Grassoline at the Pump

Scientists are turning agricultural leftovers,
wood and fast-growing grasses into a huge variety
of biofuels- even jet fuel. But before these
next-generation biofuels go mainstream, they have to compete with oil at $60 a barrel

> By George W. Huber and Bruce E. Dale
> Scientific American
> July 2009
> | Key Concepts
> | Second-generation biofuels made from the inedible parts of plants
> | are the most environmentally friendly and technologically promising
> | near-term alternatives to oil.
> | Most of this "grassoline" will come from agricultural residues such
> | as cornstalks, weedlike energy crops and wood waste.
> | The U.S. can grow enough of these feedstocks to replace about half
> | the country's total consumption of oil without affecting food
> | supplies. - Scientific American Editors
> By now it ought to be clear that the U.S. must get off oil. We can no
> longer afford the dangers that our dependence on petroleum poses for
> our national security, our economic security or our environmental
> security. Yet civilization is not about to stop moving, and so we must
> invent a new way to power the world's transportation fleet. Cellulosic
> biofuels- liquid fuels made from inedible parts of plants-offer the
> most environmentally attractive and technologically feasible near-term
> alternative to oil.
> Biofuels can be made from anything that is, or ever was, a plant.
> First-generation biofuels derive from edible biomass, primarily corn
> and soybeans (in the
> U.S.) and sugarcane (in Brazil). They are the low- hanging fruits in a
> forest of possible biofuels, given that the technology to convert
> these feedstocks into fuels already exists (180 refineries currently
> process corn into ethanol in the U.S.). Yet first-generation biofuels
> are not a long- term solution. There is simply not enough available
> farmland to provide more than about 10 percent of developed countries'
> liquid-fuel needs with first-generation biofuels. The additional crop
> demand raises the price of animal feed and thus makes some food items
> more expensive- though not nearly as much as the media hysteria last
> year would indicate.
> And once the total emissions of growing, harvesting and processing
> corn are factored into the ledger, it becomes clear that
> first-generation biofuels are not as environmentally friendly as we
> would like them to be.
> Second-generation biofuels made from cellulosic material-colloquially,
> "grassoline"-can avoid these pitfalls. Grassoline can be made from
> dozens, if not hundreds, of sources: from wood residues such as
> sawdust and construction debris, to agricultural residues such as
> cornstalks and wheat straw, to "energy
> crops"-fast- growing grasses and woody materials that are grown
> expressly to serve as feedstocks for grassoline [see box on page 57].
> The feedstocks are cheap (about $10 to $40 per barrel of oil energy
> equivalent), abundant and do not interfere with food production. Most
> energy crops can grow on marginal lands that would not otherwise be
> used as farmland.
> Some, such as the short- rotation willow coppice, will decontaminate
> soil that has been polluted with wastewater or heavy metals as it
> grows.
> Huge amounts of cellulosic biomass can be sustainably harvested to
> produce fuel. According to a study by the U.S. Department of
> Agriculture and the Department of Energy, the U.S. can produce at
> least 1.3 billion dry tons of cellulosic biomass every year without
> decreasing the amount of biomass available for our food, animal feed
> or exports. This much biomass could produce more than 100 billion
> gallons of grassoline a
> year- about half the current annual consumption of gasoline and diesel
> in the U.S. [see bottom left graph on page 57]. Similar projections
> estimate that the global supply of cellulosic biomass has an energy
> content equivalent to between 34 billion to 160 billion barrels of oil
> a year, numbers that exceed the world's current annual consumption of
> 30 billion barrels of oil. Cellulosic biomass can also be converted to
> any type of fuel- ethanol, ordinary gasoline, diesel, even jet fuel.
> Scientists are still much better at fermenting corn kernels than they
> are at breaking down tough stalks of cellulose, but they have recently
> enjoyed an explosion of progress. Powerful tools such as
> quantum-chemical computational models allow chemical engineers to
> build structures that can control reactions at the atomic level.
> Research is done with an eye toward quickly scaling conversion
> technologies up to refinery scales.
> And although the field is still young, a number of demonstration
> plants are already online, and the first commercial refineries are
> scheduled for completion in 2011. The age of grassoline may soon be at
> hand.
> The Energy Lock
> Blame evolution. Nature designed cellulose to give structure to a
> plant. The material is made out of rigid scaffolds of interlocking
> molecules that provide support for vertical growth [see box on
> opposite page] and stubbornly resist biological breakdown. To release
> the energy inside it, scientists must first untangle the molecular
> knot that evolution has created.
> In general, this process involves first deconstructing the solid
> biomass into smaller molecules, then refining these products into
> fuels. Engineers generally classify deconstruction methods by
> temperature. The low- temperature method (50 to 200 degrees Celsius)
> produces sugars that can be fermented into ethanol and other fuels in
> much the same way that corn or sugar crops are now processed.
> Deconstruction at higher temperatures (300 to 600 degrees C) produces
> a biocrude, or bio-oil, that can be refined into gasoline or diesel.
> Extremely high temperature deconstruction (above 700 degrees C)
> produces gas that can be converted into liquid fuel.
> So far no one knows which approach will convert the maximum amount of
> the stored energy into liquid biofuels at the lowest costs. Perhaps
> different pathways will be needed for different cellulosic biomass
> materials. High- temperature processing might be best for wood, say,
> whereas low temperatures might work better for grasses.
> Hot Fuel
> The high-temperature syngas approach is the most technically developed
> way to generate biofuels. Syngas- a mixture of carbon monoxide and
> hydrogen-can be made from any carbon- containing material. It is
> typically transformed into diesel fuel, gasoline or ethanol through a
> process called Fischer-Tropsch synthesis (FTS), developed by German
> scientists in the 1920s.
> During World War II the Third Reich used FTS to create liquid fuel out
> of Germany's coal reserves. Most of the major oil companies still have
> a syngas conversion technology that they may introduce if gasoline
> becomes prohibitively expensive.
> The first step in creating a syngas is called gasification. Biomass is
> fed into a reactor and heated to temperatures above 700 degrees C. It
> is then mixed with steam or oxygen to produce a gas containing carbon
> monoxide, hydrogen gas and tars. The tars must be cleaned out and the
> gas compressed to 20 to 70 atmospheres of pressure. The compressed
> syngas then flows over a specially designed catalyst-a solid material
> that holds the individual reactant molecules and preferentially
> encourages particular chemical reactions. Syngas conversion catalysts
> have been developed by the petroleum chemistry primarily for
> converting natural gas and coal- derived syngas into fuels, but they
> work just as well for biomass.
> Although the technology is well understood, the reactors are
> expensive. An FTS plant built in Qatar in
> 2006 to convert natural gas into 34,000 barrels a day of liquid fuels
> cost $1.6 billion. If a biomass plant were to cost this much, it would
> have to consume around 5,000 tons of biomass a day, every day, for a
> period of
> 15 to 30 years to produce enough fuel to repay the investment.
> Because significant logistic and economic challenges exist with
> getting this amount of biomass to a single location, research in
> syngas technology focuses on ways to reduce the capital costs.
> Bio-Oil
> Eons of subterranean pressure and heat transformed Cambrian
> zooplankton and algae into present-day petroleum fields. A similar
> trick- on a much reduced timescale-could convert cellulosic biomass
> into a biocrude. In this scenario, a refinery heats up biomass to
> anywhere from 300 to 600 degrees C in an oxygen-free environment. The
> heat breaks the biomass down into a charcoal-like solid and the
> bio-oil, giving off some gas in the process. The bio-oil that is
> produced by this method is the cheapest liquid biofuel on the market
> today, perhaps $0.50 per gallon of gasoline energy equivalent (in
> addition to the cost of the raw biomass).
> The process can also be carried out in relatively small factories that
> are close to where biomass is harvested, thus limiting the expense of
> biomass transport.
> Unfortunately, this crude is highly acidic, is insoluble with
> petroleum- based fuels and contains only half the energy content of
> gasoline. Although you can burn biocrude directly in a diesel engine,
> you should attempt it only if you no longer have a need for the
> engine.
> Oil refineries could convert this biocrude into a usable fuel,
> however, and many companies are studying how they could adapt their
> existing hardware to the task. Some are already producing a different
> form of green diesel fuel, suggesting that refineries could handle
> cellulosic biocrude as well. At the moment, the facilities co-feed
> vegetable oils and animal fats with petroleum oil directly into their
> refinery.
> ConocoPhillips recently demonstrated this approach at a refinery in
> Borger, Tex., creating more than 12,000 gallons of biodiesel a day out
> of beef fat shipped from a nearby Tyson Foods slaughterhouse [see box
> on page 59].
> Researchers are also figuring out ways to carry out the two-stage
> process using the chemical engineering equivalent of one-pot cooking-
> converting the solid biomass to oil and then the oil into fuel inside
> a single reactor. One of us (Huber) and his colleagues are developing
> an approach called catalytic fast pyrolysis. The "fast" in the name
> comes from the initial heating- once biomass enters the reactor, it is
> cooked to 500 degrees C in a second, which breaks down the large
> molecules into smaller ones. Like eggs in an egg carton, these small
> molecules are now the perfect size and shape to fit into the surface
> of a catalyst.
> Once ensconced inside the catalyst's pores, the molecules go through a
> series of reactions that change them into gasoline-specifically, the
> high-value aromatic components of gasoline that increase the octane.
> (High-octane fuels allow engines to run at higher internal pressures,
> which increases efficiency.) The entire process takes just two to 10
> seconds.
> Already the start-up company Anellotech is attempting to scale up this
> process from the laboratory to the commercial level. It expects to
> have a commercial facility in operation by 2014.
> Sugar Solution
> The route that has attracted most of the public and private investment
> thus far relies on a more traditional mechanism-unlock the sugars in
> plants, then ferment these sugars into ethanol or other biofuels.
> Scientists have studied literally dozens of possible ways to break
> down the digestion-resistant cellulose and hemicellulose- the fibers
> that bind cellulose together inside the cells [see box on page 54]-to
> their constituent sugars. You can heat the biomass, irradiate it with
> gamma rays, grind it into a fine slurry, or subject it to
> high-temperature steam. You can douse it with concentrated acids or
> bases or bathe it in solvents. You can even genetically engineer
> microbes that will eat and degrade the cellulose.
> Unfortunately, many techniques that work in the lab have no chance of
> succeeding in commercial practice. To be commercially viable, the
> pretreatments must generate easily fermentable sugars at high yields
> and concentrations and be implemented with modest capital costs. They
> should not use toxic materials or require too much energy input to
> work. They must also be able to produce grassoline at a price that can
> compete with gasoline.
> The most promising approaches involve subjecting the biomass to
> extremes of pH and temperature. We are developing a strategy that uses
> ammonia-a strong base- in one of our laboratories (Dale's). In this
> ammonia fiber expansion (AFEX) process, cellulosic biomass is cooked
> at 100 degrees C with concentrated ammonia under pressure. When the
> pressure is released, the ammonia evaporates and is recycled.
> Subsequently, enzymes convert 90 percent or more of the treated
> cellulose and hemicellulose to sugars. The yield is so high in part
> because the approach minimizes the sugar degradation that often occurs
> in acidic or high-temperature environments.
> The AFEX process is "dry to dry": biomass starts as a mostly dry solid
> and is left dry after treatment, undiluted with water. It thus can
> provide large amounts of highly concentrated, high-proof ethanol.
> AFEX also has the potential to be very inexpensive: a recent economic
> analysis showed that, assuming biomass can be delivered to the plant
> for around $50 a ton, AFEX pretreatment, combined with an advanced
> fermentation process called consolidated bioprocessing, can produce
> cellulosic ethanol for approximately $1 per gallon of equivalent
> gasoline energy content, probably selling for less than $2 at the
> pump.
> The Cost of Change
> Cost, of course, will be the primary determinant of how fast the use
> of grassoline will grow. Its main competitor is petroleum, and the
> petroleum industry has been reaping the technological benefits of
> dedicated research programs for more than a century. Moreover, most
> petroleum refineries now in use have already paid off their initial
> capital costs; grassoline refineries will require investments of
> hundreds of millions of dollars, a cost that will have to be
> integrated into the price of the fuel it produces through the years.
> Grassoline, on the other hand, enjoys several major advantages over
> fuels from petroleum and other petroleum alternatives such as oil
> sands and liquefied coal. First, the raw feedstocks are far less
> expensive than raw crude, which should help keep costs down once the
> industry gets up and running. Grassoline will be domestically
> produced, with the national security benefits that confers. And it is
> far better for the environment than any fossil fuel-based alternative.
> In addition, new analytical tools and computer- modeling techniques
> will let researchers build better, more efficient biorefinery
> operations at a rate that would have been unattainable to petroleum
> engineers just a decade ago. We are gaining a deeper understanding of
> the properties of our raw feedstocks and the processes we can use to
> convert them into fuel at an ever increasing pace. The U.S.
> government's support for research into alternative forms of energy
> should help this process to accelerate even further.
> The stimulus bill signed into law by President Barack Obama earlier
> this year contained $800 million in funding for the Department of
> Energy's Biomass Program, which will accelerate advanced biofuels
> research and development and provide funding for commercial- scale
> biorefinery projects. In addition, the bill contained
> $6 billion in loan guarantees for "leading edge biofuel projects" that
> will commence construction by October 2011.
> Indeed, if the U.S. maintains its current commitment to biofuels, the
> logistical and conversion challenges the industry now faces should be
> readily overcome. Over the next five to 15 years, biomass conversion
> technologies will move from the laboratory to the market, and the
> number of vehicles powered by cellulosic biofuels will grow
> dramatically. This move toward grassoline can fundamentally change the
> world. It is a move that is now long overdue.
> | The Fat of the Matter
> | There is a new drive to make fuel off the fat of the land. In April,
> | High Plains Bioenergy opened a biorefinery next to a pork-processing
> | plant in Guymon, Okla. The refinery takes pork fat-an abundant, low-
> | value by-product of the industrial butchering process- and converts
> | it, along with vegetable oil, into biodiesel. The plant is expected
> | to turn 30 million pounds of lard into 30 million gallons of
> | biodiesel a year. In 2010 the High Plains facility will be joined by
> | a plant in Geismar, La., that will be run by Dynamic Fuels, a joint
> | venture between Tyson Foods and energy company Syntroleum.
> | That plant will use the fat from Tyson's beef, chicken and pork
> | operations to create 75 million gallons of biodiesel and jet fuel
> | annually.
> | Yet the biodiesel industry has been battered recently, with many
> | plants sitting idle for lack of demand. Low oil prices have made
> | petroleum-based diesel fuel less expensive than biodiesel, which in
> | the U.S. is typically made from soy and vegetable oils. A $1 per
> | gallon federal tax credit for biodiesel has helped soften the blow,
> | but that credit is set to expire at the end of the year. Some
> | manufacturers worry that if the credit disappears, so will their
> | business. Tyson had earlier partnered with ConocoPhillips to produce
> | biodiesel at an existing ConocoPhillips refinery in Borger, Tex. But
> | insecurity about the status of the tax break has put the project on
> | hold. - Scientific American Editors
> More To Explore
> Breaking the Chemical and Engineering Barriers to Lignocellulosic
> Biofuels. A research road map from the Biomass to Biofuels Workshop:
> Development of Cellulosic Biofuels. Video lecture given by Chris
> Somerville, director of the Energy Biosciences Institute at the
> University of California, Berkeley:
> U.S. Department of Energy Biomass Program Web site:
> _____________________________________________