Biomethane potential of the POME generated in the palm oil industry in Ghana from 2002 to 2009

Recycling anaerobic digestate enhances the co-digestion potential of agro-industrial residues: influence of different digestates as sources of microbial inoculum

Anaerobic codigestion (AcD) of agroindustrial residues was investigated. Granular sludge from bench-scale bioreactors digesting different manure were acclimated and recycled as microbial seed sludge to demonstrate inoculum-type influence on digestion performance. The biomethane potential (BMP) assay was operated for 30 days at 40 ± 2 °C in batch-type laboratory-scale reactors (100 mL). In inoculum amended reactors, codigestion showed significant, yet distinctive, biomethanation than monodigestion with a 5-fold increase (p < 0.05) in average biogas (248.3 ± 5.30 mL gVS-1) and CH4 yield (207.5 ± 4.15 mL gVS-1). The pH, soluble chemical oxygen demand (sCOD) and volatile fatty acids (VFAs) concentrations were within limits for stable AcD process with elevated total solids (TS) and volatile solids (VS) removal efficiencies. This study reinforces advancements in the recycling of digestate in biodigesters and suggests the appropriate selection of inoculum, preferably cow manure, to essentially boost methane production from these wastes.

A Review of Commercial Biogas Systems and Lessons for Africa

Many African countries have vast biomass resources that could serve as feedstock for methane production through the adoption of commercial biogas plants. However, due to many inhibiting factors, these resources are under-utilised. This article reviews commercial biogas systems that treat organic waste from municipalities, large livestock farms, large plantations/crop farms, food/beverage production facilities, and other industries, to identify essential lessons which African countries could use to develop/disseminate such biogas systems. The review identified the critical barriers to commercial biogas development to be high initial capital costs, weak environmental policies, poor institutional framework, poor infrastructure and a general lack of willpower to implement renewable energy policies and set challenging targets. In African countries where feed-in-tariffs, quota obligations and competitive bidding programmes have been instituted, implementation has been poor, and most state-owned utilities have been unsupportive. Using knowledge from more experienced countries such as Germany and China, some key lessons have were identified. Among the key lessons is the need to institute and enforce environmental management policies to ensure that waste from medium and large livestock farms and industries are not disposed of indiscriminately, a tool China has recently used to promote commercial biogas plants to a high degree of success.