Multi-value-added products from biogas residue pyrolysis derived from kitchen waste

Resourceful food waste treatment is essential for promoting the sustainable development of anaerobic digestion and realizing a circular economy. In this study, biogas residue (BR) was used as a feedstock to produce high-value-added products (gas, tar, and char-derived high-performance adsorbents) using pyrolysis technology (at 400-800 °C). CaCO₃, the major component of ash, significantly improved the quality of the pyrolysis product by decomposing into CO₂ and CaO. The gasification reaction of CO₂ with coke generated substantial CO and facilitated the formation of a rich pore structure in the char. CaO improved tar quality by contributing to secondary cracking reactions and reducing water content. The composite material formed exhibited excellent performance in wastewater treatment, with a maximum methylene blue adsorption capacity of 969.30 mg/g. The maximum adsorption of heavy metals Cu²⁺, Pb²⁺, and Cd²⁺ was 175.44, 244.93, and 199.50 mg/g, respectively. The ash fraction on the ash-biochar composite material adsorbent surface enhanced pollutant removal by providing an alkaline adsorption environment and more oxygen-based n-π interaction sites. The economic analysis showed that the high value-added products obtained from the pyrolysis of BR make this process more productive than land use.