Biochar Boosts Clean Energy Output from Food Waste in Novel Two-Stage Digestion System

( Biochar Editorial Office, Shenyang Agricultural University/Biomass Magazine) A new study from researchers at the University of Western Australia and Universitas Brawijaya has found that adding biochar to advanced food waste recycling systems can significantly increase the clean energy yields of hydrogen and methane. This breakthrough offers promising strategies for municipalities and industries aiming to turn food scraps into valuable renewable fuels while reducing environmental impacts.

Food waste generated by households, restaurants, and processing plants is a growing environmental challenge around the world. Innovative recycling solutions are urgently needed to keep this waste out of landfills and lower greenhouse gas emissions. Anaerobic digestion, a method that uses naturally occurring microbes to break down organic matter without oxygen, is among the most effective ways to convert food scraps into biogas for heating and power.

This research focused on a state-of-the-art variation called two-phase anaerobic digestion. The system works in two consecutive steps: first, a group of specialized bacteria creates hydrogen as they digest food waste; then, another set of microbes converts the leftover material into methane. Splitting the process enables each phase to operate under ideal conditions, resulting in more efficient biogas production.

The research team was especially interested in how biochar—a porous, carbon-rich material produced by heating wood waste—affects these digestion systems. Biochar has shown promise in small-scale trials for stabilizing microbial communities, improving pH balance, and boosting gas yields, but its impact under real-world, continuous conditions remained unclear.

In laboratory experiments, the scientists ran two identical sets of digestion reactors fed with simulated food waste. One set received regular doses of biochar, while the other did not. Over a 100-day testing period, researchers closely monitored the daily output of hydrogen and methane, the chemical environment inside the tanks, and the types of microbes present.

The results were striking. Across all levels of organic waste loading, reactors with biochar produced more hydrogen and methane than those without. At higher waste inputs, reactors without biochar suffered drops in gas output and unstable microbial activity. In contrast, biochar-amended systems maintained steady performance and resisted acid build-up—a common barrier to efficient digestion.

Enhancing H2 and CH4 production with biochar addition in two-phase anaerobic digestion of food waste. / SOURCE: Yusron Sugiarto, Nimas M.S. Sunyoto, Hendrix Yulis Setyawan & Dongke Zhang

The addition of biochar was linked to beneficial changes in the microbial ecosystem. In hydrogen-producing reactors, biochar boosted populations of Clostridiaceae, a group of bacteria known for breaking down food waste into energy-rich acids. In methane-producing stages, biochar favored methanogenic microbes, including Methanosarcinaceae and Methanobacteriaceae, which drive the conversion of organic matter into methane fuel.

The biochar also acted as a natural buffer, keeping pH levels in an optimal range for these microbes, and provided surfaces that supported robust microbial communities. Notably, this positive effect was maintained even when reactors ran at higher organic loading rates, which are typically challenging for such systems.

The study suggests that using biochar in two-phase anaerobic digestion can make food-waste-to-energy systems more reliable and productive, particularly at the large scales required for municipal or industrial use. By allowing higher waste inputs and sustaining biogas yields, biochar-amended systems could lower the cost and raise the appeal of clean energy production from unavoidable food waste.

Lead author Yusron Sugiarto highlights the broad potential of this approach: “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 research is published in Energy Environment Nexus and was supported by grants from the Australian Research Council and the Future Energy Export Cooperative Research Centre. READ MORE

Sugiarto Y, Sunyoto NMS, Setyawan HY, Zhang D. 2025. Enhancing H2 and CH4 production with biochar addition in two-phase anaerobic digestion of food waste. Energy & Environment Nexus 1: e010 doi: 10.48130/een-0025-0010