All-iron ions mediated electron transfer for biomass pretreatment coupling with direct generation of electricity from lignocellulose

A coupled process of biomass pretreatment for increasing cellulose digestibility and direct conversion of biomass to electricity has been developed with ferric or ferricyanide ions as the anode electron carriers, and Fe(NO₃)₃ activated by HNO₃ as the cathode electron carriers. Pretreated substrates are subjected to enzymatic hydrolysis for release of fermentable sugars, while the pretreatment liquor is employed as anolyte for electricity generation in a liquid flow fuel cell (LFFC). Pretreatment of sugarcane bagasse with 2 M FeCl₃ in anode reactor removes ∼ 100% hemicelluloses and obtains 76% enzymatic glucan conversion (EGC), while pretreatment with 0.1 M K₃[Fe(CN)₆] in 0.5 M KOH achieves 78% lignin removal, 95.8% EGC and 85.1% xylan conversion. From 1000 g bagasse, 171.3 g fermentable sugars is produced with co-generation of 101.4 W·h electricity based on FeCl₃ pretreatment, while 519 g fermentable sugars and 28.9 W·h electricity are obtained based on K₃[Fe(CN)₆] pretreatment.