH4 emissions at the Mill in Costa Rica could be achieved in the future.Item Open Access Experiments and modeling for flexible biogas production by co-digestion of food waste and sewage sludge(2020) Liu, Yiyun; Huang, Tao; Li, Xiaofeng; Huang, Jingjing; Peng, Daoping; Maurer, Claudia; Kranert, MartinThis paper explores the feasibility of flexible biogas production by co-digestion of food waste and sewage sludge based on experiments and mathematical modeling. First, laboratory-scale experiments were carried out in variable operating conditions in terms of organic loading rate and feeding frequency to the digester. It is demonstrated that biogas production can achieve rapid responses to arbitrary feedings through co-digestion, and the stability of the anaerobic digestion process is not affected by the overloading of substrates. Compared with the conventional continuous mode, the required biogas storage capacity in flexible feeding mode can be significantly reduced. The optimum employed feeding organic loading rate (OLR) is identified, and how to adjust the feeding scheme for flexible biogas production is also discussed. Finally, a simplified prediction model for flexible biogas production is proposed and verified by experimental data, which could be conveniently used for demand-oriented control. It is expected that this research could give some theoretical basis for the enhancement of biogas utilization efficiency, thus expanding the applications of bio-energy.Item Open Access The potential of the co-recycling of secondary biodegradable household resources including wild plants to close nutrient and carbon cycles in agriculture in Germany(2022) Fendel, Veronika; Maurer, Claudia; Kranert, Martin; Huang, Jingjing; Schäffner, BenjaminThe aim of this study is to evaluate the potential for conserving natural resources (fossil resources, mineral fertilizer, fertile soil and biodiversity) with alternative circular concepts in order to contribute to the achievement of global sustainability goals. This study examines the potential contribution of substituting conventional products for three alternative circular economy concepts. This includes the household resources black water, kitchen and green waste for the production of design fertilizer, plant charcoal, biopolymers (concept 1) and biogas (concept 2), as well as the combination of household kitchen waste with wild plants for the production of biogas (concept 3). For evaluation, literature values were combined with analyzed parameters of input streams and biogas tests. The production and consumption values determined all relate to the functional unit of a person and year in Germany. Concept 1 has the highest potential for substitution in terms of the amount of recycled products. Co-recycling of organic household waste can account for 20% of NPK (nitrogen, phosphorus, potassium) mineral fertilizer, 19% of plastic consumption and 11% as a soil improving measure in soils in agriculture that are at risk of degradation. Concept 2 has the potential to contribute 12% of the final energy consumption in private households, which is an alternative solution regarding energy recovery due to the extensive practical experience. The joint recycling generates 141 kWh without, and 174 kWh with, fermentable green waste. If 75%, by weight, of fresh wild plants are added to the kitchen waste in concept 3, a wild plant area of 5 m2 is required, which could replace 41% of the biogas corn area, which is concept 3. This mix generates 193 kWh with the potential to reach 78% of corn energy production. The share of wild plants in kitchen waste of 50 or 25% by weight has the potential to achieve 115 or 104% of the corn energy yield, which is a promising concept for rural areas regarding energy recovery from an ecological point of view. The results show a considerable contribution potential of household resources in alternative cycle concepts to increase resource efficiency, and indirectly to diversify the agricultural landscape.Item Open Access The impact of using co-compost on resource management and resilience of smallholder agriculture in South India(2022) Fendel, Veronika; Kranert, Martin; Maurer, Claudia; Garcés-Sánchez, Gabriela; Huang, Jingjing; Ramakrishna, GirijaAgriculture is the main source of income in India, with most farmers being smallholders and facing multiple challenges, such as climate change and land degradation. For the sustainable implementation of alternative circular approaches, it is important that agriculture benefits. To assess this, the impact of using co-compost (organic waste and black water consisting of feces and urine) was evaluated through surveys of 120 smallholder farmers in two case studies in South India. All 149 questions related to the overarching research question: what is the impact of using co-compost on closing loops in smallholder agriculture in terms of resource management and resilience. Secondary smallholder resources were found to be well managed and local networks and economies proved to be particularly effective in pandemics, reinforcing the potential for nutrient sources from urban areas. For most farmers, using co-compost improved yields (90%), soil (80%), plant health (93%) and, consequently, profits (67%), as well as water management (53%). Water management was significantly less of a problem for co-compost users (15%) than non-users (42%). In addition, the users of co-compost were able to save resources. Chemical fertilizer use was significantly reduced from 1.42 ± 2.1 to 0.9 ± 1.35 t (acre∙year)-1, with total savings ranging from 37 to 44%. Overall, 67% were able to reduce chemical fertilizer use and 25% were able to reduce chemical spray use. Additionally, 53% reduced water consumption by 30.3% ± 19.92%. The visible benefits could motivate others to try co-composting. The reservations of non-users were due to personal or societal aspects (25%). In addition, the desire of farmers to convert to organic farming and try alternative farming methods, such as using smart technologies, vermicomposting or co-compost, was high (43%) and was positively influenced by the profitable use of alternative circular concepts. Information dissemination was mainly promoted by advertising (60%) and demonstrations (27%), which influenced openness to alternative circular concepts and products. In conclusion, co-composting and co-recycling approaches have a positive impact on the resource management and resilience of smallholder agriculture and thus, contribute to achieving sustainability goals.Item Open Access Suitability of biowaste and green waste composts for organic farming in Germany and the resulting utilization potentials(2023) Gottschall, Ralf; Thelen-Jüngling, Maria; Kranert, Martin; Kehres, BertramIn this study, the suitability of biowaste and green waste composts in organic farming is presented based on quality assurance data of approximately 21,000 compost analyses from 2015 to 2020. The evaluation of compost suitability was based on both the legal regulations of the EU 2021/1165 and the requirements of the two largest German organic farming associations Bioland and Naturland. In 2020, 70.1% of the composts agreed with the above-mentioned regulations, 21.6% exceeded the limits for heavy metals and 7.3% exceeded the limits for foreign matter. The negative influence of the single elements regarding the suitability of composts for organic agriculture declined in the order Zn > Pb > Cd > Ni > Cu. In the bio-waste composts, the impurity content subsequently decreased by more than 50% from 2015 to 2020. In 2019 and 2020, approximately 2.5 million Mg fresh mass (FM) of the analyzed composts were suitable for organic farming. With an average compost application of 5 Mg FM per hectare (ha) and year, about 500,000 ha of arable land could have been supplied in 2020.