Cellulosic Biofuel: “No Eureka Moments” – Greenwire

by Marlo Lewis on July 14, 2011

in Blog, Features

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Yesterday’s edition of Greenwire features an amazing column on cellulosic biofuels by reporter Paul Voosen. It’s got interviews with leading researchers, industrial history going back to WWII, science, economics, and the narrative suspense of a detective story.

Voosen’s main point: Despite substantial private and public investment, there have been “no Eureka moments” in the “long U.S. campaign” to scale up Nature’s digestive processes (found in fungi and the guts of termites, cows, dung beetles, and other fauna) to break down cellulose and create affordable alcohol fuels from prairie grasses, wood wastes, and other fibrous plant materials.

I’ll share some highlights from the article (subscription required) in a moment. First a few words about the policy context.

The fibrous material in plants is the most ubiquitous organic substance on the planet’s surface, and unlike corn and soybeans, the feed stocks for “conventional” or “first-generation” biofuel, cellulose is not a food crop. Thus, in principle, cellulosic biofuel could end oil’s dominance as a transportation fuel without inflating food prices or imperiling the hungry as conventional biofuels do. Call it the Great Green Hope. 

In his 2006 State of the Union Address, President G.W. Bush prophesied that cellulosic biofuels would be “practical and competitive within six years.” In December 2007, Congress passed and Bush signed the Energy Independence and Security Act (EISA). EISA expanded the Renewable Fuel Standard (RFS) — a Soviet-style production-quota scheme — created by the 2005 Energy Policy Act. Whereas RFS1, as it came to be called, required 7.5 billion gallons of ethanol to be blended into gasoline by 2012, RFS2 required 9 billion gallons of biofuel to be blended in 2008 and 36 billion gallons in 2022. In addition, RFS2 established new categories of biofuel (“advanced” and “cellulosic”), setting production quota for each.

It’s now more than six years since Bush forecast the advent of “practical and competitive” cellulosic biofuel. And since Dec. 2007, industry has had the added inducement of a politically-mandated market for cellulosic biofuel. How accurate was Dubya’s prediction?

The EISA cellulosic biofuel target for 2010 was 100 million gallons. Because commercial-scale production failed to materialize, EPA downgraded the target to 6.5 million gallons, but even that symbolic goal proved to be too ambitious. In January 2011, Climatewire (subscription required) reported that “in the second half of 2010, not a drop of cellulosic ethanol — a much-touted fuel that taps the sugars from farm wastes and other non-food sources of biomass — was commercially blended with gasoline.” In November 2010, the Energy Information Administration (EIA) forecast that cellulosic biofuel production in 2011 would max out at 3.94 million gallons – about 1.6% of that year’s 250 million gallon EISA target. In June 2011, EPA said it expected to require the blending of between 3.45 million and 12.9 million gallons of cellulosic biofuel in 2012 (Greenwire, June 22, 2011). That works out to between 0.69% and 2.5% of EISA’s 500 million gallon cellulosic target for 2012. 

Here’s the big picture. In 2010, the USA consumed 138.6 billion gallons of gasoline. So even if EPA requires and industry blends 12.9 million gallons in 2012, cellulosic biofuel would displace less than 0.01% of current U.S. gasoline consumption.

What physical and economic factors account for the vast gulf between where cellulosic is today and the scale at which it would have to produced and sold to “set America free” from reliance on oil? Voosen’s article provides the most complete explanation I’ve seen. Herewith a few highlights:

Cellulose is difficult to break down into the simple sugars required for fermentation into alcohol fuels. Millions of years of evolutionary struggle have engineered plant fibers to be tough.

For eons, plants have locked the sun’s energy into complex strands of sugar, used to build their stems and leaves. These chains are far different from table sugar or grain starch; they cling together, providing the meat of tree trunks and cotton strands. They are the most abundant organic material on the planet, and one of the most hunted.

As long as plants have built up these complex sugars, life in all its forms, from microbes to mastodons, has sought ways to unleash that energy. Since plants can’t run, and live for hundreds of years, they have built remarkable defenses, wrapping their cellulose, as the sugars are called, in a sort of barbed wire that, to this day, defies human degradation.

Research on cellulose-digesting enzymes began during WWII. In the Pacific theater, jungle rot was destroying boots, sand bags, and tarps. Harvard mycologist Lawrence White commenced research on the fungus, QM6a, to unlock its digestive secrets. Scientists have been working on it ever since. 

Growing QM6a on heavy cotton fabrics to test its strength, military scientists soon found the fungus, a variety of Trichoderma, produced the proteins needed to tear apart plant walls with a single-minded intensity. Two of these scientists, Elwyn Reese and Mary Mandels, made study of QM6 their lives’ work.

Mandels created a mutant of QM6, now named Trichoderma reesei, that produced four times the typical amount of degrading proteins, and hopes rose that the mutant would soon unlock a source of nearly unlimited sugars from agricultural waste and trees.

The year was 1982.

Thirty years on, T. reesei remains the source of nearly all the industrial proteins — enzymes — used to break down plant walls, mostly in the paper business. One of the first studies JGI [Joint Genome Institute] undertook was to sequence its genome. By exploring its DNA, they hoped to identify a bounty of enzymes. What they discovered was a very simple genome, with limited variety, said Jim Bristow, the institute’s deputy director.

It was disappointing. “We assumed it would be a gold mine,” he said.

Scientists have also tried — so far without success — to scale up the bacteria-based enzymes some animals use to break down cellulose. A lot of research has therefore gone into finding solvents that could “reduce the sheer amount of enzymes needed to transmute grass into simple sugars.”

For decades, one solvent after another has failed. High temperatures and harsh acids could work, but such processes, common in the paper industry, are expensive and energy intensive.

“People have been going crazy,” [Seema] Singh [of DOE’s Joint BioEnergy Institute – JBEI] said. “Is there anything that can dissolve it?”

JBEI believes the answer lies in ionic liquids, “salts that remain fluid at room temperature rather than crystallizing into the familiar table seasoning,” Voosen reports. JBEI’s solvents can remove 80% of the substance — lignin — that stiffens plant tissues and binds cellulose molecules to other molecules in plants. However . . .

The problem is far from solved. The 20 percent of lignin that remains hooked onto the sugars still fights the good fight, inhibiting enzymes and slowing down what should be an hour-long process to eight hours. That is far from fast enough for the cut-rate margins of the fuel business. The lignin is holding its ground.

UC Berkeley’s Energy Bioscences Institute (EBI), funded by a $500 million grant from BP PLC, is engineering strains of yeast that feed on all glucose in plant matter, including the sugar locked up in cellulose. Using this process, BP has begun a commercial-scale project. The company broke ground this year on its first cellulosic ethanol refinery. Located in Highlands Country, Fla., the “facility will produce 35 million gallons of cellulosic ethanol a year beginning in 2013, BP says.” But . . .

Even this new yeast strain, which eliminates a whole step and cuts enzyme costs by a third, won’t make BP’s Florida plant profitable. BP has accepted that it will lose money on the biorefinery, which is “almost certainly not going to work well,” [EBI Director Chris] Somerville said. And it will be expensive.

“They’re putting down $400 million for only 35 million gallons a year of capacity,” Somerville said. “Let’s call that $10 per annual gallon. That’s about two to three times as high as the corn ethanol guys.”

Genetic sequencing has identified genomes previously unknown to science, vastly expanding the sheer number of cellulose-digesting enzymes scientists can test. However, this is no guarantee that any enzyme from animal guts or fungi can produce alcohols on an industrial scale.

There are limits to where this genetic prospecting can go.

Imagine a fungus on a log. It digests the log only as quickly as it can use the sugars, and no faster. It wants to sustain itself, not the whole forest, said John Grate, the chief science officer of Codexis, a bioengineering firm that specializes in evolving known enzymes.

“The rotting log in a forest is not an industrial environment,” he said. “A termite’s gut is not an industrial environment. Natural evolution does not get you what industrialized mankind needs.”

Greg Veerman July 15, 2011 at 8:14 am


I really appreciate this post and Mr. Voosen’s research — but I’m kind of blown away at what’s missing here. Your piece, along with the extracts from Greenwire, focus on technological approaches to breaking down cellulose, enzymes in particular. It’s a fascinating subject. I work with a handful of the pioneers in this space and have to tell you they’re way, way farther ahead in the performance of their biotechnology than you suggest. Check out this demonstration video (full disclosure: my shop produced it) and I think you’ll get the picture:


Enzymatic hydrolysis has been a huge barrier mainly because of the economics — historically it’s taken a lot of enzymes (at a cost-prohibitive level) to hydrolyze cellulose into simple sugars that can be fermented into alcohol. In the last two years those barriers have been obliterated and the industry is abuzz with new excitement over it. From an enzyme standpoint, contrary to your post and Mr. Voosen’s research, the technology is ready and continues to get better in term of efficiency, yield and cost — literally every 12 months or so.

Important factors beyond enzyme technology have slowed the production of cellulosic ethanol — economics and logistics of biomass production, collection and distribution and the biggest: how do you grow it, how to you collect and store it, and what will people pay for it? Those issues are tough but are being worked out. Plus it costs enormous sums of money to move an industry from the lab to full-scale commercial production. And we’re coming out of the biggest financial crisis since the Depression. Could that be the focus of a follow-up post?

Meanwhile, one full-scale cellulosic biorefinery has become a case study: Inbicon (www.inbicon.com) is using wheat straw to produce and distribute 100% cellulosic biofuel to 98 gas stations in Denmark.

Yes, the industry is behind schedule, but much of the science — especially the enzyme technology — is more than ready, and that to me is a “Eureka” worth getting excited about. Thanks and keep cooking!

polistra July 15, 2011 at 8:30 pm

There’s an easier way to get energy out of cellulose. Raise it to a high enough temperature, and it will spontaneously oxidize, releasing far more energy than the initial input. I’m not sure if scientists have investigated this yet. Perhaps they could start with the somewhat speculative ideas reported here:


After a hundred years of intensive development, perhaps they could turn this sci-fi blue-sky concept into a useful way of producing mechanical motion.

Guthrum July 20, 2011 at 10:28 am

I will buy a “green” car (electric, hydrogen, solar, whatever) if the government (Federal or state) promises to not place any taxes on its operation such as the exorbitant gas tax that we pay now. No mileage fees, battery recycling fees on electric vehicles, no hydrogen tax, no solar panel fees. And since a green car has no pollution, there will be no phony emissions inspection which only lines the pockets of politicians. If the government would do this, you would see the development and sales of green cars go out the roof. To help repay the “trust” fund for highway maintenance, the President would have to park Air Force 1 and take a “green” bus or commercial jet on his trips. This would get the working citizens out of the greedy hands of Arabian oil and Chavez, the big oil companies, and the government. The government needs to quit trying to run the car companies (The Obama appointed GM president wants to raise gas taxes). Let the car people do what they do best and you will see real “green” car development

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