Steps to biorefining: new products from biofuel leftovers

The vision behind the emerging bioeconomy is the creation of integrated biorefineries that turn any given stream of biomass into an optimal range of finished products, green platform chemicals and specialty chemical compounds. The goal is to make the processing steps as efficient as possible, and to have them 'cascading' so that one bioconversion step's 'waste' stream becomes an input for a next step. Ultimately, biofuels will be just one of the many renewable, low-carbon products and compounds manufactured in the biorefinery.

Many researchers are pursuing on this concept, and the most common approach is to utilize currently available byproducts from biofuels - distillers’ dry grain from corn ethanol, lignin from cellulosic ethanol or glycerin from biodiesel - as a starting point for research. But some sciensists are going further already, and are adapting the biofuel production process itself in such a way that it may yield more interesting co-products (overview of some potential biobased products, schematic, click to enlarge). This is the way forward to genuine biorefining.

Here are some of the latest developments.

Using current byproducts
Several scientists are working with glycerol (glycerin), the main byproduct of biodiesel. Each batch of vegetable oil yields around 9 parts of biodiesel and 1 part of glycerol - currently in over-supply. Low-value uses are burning the glycerol as an energy source, using it as a substrate for the production of biogas (previous post), or as an animal feed (for poultry and cattle). The goal is to find products with a higher value.

• Ronald Holser, research chemist at the United States Department of Agriculture’s research center in Athens, Ga., and Steven F. Vaughn, a plant physiologist, at the department’s National Center for Agricultural Utilization Research in Peoria, Ill., are instead using the product to create biodegradable weed barriers and sticky films intended to hold grass seeds on the ground long enough to germinate.
• Peggy M. Tomasula and her colleagues at the Agricultural Research Service's Eastern Regional Research Center's Dairy Processing and Products Research Unit in Wyndmoor found that combining the milk protein casein with water and glycerol, produces a water-resistant biodegredable film that can be used as an edible coating for food products (previous post).
• Ramon Gonzalez, William Akers Assistant Professor in Chemical and Biomolecular Engineering, and team recently identified metabolic processes and conditions that allow a known strain of the E. coli bacterium to ferment glycerin into ethanol under anaerobic conditions. The process is highly efficient, with the scientists estimating the operational costs to be about 40 percent less than those of producing ethanol from corn (more here).
• Dow Chemical Company recently reached a significant milestone in its pursuit of plant-based chemistries, with the development of propylene glycol (PG) derived biodiesel's glycerin. PG will be used in such applications as unsaturated polyester resins (UPR) for boat hulls and bathroom fixtures as well as aircraft deicers, antifreeze for automobiles, recreational vehicles and marine and heavy-duty laundry detergents (more here).

Another currently available biofuel byproduct is distillers’ dry grain (DDG) — a main byproduct of corn ethanol that is largely sold as animal feed (previous post) or alternatively used as an organic fertilizer and herbicide (more here). Several researchers think DDG can be used for a range of more valuable products.

• Robert C. Brown, a lab researcher in Iowa, is using it to produce hydrogen and a compound called polyhydroxyalkanoate (PHA). The PHA family of compounds is used for the production of biodegradable plastics. For PHA bioplastics to become competitive, they must be produced from a cheap and abundant feedstock - DDG is one such feedstock.

energy :: sustainability :: biomass :: bioenergy :: biofuels :: byproducts :: coproducts :: biorefinery :: bioeconomy ::

• Working with DDG as well is Steven F. Vaughn, of the National Center for Agricultural Utilization Research. He is looking at making a methylester biofuel from it. DDG contains more than 10 percent oil, and one ton of it can yield 30 gallons (113 liters) of the fuel.

New bioconversion techniques, new bioproducts
Ultimately, in the biorefineries of the future, traditional biofuel production techniques are up for redesign. They will be finetuned or if necessary radically altered in function of finding the most optimal mix between fuel production and the creation of green products. Two examples of this type of developments, that come closest to genuine biorefining:

• Colorado-based PureVision Technology is making lignin, the natural compound that helps provide strength and rigidity in plants, lignin makes up 15 to 25 percent of most plants. Most plans for cellulosic ethanol processing call for burning the lignin to generate steam and heat to run the process. As a fuel, lignin is worth around $40 a ton. PureVision' Ed Lehrburger has devised a way to make a different form of lignin — one with a molecular composition that makes it an attractive material for a variety of green industrial products like glues, sealants and detergents. This type of lignin could sell for $300 a ton or more. According to the scientist, lignin is going to be one of the big drivers of the switch from oil-based to biobased products.
• Dr. Victor Lin, chemistry professor and the associate director of the Center for Catalysis at Iowa State University and founder of Catilin, and George Kraus, a professor of chemistry at Iowa State, where he is director of the Center for Catalysis, have created a technology that changes the production process for biodiesel. Among other attributes, Lin’s invention yields a higher quality form of glycerol, which could be more easily converted into useful industrial materials. The new production process utilizes a catalyst that is safer and easier to use and reduces impacts on the environment. Lin and his colleagues are trying to use the higher-quality glycerol from their new process as a starting point for the production of 1,3 propanediol (PDO) the base material for a substance used in upholstery, carpets, clothing and other applications. If Lin succeeds, glycerol could become 15 times more valuable than current projected prices.

Image: PureVision’s chief executive Ed Lehrburger, showing his new form of ligning, which he thinks could sell for $300 a ton. Credit: New York Times.

References:
New York Times: Cooking Up More Uses for the Leftovers of Biofuel Production - August 8, 2007.

Biopact: An in-depth look at biorefinery concepts - July 10, 2007