Monday, April 30, 2007

Alkali buffering capacity of straw-based feedstocks

Supaporn Sophonputtanaphoca and Michael H. Penner. Food Science & Technology, Oregon State University, 100 Wiegand Hall, Corvallis, OR 97331

A major factor impacting the cost of chemical-based pretreatments is the reagent load required to achieve final pretreatment conditions. In the case of alkali pretreatments, the reagent load is most typically dependent on that amount required to maintain a given pH.  The buffer capacity of the feedstock directly affects this value. The buffer capacity, and related time courses for pH establishment, of three commercial grass seed straws (perennial ryegrass, Kentucky bluegrass, tall fescue) were evaluated and compared with that of wheat straw. Buffer capacities based on classical titration approaches were hampered due to the time and temperature dependence of buffer capacity development. The buffer capacities for each of the feedstocks were similar, initial pH changes approached a requirement of 1 meq hydroxide ion per gram feedstock per unit pH change.   Time courses of acetic acid production mirrored buffer capacity development; acetic acid yields could account for the majority of the observed buffer capacity. Back titration data suggests that each of the feedstocks have significant amounts of particulate bound buffering components with pKas at or above neutrality.