Posts Tagged ‘biomass’
Biomass gasification is different from cellulosic ethanol in at least two major respects. First of all, it is a combustion process, not a fermentation process. As a combustion process, it can be self-sustaining once the combustion is initiated. It does not require continual inputs of energy as is the case with a fermentation process. The products of biomass gasification are syngas and heat, if the reaction is operated in an oxygen-deficient mode, or CO2 and steam (and much more heat) in the case where sufficient oxygen is supplied. In the case of the former, the syngas can be further reacted to make a wide variety of compounds, including methanol, ethanol, or diesel (via the Fischer-Tropsch reaction). A biomass gasification process followed by conversion to a liquid fuel is commonly referred to as a biomass-to-liquids (BTL) process.
However, there is one other major factor that differentiates biomass gasification from cellulosic ethanol. Biomass consists of a number of different components, including cellulose, hemicellulose, and lignin. In the case of cellulosic ethanol, only the cellulose and hemicellulose are partially converted after being broken down to sugars. The lignin and other uncoverted carbon compounds end up as (wet) waste, suitable for burning as process fuel only if thoroughly dried. Conversion is limited to those components which can be broken down into the right kind of sugars and fermented.
Gasification, on the other hand, converts all of the carbon compounds. Lignin, a serious impediment and waste product in the case of cellulosic ethanol, is easily converted to syngas in a gasifier. The conversion of carbon compounds in a gasification process can be driven essentially to completion if desired, and the resulting inorganic mineral wastes can be returned to the soil.
PureVision’s core technology separates the primary constituents of cellulosic biomass within one pressurized reaction chamber into three streams. This continuous process employs a counter-current extraction technique that removes and recovers the hemicellulose and lignin fractions in two liquid streams, resulting in a solid fraction containing a relatively pure cellulose or fiber. This patented biomass fractionation process occurs within approximately 10 minutes.
In the PureVision process, cellulosic biomass is size-reduced and fed into a pressurized reaction chamber uniquely designed for counter-current processing. The PureVision technology can be accomplished in a single stage or in multi-stages, depending upon the desired products. A distinguishing feature of the PureVision process is the ability to efficiently separate (fractionate) biomass into its three main constituents: hemicelllulose, lignin and cellulose.
In a two-stage setup, the target within the reaction chamber is to first wash out most of the hemicellulose in the form of hemicellulose sugars while keeping as much of the lignin and cellulose intact in a solid form. After the solids enter the second half of the reaction chamber, the pH, temperature and pressure are adjusted to wash and remove as much lignin as possible. These two washing stages yield (1) the xylose-rich liquor fraction, (2) the lignin-rich liquor fraction and (3) the remaining solid and relatively pure cellulose fraction.
In the first stage most of the solid hemicellulose can be converted into hemicellulose sugars. These sugars can then be fermented to produce products such as ethanol, xylitol or furfural or can be processed into a purified xylose stream. The first wash liquor fraction also contains smaller portions of the lignin, cellulose, protein, and ash components of the biomass, most of which can be recovered.
After the counter-flow washing of the hemicellulose occurs, most of the lignin and possibly the remaining hemicellulose are washed out in a second stage. This second stage wash liquor fraction contains most of the lignin and any targeted amount of the remaining hemicellulose sugars. This lignin-rich fraction is then further processed to produce a high quality, low-molecular weight lignin that can be sold as an industrial raw material to produce hundreds of industrial and consumer products. The lignin can also be used as a bio-fuel to provide energy for making electricity and steam to run the biorefinery.
The remaining cellulose fraction is between 90% to 97% cellulose, as most of the lignin, hemicellulose and extractives have been stripped off in the wash liquor fractions. Because of the high purity of the cellulose fraction, it can be sold as a pulp or enzymatically hydrolyzed into glucose requiring far less enzymes compared to competing technologies.
The PureVision process has enormous versatility and flexibility due to the many processing variables that can be achieved with steady state, counter-current processing. If the primary target is to produce a quality pulp for making paper products, the process targets the pulp specifications required by the pulp and paper industry to make paper products or dissolving pulps to make numerous industrial products. Alternatively, if the objective is to produce ethanol or other industrial chemicals, then the processing parameters will be targeted to maximize sugar production from the cellulose and hemicellulose fractions.
Verenium Corp. has a pilot plant making 50,000 gallons a year of the motor fuel additive in Jennings, La., in Jefferson Davis Parish, which is about a couple of hours’ drive from Beaumont.
Verenium, based in Cambridge, Mass., is building a demonstration plant capable of converting biomass – the general name for plant material that can become ethanol – into 1.5 million gallons a year.
That demonstration plant is a necessary step toward developing a commercial-scale plant capable of producing 30 million gallons a year.
Last week, about 30 Southeast Texans – farmers, economic developers, members of the region’s BioFuels Alliance, and others went to Jennings to see the operation and learn more about it from Verenium officials.
Verenium already has an option to buy several hundred acres of land between Nome and Winnie to build a commercial-scale plant. The company also is looking at other areas along the Gulf Coast such as in Florida and Louisiana. The company plans to build several distilleries to produce ethanol.
However, the demonstration plant is an intermediate step, much the same as creating a kind of beer from the biomass is an intermediate step in distilling the pure alcohol, said Charlie Butler, human relations manager for Verenium.
“We have a master brewer on staff from Anheuser Busch,” Butler said.
That’s to control and to ensure the quality of the fermentation of the biomass early in the process.
Butler compared the start of the process with that of a pulp mill.
The biomass is fed into a chopper and is ground down to small bits. The mass comes in at about 50 percent moisture, so it contains a good deal of water anyway.
The mass is given the steam treatment and it becomes a slurry. From there, it is mixed with the company’s proprietary enzymes and bacteria, which help to create that beer of which Butler spoke.
From the beer vessel, the liquid then goes into distillation, which is where boilers come into play.
Solids drop out of the mix and are drawn off to become part of the fuel that heats the boilers.
The water that is drawn off during distillation is fed back to the steam vessels.
The pure alcohol – which might test out at 190 proof – becomes the fuel-grade ethanol.
Chuck Davis, head of commercial development for Verenium, said the demonstration plant will exist only to prove the concept.
That’s what will attract the financing to help make the commercialization possible, he said.
The demonstration plant, which will cost about $35 million to build, is about 50 percent completed and should be ready for operations by spring 2008, he said.
He said Verenium wants to be in a position to begin building a commercial plant by the end of 2008.
Construction would take 18 months to two years, he said.
The farmers were invited along because it is they who must decide whether to support such a plant with appropriate crops that they would grow expressly for Verenium’s ethanol plant.
No one at Verenium has yet put a price to the kind of crop that farmers would grow – and that’s something that farmers need to know before agreeing to a contract.
However, Verenium does need about 325,000 tons per year of biomass to produce its 30 million gallons of ethanol.
Davis said the company figures on production of 20 tons per acre of land, which would require about 16,000 to 18,000 acres of land.
Ted Wilson, director of the Texas A&M Agriculture Research and Extension Center west of Beaumont, said he thinks the 20 tons per acre is too aggressive a figure.
Wilson said he doesn’t think farmers in Southeast Texas could consistently raise that amount from each acre.
And the data for ethanol specific crops like energy cane – a more fibrous and less sucrose-heavy variant of sugar cane – or sorghum doesn’t yet exist for this area, Wilson said.
Davis was unworried.
“As we evolve, I expect costs to go down and yields to go up,” he said.
Davis said the kind of plant Verenium is pursuing is based on fibrous plants and not grain such as corn, which is now the main ethanol raw material.
The capital cost to build a distillery for the fibrous plants is higher than that for corn, Davis said. But the operating costs are lower, he said.
Richard Schroeder, a biomass consultant for Verenium, said farmers and the ethanol producer have to agree on prices or the project won’t work.
“We don’t expect anyone to grow a crop and lose money,” he said. “And we don’t expect anyone to switch crops so they can make more money. This is not ‘get-rich-quick.’
“One answer to your (Beaumont rice farmer Chuck Kiker’s) question is ‘how cheap can you grow it?’
“We want to build where we can get the cheapest crop,” Schroeder said.
He said Verenium is making a massive investment and commits to an area for “the long haul.” The service span of an ethanol plant should be 20 years, he said.
“On a per-ton basis, this is not worth what a food crop is,” Schroeder said. “But on a per-acre basis, it is feasible.”
Verenium’s kind of ethanol – called cellulosic – would yield between 1,400 and 1,800 gallons per acre. That compares with corn’s usual 400 gallons per acre, Schroeder said.
Twenty tons of biomass per acre would yield about 80 gallons per ton of biomass, he said.
Plenty of other unanswered questions remain for farmers, such as who harvests and who transports?
Also, Verenium was unable to offer specifics on a contractual minimum for a crop.
Rice farmer Alan Gaulding, who works land between Hamshire and Fannett, said Verenium’s operations were interesting to see.
“They still have a lot of work to do with the farmers,” he said.
For many on the trip, the most important thing they saw is Verenium’s intent is serious.
“They’re earnest,” said Lee Tarpley, a plant physiologist from the A&M research center.
“The importance of (the trip) is that Verenium is for real.”
San Ramon-based Chevron (NYSE: CVX) and Federal Way, Wash.-based Weyerhaeuser (NYSE: WY) each own half of the new company, called Catchlight Energy LLC. Michael Burnside, a 33-year veteran of Chevron, is CEO of the new venture. Densmore Hunter of Weyerhaeuser is chief technology officer.
Catchlight will seek biofuels made from non-food sources, particularly cellulose-based biomass. It will have offices in both San Ramon and Federal Way for the time being, said a Chevron spokesman.
Cellulosic feedstocks have many advantages over using corn to produce ethanol. Because cellulosic crops are not used for food, there is inherently less price volatility. And because a wide variety of crops can be used, they can be grown in a wide variety of geographic locations–even on marginal lands–and can, therefore, be more abundant. Plus, with certain crops, more ethanol can be produced per acre than can be made with corn.
With so many advantages, it seems only natural that we have dedicated energy crops, rather than using food crops for ethanol production.
Here are some numbers to think about.
Right now, corn yields, on average, about 160 bushels per acre, with industry predictions climbing all the way up to 300. And we get about three gallons of ethanol per bushel. That means for every acre of corn harvested, about 900 gallons of ethanol can be made.
Add in four tons of stover (converted cellulosically) per acre, with which you can produce 100 gallons per ton, and we’re looking at additional ethanol production of 400 gallons per acre–for a grand total of 1,300 gallons per acre. And that’s using two different feedstocks, with two different harvest times, two different costs and two different conversion processes.
Now consider a dedicated biomass energy crop like switchgrass, miscanthus or sorghum. These crops can be harvested, at the present time, at a rate of 20 tons per acre(very high estimate), with ethanol production of 100 gallons per ton(very advanced technology), for a total of 2,000 gallons per acre. You can see why energy crops and the cellulosic process will be huge successes.
And that’s with the current numbers. Imagine how big this would be if crop yields and gallons per acre were increased and cost were continually driven down. That’s exactly where this industry is heading.
Bioengineered varieties of dedicated energy crops such as switchgrass could triple cellulosic ethanol yields from current levels within a decade, a plant biotechnology expert said on Tuesday.
The first wave of commercial biomass ethanol plants will use readily available agricultural waste such as corn stalks or wheat straw to produce the biofuel, but crops grown exclusively for energy production promise much higher yields, said Anna Rath, director of business development at Ceres Inc.
Cellulosic ethanol is produced from plant matter broken down by enzymes and distilled into produce ethanol.
“If you’re thinking in terms of ethanol per acre, switchgrass is already as good as your average corn field at generating ethanol per acre, but it’s a much less mature crop than corn,” Rath told Reuters reporters at the Reuters Biofuel Summit by telephone from Thousand Oaks, California.
“With corn you’re getting a couple percent yield improvement year over year. With switchgrass we think there will be much greater breakthrough improvements, especially in the early years,” she said.
Traditional breeding methods could produce a switchgrass hybrid that could yield 10 to 12 tons of biomass per acre in the next five years, up from about 5 tons per acre currently, Rath said. Genetic engineering could push that to 12 to 15 tons per acre by 2015, she said.
Cellulosic ethanol yields could also grow from the current 70 to 80 gallons per ton of biomass to more than 100 gallons per ton as production costs decline and plants become more efficient, she said.
By comparison, the most efficient corn ethanol plants can produce just under 3 gallons of ethanol per bushel of corn, according to industry experts.
The average U.S. corn yield per acre in 2006 was about 149 bushels per acre, according to the U.S. Department of Agriculture.
U.S. ethanol plants produced about 5 billion gallons of ethanol in 2006, mostly from corn grain.