In the face of increasing world energy demands, could the abundance of woody biomass in the South provide some relief? William Batchelor certainly believes so.
“A bit over a third of the world's population is beginning to be unlocked in terms of diet,” said the head of the Mississippi State University Agricultural and Biological Engineering Department at the LSU AgCenter-sponsored AgOutlook 2008 Conference in Monroe, La., on Feb. 26. “We're beginning to reach a breaking point between food and energy on our agricultural lands.”
One thing that could help push that breaking point further into the future is the “vast amount of woody, biomass resources.” There are three main areas researchers are looking at to convert woody biomass to energy for profit.
Cellulosic ethanol: “This is the one you hear about (on TV networks) and is the U.S. Department of Energy's (DOE) chosen pathway to convert woody biomass to ethanol, a transportation fuel. You take woody biomass and use enzymes to deteriorate the cell wall. The sugars within the cells are then released into a stream that can be fermented and turned into ethanol.”
While technology already exists to make such fuel, it is expensive and needs further refining.
“The DOE has chosen to dump lots and lots of money into this over the next couple of years. Last year, they funded about $300 million in projects called ‘genomics to life.’ They want to understand how to break down the cell walls and drive down the cost of the enzyme technology.”
There's a lot of “high hope and expectations” that eventually 200 bio-refineries will be found around the country. In order to reach government mandates, said Batchelor, all would bring in biomass, convert it to ethanol and then pump that into the transportation fuel network.
Fast pyrolysis: This is another technique to convert woody biomass into an oil — a bio-oil. The process requires biomass to be heated at 500 to 600 Celsius, under no oxygen, before it liquefies.
“The advantage is it can be produced in existing petroleum refineries. We, the public, have already made the investment in the huge infrastructure that supplies our transportation fuel.
“To me, the disadvantage of cellulosic ethanol is the model currently requires the development of about 200 bio-refineries that would compete with petroleum refineries, which are currently sitting on a lot of cash. (The petroleum industry) can probably knock the knees out from under (competing bio-refineries) any time they want to.”
Syngas: A third conversion technology — synthesis gas — has been around for decades. It was developed in the 1930s during WWII when Hitler realized he wouldn't have unlimited petroleum supplies to fight the war.
“Basically, you burn the biomass and capture the gas stream that comes off…The exhaust can be converted to transportation fuel.”
The top research priority for Batchelor and colleagues is to make bio-oil from woody biomass. Their second priority is to make gasoline from synthesis gas.
When creating bio-oil, the team currently makes use of a pyrolysis reactor, a mobile unit that can be put on a trailer. The trailer can be pulled to the site where biomass is being harvested.
“That begins to eliminate the 50-mile radius hauling (restriction that is commonly cited). This is a business model we believe will be very fruitful in the Southeast. It will allow more Mom-and-Pop companies making bio-oil, circulating dollars in rural economies where jobs are needed.”
While mobile reactors can go where needed — including disaster areas where they could help with recovery efforts — Batchelor envisions regional reactors, as well. “The regional reactors could be tied to an area where there are several pulp and paper companies in a tight radius.”
Bio-oils can be produced from many different types of biomass. Anything that contains lignin can be converted into bio-oil. Feedstock can include perennial grasses like switchgrass, elephant grass, sorghum-sudan grass, giant miscanthus, cotton gin trash, and kenaf.
“When you think about cotton gin trash, you see the pile and think there's an awful lot available. But when you calculate the tons and converting it to barrels of bio-oil going into a refinery, there really isn't a lot of it.”
A typical bio-oil may contain more than 200 chemical compounds. The unique thing about it is the molecules can be rearranged to make petroleum products.
“Bio-oil has about 50 percent of the energy content of petroleum — anywhere from 7,500 to 8,000 Btu per pound. That translates to about 75,500 to 80,000 Btu per gallon compared to home heating oil of 130,000 Btu per gallon. Bio-oil is (economically) competitive when oil is anywhere from $50 to $80 per barrel.”
How many biomass tons are required to produce a barrel?
“There's about a 50 to 60 percent weight conversion. So a ton of biomass will produce about a half-ton of bio-oil. That's on a dry basis.”
When making bio-oil, “you can't immediately send it to Conoco or Shell and have them turn it into gasoline. It needs some upgrade.
“Part of the debate in our circle is who should upgrade the bio-oil? Should it be upgraded at the source? Or, if it can be transported and moved fast enough, do you let the refineries upgrade it? We're in discussion with several refineries on that very issue.”
Bio-oil isn't without problems:
High acidity (2.2 to 3.0). “It'll rust things quickly. You can actually inject it into a diesel engine but it would corrode it.”
Pungent odor. “For those of you that have been around 100 percent bio-diesel tractors that smell like McDonald's fries — that isn't how it would smell running on bio-oil.”
Lower energy density.
The fact that bio-oil can be refined in existing infrastructure “is a big key going forward and will be part of the national debate over the next couple of years. How much is the U.S. public willing to invest in an independent bio-refinery industry?”
The estimated cost of building a single bio-refinery is between $100 million and $200 million. That will mean huge investments by taxpayers.
“A lot of these companies may very well be built on our backs. Already, several bio-refineries have been funded at $50 million each.”
Batchelor says such comments aren't “very popular…in DOE circles. They're placing all their bets on developing an entirely new industry that will be competitive with the existing petroleum refinery industry.”
Until it was cancelled around 2003, the DOE had a long-running bio-oil program. “They were the experts. Then, they began putting a lot of bets on ethanol and redirected a lot of that research.”
Meanwhile, “the petroleum companies, in my opinion, have become concerned there may be a mandate for 10 or 20 percent renewable transportation fuel. They've gotten serious about looking at what kind of transportation fuel would best fit their industry model and impact their bottom line.”
Recently, in a bid to further bio-oil research, ConocoPhillips pledged some $21 million to Iowa State University.
“Interestingly, as we've spoken with petroleum companies, the question comes up: will Exxon and BP begin buying a lot of forestland? I think the answer is no. They've no idea how to move biomass around. They know how to move liquids in an economic fashion.”
The big question now is how to move the entire industry “a step forward to some pilot scale where petroleum (industry researchers) can get their hands on barrels of bio-oil and begin playing around with reactions and figure out how to refine it.”
Syngas is a nasty thing to work with. “Syngas contains a lot of carbon dioxide — you can't breathe this stuff — and hydrogen resulting from burning biomass. That burning process is called gasification.”
Gasifiers can be bought from various companies around the world. The one used by MSU researchers was designed to burn biomass in tribal areas of Africa. It's totally automated — biomass is placed in a hopper then burned. The resulting syngas is used to run a generator allowing the tribes to have electricity.
The feedstock for the gasifier is mostly pellets or small wood chips. “We've been working on also using switchgrass and other biomass — gin trash, for instance — and making pellets to be burned in the gasifier. We want to understand the differences in chemical composition and energy content.
“You can make an awful lot of things out of syngas. The molecules can be rearranged to produce all sorts of different chemical compounds. Methanol is one of the intermediate products from converting it to gasoline.
“We've developed a method to convert it directly into high-octane gasoline. Others have successfully converted syngas into higher-level alcohols. Some of the deep thinkers think that's the more advantageous routes to take.”
Syngas can be injected into an engine as a substitute for petroleum fuel.
“We have a 5-kilowatt home generator we bought that ran on propane. Now, we run it on 100 percent syngas. As we produce syngas, we pull off part and run it into the generator and generate electricity.”
Syngas can also be converted into ethanol through a fermentation process. However, the conversion rate is very low.
“We've been down that path at MSU and have about given up on it. The microbes take the carbon dioxide, pull the carbon out and convert it to ethanol. But the microbes aren't very efficient.”
What's the best feedstock when working with syngas?
“A lot of that depends on the feeding mechanism. There are several on the market. Ours is a downdraft gasifier that works very well with pellets or chips. There are fluidized bed gasifiers that work better with sawdust.”