The refinery concept is the work of biofuel researchers at the Joint BioEnergy Institute (JBEI) in Emeryville, California. They are eyeing waste lignin as the process solvent for their self-sustained biorefinery.
Lignin is a waste material of many wood-based industrial processes such as paper making and ethanol production. The JBEI researchers used this waste to create deep eutectic solvents (DES), a group of solvents that are cheap, environmentally benign, and sustainable alternatives to industrial chemicals.
The deep eutectic solvents have been combined with other liquids and used to pre-treat grassy feedstocks. They are able to extract sugars from biomass; these sugars are then processed into useful chemicals and fuels.
There are many advantages in switching from existing solvents to deep eutectic solvents for pre-treatment of biomass. DES are made from cheap waste lignin, so they are much cheaper and easier to synthesize than the standard ionic liquids. They are potentially much cheaper and easier to scale up in terms of production. (Related: Enzyme discovery enables production of renewable biofuel; could replace petroleum-based gasoline additive.)
Lignin goes from waste material to valuable solvent
Lignin comprises anywhere from 20 to 30 percent of the dry weight of plant biomass. It is, therefore, a common and sizable waste product after the biomass has been processed.
If lignin could be transformed from waste material into a valuable asset, the renewable solvents could provide a new way to convert biomass into cheaper bioproducts. These solvents could eventually supplant existing solvents in other processes.
Finally, DES are sustainable products made from planted-based biomass. They are better for the environment compared to standard solvents, which are made from non-organic materials for the most part.
The increasing commercial availability of biofuels and bioproducts will spur a demand for lignin. The former waste product will now become a raw material that can be turned into profitable products.
Researchers will, therefore, need to tackle the issue of establishing, maintaining, and/or raising the price of lignin. This will aid the development of a U.S. bioeconomy.
New deep eutectic solvents can be reused for biomatter processing
In an experiment, the JBEI researchers tested 10 lignin-based phenolic compounds as hydrogen bond donors. The compounds were combined with different mixtures of choline chloride to create deep eutectic solvents that melted at lower temperatures compared to the individual DES.
The researchers screened the resulting DES and picked four of the solvents. They applied the chosen solvents to biomass in the form of switchgrass, a grass that is used to feed livestock.
The pre-treated biomass was thoroughly washed to eliminate any chances of inhibiting the next processes. The material underwent enzymatic hydrolysis and fermentation in order to extract useful glucose.
The results of their experiment showed that fresh DES-chlorine chloride mixture extracted 87 percent of the glucose from the switchgrass biomass. Reusing the solvent decreased the yield of the process; the second round of use managed to get 78 percent of the glucose while the third round extracted only 70 percent.
The JBEI researchers concluded that using these renewable deep eutectic solvents in biomass processing will be able to decrease operating costs. A closed-loop biorefinery can produce these effective solvents from the biomass conversion process itself.
Find out what happens to other less savory industrial waste products at BioSludge.news.
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