Evaluation of nutrient extraction and membrane processes to facilitate the reuse of water, chemical consumables and macronutrients during lignocellulosic biomass-to-fuel processing in rural communities

In the 1970s and early 1980s, interest in United States energy self-sufficiency prompted research into using herbaceous crop residues for energy production, such as cellulosic ethanol. Sustainable feed stocks for cellulosic ethanol production include low-cost agricultural residues such as corn stover. Corn stover removal from the soil surface may lead to soil erosion and macronutrient loss. Following harvest, the corn stover is delivered to a lignocellulosic processing facility (aka biorefinery) for pretreatment or pre-hydrolysis (delignification), which (in this study) involves the sequential addition of strong acid and base. For cellulosic ethanol to become a realistic alternative to conventional liquid fuels such as gasoline, there are important economic and environmental barriers to overcome.;This study investigated several processes to facilitate the reuse of water, macronutrients and chemical additives during lignocellulosic biomass-to-fuel processing. This study was conducted in three sections: (1) wet stover storage and macronutrient recovery prior to biomass pretreatment, (2) fractionation of pre-hydrolysis products and (3) concentration and reuse of alkaline species in the pre-hydrolysis waste stream.;The first section evaluated bench scale sequential leaching-ultrafiltration (UF)-hyperfiltration (HF) operations on fresh wet stover. Two extraction (water-leaching) techniques were investigated, stirred and packed bed. Both methods were shown to successfully remove approximately 85% or greater of the water-soluble nutrients in the stover. The approximate overall water and nutrient recovery from the integrated packed bed extraction-UF-RO system were ∼35% water recovery as the RO (reverse osmosis) permeate and ∼80% PO43- , ∼55% Cl-, ∼40% TOC, ∼35% Na+ and ∼0.45% K+ in the RO retentate.;The second section evaluated a bench-scale gamma-alumina ultrafiltration ceramic tubular membrane (CTM) membrane unit for the separation of high molecular mass organics, such a lignin, and alkaline chemical consumables, such as sodium hydroxide (NaOH). This filtration method rejected 100% of the total suspended solids (TSS) and 43% of total organic carbon (TOC), and recovered 80% Na +ions from the pre-hydrolysis waste stream.;The third section evaluated a bench-scale electrodialysis unit for the fractionation of alkaline species (such as sodium) and small molecular mass lignin fragments recovered during ultrafiltration. The sodium ion and TOC recovery (in the concentrate stream) was ∼80-100% and ∼60%, respectively, and the average Na+/TOC selectivity ratio was ∼1.6 and 0.45 for the IonicsRTM and SelemionRTM ion-exchange membrane arrangements, respectively.