Fertilizer quality and carbon sequestration potential of compost generated from municipal organic solid wastes in Uganda

Abstract

Municipal Organic Solid Wastes (MOSW) remains a major urban challenge in developing countries, yet it is a valuable resource for agricultural production. Large quantities of MOSW cause environmental pollution via greenhouse gas (GHG) emission. A study on nine municipal waste management plants estimated GHG mitigation using the IPCC Tier 1 model and evaluated the quality of compost. Composting MOSW reduced CH4 emission from 4391.7 Mg year-1 by landfill to 516.8 kg year-1. The compost generated added 3886 and 7.8 Mg year-1 of organic carbon and stable carbon into the soil, respectively. The plants produced compost with a fertilizer potential of 9,886, 20,247 and 102,892 ha of N, P and K, respectively. The quality of compost significantly varied across the plants and months attribute aligned to different agroecological zones and agricultural seasons, respectively. The concentrations of total nitrogen ranged between 7.06 - 15.44 g kg -1, whereas it was 81.7 - 160.6 g kg-1 for organic carbon; with C: N ratio < 12 indicative of matured compost. The concentrations of phosphorus in the CDM compost ranged between 3.03 to 3.37 g kg-1 while potassium was 10.30 to 51.42 g kg-1, calcium 12.42 to 55.56 g kg-1 and magnesium 1.3 to 5.48 g kg-1. The maximum detected concentration of Pb was 51.1 mg kg-1 indicating low risk of Pb accumulation in soil following application of compost. Therefore, composting the MOSW reduced GHG emi ssion and recovered ferti lizer resources wi th low-risk heavy metal contaminants. The MOSW compost could substitute for the imported organic fertilizer forms into the country.