Effects and optimization of the use of biochar in anaerobic digestion of food wastes

Abstract

The addition of various amounts of biochar to anaerobic digestion of food wastes at different ratios of inoculum to substrate (ISR) was investigated to evaluate the effect of biochar as a functional additive and to optimize the additive dosage of biochar. The biochar treatments at ISR 2, 1, and 0.8 shortened the lag phase of digestion by -20.0%-10.9%, 43.3%-54.4%, and 36.3%-54.0%, and raised the maximum methane production rate by 100%-275%, 100%-133.3%, and 33.3%-100%, respectively, compared to control without biochar. Biochar also enhanced the degradation rate of dissolved organics and volatile fatty acids. Furthermore, the amount of biochar with best effectiveness at ISR = 2, 1, and 0.8 was 2.5, 0.625, and 0.5 g g(-1)-waste, respectively. Therefore, the effectiveness of biochar depended on the additive amount of biochar and at the same time the inoculum amount, implying a complementary role of abiotic biochar to biotic inoculum.

Addition of biochar and trace elements in the form of industrial FeCl3 to stabilize anaerobic digestion of food waste: dosage optimization and long‐term study

“…In the single other study dealing with biochar addition during FW AD, biochar supplementation improved the kinetics of methane production in batch reactors, dividing by two the lag phases and increasing the maximum methane production rates. 45 Considering the obtained results and other scientific studies, it can be hypothesized that the improved VFA degradation kinetics could be related to a enhancement of the syntrophic interactions between microorganisms via biofilm formation and to the occurrence of DIET. Biochar has been found to promote the growth of bacteria known to participate in DIET (i.e.…”

“…observed that biochar supplementation increased the methane production rates and enhanced the consumption of HAc and HBu in the second stage of a 2‐phase AD reactor treating aqueous FW. In the single other study dealing with biochar addition during FW AD, biochar supplementation improved the kinetics of methane production in batch reactors, dividing by two the lag phases and increasing the maximum methane production rates …”

“…The biochar was natural slow‐pyrolyzed wood charcoal, commonly found in the market for several applications. General characteristics reported for biochars with similar origins are: high carbon contents (78–84%), low sulfur proportions (0.1–0.5%), high pH of the water‐extractable fraction (8.6–9.6), Brunauer–Emmett–Teller surface areas of 130–210 m 2 g −1 and relatively high conductivities (4–5 µS cm −1 g −1 ) . Before utilization, the biochar was ground and sieved at 600 µm.…”

“…Geobacter species) were attached onto the biochar surface. Cai et al 45 studied the effect of biochar addition in batch digestion of FW at different substrate to inoculum (S/X) ratios, concluding that when biochar was supplied at sufficient concentrations (>10 g L −1 ), its addition could significantly improve methane production rates, reducing at the same time the lag phases observed. Similar conclusions were drawn by Wang et al, 46 in another batch experiment using sludge and FW as substrates.…”

Anaerobic Digestion of Fruit Waste Mixed With Sewage Sludge Digestate Biochar: Influence on Biomethane Production

“…Indeed, this would result in a decrease in the microbial lag phase (Fagbohungbe et al, 2016(Fagbohungbe et al, , 2017. Biochar added in the AD can also optimize and balance the trace minerals, micronutrients and macronutrients, buffering agents, compounds able to mitigate ammonia inhibition, and substances with high biomass immobilization capacity; remove the toxic materials; and enhance the degradation rate of dissolved organics and VFAs (Cai et al, 2016). Moreover, the direct addition of biochar would enhance significantly the production rate of H 2 , which favors the hydrogenotrophic methanogenic route of the AD process (Sunyoto et al, 2016).…”