Standardizing a process design is much more calculable when every project is designed to use the same feedstock. For those processes based on locally or regionally available feedstock supplies, which include wood, stover, straw, dedicated energy crops or hundreds of other lignocellulosics, standardizing any one process for a myriad of potential feedstocks has proven to be more difficult. This is why so many viable processes have emerged in second-generation ethanol project development, including thermochemical, biochemical and hybrid technologies.
For biochemical processing, enzymatic hydrolysis can play an important role in overall process design but even within this specified aspect of biochemical conversion, there is no clear-cut image of what the second-generation enzyme manufacturing and supply chain will look like. Those closest to the situation tell EPM there are still a lot of factors that will influence how this particular aspect of a second-generation ethanol industry is likely to unfold. Moving forward, however, it seems evident enzyme manufacturing and delivery will be as varied as project location, feedstock choice and process design.
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In corn-ethanol production, alpha amylases help break down complex starch carbohydrates into polysaccharides during liquefaction. Then, during saccharification, glucoamylases further deconstruct polysaccharides into simple glucoses ready for fermentation.
For first-generation enzymes, centralized production by major enzyme-manufacturers is the norm, followed by transportation and delivery to the various dry-grind ethanol plants. Novozymes has one enzyme manufacturing plant in the United States, located in Franklinton, N.C., from which it serves U.S. customers as far away as the West Coast. According to Emmanuel Petiot, Novozymes global business development manager, this centralized model has been successful thus far in first-generation ethanol enzyme production and delivery, but times are changing. “Yes this model has been one that has worked but, because of the increased size of the first-generation ethanol industry, in addition to the volume of enzymes needed for biomass [hydrolysis], we need to get closer to our customers,” he says. “That’s a given.”
The Case for On-Site or Near-Site Enzyme Manufacturing
Novozymes’ first step in developing what Petiot coins as its near-site model for enzyme production, as compared with its current strategy of centralized manufacturing, is its new enzyme plant project in Blair, Neb. Construction on the enzyme plant is slated to begin late this year, with operations expected to start in late 2010.
“Initially, the [Blair] plant will primarily serve first-generation plants,” Petiot says. “But as pilot, demonstration and the first commercial biomass ethanol facilities come on line, we’ll serve these plants as well. The number of biomass plants will be small in the beginning—maybe six, eight or 12 of them by 2012—but it will put us in the position to serve all of the needs of the biomass industry in its first years of development.”
In order to deconstruct and hydrolyze the polymeric sugars imbedded in extremely complex structures of lignocellulosic materials, cocktails of cellulases and hemicellulases are required. “The volumes of enzymes required for biomass are going to be much higher than for first-generation ethanol because the feedstocks are much more complex,” Petiot says.
Verenium Corp. vice president of research and development, Nelson Barton, agrees. “We are talking very large volumes of enzymes,” Barton tells EPM. “The nature of the lignocellulosic substrate will require more complex enzyme cocktails and, when you start talking about manufacturing very large volumes of enzymes, you’re talking about transporting large volumes of water around as well.”
In 2007, Verenium was formed through the merger of Cellunol (formerly BC International) and enzyme-maker Diversa Corp., putting Verenium in the unique position of possessing its own specialty enzymes division. “Out of our Diversa heritage comes our development of process-optimized enzymes,” Barton says. “We do plan to produce a targeted set of [second-generation] enzymes, but we also have the ability to optimize and evolve these enzymes and make them more stable.”
Within minimal processing and minimal stabilization models, Verenium is working to process-optimize and stabilize its cellulase and hemicellulase cocktails for biomass hydrolysis. “The farther you need to transport the enzymes, the more you need to start thinking about stability issues during transport,” Barton says. Issues of cost are huge in all aspects of the emerging biomass industry, so if second-generation enzyme cocktails are transported long distances to a biorefinery and the enzymes destabilize en route, how much processing of the enzymes can you afford to do after you’ve produced them in order to stabilize them? Barton furthers this question by asking, “Could you even afford to do any sort of formulations to stabilize them in any way?” He responds to his own question by stating, “The answer is minimal, if any. So really it becomes a matter of being much more amenable to on-site manufacturing of enzymes.”
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