Research Project Summary Information
Electron Beam Irradiation of Cellulose(ST10230-1)
Radiation Dynamics, Inc.
New York has abundant biomass, and is heavily dependent on fossil fuels. Cellulose, a component of biomass, is underused in fuels and chemicals because it is crystalline and insoluble. For a biomass-based product industry to develop in New York, cellulose needs better processing methods. Radiation can reduce its molecular weight and crystallinity, making it more susceptible to acid or enzymatic hydrolysis, two techniques used to create wood sugars that then may be processed into various chemicals.
The goal was to demonstrate the reduction in molecular weight and crystallinity of cellulose. Specific objectives included: 1) develop a dose response curve from 10-1000 kGy with commercial cellulose using a high dose electron beam (optimum dose was expected to be 100 kGy at most); 2) repeat dose response experiments with wood chips and paper pulp; and 3) use optimum dosage to treat wood chips and paper pulp, both dry and in a slurry. [Planned work using X-rays in addition to the electron beam was dropped because researchers determined the doses were not economically feasible.]
Electron beam radiation was applied to cellulose substrates to improve the yield of glucose. Researchers studied pure cellulose, microcrystalline cellulose, wood pulp (both hardwood and softwood), recycled pulps and wood chips. Additional work was conducted to help improve the cost effectiveness of electron beam pretreatment of cellulose.
Samples were irradiated under four different conditions: (1) in air and dry, (2) in air and wet, (3) in nitrogen and dry and (4) in nitrogen and wet. For the wet conditions, cellulose samples were saturated with deionized water before placement in polyethylene bags. For nitrogen treatment, polyethylene bags containing samples were flushed with nitrogen.
Cellulose substrates were characterized according to crystallinity, available surface area and molecular weight because changes in these parameters affect the enzymatic hydrolysis rate of cellulose.
If the project is successful, the proposer claims they would see an increase in sales totaling tens of millions of dollars annually. A unit treating 30,000 kg biomass/hour is projected to cost $8.43/tonne biomass. This appears to mesh well with the USDOE targeted cost of 10 cents/lb for wood sugars by 2012. Assuming the US will build 150 ethanol plants, and 100% market penetration of a $3.2M unit, the market size is $480M. There are few other firms that make this equipment. Two students based their thesis on this work.
Even at a dose of 100 kGy there were significant reductions in crystallinity and average molecular weights. Benefits taper off after 750 KGy; the optimum dose is 500 to 750 KGy. There was no significant difference in dry or wet samples, or irradiation in air or nitrogen. Available surface area changed at higher doses (>500 KGy). Changes expected at lower doses were not observed; the internal surface area may be changing but unfortunately the dye adsorption method only measures surface changes.
Irradiation was assessed in combination with biodelignification and hot-water extraction. All three pretreatments improve cellulose hydrolysis, however the combinations made specific causes less obvious. Irradiation had a much weaker effect, possibly because it attacks cellulose, while the other two attack the lignin/hemicellulose matrix. Irradiation at higher dosage also appeared to partially degrade lignin, enabling higher access to cellulose. Researchers speculate that irradiation produced more inhibitor chemicals in hot-water extracted samples, leading to reduced digestibility in some conditions. On the other hand, if coproducts are valued more than ethanol production, less radiation is needed to optimize hot water extraction than that needed for cellulose pretreatment.
Irradiation was studied to decrease milling (size reduction) costs. As expected the toughness of the wood samples decreased as the radiation dose increased. One irradiated sample needed 5.5 times less energy
Radiation Dynamics, Inc.
151 Heartland Blvd
Edgewood, NY 11717
SUNY College of Environmental Science an
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R&D - Environment & Energy Res