Targeting Complete Utilization of Sugar Beet Pulp as Feedstock for Ethanol Production

Sugar beet pulp is a by-product from the processing of sugar beet, a high-sucrose-containing crop which is cultivated for sugar (sucrose) production. It is largely lignocellulosic in nature. The high fiber (i.e. cellulose) content of sugar beet pulp makes it a good material for fodder. With the present trend toward the use of lignocellulosic biomass for "second generation biofuels", sugar beet pulp is considered a potential biofuel feedstock. The low lignin and high sugar contents of sugar beet pulp particularly good material characteristics. A feedstock with low lignin content translates to lower pretreatment cost, while one with a high sugar content translates to higher ethanol yields.

Pretreatment of lignocellullosic biomass is the process by which the lignin in the biomass is removed, resulting in a cellulose/hemicellulose-rich material which can be more easily processed for ethanol production. Pretreatment is usually followed by enzymatic treatment; the enzymes convert the cellulose/hemicellulose into ethanol-fermentable sugars.

Scientists from the Laboratory of Food Chemistry, Wageningen University (Netherlands) investigated the pretreatment conditions of sugar beet pulp which can be done within "commercially reasonable time spans" and "with economically reasonable enzyme levels". They found that hydrothermal treatment at 140 degrees Celsius allowed lower enzyme levels which could convert 90% of cellulose into ethanol-fermentable sugars in 24 hours. More severe treatments (such as acid treatment) destroyed and solubilized the sugars, with the production of subsequent production of the sugar-degradation products (furfural, hydroxymethylfurfural, acetic acid and formic acid). These products can inhibit ethanol fermenting organisms.

The full paper is published in the open access journal, Biotechnology for Biofuels (URL above).