Effects of Lipase Addition, Hydrothermal Processing, Their Combination, and Co-Digestion with Crude Glycerol on Food Waste Anaerobic Digestion

Abstract

To enhance anaerobic fermentation during food waste (FW) digestion, pretreatments can be applied or the FW can be co-digested with other waste. In this study, lipase addition (LA), hydrothermal pretreatment (HTP), and a combination of both methods (HL) were applied to hydrolyze organic matter in FW. Furthermore, the effects of crude glycerol (CG), which provided 5%, 10%, and 15% of the volatile solids (VS) as co-substrate (denoted as CG5, CG10, and CG15, respectively), on the anaerobic digestion of FW were assessed. With an increasing proportion of CG in the co-digestion experiment, CG10 showed higher methane production, while CG15 negatively affected the anaerobic digestion (AD) performance owing to propionic acid accumulation acidifying the reactors and inhibiting methanogen growth. As the pretreatments partially decomposed hard-to-degrade substances in advance, pretreated FW showed a stronger methane production ability compared with raw FW, especially using the HL method, which was significantly better than co-digestion. HL pretreatment was shown to be a promising option for enhancing the methane potential value (1.773 NL CH4/g VS) according to the modified Gompertz model.

Biochar-promoted methane production and mitigation of acidification during thermophilic anaerobic co-digestion of food waste with crude glycerol: Comparison with re-inoculation

“…Compared with other co-substrates (agricultural waste, livestock manure), CG has the advantages of easy digestion and long-term storage. In previous research [5], we con rmed that FW co-digestion with 10% (w/w) CG based on volatile solids (VS) proportion improved methane production because of the decomposability and supplementation of the carbon source. However, the accumulation of volatile fatty acids (VFAs), especially propionic acid, in the reactor is recognized as an obstacle to long-term stable operation of AD systems.…”

“…According to our previous experimental results [5], FW and CG were mixed in a ratio of 9:1 (based on the weight of VS provided) for use as feed material. Schott Duran bottles (1.0 L total volume; 0.9 L working volume) with rubber stoppers were used as anaerobic testing reactors.…”

Effect of waste pretreatments on growth parameters, bioconversion and quality of Black Soldier Fly Hermetia illucens (Diptera: Stratiomyidae)

“…The globe generates more than 2.1 billion tons of municipal solid waste each year. Approximately 1.3 billion tons of this municipal waste is food waste worth up to US$7.5 billion (Li and Shimizu, 2021). The United Nations and the FAO estimate that a one third of food intended for human consumption is wasted worldwide.…”

Zero-Valent Iron and Activated Carbon Coupled to Enhance Anaerobic Digestion of Food Waste: Alleviating Acid Inhibition at High Loads

“…FW is one of the main causes of greenhouse gas emissions, and traditional treatment methods, such as incineration and landfill, contribute to greenhouse gas emissions and leachate pollution [6]. According to statistics, global FW contributed 8-10% of all anthropogenic greenhouse gas emissions from 2010 to 2016 [7]. Therefore, material or energy recovery of FW is important for reducing carbon emissions and achieving environmental sustainability.…”