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Co-products – The Path Forward for Renewable Biofuels

Sylvia Kantor, Washington State University

As the economic landscape for biofuels has shifted in recent years, Advanced Hardwoods Biofuels Northwest (AHB) has added other bio-based co-products, to the project’s renewable fuels research portfolio.

With a more plentiful supply of domestic oil and natural gas, the economic outlook for biofuels in the United States has dipped. “Energy in general is cheap,” said Rick Gustafson, AHB director and professor of Bioresource Science and Engineering at the University of Washington. “The push has been to develop biofuels to improve our domestic supply of fuel, but now there’s talk of exporting oil and natural gas from the United States.” Gustafson said that the drive to develop a biofuels industry is further challenged by a lack of mechanisms to monetize carbon emissions.

Nonetheless, producing hydrocarbons for drop-in biofuels from poplar feedstock with a lower carbon footprint than that of fossil-based fuels remains AHB’s chief goal. But developing high-value co-products along the way offers more immediate promise for the emerging biofuels industry and for rural communities in need of economic opportunity.

Petroleum companies profit significantly from a small volume of chemicals in addition to fuel production, according to Gustafson. But the biofuels industry is poised to capture its own share of the chemicals market with products that come from renewable sources and have a smaller carbon footprint. Because the feedstock production, conversion, and processing for biochemicals are the same as for biofuels but with fewer steps, producing chemicals for co-products makes sense economically and environmentally as a step along the path to producing biofuels.

Bio-based products

Biomass-based products are increasingly used as an alternative to petroleum-based products. High-value co-products such as acetic acid, ethyl acetate, ethylene, and ethanol can be produced from woody biomass for use in products like paints, plastics, solvents, packaging, pharmaceuticals, cosmetics, and even nutritional supplements and textiles.

Plastic cups, plastic bowls, plastic utensils, and poplar wood chips sitting on a picnic table
Woody biomass from poplar trees can be used to make chemicals for the production of many common products including plastics and textiles.

Acetic acid is in high demand globally for the manufacture of paints, adhesives, polymers, and solvents. It can be produced through fermentation, one of the early steps in the AHB conversion process in which the poplar-feedstock is converted to chemicals. Advanced Hardwood Biofuels Northwest partner ZeaChem uses a proprietary fermentation process to produce acetic acid from poplar feedstock that results in a product that is more valuable than biofuel, gallon for gallon.

For ZeaChem, producing acetic acid from poplar feedstock is a logical starting point and a critical aspect of their commercialization plan, as they continue research to produce biofuel from poplar feedstock. “Future ZeaChem biorefineries will very likely produce hydrocarbon fuels as well as valuable intermediate products,” Gustafson said.

A can of white paint and a paint roller with poplar wood chips.
Acetic acid can be made from poplar wood and is an important component of paint.

Modeling the costs of production

To be price-competitive, estimating costs of biofuels and co-products is key to success of the industry. Jordon Crawford, a research analyst in Gustafson’s lab, is developing a model to estimate biofuel production costs based on technical and economic inputs. His goal is to estimate the price at which a biorefinery would need to sell biofuel in order for investments to pay off, information that could be useful for potential investors.

Crawford uses Aspen, a technical modelling tool, to estimate how big biorefinery equipment, like fermentation reactors, needs to be and how much the equipment will cost. Adding up the individual components of a system, he is able to estimate the total capital investment needed to build a biorefinery. Crawford’s model estimates operating costs as well. But he is careful to point out that some costs, like feedstock production, remain somewhat uncertain until the industry matures.

The next phase for Crawford is to run his model to estimate capital and operational costs for valuable co-products like acetic acid. He will adapt the model to account for any additional purifying steps that are needed to produce acetic acid and other co-products.

“Biorefineries like ZeaChem are very interested in producing and selling intermediate products in order to diversify their product portfolio,” Crawford said. “Diversifying, in general, reduces risk for the biorefinery from a business perspective.”

In the long-run, biofuels remain a key part of the solution for reducing greenhouse gas emissions and ensuring a domestic fuel supply. But with the cost of jet biofuel currently estimated to be up to twice as much as petroleum jet-fuel, establishing a supply chain and the technology for producing high-value co-products for near-term commercialization makes good economic sense.