Characteristics of tofu whey degradation during self-sustaining batch anaerobic process for methane production

Abstract

Tofu whey is produced during protein coagulation and tofu pressing in tofu processing. It is highly potential for use as a substrate in biogas production. As a protein-rich substrate, tofu whey potentially provides nitrogen, the main nutrient required by anaerobic microorganisms; and Volatile Fatty Acids (VFA) neutralization effect by ammonia generation. In tropical climates, relatively stable warm temperatures can be maintained throughout the year and create a mesophilic condition. Therefore, biogas production from tofu whey can potentially be conducted in a self-sustaining manner, without any physicochemical addition or intervention, including chemical addition and temperature control, during the process. This research studied characteristics of tofu whey degradation to observe its VFA neutralization effect and methane production in the laboratory self-sustaining batch anaerobic process. The VFA neutralization effect was investigated by comparing the digestion performance of tofu whey as a substrate to glucose as the positive control substrate. This study also evaluated the distribution of individual VFA and gas products. Self-sustaining methane production from tofu whey ran well without any indication of process failure. Tofu whey provided a VFA neutralization effect and could maintain pH levels between 6.8 and 8.4 during the process. The modified Gompert model predicted the experimental data well. This technology offers environmental and economic benefits. It potentially provides energy-saving and greenhouse gas (GHG) emission reduction based on the LPG substitution to biogas.