The PDU's four 2,300-gallon fermenters can process about one ton of feedstock material per day. Production of ethanol from biomass involves a multi-step operation. A pretreatment step reduces the feedstock size and breaks a portion of it into sugars. Enzymes and microorganisms grown on site are added to the 2,300-gallon fermentation tanks along with the pretreated biomass to produce sugars and convert those sugars to bioethanol. A 12-meter distillation column then concentrates the ethanol for use.
Solid residue is concentrated in centrifuges.
The PDU is also available to support other industrial clients interested in either bioethanol production, or development of technologies to produce other fuels and chemicals from biomass, such as butanol and lactic acid. The AFUF contains two process development laboratories in which the various process steps necessary for biofuels production are linked together and tested as an integrated process at the bench scale. These steps are typically developed independent of one another initially and must be evaluated under actual production conditions to ensure chemical and biological interactions are accounted for. Reducing Costs Recent genetic engineering breakthroughs at NREL have produced a new organism that expands the amount of biomass converted to ethanol by up to 50 percent, significantly reducing the cost of producing bioethanol.