Anaerobic fermentation integrated with pyrolysis for carbon resource recovery from food waste and biogas sludge: Effects of inoculation ratio and pyrolysis temperature

In view of the food waste (FW) as well as its digestate are both the organic sources of municipal solid waste, this study explored the anaerobic fermentation (AF) and following pyrolysis carbonization to co-disposal the two wastes for carbon resource recovery, including short chain organic acid (SCOAs), pyrolysis gas and biochar. Results indicated that both the rate and yield of SCOAs production both increase with the rising ratio of biogas sludge (BS) to FW, enhancing the soluble carbon recovery. The highest SCOAs production of 474.33 mg/g-VS was achieved at the ratio of 2:1 in 72 h. To further utilize the carbon source, the solids from the fermented residue (FR) was pyrolyzed at 400, 600 and 800 °C, respectively. Findings showed that the carbon content in biochar decreases with the increasing pyrolysis temperature, while the carbon in pyrolysis gas exhibits the opposite trend. Integrating the AF and pyrolysis contributed to a carbon recovery about 56.39% when the FW and BS were co-fermented at a 2:1 ratio, followed by its FR was pyrolyzed at 600 °C. Additionally, the biochar prepared under these conditions displayed a specific surface area (SSA) of 313.10 m²/g, along with abundant pore structures and functional groups, indicating its potential applications as pollutant adsorbents and soil amendments. This research offers a new perspective on efficiently recovering high-value carbon sources through the co-treatment of FW and its digestate via AF integrated with pyrolysis.