Effect of Ferrous Sulfate on Sugar Yields in Softwood Pretreatment

Researchers from the Department of Chemical Engineering, Lund University, Sweden investigated the effect of the presence of ferrous sulfate on sugar yields in the dilute-acid pretreatment of softwood (Picea abies) for the production of bioethanol. Pretreatment is a key process in biofuel production in which carbohydrates are liberated from the tight lignin wrapping. The liberated carbohydrates (mainly cellulose and hemicellulose) are then converted to simple sugars by a process called, "enzymatic saccharification", and the sugars are eventually fermented to ethanol.

Among the types of pretreatment, one of the most promising method for commercialization is the dilute-acid pretreatment. Addition of inorganic salts such as ferrous sulfate can be used In order to improve dilute acid pretreatment. In their paper, the Swedish researchers compared the sugar yields with and without the presence of ferrous sulfate during the pretreatment of softwood, . They performed the pretreatment experiments using two catalysts: (1) Sulfuric acid (H₂SO₄), and (2) combination of sulfurtrioxide (SO₃) and sulfurous acid (H₂SO₃). Results showed that using H₂SO₄catalyst, the sugar yields from the pretreatment was not improved. On the other hand, the sugar yield from softwood pretreatment using SO₃-H₂SO₃catalyst increased from 73.9% to 78.5% of the theoretical value.

The full paper is published in the journal, Bioresource Technology (URL above).