Anaerobic digestion is a method for producing biogas from organic material by means of microbial activity in the absence of oxygen. In the two-phase configuration, bacteria first generate hydrogen from food waste, then a separate set of microbes produces methane from the remaining material. Each phase is optimized for the respective microbial processes, improving overall gas yield.
The investigation focused on the influence of biochar, a carbon-rich, porous material derived from heated wood waste, on these systems. Previous small-scale studies suggested biochar could stabilize microbes and enhance biogas production, but its long-term performance required additional validation.
The team operated duplicate reactor sets under laboratory conditions with simulated food waste, dosing biochar in one set and omitting it in the other. Over the 100-day trial, reactors were analyzed for hydrogen and methane output, chemical stability, and microbial populations.
The biochar reactors consistently achieved higher yields of hydrogen and methane under all tested organic loading rates. Systems without biochar displayed decreased gas generation and unstable microbial activity at higher waste inputs, while reactors containing biochar maintained stable operation and avoided acidification, a common problem in digestion systems.
Microbial analysis revealed that biochar enhanced populations of Clostridiaceae, beneficial for hydrogen production, and increased communities of methanogenic organisms such as Methanosarcinaceae and Methanobacteriaceae. Biochar buffered the environment, kept pH levels in the optimal range, and provided surfaces for robust microbial colonies. These benefits persisted under high organic loads.
Lead researcher Yusron Sugiarto stated, "Our findings show that biochar is not only a cost-effective and sustainable additive but also a key enabler for scaling up renewable gas production from food waste. These insights can inform practical solutions for energy recovery and environmental protection."
The study was published in Energy Environment Nexus with support from the Australian Research Council and the Future Energy Export Cooperative Research Centre.
Research Report:Enhancing H2 and CH4 production with biochar addition in two-phase anaerobic digestion of food waste
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