Browsing by Author "Lederer, Jakob"

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    Assessment of a Cattle Manure Vermicomposting System Using Material Flow Analysis: A Case Study from Uganda
    (Sustainability, 2019) Jjagwe, Joseph; Komakech, Allan John; Karungi, Jeninah; Amann, Arabel; Wanyama, Joshua; Lederer, Jakob
    Growth in cattle population is associated with increased manure generation whose current management in low-income countries is associated with health and environmental problems as well as low utilization rates. This trend can be reversed by promoting better manure management technologies. This study assessed vermicomposting as one of the technologies to manage organic wastes, using the case study in Uganda. A vermicomposting system using cattle manure and earthworms (Eudrilus euginea) was monitored for one year with the harvesting of products (compost, earthworm biomass) after every three months. Vermicompost samples from the beginning of the experiment and after every harvest were analyzed for the following parameters: pH, ash content, volatile and total solids, nutrients N, P, K, and C. Emissions of CO2, CH4, NH3, and N2O were also measured. Material flow analysis was used to determine the flows and retention of nutrients within the system. Results showed that total solids, ash, N, P, and K content significantly increased, while contents of volatile solids and C, as well as the pH, significantly decreased over time. Of the materials that entered the vermicomposting system, 46% went to vermicompost, 2% into earthworms, and 52% was lost to the atmosphere. Substance flow analysis showed that 30% of C went to vermicompost, 69% was emitted to the atmosphere, and 2% ended up in earthworms while 75% of N was transferred to vermicompost, 7% went to earthworms, and 18% escaped into the atmosphere. The cumulative emissions were 102 g CO2 kg􀀀1 waste, 7.6 g CH4 kg􀀀1 waste, and 3.943 10􀀀5 g N2O kg􀀀1 waste on a dry basis, while NH3 was not detected throughout the measurement time. Compared to other manure management methods, vermicomposting demonstrated good potential in conserving nutrients as well as reducing greenhouse gas emissions.
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    Can Local Nutrient-Circularity and Erosion Control Increase Yields of Resource-Constraint Smallholder Farmers? A Case Study in Kenya and Uganda
    (Journal of Cleaner Production, 2021) Amann, Arabel; Herrnegger, Mathew; Karungi, Jeninah; Komakech, Allan John; Mwanake, Hope; Schneider, Lea; Schürz, Christoph; Stecher, Gabriel; Turinawe, Alice; Zessner, Matthias; Lederer, Jakob
    As many regions in sub-Saharan Africa, the border region of Kenya (KE) and Uganda (UG) has faced a declining soil fertility for decades, resulting from soil erosion, intensely managed agricultural soils due to population pressure and small inputs of mineral and organic fertilisers. With limited financial means, farmers need measures and/or technologies that effectively reduce nutrient losses or increase inputs at a low cost. In this study, four such measures are in focus, namely erosion reduction practices, vermicomposting of animal manure, collection of human urine in jerry cans and, collection of human excreta in urine-diverting dry toilets. Current soil nutrient balances in five districts in the Sio-Malaba-Malakisi River Basin and the potential of these measures to reduce the soil nutrient deficit are studied using the method of material flow analysis and the software STAN. Furthermore, crop14 nutrient-response functions are used to determine their potential impact on maize harvests. Overall, results reveal that there exists a non-negligible and exploitable potential of local resources to reduce the soil nutrient deficit, improve harvests and in turn food security of the smallholder farmers in the region. Soil nutrient deficits could be reduced by 20 — 30 %, 23 — 42 % and 9 — 15 % for nitrogen (N), phosphorus (P) and potassium (K), respectively. Subsequently, maize harvests could be increased by 8 – 40 %, depending on the applied technology and area. This research provides useful insights for agricultural extension workers, politicians and researchers alike, highlighting that simple and easily available technologies can harness similar amounts of nutrients as more complex and expensive ones if all specific technology constraints are adequately incorporated in the analyses.
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    The potential of wastes to improve nutrient levels in agricultural soils: A material flow analysis case study from Busia District, Uganda
    (Agriculture, Ecosystems & Environment, 2015) Lederer, Jakob; Karungi, Jeninah; Ogwang, Francis
    Like many other countries in Sub-Saharan Africa (SSA), Uganda faces a remarkable soil nutrient deficit in farmland soils. In order to cope with this deficit, many authors suggest increasing the recycling of hitherto unused nutrient sources from human excrement and urban municipal solid waste (MSW). However, a quantification of the potential of these nutrient sources to overcome soil nutrient deficits in Uganda has not been carried out so far. This research paper presents a case study calculating the soil nutrient balance for nitrogen (N), phosphorus (P), and potassium (K), as well as the potential of hitherto unused human excrement and urban MSW to decrease soil nutrient deficits in agricultural land by applying the method of material flow analysis (MFA) in Busia District (Uganda). Results show a high soil nutrient deficit of agricultural soils in the district, with values of 33 kg N ha 1, 6 kg P ha 1, and 41 kg K ha 1. The potential to reduce these negative balances is negligible for hitherto unused urban MSW (1–3%), but higher for human excrement (17–60%). The low potential of urban MSW as well as the hygienic problems associated with human excrement (particularly feces) means that other measures such as soil conservation and mineral fertilizer application should not be ignored in the effort to increase agricultural productivity. This is not only valid for Busia District, but also for other regions in SSA.