Thinning forests to prevent wildfires include the removal of diseased trees and other debris by private, state, and federal land managers. The byproduct of that thinning is called woody biomass. Removal of woody biomass from forests can help mitigate disastrous wildfires in fire-prone states like California.
Reducing wildfire risk
Some of the biomass material is left to decay, is burned in place, or is hauled to landfills. However, this byproduct of reducing wildfire risk can also be used to produce engineered lumber, paper and pulp, and a range of other wood products. Woody biomass is a compelling organic feedstock for conversion to renewable liquid fuels
Alternatively, it can be used to produce bio-based fuel products such as ethanol. In fact, woody biomass is a compelling organic feedstock for conversion to renewable liquid fuels. However, there are obstacles, such as resistance to chemical breakdown and possible toxicity of pre-treatment methods.
New conversion methods
Researchers at Lawrence Berkeley National Laboratory and Sandia National Laboratories are developing new treatment methods to pave the way for more efficient conversion of woody biomass into ethanol.
In one study, researchers have optimized pre-treatment and scale-up of an integrated one-pot process to deconstruct California woody biomass using ionic liquid (cholinium hysinate) as a pretreatment solvent. In scaling up the process, researchers streamlined and optimized the impact of solid loading, solid removal, yeast acclimatization, fermentation temperature, fomentation pH, and nutrient supplementation to maximize final ethanol yields.
First-ever end-to-end process
With the refinement of the processes, researchers reached ethanol production at $3 per gasoline gallon equivalent (GGE) via the conversion pathway. It is the first-ever end-to-end process that combines both high conversion efficiency and a simple one-pot approach.
The simplified process is also the largest scale demonstration of ionic liquid pretreatment and biofuel conversion known to date, and overall biomass-to-ethanol efficiencies are the highest reported so far. The research was published in the journal ACS Sustainable Chemistry & Engineering.
There will be 38 million tons of dry woody biomass available each year by 2050, making it an abundant carbon source for biofuel products, say the paper’s authors.
Converting Biofuel to ethanol
In another study, at the Joint BioEnergy Institute (JBI) at Berkeley Lab, researchers evaluated woody biomass types (pine, almond, walnut, and fir) from California as potential biofuel feedstocks. The feedstocks were pre-treated with two ionic liquids (cholinium lysinate and ethanolamine acetate) followed by enzymatic hydrolysis and fermentation to produce ethanol. The demonstration of the use of ionic liquids for pretreatment of woody biomass blends results in high overall efficiency
The study represents the first demonstration of the use of these ionic liquids for pretreatment of woody biomass blends that results in high overall efficiency for ethanol products. In addition to providing new sources of ethanol to contribute to fuel supply, the techniques transform biomass sources that would otherwise be burned in the field, thus increasing the risk and severity of seasonal wildfires.
Tackles wildfire risk
Converting woody biomass into fuel simultaneously tackles the multiple problems of wildfire risk, air pollution caused by burning of crop residues, and dependence on fossil fuels. In addition, the approach will reduce carbon in the atmosphere and create new jobs in the bioenergy industry.
The research was supported by the California Energy Commission and the U.S. Department of Energy (DOE) Office of Science. Additional authors of the research are affiliated with the Advanced Biofuels and Bioproducts Process Demonstration Unit, the National Corn to Ethanol Research Center, and Southern Illinois University.