Cellulosic Ethanol

Ethanol Pace Car
The pace car for the 2008 Indianapolis 500 ran
on E85; the race cars burned 100% ethanol fuel.

Last month, for the first time in history, the cars racing in the Indianapolis 500 were fueled by pure ethanol. This should put to rest any concerns about ethanol lacking sufficient energy density to function as a motor fuel.

While the absolute amount of energy contained in ethanol is somewhat lower than gasoline – about 76,000 BTUs per gallon for ethanol compared to about 116,000 BTUs per gallon of gasoline – ethanol has higher octane, generally speaking 110 or more vs. 90 or less, allowing ethanol to run in higher compression, higher efficiency engines. A car optimized to run on ethanol can get comparable mileage to a car optimized to run on gasoline.

There are other concerns about ethanol, for example, the notion that it takes more energy to manufacture ethanol than the energy value of the fuel itself, the suggestion that it isn’t “carbon neutral” after all, and the whopper, the accusation that ethanol production has taken food crops out of production. All of these concerns have some validity, but are shrouded in complexities that defy simple characterizations or easy conclusions. Yet that is what has happened. A few years ago, biofuel in general, and ethanol in particular, could do no wrong. Today the situation is reversed, and around the world, for the most part the powerful media and environmentalist communities have turned on biofuel.

In many respects this awakening is healthy – when mandatory carbon offset trading in the European Community was subsidizing rainforest destruction in southeast asia to make way for oil palm plantations, something was clearly out of whack. But corn ethanol in the USA has drawn the most visible criticisms. California’s Air Resources Board, struggling to implement a lower carbon fuel standard, has recently determined, perhaps correctly, that hauling tank cars by rail over the Rocky Mountains from Iowa to the west coast probably eliminates any carbon neutrality ethanol may have otherwise enjoyed. In Washington D.C., the political backlash continues to build against the subsidies corn ethanol receives, with increasing urgency due to the global food shortages that are allegedly exacerbated by dedicating so much acreage to corn for ethanol.

Corn Field for Ethanol
In the USA, 10 billion gallons of corn ethanol
will be produced annually within a few years.

There are many responses to these concerns, however. When producing ethanol from Brazilian sugar cane, for example, the energy payback can go as high as 8 to 1. In the case of corn ethanol, most analysts put the payback around 1.5 to 1, and at a margin that thin, there is plenty of room for interpretation. But the analyses that claim corn ethanol’s energy payback is insufficient to justify its use as a fuel ignore the caloric value of the distiller’s grain, a byproduct of corn ethanol production.

Critics of corn ethanol subsidies ignore the value of keeping these dollars in the U.S. to reduce the trade deficit. Those environmentalists concerned about the growing “dead zone” caused by agricultural runoff, presumably destined to grow even faster as we turn more acreage to biofuel, are certainly justified. But it is disingenuous to suggest that because we are distilling corn instead of harvesting grain there is somehow a more urgent problem than before. The dead zone in the Gulf of Mexico needs to be cleaned up. Agricultural runoff is an environmental challenge that awaits cost effective solutions – with or without the reality of biofuel.

The most problematic challenge to corn ethanol undoubtedly comes from those who are concerned it is causing rising food prices. But here again there are many significant factors that in aggregate eclipse the impact of corn ethanol, possibly by orders of magnitude. Rising per capita income in Asia and elsewhere has caused increased consumption of meat products, and livestock requires grain. Estimates vary, but for every calorie of meat consumed, about eight calories of grain have to be grown and fed to the livestock. This phenomenon has caused global demand for grain to grow far faster than it would already be growing due to increasing human population. At the same time, there have been temporary but severe setbacks to global grain output – a drought in Australia, flooding in the American mid-west. If that weren’t enough, commodities speculators have hedged themselves against devaluing dollars and falling asset values in stocks and real estate by purchasing commodities futures – driving prices up more than the forces of normal supply and demand already have.

Ethanol proponents have answered the critics in a variety of ways. The “25×25 Alliance,” an industry group committed to the goal of the USA producing 25% of its energy from renewable sources by 2025, has issued “sustainability principles” for biofuel production. The National Corn Growers Association has compiled a great deal of data in an attempt to debunk the position that corn ethanol is the primary cause of worldwide food shortages and commodity price increases. Automakers are caught in the middle – a powerful environmental lobby demands cars capable of being fueled with alternatives to gasoline, then savagely turns on corn ethanol, despite the fact it is the only motor fuel alternative we’ve got that we can produce in meaningful quantities today.

In any event, corn ethanol isn’t the ultimate solution to biofuel supplies, it is only a transitional fuel. This crucial point is often lost amid the controversy surrounding corn ethanol. It is cellulosic ethanol that has the potential to completely replace petroleum based fuel, and when cellulosic ethanol begins to arrive in high volume, a preexisting ethanol infrastructure – cars that run on ethanol, fueling stations that sell ethanol, and a transportation network to deliver ethanol to retailers – will need to be in place. Corn ethanol is priming the pump for the arrival of cellulosic ethanol.

Within the next few years corn ethanol production in the United States is predicted to top 10 billion gallons. This is not a trivial amount of fuel, given the entire light vehicle fleet in the USA consumes only 15 times that amount. Corn ethanol has already reduced the demand for foreign oil for light vehicle use by about 6.5%. Nonetheless, critics who claim corn ethanol production cannot possibly increase enough to replace petroleum are correct. The math of these critics is elegant – 10 billion gallons of corn ethanol, at 2.8 gallons per bushel and 155 bushels per acre equates to 23 million acres, about 7% of America’s active farm acreage. If you use corn ethanol to service 100% of America’s fuel requirements for light vehicles, you use 100% of America’s farmland.

Once again, however, this math is missing the point. Corn ethanol, distilled from corn mash, is not the end of biofuel, it is just the beginning of biofuel. Even the impressive global production of ethanol from sugar cane is easily eclipsed by the potential of cellulosic extraction. So what is cellulosic ethanol, where does it come from, how can it be produced, and how long will it be before meaningful quantities of this fuel arrive at the corner filling station?

One of the most visible and visionary proponents of biofuel is the noted venture capitalist Vinod Khosla, who early in his career was one of the four co-founders of Sun Microsystems, and has parlayed this spectacular victory into an impressive portfolio of investments in private sector companies. Over the past few years Khosla Ventures has invested in dozens of clean technology and sustainable energy companies, including several top tier biofuel ventures, including Coskata and Mascoma, mentioned later in this report. In a recent research paper written by Vinod Khosla entitled “Where will Biofuels and Biomass Feedstocks Come From ,” Khosla identifies and quantifies the many potential sources of cellulosic feedstock for ethanol fuel. Some of the information on the table below borrows from Khosla’s research, but changes some of the assumptions; other data comes from the U.S. Dept. of Energy.

Ethanol Feedstock Chart
At least 1.0 billion tons of ethanol feedstock can be
sustainably harvested each year in the United States.

The figures on this table are arguably realistic, not optimistic, based on the following assumptions for each feedstock:

Dedicated land use refers to cellulosic crops, such as miscanthus or switchgrass, planted on 5% of American farmland (total US farmland is estimated currently at 317 million acres), less than is currently planted for corn ethanol production. At a yield of 15 tons of cellulosic feedstock per acre and 100 gallons of ethanol per ton of feedstock, nearly 24 billion gallons of ethanol can be produced each year. While 15 tons of feedstock per acre is more than can currently be grown, it is considerably lower than forecasts of yields expected within the next couple of decades, which range as high as 25 tons per acre.

Winter cover crops would not displace existing farmland, and if they were profitable to grow it isn’t unlikely they could become additional income for farmers on 25% of land already under summer cultivation. At a yield of 3 tons per acre – projections go as high as 5 tons per acre – another nearly 24 billion gallons of ethanol can be produced each year.

Redwood Trees
California’s Redwoods. Forest thinning could help
prevent catastrophic fires, reduce infestations,
and provide hundreds of millions of tons of cellulose.

Excess forest biomass is a difficult number to calculate, but when one considers there are about 750 million acres of forest in the USA (ref. Forest Resources of the United States), as well as the fact nearly all of them have become dangerously overgrown (major factors in more catastrophic fires and beetle infestations, ref. Restoration Forestry), the figure we’ve used of 226 million tons per year is probably quite low. It would suggest a growth in forest mass of less than one-third of a ton per acre per year. And in our estimate, even the figure of 226 million tons is only assumed to be 70% utilized. Forest thinning is a form of stewardship long overdue, it will return America’s forests to their healthier historical densities, and their excess mass will power our engines instead of burn in forest fires.

Construction debris and municipal solid waste are obvious candidates for cellulosic harvesting, and even the non-cellulosic materials can be used as fuel for the extraction of syngas (which is converted into ethanol), or reclaimed as building materials. According to the Dept. of Energy, 325 million tons of these waste resources are produced each year. We have assumed 90% utilization, and only 75 gallons of ethanol per ton, a yield that is below most projections.

Other waste resources are deliberately understated – just our industrial emissions are probably sufficient to deliver 100 million tons of feedstock. Also not included in this analysis anywhere else are crop residue, a huge source of feedstocks, some percentage of which can certainly be allocated sustainably to ethanol production without sacrificing soil health.

It isn’t easy to estimate just how much cellulosic feedstock could be sustainably harvested each year in the USA, but but two things are clear from this analysis. (1) When cellulosic ethanol extraction becomes a commercially competitive process, and the industrial capacity is in place to produce high volumes of ethanol from cellulosic materials, there will be plenty of feedstocks – at least 1.0 billion tons per year; possibly twice that. Cellulosic ethanol definitely has the potential to become a significant source of transportation fuel, and (2) Khosla’s contention that land use dedicated to ethanol production in the USA might actually decrease when cellulosic processing takes over is completely plausible. In the example above, no corn ethanol was produced, and the dedicated acreage committed to cellulosic ethanol was assumed to be 5% of America’s farmland, whereas today corn ethanol is grown on about 7% of America’s farmland.

So how will we convert cellulosic material into ethanol? There are hundreds of companies around the world working on ways to accomplish this, using a variety of technological approaches. Last month, while on a General Motors sponsored tour for automotive journalists, I had the opportunity to visit two companies who are pursuing promising, and very different, solutions to the cellulosic ethanol puzzle.

Our trip began in Chicago on the morning of May 21st, where about a dozen journalists assembled to drive a convoy of GM vehicles, all equipped to run on E85 ethanol. In a completely unexpected turn of events, I found myself behind the wheel in a high riding Chevy Silverado, painted with GM colors that announced to the world the truck’s status as an ethanol fueled vehicle, with extended cab and a monstrous bed. Although I was unaccustomed to piloting such a behemoth, there was excellent road visibility from the cab, and GM’s OnStar tracked my position and provided constant audio directions, so I swung into downtown Chicago traffic, and joined the late morning rush out of town. At one point it was clear we needed to move across a couple of lanes to catch our exit, and to make sure we would safely execute this maneuver amidst the 18 wheelers and such, I found it appropriate to smash the gas pedal to the floor and hold it there. The tactic was brilliantly successful, as this gigantic truck leapt forward with impressive accelleration and increased our speed from 45 to 75 in a matter of seconds. Safely in our place on the correct route, I let off the accelerator and knew the power of corn.

Bill Roe, Richard Wagoner, and Vinod Khosla
Coskata CEO Bill Roe and General Motors
Chairman Richard Wagoner seal the deal, as
early Coskata investor Vinod Khosla looks on.

About 40 miles west of Chicago, in Warrenville, Illinois, are the labs of Coskata, a company that is contending to be the first to commercialize production of cellulosic ethanol.

In February 2008 General Motors invested an undisclosed sum in this three year old private company, whose CEO, Bill Roe, stated “we do not believe we have any remaining technological hurdles.” Coskata is betting on this with a pilot plant they are building in Madison, Pennsylvania, near Pittsburgh. They expect to have this plant operating early in 2009, producing 40,000 gallons of fuel per year. GM intends to use the fuel to test their growing fleet of E85 flexfuel vehicles.

Coskata’s technology for extracting ethanol from cellulose is elaborate, but apparently closer to commercialization than competing processes. Whether or not Coskata’s technology ultimately dominates is harder to assess, but according to Roe, the variable costs to produce a gallon of ethanol using their technology is expected to be under $1.00 per gallon. Here’s how Coskata intends to produce ethanol:

In the diagram below, “Coskata’s Manufacturing Process,” there are three primary steps. First the feedstock is shredded and dried, and fed into the gasifier, where it is reduced to syngas at a temperature of 5,000 degrees. Some of the syngas is used to provide the energy for the conversion process, but about 85% of the syngas is converted into ethanol in step two. A recent study by Argonne National Labs estimates Coskata’s process yields an energy payback of about 8 to 1.

The second step is to feed the syngas into a bioreactor, where microbes eat the syngas and excrete ethanol. These microbes are anerobic, meaning they can’t survive in atmosphere, and they are the result of careful selective breeding whereby they are now 100 times more efficient converting syngas into ethanol than they were when they began the process a few years ago. “We know our microbes can convert syngas to ethanol at commercial quantities, cost effectively,” said Roe.

The final step in the process is to feed the ethanol and water out of the bioreactor into a recovery tank, where the ethanol is extracted and the water is recycled back into the bioreactor.

From the look of things during our visit to Coskata’s lab in Warrenville, about the only bugs left in their process are the bugs in the bioreactor. According to Wes Bolson, Coskata’s Chief Marketing Officer, the company is actively seeking partners among the companies who have access to huge quantities of cellulosic feedstock, and currently have nothing they can do with it. These candidates include timber companies, sugar cane refiners, pulp and paper mills, and waste management companies. Coskata can also partner with companies who already are generating syngas, but haven’t got the bioreactor technology.

Diagram of Coskata's Manufacturing Process
Coskata executives believe their technology is ready today.

After spending a half-day at Coskata, our corn fueled convoy got back on the highway and headed south to Indianapolis, driving most of the way on southbound Interstate 65. And as our expedition hurtled through America’s heartland on this beautiful afternoon, as far as the eye could see, across the rain watered endless fertile fields of Indiana sprouted new shoots of spring corn.

If you are within blocks, long blocks, of the Indianapolis Motor Speedway, during the last full week in May, you will likely hear the roar of the engines. And as we neared the track on the morning of May 22nd, we too heard and felt the sound as the drivers did qualifying laps in advance of the 92nd running of the Indianapolis 500. In a thankfully soundproof auditorium on the massive infield of the racetrack, we attended an ethanol summit co-sponsored by GM, where I had an opportunity to meet Dr. Mike Ladisch, Chief Technical Officer of Mascoma. This company, like Coskata, is hot on the trail of commercializing cellulosic ethanol production, but they are pursuing a solution that will not rely on high temperature gasification. Instead, Mascoma is developing a biochemical method to convert cellulose into ethanol. Ladisch, a genial scientist who has taken a leave of absence from Purdue to serve as CTO at Mascoma, was understandably guarded about his company’s technology, but characterized it in the following way:

“The work at Mascoma is based on organisms and processes designed to rapidly break down the components of biomass, convert a range of sugars and polymers of sugars to ethanol, and thrive in a manufacturing environment.”

Mascoma intends to do this in one step using genetically engineered microbes that are capable of performing both processes. This is known as consolidated bioprocessing, or CBP, and perhaps represents the ultimate technology to extract ethanol from cellulose.

Another informed opinion on Mascoma (and cellulosic technology in general) was obtained via email from Dr. Lee Lynd, a professor at Dartmouth who, along with Ladisch, is one of the leading scientists in the world pursuing advanced cellulosic technologies. Here is what he wrote:

“Mascoma has the largest and most focused effort worldwide on consolidated bioprocessing, which I consider to be the ultimate low-cost conversion strategy. If Mascoma is able to continue this aggressive effort, I believe that they will succeed and that they will have the lowest cost technology for converting herbaceous and woody angiosperms (e.g. grass and hardwoods) to ethanol and other biofuels. It is less clear that the Mascoma approach will be best for gymnosperms (softwoods), and this could be a long-term niche for thermochemical processing along with processing residues from biological processing. Mascoma’s business strategy features a ‘staircase’ of process configurations, starting with options that can be commercially implemented very soon and progressing ultimately to CBP.”

How soon will Mascoma and others deploy these technologies? Although Mascoma’s website has an excellent description of the various cellulosic technologies (ref. Consolidated Bioprocessing), exactly when they expect their technology to be ready for commercialization appears to be a closely guarded secret. Other observers, off the record, have stated commercially viable enzymatic processing is 5-10 years away. But advances in biotechnology are happening at a staggering pace, and unforeseen breakthroughs are not something to bet against. On the other hand, even if Coskata, Mascoma, and countless other credible contenders to deliver commercially competitive cellulosic ethanol technologies were all ready tomorrow, it will still take years to build the new refineries and transform America’s light vehicle fleet.

In the meantime, corn carries the weight of being the primary source of ethanol in the USA, as the rest of the infrastructure falls into place. There are already 1,600 ethanol stations in the U.S. – about 1% of all gasoline retailers – and with UL certification imminent the big box chains are going to begin offering ethanol fuel, greatly increasing access. General Motors now offers 15 models of flexfuel vehicles; and they are now producing over 1.0 million of them per year. Other automakers are following suit. All over the world, governments are determining what percentages of ethanol fuel – along with other biofuels, biodiesel in particular – to blend into their transportation fuels.

How long can corn carry the weight of this growth, serving as the transitional feedstock? How soon can hybrids and extended range electric vehicles level off or even reduce the demand for transportation fuel? There is little doubt ethanol is a viable fuel for light vehicles, and there is little doubt cellulosic ethanol feedstocks exist in sufficient sustainable abundance to greatly offset petroleum consumption. Finally, there is little doubt that money and support for cellulosic ethanol commercialization is ongoing; from Washington DC to Detroit to the Silicon Valley, everyone is on board. The uncertainty lies in whether or not the new technologies to extract ethanol from cellulose will emerge in months or decades, and in how fast we can build large scale industrial capacity to exploit these new technologies. Look to pilot plants in Madison, Pennsylvania, and elsewhere, for early indications of what may come, and when.

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One Response to “Cellulosic Ethanol”
  1. Dave Ode says:

    My compliments to author Ed Ring. This is one of the best summaries I’ve read on this issue.


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