The global push for carbon neutrality has sparked significant interest in sustainable and environmentally friendly energy sources, with biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More emerging as a promising alternative to fossil fuels. In India, the extensive agriculture sector produces over 126 million tonnes of rice straw annually, with a substantial portion—up to 16%—often burned in fields, contributing to air pollution and greenhouse gas emissions. Addressing both waste management and energy demand is a pressing challenge. A recent study by P. Sivakumar et al., published in Cleaner Waste Systems, proposes an economically feasible method to tackle this dual problem by enhancing biogas efficiency. The research investigates the use of coconut husk biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More (BC) as a catalyst to improve methane yield during the co-digestion of cow dung (CD), food waste (FW), and rice straw (RS).

Anaerobic digestion (AD) of biomass is a proven method for producing biogas, but its efficiency is often hampered by the complex structure of feedstocks and the delicate balance of parameters like pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More, temperature, and carbon-to-nitrogen (C/N) ratio. The study’s baseline experiments confirmed these challenges, finding that blends with high food waste content had lower pH values, which can inhibit microbial activity. The inclusion of rice straw helped to balance these pH levels and provide essential nutrients for microbes, improving the thriving environment for gas conversion. However, the most significant improvements came from the addition of biochar.

Biochar’s physical and chemical properties make it an ideal catalyst for anaerobic digestion. The coconut husk biochar used in this study, for instance, had a high fixed carbon content of 68.66% and an alkaline pH of 9.29, which helps to stabilize pH levels in an acidic digestion environment. Its porous micro-structure, with a BET surface area of 52.13 m²/g, provides a large colonization area for microbes and serves as a nucleation site for electron transfer. This porous structure also gives microbes a physical habitat to multiply, even at increased time periods. Furthermore, biochar’s buffering ability helps regulate pH and transform intermediates like hydrogen sulfide (H2S) and carbon dioxide (CO2) that can inhibit microbial activity.

The study’s results demonstrated a clear and significant increase in methane yield when biochar was added to the co-digestion blends. For a blend of 100% cow dung, the addition of biochar increased the methane yield by 78.7% compared to the same blend without biochar. In another instance, the methane yield of the food waste blend improved by 123% with the addition of biochar. However, the most effective outcome was a synergistic combination of biochar and a specific co-digestion ratio. The mixture containing 30% cow dung, 50% food waste, and 20% rice straw, with biochar, produced a peak methane yield of 221.08 mL. This specific blend’s peak methane yield was 55.9% higher than the 100% cow dung mixture, 25.44% higher than the 100% food waste mixture, and 10.75% higher than a cow dung/food waste blend.

Beyond the experimental results, the research also focused on creating a predictive model to forecast methane yield. The statistical model developed using Response Surface Methodology (RSM) was able to predict methane yield with an impressive accuracy of 99.07%. This model was found to be superior to the existing Gompertz kinetic model, indicating its higher performance and reliability for all stages of digestion. The ability of this statistical model to accurately predict methane production is a significant step toward optimizing the digestion process and scaling up this technology for widespread adoption.

In conclusion, this research highlights biochar’s pivotal role in accelerating biogas production from agricultural and food waste. Its ability to act as a catalyst by providing a porous micro-structure for microbes and stabilizing the digestion environment led to a significant increase in methane yield. The optimized co-digestion blend, enhanced by biochar, provides a tangible and economically feasible method to achieve sustainable energy production and effective waste management.

Source: Sivakumar, P., Saravanane, R., Mohan, S., & Sankar, B. (2025). Biochar as a catalyst for methane enhancement in anaerobic digestor containing cow dung, food waste, and rice straw: An experimental and statistical study. Cleaner Waste Systems, 12, 100388.