DECREASE: Development of a Commercial Ready Enzyme Application System for Ethanol (Final Technical Report)

Abstract

Conversion of biomass to sugars plays a central in reducing our dependence on petroleum, as it allows production of a wide range of biobased fuels and chemicals, through fermentation of those sugars. The DECREASE project delivers an effective enzyme cocktail for this conversion, enabling reduced costs for producing advanced biofuels such as cellulosic ethanol. Benefits to the public contributed by growth of the advanced biofuels industry include job creation, economic growth, and energy security. The DECREASE primary project objective was to develop a two-fold improved enzyme cocktail, relative to an advanced cocktail (CZP00005) that had been developed previously (from 2000- 2007). While the final milestone was delivery of all enzyme components as an experimental mixture, a secondary objective was to deploy an improved cocktail within 3 years following the close of the project. In February 2012, Novozymes launched Cellic® CTec3, a multi-enzyme cocktail derived in part from components developed under DECREASE. The externally validated performance of CTec3 and an additional component under project benchmarking conditions indicated a 1.8-fold dose reduction in enzyme dose required for 90% conversion (based on all available glucose and xylose sources) of NREL dilute acid pretreated PCS, relative to the starting advanced enzyme cocktail. While the ability to achieve 90% conversion is impressive, targeting such high levels of biomass digestion is likely not the most cost effective strategy. Novozymes techno economic modeling showed that for NREL's dilute acid pretreated corn stover (PCS), 80% target conversion enables a lower total production cost for cellulosic ethanol than for 90% conversion, and this was also found to be the case when cost assumptions were based on the NREL 2002 Design Report. A 1.8X dose-reduction was observed for 80% conversion in the small scale (50 g) DECREASE benchmark assay for CTec3 and an additional component. An upscaled experiment (in 0.5 kg kettle reactors) was performed to compare the starting enzyme mixture CZP00005 with CTec3 alone; these results indicated a 1.9X dose- reduction for 80% conversion. The CTec3 composition does not include the best available enzyme components from the DECREASE effort. While these components are not yet available in a commercial product, experimental mixtures were assayed in a smaller scale assay using DECREASE PCS, at high solids loadings (21.5% TS). The results indicated that the newer mixtures required 2.9X-less enzyme for 90% conversion, and 3.2X-less enzyme for 80% conversion, relative to the starting enzyme cocktail. In conclusion, CTec3 delivers a 1.8-1.9X dose reduction on NREL PCS at high solids loadings, and the next generation enzyme from Novozymes will continue to show dramatically improved biochemical performance. CTec3 allows reduced costs today, and the experimental cocktails point to continued biotechnological improvements that will further drive down costs for biorefineries of tomorrow.