Anaerobic Compost Production from Elephant Dung in Combination with Elephant Food Wastes and Fermented Slurry by Biogas recirculation

Abstract

Elephant camps are the source of massive amounts of waste, mainly from elephant food scraps and dung. These wastes can be used for anaerobic composting to achieve usable waste management goal and reduce greenhouse gas emissions. The objective of this study was 1) to study the appropriate co-fermentation formula based on the characteristics of the compost and 2) to compare the macronutrient value of each formulation of compost with recirculating biogas accumulated in the compost bin with non-recirculating fermentation. The initial carbon to nitrogen ratio (C:N ratio) was varied at 30, 50, and 75 by calculation. The substrates used were fresh elephant dung, Napier grass, Napier grass stems, pineapple leaves, pineapple rhizomes, rice straw, and fermented slurry. This experiment modified the biogas recirculation model with biogas accumulation occurring in the system and no biogas accumulation. The results showed that biogas recirculation and the carbon to nitrogen ratio resulting from different compost materials affect the complete composting characteristics. The products with C:N ratio of 30 NRB and 50 RB are qualified to be organic fertilizer according to the organic fertilizer standard set by the Department of Agriculture. Nitrogen contents were 1.77% and 1.64%wt, phosphorus contents were 1.06 and 0.62% as P₂O₅, and potassium contents were 4.7 and 2.1%wt for the experimental set at C:N 30 NRB and C:N 50 RB, respectively. Therefore, anaerobic composting from the wastes produced by elephant husbandry is a sustainable development for the community and can lead to zero waste management. In addition, circulating gas back into the system without being released into the atmosphere can help reduce greenhouse gas emissions as well.