Manure recycling from urban livestock farms for closing the urban–rural nutrient loops

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.

Exploring the Recycling of Manure From Urban Livestock Farms: A Case Study in Ethiopia

“…Common features of UPA livestock farms are also the need to import a large fraction of the required feed from elsewhere and the shortage of land for rational manure disposal. As a consequence, UPA livestock farms often have large manure nutrient surpluses [11,52,55] , as was the case in Jimma especially in the URBAN and UPALP scenarios (Fig. 7).…”

“…This contrasts with the increasing number of large specialized animal feeding operations in urban and peri-urban areas in countries with emerging economies such as China [51] , where the specialized pig and poultry farmers often partner with animal breeding or feeding companies (contract farmers). Basically, most UPA livestock farms around the world have a relatively high farm income from a small farm area [11,51,52] , and specialization and intensification are common trends [53,54] . Common features of UPA livestock farms are also the need to import a large fraction of the required feed from elsewhere and the shortage of land for rational manure disposal.…”

“…Many UPA livestock farms in Ethiopia do have some land for cropping, grazing and manure disposal [11,52] , but the area is insufficient to provide the required feed and to dispose of all the manure in an agronomically and environmentally sound manner. Therefore, most of the feed is imported from the rural areas, but we assumed that 20% of the required feed of UPA livestock will be scavenged from the neighborhood, based on earlier surveys [19] .…”

Nutrient use and recycling in urban, peri-urban and rural farms in Ethiopia

“… Sensitivity analyses suggests that through promotion of improved manure management and introduction of more efficient livestock breeds, the NUE of MC-LS farms can be improved by 20 to 25% and N recycling by 10 to 20% over the current condition. Therefore, to improve the environmental and economic performance of MC-LS peri-urban farms in Ethiopia, (1) NUE and N recycling enhancing measures including livestock feed quality improvement, exchange of crop residues and manure between crop and livestock compartments within and between farms, and provision of alternative and low cost energy sources for satisfying the fuel demand of the farming families; in combination with (2) improving the NUE at animal level through animal breeding for the genetic improvement of livestock breeds and precision animal feeding; should be put in practice. Due to the extreme shortage of land in urban and peri-urban areas, future research should incorporate the effects of changing land allocation as a key aspect in the sensitivity analysis of the impacts of improved livestock breeding and feeding strategies of MC-LS farms.…”

“…Although, the importance of nutrient recycling is known for long, the adoption of the concepts of recycling and circular food systems is insignificant in Ethiopian agriculture in general and in UPA in particular. This could be attributed to: (1) Shortage and competing use of crop residues for animal feed, biofuel and soil amendment; (2) Shortage and competing use of animal manures for biofuel, house construction and soil amendment; (3) Lack of knowledge, good farm data, advisory services, incentives and policies for the recycling of manures and wastes in crop farms.…”