Optimization of substrate mixing ratios for wet anaerobic digestion of selected organic waste streams for productive biogas systems

Abstract

In order to realize the objective of productive biogas systems, which is to provide waste management and modern renewable energy services, sustainable biogas production is paramount. While there are several factors that affect sustainability, quality of substrate for biogas production is one key anaerobic digestion (AD) parameter that should be optimized for improved and sustainable biogas yield. Since heterogeneity is an inherent characteristic of biomass, it is important that before application of any given biomass material for AD, its key characteristics are first examined to guide further processing to meet standards for optimal biogas recovery. In this study, physical and chemical characteristics of selected feedstocks were examined with intent to develop optimal substrate mixing ratios to improve quality of substrate for optimal biogas yield. Mathematical modeling of the required substrate moisture concentration was done, which gave way to the determination of optimal substrate mixing ratios. Results indicate that characteristics of feedstock vary widely according to source and type, as well as their substrate mixing ratios. However, for chicken litter with rice hull, the substrate mixing ratio was statistically not different from that of chicken litter with coffee husks and wood shavings, and therefore can be used on all the three feedstocks without significant effects on biogas yield.

Keywords

• Anaerobic digestion
• Productive biogas
• Optimization
• Feedstock characteristics
• Mixing ratios