14-01: Producing high sugar yields from softwood using wet explosion pretreatment

Woody residues from forestry are an abundant biomass source in major parts of the world. However, until now no technology has been able to pretreat softwood with a high sugar yield and with moderate need for enzyme addition demanding a high enzymatic convertibility of high concentrations of pretreated biomass material. Most pretreatment technologies on the market makes use of chemicals such as SO₂ or sulfite which will produce unwanted inhibitory compounds and will add sulfur species to all streams from the process including lignin.

Wet explosion has no need for addition of chemicals and only demands addition of moderate concentrations of oxygen or air. The process can occur at moderate temperatures (between 170 and 185^oC) and pressure (less than 10 bars) at short reaction times (less than 30 minutes). After flashing the pretreated material is pumpable even at dry matter concentration of 35% and enzymatic hydrolysis of the material using commercial enzymes can occur with moderate loadings of enzymes (less than 40 mg enzyme protein per g of cellulose) without any need for further dilution of the biomass material. This allow for production of very high concentration of sugars (over 300 g per liter hydrolysate), much higher than previously published for this type of materials. Only low concentrations of inhibitors such as HMF and furfural were produced.

In the presentation we will show data for pretreatment of loblolly pine, Douglas fir and Hog fuel (slash) and discuss the economics of the wet explosion process.