In the biomass field converting lignocellulosic biomass to ethanol is a common practice. If the biomass is a polysaccharide-containing biomass and it is lignocellulosic, a pre-treatment is often used to ensure that the structure of the lignocellulosic content is rendered more accessible to the enzymes, and at the same time the concentrations of harmful inhibitory by-products such as acetic acid, furfural and hydroxymethyl furfural are usually high and present problems in further processing.
In general terms the more severe the treatment, the more accessible are the cellulosic contents of the material. The severity of the steam explosion is known in the literature as Ro, and is a function of time and temperature expressed asRo=t·e[(T−100)/14.75]with temperature, T, expressed in Celsius and time, t, expressed in common units. The formula is also expressed as Log(Ro), namelyLog(Ro)=Ln(t)+[(T−100)/14.75].
It is generally considered that a high Ro value is associated with a high number of unwanted by-products which inhibit the hydrolysis and fermentation of the biomass, such as furfural.
NREL Report No. TP-421-4978, November 1992, McMillan J. D., “Processes for Pretreating Lignocellulosic Biomass: A Review” even affirmed in its conclusions that “steam explosion-based processes . . . are unattractive in the long run because the formation of degradation products reduces yields” and exhorted to research alternative processes, such as ammonia fiber explosion and supercritical fluid-based treatments.
There exists therefore, the need to have a severe process with a high Ro which at the same time produces a product with low furfural.