Co-Digestion-Based Circular Bio-Economy to Improve Biomethane Generation and Production of Nutrient-Enriched Digestate in Bangladesh

Abstract

Anaerobic co-digestion (ACoD) of cow dung (CD) and maize cob (MC) may be envisaged as the best way to enhance biomethane formation and production of nutrient-enriched fertilizer for the implementation of a circular bio-economic system. The study aimed to find out the optimum ratio for the highest biogas production to produce heat and energy and also the generation of nutrient-enriched organic fertilizer to use in crop land. A batch study was carried out for 99 days in an incubator maintaining 35 ± 1 °C temperature for seven different test groups of CD and MC (100:0, 90:10, 70:30, 50:50, 30:70, 10:90, and 0:100). The highest biogas production (356.6 ± 21.2 mL/gVS) was at 50:50 ratio with 138.05% and 32.02% increments compared to the digestion of CD and MC alone, respectively. Kinetic modeling showed the best fit using a Logistic model to evaluate ACoD of CD and MC mathematically. ACoD of available CD and MC in Bangladesh could produce 716.63 GWh/yr electricity for consumption and a large volume of nitrogen-enriched fertilizer to use in nitrogen-deficit soil. There was no significant difference in nutrient enrichment among different test groups. Awareness about ACoD technology and proper use of digestate might bring this technology to field-level utilization and thus help to implement the circular bio-economic concept through zero waste generation.