Advancing biogas production with biochar: Mechanistic insights, emerging materials, and future opportunities

Biochar (BC) is emerging as an additive that can enhance biogas production in Anaerobic Digestion (AD) by improving processes and providing environmental advantages. This review provides a summary of the scientific literature from 2010 to 2026 regarding BC addition to enhance biogas production in AD. The application of BC not only boosts the efficiency of biogas generation but also provides extra environmental advantages like carbon sequestration as well as waste valorization. Examples of real-world application of this technology include treatment of food wastes (FW), municipal wastewater treatment plant sludges, animal manures and crop residues. Examples of engineered and modified BC include magnetic BC, iron-rich BC, chemically functionalized BC and activated BC. Amongst the many benefits associated with adding BC to AD systems are carbon sequestration opportunities, waste management through conversion into energy products, and incorporation into a broader sustainability/circular economy context. There are little known concerning long term impacts of BC additions to AD systems. Most of the previous investigations have focused on “how” rather than “whether” it would be economically viable to add BC to an existing AD system. The present review discusses electron transfer (ET) mechanism, pH buffering, ammonia and volatile fatty acids (VFA) mitigation, microbial influence and trace metal supply.