The anaerobic fermentation of waste activated sludge (WAS) offers a sustainable method to recover short-chain fatty acids (SCFAs), valuable for bioenergy and bioplastics production. However, challenges like slow electron transfer and the rigid structure of organic matter have limited SCFA yields. A recent study published in the Journal of Environmental Chemical Engineering explores how biochar pretreatment can significantly enhance SCFA production.

Researchers found that biochar pretreatment boosted SCFA production by 9.6 times compared to untreated sludge, achieving a peak yield of 348.61 mg COD/g VSS. Acetic acid, a key SCFA, accounted for 44.4% of the output under optimal conditions (2.0 g biochar/g VSS). Mechanistically, biochar disrupted extracellular polymeric substances and cell walls, improving the solubility and biodegradability of organic matter. Additionally, biochar facilitated direct electron transfer between microorganisms and increased the activity of key enzymes involved in SCFA accumulation.

Microbial analysis revealed that biochar enriched hydrolytic and acid-producing bacteria like Tissierella sp. and Proteiniborus sp.. The relative abundance of electron-transporting Proteiniclasticum sp. rose markedly. FTIR spectroscopy confirmed that biochar’s functional groups (e.g., C=O, C=C) contributed to its redox and electron transfer capabilities.

This study underscores the economic and environmental potential of biochar pretreatment for SCFA production. It presents a promising approach to enhancing energy recovery from WAS while addressing environmental and cost challenges in wastewater management.