Converting biomass into value-added products on a commercial scale is crucial to a sustainable biofuel supply chain. While waiting for the biofuel market to develop, biorefineries must find profitable products to keep them in business.
Many of those products may not look much like transportation fuel. Take biochar: long consigned to use as a feedstock for low-value process heat, it is gaining favor as a soil amendment, and CenUSA Bioenergy’s Feedstock Conversion and Refining Team is helping to support that advance. The team’s soil scientists and agronomists, led by Robert Brown, Mechanical Engineering Professor Iowa State University discovered that this carbon-rich by-product of the pyrolysis process can markedly improve soil quality. Biochar is highly porous, helping soil retain water and fertilizer and curb runoff. It has been shown to reduce nitrate leaching by 10% and phosphorus leaching by 40 to 70%, and boost soil aeration, allowing roots to grow. So it’s no surprise that research has also found that biochar can increase crop yields. The team’s findings show that value-added biochar can make biomass production for renewable energy more profitable and therefore sustainable.
Biochar was just one objective of the Feedstock Conversion and Refining Team, whose work begins after a perennial-grass feedstock arrives at the biorefinery. What to do with the raw product to make it useful for the producer and for the processor? One of the team’s first objectives was to develop a technoeconomic analysis (TEA) model of the potential for converting perennial grasses used for biofuels and biorefinery co-products into value-added fuels and useful chemicals, through fast pyrolysis and catalytic pyrolysis processing. A TEA is a method of determining the profitability of a technology, using available data from commercial operations. The model can determine the economics of turning perennial grass feedstocks and their components, especially lignin, into marketable, value-added products that can help a biorefinery turn a profit.
In another objective, aimed at commercialization, the team worked closely with two partners: global food processor ADM, and Renmatix, a technology company based in Pennsylvania. Both companies fractionate—or break down into various components—biomass. The cellulose and hemicellulose components are readily marketable, but another major component, lignin, has few profitable uses, so it is mostly burned as a low-value fuel in boilers.
Much of the research looked at how to maximize the value of lignin from the two commercial partners’ processes and improve their economic performances, by developing two processes to convert lignin into streams of stable, phenolic-rich oil that can be upgraded to fuels, chemicals, and other products. New thermochemical-process technologies developed by the team at Iowa State University will help the partners get more value from the lignin than they currently generate.
In the long run, these advances will lead to conversion of grasses into biofuels and such value-added products as bioasphalt, cellulose pulp, fermentable sugars, and carbon fibers.
Future research by the team will focus on:
- Developing lignin-specific conversion technology and working with companies that don’t have a good home for their lignin co-product.
- Working with industrial collaborators to develop demonstration- and commercial-scale pyrolysis.
- Developing nonfuel uses, in addition to biochar, for perennial grasses. The team’s TEA showed that chemical and other nonfuel uses of perennial grasses can be more profitable than producing transportation fuels right now.
Some day, small biorefineries will be able to make money turning biomass into fuel. But at the current time, they must rely on nonfuel products to turn a profit and stay in business. Meanwhile, new conversion and refining technologies are establishing themselves in the commercial supply chain, waiting for the large-scale development of transportation fuels sure to happen in the future.