New, streamlined process turns wood waste from agriculture and forestry into ethanol

Dependence on petroleum fuels and raging forest fires: two distinct large-scale challenges that could be addressed by a scientific breakthrough.

Teams from the Lawrence Berkeley National Laboratory (Berkeley Lab) and Sandia National Laboratories have collaborated to develop a streamlined and efficient process for converting woody plant material such as forest overgrowth and agricultural waste – material that is currently burned intentionally or unintentionally. – in liquid biofuel. Their research was recently published in the journal ACS sustainable chemistry and engineering.

“According to a recent report, by 2050, 38 million metric tonnes of dry woody biomass will be available each year, making it an exceptionally abundant carbon source for biofuel production,” said Carolina Barcelos, process engineer senior at Berkeley Lab’s Advanced Biofuels and Bioproducts Process Development Unit (ABPDU).

However, efforts to convert woody biomass into biofuel are generally hampered by the intrinsic properties of wood which make its chemical degradation very difficult, added Eric Sundstrom, researcher at ABPDU. “Our two studies detail a low-cost conversion route for biomass sources that would otherwise be burned in the field or in litter piles, or increase the risk and severity of seasonal forest fires.” We have the capacity to transform these renewable carbon sources from air pollution. and the risk of fire in sustainable fuel. “

In a study by Barcelos and Sundstrom, scientists used non-toxic chemicals, commercially available enzymes, and a strain of yeast specially designed to convert wood into ethanol in a single reactor, or “pot.” Additionally, subsequent technological and economic analysis helped the team identify the improvements needed to achieve ethanol production at $ 3 per gallon of gasoline (GGE) equivalent via this conversion route. The job is the very first end-to-end process for the production of ethanol from woody biomass with both high conversion efficiency and a simple one-pot setup. (As any cook knows, one-pan recipes are always easier than those requiring multiple pans, and in this case, that also means less water and energy consumption.)

In a follow-up study, led by John Gladden and Lalitendu Das at the Joint BioEnergy Institute (JBEI), a team refined the process into a single pot so that it could convert California woody biomass – such as pine, almond, walnut and fir debris – with the same level of efficiency as existing methods used to convert herbaceous biomass, even when the input is a mixture of different types of wood.

“By removing woody biomass from forests, like the overgrown pines of the Sierra, and agricultural areas like the almond orchards of the central valley of California, we can solve several problems at once: disastrous forest fires in the Fire prone states, air pollution hazards from controlled burning. crop residues and our dependence on fossil fuels, ”said Das, postdoctoral fellow at JBEI and Sandia. “On top of that, we would dramatically reduce the amount of carbon added to the atmosphere and create new jobs in the bioenergy industry.”

Ethanol is already used as an emission reduction additive in conventional gasoline, typically making up about 10% of the gasoline we pump into our cars and trucks. Some specialty vehicles are designed to run on fuel with higher ethanol compositions of up to 83%. In addition, ethanol produced from plant biomass can be used as an ingredient to make diesel fuels and more complex jet fuels, which help decarbonize the hard-to-electrify sectors of aviation and freight. Currently, the most common source of organic ethanol is corn kernels – a starch that is much easier to chemically break down, but requires soil, water, and others. resources to be produced.

These studies indicate that woody biomass can be efficiently broken down and converted into advanced biofuels in an integrated process that is competitive with starch-based corn ethanol. These technologies can also be used to produce “drop-in” biofuels that are chemically identical to compounds already present in gasoline and diesel.

The next steps in this effort are to develop, design and deploy the technology on a pilot scale, which is defined as a process that converts 1 ton of biomass per day. Berkeley Lab teams are working with Aemetis, an advanced renewable fuels and biochemicals company based in the Bay Area, to commercialize the technology and scale it up once the pilot phase is complete.

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