Feedstock Recovery From Municipal Food Waste

Sammanfattning: Volatile Fatty Acids (VFAs) are a by-product when producing methane through anaerobic digestion (AD). Due to their many uses as building block chemicals, it is of interest to look into ways to optimize anaerobic digestion toward VFA production instead of methane generation. This report will focus on different parameters to produce VFA from food waste (FW), primary sludge (PS), and digested sludge (DS) in different ratios. In this project, three different experimental sets were run over a period of 25 days. The three different sets were 100 % FW, 100 % PS, and 50/50 % FW and PS mixture. Reactors were adjusted to an initial pH-value of 10 and then sparged with nitrogen to create an anaerobic environment. Measurements of the pH were done by sampling at each retention time. Gas chromatography (GC) was used at the end of the project to determine the concentrations of the VFA in the samples. The results showed that, with pH 10, a retention time of 15 days and using only FW, was optimal for VFA production as it gave the highest total concentration of 14.03 g VFA/L. Acetic acid was found in the highest concentration in all ratios. A mixture of FW and PS had an optimal retention time of 12 days, but did not generate as high concentrations of VFAs as only using FW, with a maximum concentration of 9.34 g VFA/L. Using only PS generated even lower concentrations, with a maximum of 5.33 g VFA/L, but did not start decreasing during the experimental run, and no clear conclusion can, therefore, be drawn.