Removal of Furfurals (Inhibitory By-Products After Biomass Acid Pretreatment) by Activated Biochar

Acid treatment is a common and non-expensive method for the pretreatment of lignocellulosic biomass for biofuel ethanol production. One of the possible effects of acid pretreatment, however, is the formation of compounds which might be inhibitory to ethanol fermenting microorganisms. The dehydration of hexose and pentose sugars in the biomass after acid pretreatment can lead to the formation of a class of inhibitory compounds called, furans: (1) furfural from dehydration of pentose sugars, and (2) hydroxymethyl furfural (HMF) from dehydration of hexose sugars. Further degradation of furfurals may produce organic acids, which are also known to inhibit ethanol fermentation.

Researchers from the Southern Regional Research Center of the United States Department of Agriculture (USDA), Agricultural Research Service (ARS) report the removal of furans through the use of ‘activated biochar". The activated biochar was obtained from the pyrolysis (air-free heating) and subsequent chemical activation of agricultural residues, such as cotton seed hull, flax shive and cotton gin waste. The chars were tested on model solutions containing furural and HMF.

Results showed that phosphoric-acid-activated biochars and steam-activated biochars from cotton/linen production residues could adsorb furfural and HMF, with steam-activated biochars giving the best results. The addition of 2.5% biochar to a sugar solution containing 1 g per liter of either furfural of HMF, could achieve a 99% furan removal efficiency. The full paper is published in the journal, Bioresources (URL above).