Ecobiotechnological Strategy to Enhance Efficiency of Bioconversion of Wastes into Hydrogen and Methane

Abstract

Vegetable wastes (VW) and food wastes (FW) are generated in large quantities by municipal markets, restaurants and hotels. Waste slurries (250 ml) in 300 ml BOD bottles, containing 3, 5 and 7 % total solids (TS) were hydrolyzed with bacterial mixtures composed of: Bacillus, Acinetobacter, Exiguobacterium, Pseudomonas, Stenotrophomonas and Sphingobacterium species. Each of these bacteria had high activities for the hydrolytic enzymes: amylase, protease and lipase. Hydrolysate of biowaste slurries were subjected to defined mixture of H 2 producers and culture enriched for methanogens. The impact of hydrolysis of VW and FW was observed as 2.6-and 2.8-fold enhancement in H 2 yield, respectively. Direct biomethanation of hydrolysates of VW and FW resulted in 3.0-and 1.15-fold improvement in CH 4 yield, respectively. A positive effect of hydrolysis was also observed with biomethanation of effluent of H 2 production stage, to the extent of 1.2-and 3.5-fold with FW and VW, respectively. The effective H 2 yields were 17 and 85 l/kg TS fed, whereas effective CH 4 yields were 61.7 and 63.3 l/kg TS fed, from VW and FW, respectively. This ecobiotechnological strategy can help to improve the conversion efficiency of biowastes to biofuels.

Biorefinery for Glycerol Rich Biodiesel Industry Waste

“…Codigestion of macroalgae: (1) Gracilaria vermiculophylla and 2 % glycerol resulted in 18 % enhancement, and (2) Sargassum sp. and 0.3 % glycerol lead to 1.5-fold increase in CH 4 yield and 1.38-fold enhancement in CH 4 productivity [77].…”

“…It helps to ensure successful completion of the bioprocess [4,55,56]. Apple pomace and CG mixture provide nutrition suitable for microbial processes.…”

“…Codigestion of wastes is more advantageous than single feed [4,71]. Digestion of mixed wastes along with 3-6 % glycerin lead to 570-680 L CH 4 /kg VS, which was equal to a threefold enhancement over animal manure alone [72].…”

“…Continuous stirred tank reactor reached a stable level within 100 days of operation. These processes allowed 0.74-0.80 mol CH 4 and 0.63-0.70 mol-acetate/mol feed, with the aid of Thermoanaerobacter spp. [79].…”

“…The best option is to operate the two types of processes in a sequential manner, depending upon the bioproduct under consideration. The concept has moved into a new direction, where pure microbial culture driven processes are being replaced with the use of well defined microbes with high activity are mixed together to ensure two things: (1) at least one of the organisms can act under a given set of conditions, and (2) the risk of getting contaminated is reduced because the diversity of inoculum can out beat the inherent or contaminating organism(s) [4].…”