New Ammonia Biomass Pretreatment Process Improves Yield with Lower Enzyme Loading; Improving Cellulosic Biofuel Economics

(Green Car Congress) A team from the US, China and India, led by researchers from Michigan State University, has developed a new liquid ammonia biomass pretreatment methodology called Extractive Ammonia (EA). EA-pretreated corn stover delivers a higher fermentable sugar yield compared to the older Ammonia Fiber Expansion (AFEX) process while using 60% lower enzyme loading.

As described in a paper in the RSC journal Energy & Environmental Science, the single-stage EA process achieves high biofuel yields (18.2 kg ethanol per 100 kg untreated corn stover, dry weight basis), comparable to those achieved using ionic liquid pretreatments. The EA process achieves these ethanol yields at industrially-relevant conditions using low enzyme loading (7.5 mg protein per g glucan) and high solids loading (8% glucan, w/v).

The EA-pretreated biomass hydrolysates are readily fermentable due to removal of lignin-derived inhibitors while preserving the microbial nutrient availability.

The EA process also preserves extracted lignin functionalities, offering the potential to co-produce lignin-derived fuels and chemicals in the biorefinery.

During the recovery stage, the ammonia is evaporated from the extractives, which are subsequently recovered as a dark brown viscous liquid. About 0.022 g ammonia per 100 g biomass input cannot be recycled due to reactions between ammonia and the biomass. The remaining ammonia is recoverable and can be recycled.

EA simultaneously converts native crystalline cellulose to a highly digestible cellulose allomorph and selectively extracts up to ∼45% of the lignin from lignocellulosic biomass with near-quantitative retention of all polysaccharides.

Although CIII can be produced at room temperature, the EA pretreatment is more effective at higher temperatures, which are required to maximize ester bond cleavage, lignin solubilization, and thereby improve enzyme accessibility to CIII. READ MORE Abstract (Energy & Environmental Science)