Silage produces biofuel for local consumption

Hiroko K Kitamoto,Yimin Cai,Yukiko Shinozaki,Keiji Sakaki,Mitsuo Horita

doi:10.1186/1754-6834-4-46

Abstract

BackgroundIn the normal process of bioethanol production, biomass is transported to integrated large factories for degradation to sugar, fermentation, and recovery of ethanol by distillation. Biomass nutrient loss occurs during preservation and degradation. Our aim was to develop a decentralized ethanol production system appropriate for farm or co-operative level production that uses a solid-state fermentation method for producing bio-ethanol from whole crops, provides cattle feed, and produces no wastes. The idea is to incorporate traditional silage methods with simultaneous saccharification and fermentation. Harvested, fresh biomass is ensiled with biomass-degrading enzymes and yeast. Multiple parallel reactions for biomass degradation and ethanol and lactic acid production are induced in solid culture in hermetically sealed containers at a ranch. After fermentation, ethanol is collected on site from the vapor from heated fermented products.ResultsThe parallel reactions of simultaneous saccharification and fermentation were induced efficiently in the model fermentation system. In a laboratory-scale feasibility study of the process, 250 g of freshly harvested forage rice with 62% moisture was treated with 0.86 filter paper units/g dry matter (DM) of cellulase and 0.32 U/g DM of glucoamylase. After 20 days of incubation at 28°C, 6.4 wt.% of ethanol in fresh matter (equivalent to 169 g/kg DM) was produced. When the 46 wt.% moisture was gathered as vapor from the fermented product, 74% of the produced ethanol was collected. Organic cellular contents (such as the amylase and pronase degradable fractions) were decreased by 63% and organic cell wall (fiber) content by 7% compared to silage prepared from the same material.ConclusionsWe confirmed that efficient ethanol production is induced in nonsterilized whole rice plants in a laboratory-scale solid-state fermentation system. For practical use of the method, further study is needed to scale-up the fermentation volume, develop an efficient ethanol recovery method, and evaluate the fermentation residue as an actual cattle feed.

Highlights

In the normal process of bioethanol production, biomass is transported to integrated large factories for degradation to sugar, fermentation, and recovery of ethanol by distillation
Enzymatic hydrolysis of whole plants in a solid-state fermentation model system We hypothesized that the inoculation of a greater amount of carbohydrate-hydrolyzing enzymes and ethanol-fermenting yeast at ensiling would induce the degradation of biomass, and the produced sugars would be simultaneously converted to lactic acid and ethanol by lactic acid bacteria and yeast, respectively, during the solidstate fermentation of biomass (Figure 1B)
It was found that non-structural carbohydrates are the main carbon source for simultaneous saccharification and fermentation (SSF) in ethanol and lactic acid fermentation

Summary

Introduction

In the normal process of bioethanol production, biomass is transported to integrated large factories for degradation to sugar, fermentation, and recovery of ethanol by distillation. Multiple parallel reactions for biomass degradation and ethanol and lactic acid production are induced in solid culture in hermetically sealed containers at a ranch. Harvested biomass of low bulk density is transported to integrated large factories for pretreatment under acid or alkaline conditions to degrade the structural carbohydrates (Figure 1A). Cattle feed is mainly prepared and preserved as lactic acid fermented crops, so-called silage. The silage process consistently produces high-quality feed with a minimum of harvesting losses, regardless of weather conditions. This process should be a suitable method for preserving biomass for fuel production. The WSC contents of cereals used for silage are 80 g/kg DM

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