Lignocellulosic biomass, an economical and abundant carbon source, can be converted to various fuels and chemicals through fermentation. Under the current conventional biorefining approach, the production of a fermentable sugar mixture requires saccharolytic enzymes, commercial nutrient supplements and detoxification. The costs associated with these three steps, which are projected at 45% of the total processing cost, must be reduced to improve overall economics of cellulosic biofuels.

Ammonia fiber expansion (AFEX) produces reactive, highly fermentable plant materials by reducing inhibitory degradation product generation and enriching the nitrogen content of the pretreated materials. Based on these advantages, we are developing an integrated cellulosic biorefinery approach which features ethanol, enzyme and yeast production based on AFEX-pretreated corn stover.

Specifically, we will report: (i) the nutrient content (protein, vitamins and trace elements) of the AFEX-corn stover enzymatic hydrolysate at high solids loading (18%), (ii) process design that supports both ethanol and in-house enzyme production using AFEX-pretreated corn stover and (iii) comparative economic modeling study on the proposed scheme relative to the conventional approach. Ultimately, we seek to demonstrate a new paradigm in which AFEX- pretreated biomass, without washing, detoxification or nutrient supplementation, can serve as the sole source of carbon, nitrogen and other nutrients for the biorefinery.