Pilot Scale System of Two Horizontal Rotating Bioreactors for Bioethanol Production from Household Food Waste at High Solid Concentrations

Household food wastes (HFW) a complex biomass containing soluble sugars, lipids, proteins, cellulose, starch was used for bioethanol production in a newly designed pilot scale system consisting of two horizontal rotating bioreactors (HRRs) operating at high solids content under non-isothermal simultaneous saccharification and fermentation (NSSF) in fed-batch mode. Operational conditions were determined in lab-scale experiments. More specifically, enzymes including cellulases, alpha-amylase and glucoamylase at different loadings were tested one at the time for the pre-hydrolysis and subsequent fermentation by Saccharomyces cerevisiae of the pretreated HFW. The highest ethanol production (42.74 g/L, corresponding to 72.33% of the maximum theoretical) was obtained when cellulases (at 60 FPU/g cellulose) and glucoamylase (60 FPU/g starch) were used. Fed-batch experiments were conducted in a 20 L bioreactor. Increasing batch additions resulted in a higher ethanol titer. Ethanol production of 60.69 g/L (corresponding to 69.77% of the maximum theoretical) was achieved when three additions were made. Implementation of the NSSF process operating in fed-batch mode in the pilot scale facility resulted in ethanol production of 53.90 g/L (corresponding to 73.26% of maximum theoretical yield). The pilot scale facility of the present study can produce 188 L of ethanol from one ton of dry HFW.