Sustainable enhancement of biogas production using integrated process optimization and low-cost upgrading techniques

This study concerns on optimization of operating parameters for biogas production through anaerobic co-digestion. Response-Surface-Methodology (RSM) was used in this study to maximize the biogas volume and methane content and then from the investigation, the maximum biogas yield of co-digestion of co-substrates banana-peel (BP), food-waste (FW), and poultry-manure (PM) with cow-dung (CD) were at a ratio of 2 CD:1 BP, 1 CD: 1 FW, and 2 CD: 1 PM respectively, and coded as ‘A’, ‘B’, and ‘C’. The data from the optimization experiment was analyzed and modeled using Design-Expert version 13 with two numeric factors temperature (25 °C–45 °C), retention time (15 days–30 days), and one categoric factor substrate type (A, B, and C) in three levels. The investigation was accepted and significance level of probability (P < 0.05). Highly statistically significant regression model equations with R2 = 0.9961, and R2 = 0.9927 for biogas volume and methane content respectively, were obtained by analyzing the experimental trial data. The greatest results were 600 mL, 550 mL, and 465 mL of biogas volume and 70.78%, 65.84%, and 62.54% of methane content for substrates A, B, and C, respectively, at a temperature of 35 °C and retention period of 22.5 days. Besides, Biogas upgrading using wood ash leachate for CO2 removal were conducted, and resulted CH4 increased to 88.79%, 84.06%, and 81.12% with CO2 removal efficiency of 60.96%, 52.65, and 48.75% for substrate A, B, and C respectively; it can replace 1 M NaOH. This research advances our understanding of anaerobic digestion as a sustainable waste management and renewable energy solution that supports the shift to a circular economy particularly for sub-Sahara country Ethiopia.