Splitting Wood into Biodiesel, Pellets

An interesting approach to biorefining
By Ron Kotrba | May 20, 2011

The biomass and biodiesel industries collided in St. Louis this spring at the International Biomass Conference & Expo as Dino Mili, co-founder and CEO of Montreal-based New Forest Industries, gave a presentation titled Low Severity Process Yields Functionalized Wood Pellets and Biodiesel.

The process Mili discussed is an ideal biorefining retrofit strategy for a distressed pulp and paper mill, the end products from which would be wood pellets and biodiesel—a counterintuitive pair of products. It involves hydrotorrefaction in which wood chips are cooked in a digester with water, “just like the pulp industry has been doing for years,” he tells Biorefining Magazine, at about 160 degrees Celsius for an hour and a half. The hemicellulose (woody biomass consists of three main components: cellulose, or six-carbon sugars; hemicellulose, or five-carbon sugars; and lignin) and soluble fractions like ash and chlorides are separated out, and the lignin and cellulose portions are used for high-grade wood pellets optimized for combustion.

Mili says the resulting wood pellets are harder, more energy dense and hydrostable, since the hydrophilic fractions are removed.

The hemicellulose is separated and hydrolyzed to five-carbon sugars, a base feedstock for many advanced ethanol projects; but rather than make ethanol from these sugars that are more difficult and costly to ferment, Mili says the project reverts to more robust, homogeneous organisms to convert the five-carbon sugars to lipids for use to make fatty acid methyl esters (biodiesel). New Forest Industries has hired FPInnovations to help put the project together.

“The biggest issue is the conversion of the sugars to lipids,” Mili says. He says most of the organisms the project will use were originally developed for the wastewater treatment industry. In explaining the process, he also noted that if we eat too much sugar, our bodies will convert those sugars to fat, or lipids; so these microorganism conversions work in a similar way. Mili couldn’t give too much detail because his company is still finalizing patent applications on the process.

The oil properties from the converted sugars to lipids—the microbial oils—fall between those of vegetable oils and animal fats, Mili says.

Mili says he predicts 60 percent of the revenue stream from the process will come from pellet sales, while the remaining 40 percent will be equally distributed between green power and biodiesel.

While this biorefining approach would work well in a pulp and paper mill, finding one to work with might be more difficult than it appears. Mili likened a partnership between a biorefining startup and pulp and paper mill as a man with a cart who wants to hook it up to a horse. The stable owner (the mill owner) has only thoroughbreds (new, efficient mills) and crippled horses (outdated, inefficient or mothballed mills). The stable owner isn’t about to let the man with the cart slow down his thoroughbred, and the cart can’t be pulled by the crippled horses because they have to be put down.  —Ron Kotrba