Impact of blending on hydrolysis and ethanol fermentation of garden wastes

Mixed biomass has the characteristics of stable supply and low cost of collection, and its bio-refinery could provide an effective contribution to the sustainable development of fuel ethanol production. Compared to traditional single energy crops, the key challenge of mixed biomass conversion lies in overcoming the non-uniformity of blended materials. In this study, the influence of blending on hydrolysis and ethanol fermentation of garden wastes was investigated. There was an unexpected result in that the total xylose yield during a liquid hot water process was enhanced when different garden biomasses were mixed. The peak of total xylose recovery appeared at the value of ∼0.5 for the ratio of xylan to lignin, which was further confirmed by blending multiple biomasses. Moreover, the non-uniformity of physio-chemical characteristics in mixed garden wastes restricted the co-hydrolysis of cellulose, particularly in the mixed-five-biomass. In spite of this disadvantage, blended feedstocks showed a better flow behavior, which could make them more suitable for enzymatic hydrolysis and ethanol fermentation with high substrate loading. The 72 h enzymatic digestibility and glucose concentration of treated mixed-three-biomass reached 100 ± 5% and 52.3 ± 2.6 g/l under the conditions of 15% (w/v) substrate loading, with the addition of 1% (v/v) Tween 20, which gave a maximum ethanol concentration of 16.9 ± 0.8 g/l. Overall, these results have shown that the complementary or synergistic effects of different individual biomasses make it feasible to produce ethanol from mixed biomass.