1. Department of Horticulture and Plant Sciences, College of Agriculture and Veterinary Medicine, Jimma University, Jimma, Ethiopia. 2. Department of Soil Quality, Wageningen University and Research, 6700 AA Wageningen, the Netherlands. 3. Wageningen Environmental Research, 6700 AA Wageningen, the Netherlands. 4. SoilCares Foundation, Nieuwe Kanaal 7c, 6709 PA Wageningen, the Netherlands.
• Livestock manure was the main organic waste in urban and peri-urban areas.
• Manure production will increase by a factor of 3–10 between 2015–2050.
• Only 13%–38% of excreted N by livestock will be recycled in croplands.
• Intensification of urban livestock production greatly increased N surpluses.
• Reducing population growth and increasing livestock productivity needed.
Urban population growth is driving the expansion of urban and peri-urban agriculture (UPA) in developing countries. UPA is providing nutritious food to residents but the manures produced by UPA livestock farms and other wastes are not properly recycled. This paper explores the effects of four scenarios: (1) a reference scenario (business as usual), (2) increased urbanization, (3) UPA intensification, and (4) improved technology, on food-protein self-sufficiency, manure nitrogen (N) recycling and balances for four different zones in a small city (Jimma) in Ethiopia during the period 2015-2050. An N mass flow model with data from farm surveys, field experiments and literature was used. A field experiment was conducted and N use efficiency and N fertilizer replacement values differed among the five types of composts derived from urban livestock manures and kitchen wastes. The N use efficiency and N fertilizer replacement values were used in the N mass flow model.
Livestock manures were the main organic wastes in urban areas, although only 20 to 40% of animal-sourced food consumed was produced in UPA, and only 14 to 19% of protein intake by residents was animal-based. Scenarios indicate that manure production in UPA will increase 3 to 10 times between 2015 and 2050, depending on urbanization and UPA intensification. Only 13 to 38% of manure N will be recycled in croplands. Farm-gate N balances of UPA livestock farms will increase to>1 t·ha−1 in 2050. Doubling livestock productivity and feed protein conversion to animal-sourced food will roughly halve manure N production.
Costs of waste recycling were high and indicate the need for government incentives. Results of these senarios are wake-up calls for all stakeholders and indicate alternative pathways.
. [J]. Frontiers of Agricultural Science and Engineering, 2021, 8(1): 159-174.
Solomon Tulu TADESSE, Oene OENEMA, Christy van BEEK, Fikre Lemessa OCHO. EXPLORING THE RECYCLING OF MANURE FROM URBAN LIVESTOCK FARMS: A CASE STUDY IN ETHIOPIA. Front. Agr. Sci. Eng. , 2021, 8(1): 159-174.
Change in animal-sourced food consumption (% per year?
Urban
0
1
2
2
Rural
0
1
1
1
Self-sufficiency animal-sourced food (%)**
Urban
20
20
40
40
Rural
100+
100+
100+
100+
Decrease in cropland area (% per year?
Urban
0
2
2
2
Rural
0
0
0
0
Increase in crop yield (% per year?
All
0
3
3
3
Food waste losses (%)
All
20
20
20
10
Feed scavenged from neighborhood (%)
All
20
10
10
10
Feed N conversion dairy cattle (%)
All
10
10
10
20
Feed N conversion beef cattle (%)
All
5
5
5
10
Feed N conversion poultry (%)
All
20
20
20
40
Manure & waste N losses during storage (%)
All
50
50
50
25
Manure and kitchen waste collection (%)
All
50
50
50
75
Sewage waste collection (%)
All
0
0
0
0
Composting losses (%)
All
30
30
30
30
N use efficiency of fertilizer N (%)
All
40
40
40
60
Fertilizer N effectiveness of compost (%)
All
40
40
40
60
Tab.2
Fig.1
Fig.2
Fig.3
Fig.4
Fig.5
Fig.6
Fig.7
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