Transforming triticale straw
By Carolyn King
Ethanol is usually produced from the starch in grain or the sugar in sugar cane.
By Carolyn King
Ethanol is usually produced from the starch in grain or the sugar in sugar cane. It can also be made from the sugars in straw and wood, but finding cost-competitive methods to get at those sugars has been tough because they are tightly tied up in the lignocellulose of the plant cell walls. Now a major initiative is exploring processes to, not only release the sugars in triticale straw to make ethanol, but to also create high-value co-products like specialty chemicals.
|Triticale has the highest potential grain and biomass yields among cereals grown in Western Canada. Photo courtesy of CTBI.|
Triticale, a man-made cross between durum wheat and rye, grows well in a wide range of conditions, has relatively low input requirements and has the highest potential grain and biomass yields among cereals grown in Western Canada. Despite these advantages, triticale acres remain low because the markets are relatively small; it is currently used for feed or milling grain and silage. But the Canadian Triticale Biorefinery Initiative (CTBI) sees a very bright future for triticale in the bioindustrial marketplace.
The 10-year, Alberta-driven, Canada-wide research and development initiative began in 2005. Its mission is “to drive the development and commercialization of triticale crop, process and product technologies, contributing to a globally competitive Canadian bioindustry.” As of fall 2008, federal and provincial sources have invested $20 million to drive the CTBI forward. A network of 130 scientists, engineers and industry developers is conducting 30 projects to explore opportunities to harvest value from both the grain and the straw.
The initiative’s straw-related projects range from developing fractionation processes for production of energy and biochemicals, to creating biocomposites for the biofibre industry. “Use of triticale straw is an integral part of the whole-crop utilization,” says Dr. George Pan, a scientist with the Bio-Industrial Technologies Division of Alberta Agriculture and Rural Development. “One conventional use, for example, would be to convert the triticale straw into pulp and paper. Pulp and paper processing is a form of biorefining where typically wood is fractionated into various grades of pulp using processes that include removal of hemicellulose (one component of lignocellulose). Further refining can produce fermentable sugars and lignin byproducts, which can be sold as a valuable commodity or used to produce energy to run the biorefining process. This is why we are interested in triticale as a bioindustrial cereal; it can fit into existing biorefining processes like this and provide rapidly renewable feedstock options for processors to utilize
Many applications possible
CTBI marketing manager Richard Gibson emphasizes the importance of producing multiple co-products from straw processing. “The economics of production, collection, transportation and processing of the straw become more competitive as an industrial feedstock when many products are produced from the single resource.”
The initiative is investigating several approaches to fractionating triticale straw. “Biomass fractionation technologies are in their nascent stages. There are many promising approaches to resolving the challenges of breaking down the lignocellulosic material at an efficient, industrial scale. There is no one-size-fits-all solution at the moment,” says Gibson.
Funding agencies for the CTBI straw fractionation projects include the Alberta Agricultural Research Institute, Alberta Agriculture and Rural Development, Alberta Research Council, Alberta Crop Industry Development Fund, and Agriculture and Agri-Food Canada.
One of these projects involved PureVision Technology Inc.’s biomass fractionation technology. This technology can quickly separate lignocellulose into three main fractions: cellulose, hemicellulose and lignin. Previously, the company had tested its technology with several types of biomass, including corn stover, wheat straw and sugarcane residues. In the CTBI project, conducted in 2007, PureVision optimized its process for use with triticale straw at the small pilot scale. “PureVision Technology has developed a technology that uses a continuous extrusion type of reactor to fractionate the straw into the three chemical streams in one single reactor. We were interested in assessing the technical feasibility of using their technology to fractionate triticale straw,” says Pan.
The purified cellulose resulting from the PureVision process is much easier to convert into sugars for ethanol or various industrial biochemical products. Alternatively the cellulose pulp can be sold for paper products.
The hemicellulosic sugars can be used to make ethanol and specialty chemicals such as furfural, which can be used as a solvent or as a building block for manufacturing other chemical products such as resin.
The purified lignin can be sold into many high-value markets. Pan says, “Technically you can make hundreds of products from lignin. For example you can use lignin to make a bio-adhesive to replace phenol formaldehyde resin for wood panel manufacturing. By using this bio-adhesive you could reduce formaldehyde emissions from products. Also lignin is an antioxidant so you can find many other applications. For example you can blend lignin with asphalt to extend the life of the pavement.”
Pan is now involved in a four-year CTBI project exploring other approaches to fractionating triticale straw into ethanol and other high-value applications. This new project involves three research groups: Pan’s Edmonton-based group, another group led by Dr. Joe Mazza with Agriculture and Agri-Food Canada at Summerland, British Columbia, and a third group led by Dr. Fanny Monteil-Rivera with the National Research Council in Montreal. “We are working together under the same umbrella with the same goal, but our experimental approaches are a little bit different,” Pan explains. “I am using the combination of mild acid hydrolysis and enzymatic hydrolysis. My colleague in BC is using high-pressure water extraction, and the Montreal group is using a catalytic process.”
Each group will be focusing on optimizing the process for different results. For example, Mazza’s group is interested in certain speciality chemical applications, while Pan’s group is working on the clean separation of the three major
Pan sees great long-term potential for ethanol-related straw fractionation. “I think it’s very important to do this research and technology development on agricultural residue. It is a sustainable feedstock and will help reduce our dependence on fossil fuels. It will also have a huge positive impact on greenhouse gas emission reduction. The US Department of Energy lab did a comparison between grain-based ethanol and lignocellulosic-based ethanol regarding greenhouse gas emissions. The benefit from the lignocellulosic ethanol is much better than grain-based ethanol.”
To spur along commercialization of triticale biorefining, the CTBI is currently developing a biorefinery pilot plant. Gibson says, “The goal is to have an operational pilot-scale biorefinery by 2011 which will represent an integrated approach to the utilization of triticale; this includes processing both grain and straw.” The pilot plant’s approach to straw processing will become clearer as the CTBI’s investigations into the available technologies continue.
Gibson is optimistic about the future for commercial biorefining of triticale straw and grain. “My belief is that we will see integrated refineries as part of the rural setting creating local jobs and career opportunities.”