Currently, biorefining technology is still on the early stage of commercialization with only limited number of commercial scale plants in operation. The overall cost of cellulosic ethanol by the most advanced technologies is obviously greater than the current corn ethanol selling price (below $2/gal, the average value in the period of 2012-2017, http://www.tradingeconomics.com/commodity/ethanol), along with multiple inherent difficulties in the major biomass producing regions. Reducing the overall cost of cellulosic ethanol by practically applicable technologies to the profitable level or at least competing level of corn ethanol is strongly required for establishing the full scale industry of cellulosic ethanol.<br/>Low conversion yield, high energy consumption and vast wastewater generation in cellulosic ethanol production are among the determinant factors on overall cost and technology penetration into fuel ethanol industry. Here we demonstrate an advanced dry biorefining platform technology, the dry acid pretreatment and biodetoxification (DryPB), for maximizing the commercialization potentials of cellulosic ethanol to compete with corn ethanol on the fuel ethanol market. DryPB converts lignocellulose feedstocks (corn stover, wheat straw, rice straw, sugarcane bagasse) to the 11-13% (v/v) of ethanol titer with 85% of the overall conversion yield from cellulose and hemicellulose at the minimum cellulase usage of 10 mg proteins per gram of cellulose, highly approaching to the 11-13% (v/v) of ethanol titer in corn ethanol production. DryPB minimizes the wastewater generation to zero starting from dry acid pretreatment, biodetoxification, to simultaneous saccharification and co-fermentation (SSCF). The overall steam consumption of 8.63 GJ and wastewater generation of 7.71 tons in the core steps per one ton of ethanol are exactly in the range of 7.83 GJ and 8.33 tons in corn ethanol production, respectively. The relatively higher electricity consumption is compensated by large electricity surplus from lignin residue combustion. The minimum ethanol selling price (MESP) by DryPB is below $2/gal and falls into the range of corn ethanol production cost. The results indicate that the cellulosic ethanol production technology has already significantly advanced to the level for competing with corn ethanol production technology from both technical and economic viewpoint under the proper capital investment, feedstock logistic system and on-site cellulase supply chain.

Filling the technical and economic gap between cellulosic ethanol and corn ethanol by dry biorefining technology

256th National Meeting (2018)

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