Abstract
Rapid urbanization in developing countries is attracting urban livestock farming, which is associated with feed nutrient imports and manure nutrient accumulations. Here, we report on manure nutrients (N, P and K) production on urban livestock farms in Addis Ababa and Jimma in Ethiopia, and estimate manure recovery on these farms and its recycling in urban, peri-urban and rural crop farms. Estimates were based on data from farm surveys, statistics, literature and model calculations. Urban livestock farms had on average 13 tropical livestock units and positive N, P and K balances. Urban crop farms had negative N and K balances, and did not use manure from urban livestock farms. We estimated that 0.5–2.6 Gg N, 0.2–0.8 Gg P and 0.9–3.7 Gg K can be collected in manure from the 5,200 urban livestock farms in Addis Ababa year−1, and can be recycled in crop land. Two manure allocation strategies were explored: balanced P fertilization and balanced N fertilization. The former allowed greater precision in matching nutrient supply to demand, and was associated with greater manure transport and distribution, up to rural areas. Manure recycling has several benefits: synthetic fertilizer savings (75–300 million Ethiopian Birr year−1 for Addis Ababa), soil fertility replenishment, and reductions in water pollution. However, there are various cultural, educational and institutional barriers for manure recycling. We argue that more quantitative data and scenario analyses are needed for deliberative decision making and for exploring more sustainable development pathways of urban livestock farms, re-connected to crop farms via manure recycling.
Highlights
Global population is projected to reach 9–10 billion by 2050 (FAO 2017) and 68% of the population is projected to be urban (UN 2019)
We argue that more quantitative data and scenario analyses are needed for deliberative decision making and for exploring more sustainable development pathways of urban livestock farms, re-connected to crop farms via manure recycling
The purpose of this study was threefold: (i) to estimate the amounts of manure nutrients that can be recycled from urban livestock farms to crop farms in urban, periurban and rural areas, (ii) to explore strategies for increased manure recycling, and (iii) to estimate fertilizer saving and reductions in nutrient pollutions in urban, peri-urban and rural areas, in Addis Ababa and Jimma in Ethiopia
Summary
Global population is projected to reach 9–10 billion by 2050 (FAO 2017) and 68% of the population is projected to be urban (UN 2019). These changes are accompanied by fast growing food demand and dietary transitions in urban areas (Satterthwaite 2017). Most of the food for urban people is imported from rural areas (Jones et al 2013), but significant amounts are provided by urban and peri-urban farms (Roessler et al 2016). Urban and peri-urban agriculture (UPA) contributes to the livelihood of urban dwellers, providing jobs, income and food security, especially in developing countries (Chihambakwe et al 2018; Khumalo and Sibanda 2019; Mugisa et al 2017). UPA farms mainly supply perishable vegetables and animal products to urban areas, due to the proximity to and high prices in urban markets (Djurfeldt 2015; Mugisa et al 2017)
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