Recirculating calcium hydroxide solution: A practical choice for on-farm high solids lignocellulose pretreatment

Pretreatment is considered a necessary step in the use of lignocellulosic biomass for biochemical conversion to higher value products. There are multiple choices of chemicals for pretreatment in industrial settings, however on-farm choices are constrained to those that function well at near ambient conditions with minimal specialized equipment, personnel training, and require limited waste disposal. This work presents a novel pretreatment system biomass using a recirculating, saturated calcium hydroxide (lime) solution in an up-flow, high solids (14-16% w/w) configuration at ambient conditions. In this system, lime solids were efficiently consumed, post-pretreatment washing of substrate was not required, and energy and resources were conserved. Pretreatment effectiveness was assessed by glucose yield comparisons for both switchgrass and corn stover. Based on mean glucose yields from 5 mm corn stover, lime pretreatment would require 350 kg of dry stover to produce 100 kg glucose at a chemical cost of $8.67 while NaOH pretreatment would require 300 kg of chemical at a cost of $22.38.