Back to the Future Fuels

Stephen DeAngelis

March 02, 2010

In the sequel to the popular 1985 movie Back to the Future, the DeLorean automobile that was converted into a time machine was powered by the Mr. Fusion model fusion generator, which used garbage as fuel. The fusion generator was supposed to be a small nuclear reactor that used nuclear fusion to turn garbage into electrical energy to power the car. Although fusion remains an elusive source of power, the idea of turning garbage into fuel remains at the forefront of science and innovation. In a post entitled Changing Business Models in the Energy Sector, I discussed a company called BioFuelBox that collects waste from facilities such as meatpacking plants and sewage processors and converts it into biodiesel. Most people understand why and how a company can use oily waste material as feedstock for producing biodiesel fuel. Scientists, however, are now working on way of using a wide variety of waste materials to produce biofuel [“Cleaner, cheaper fuel from orange peels and newspaper,” by Darren Quick, Gizmag, 18 February 2010]. Quick reports:

“While it may not quite be the Mr. Fusion energy reactor Doc Brown uses to convert household scraps into power for his time-traveling DeLorean, scientists have found a way to turn discarded fruit peels, newspapers and other waste products into cheap fuel to power the world’s vehicles. Its developer says the new approach is greener and less expensive than the current methods available to run vehicles on cleaner fuel and is part of his goal to relegate gasoline to a secondary fuel. University of Central Florida professor Henry Daniell developed a technique with the U.S. Department of Agriculture that uses plant-derived enzyme cocktails to break down orange peels and other waste materials into sugar, which is then fermented into ethanol. The breakthrough can also be applied to several non-food products including sugarcane, switchgrass and straw.”

Quick explains why this new approach is revolutionary:

“Currently cornstarch is fermented and converted into ethanol, but ethanol derived from corn produces more greenhouse gas emissions than gasoline does. Daniell says ethanol created using his approach produces much lower greenhouse gas emissions than gasoline or electricity. There’s also an abundance of waste products that could be used without reducing the world’s food supply or driving up food prices – a common concern for deriving fuel from biomass. In Florida alone, discarded orange peels could create about 200 million gallons of ethanol each year, Daniell said. According to Daniell no company in the world can produce cellulosic ethanol – ethanol that comes from wood or the non-edible parts of plants.”

Quick notes that the “cocktail” of enzymes used to convert waste products into biofuel changes depending on the waste product being used as feedstock. He continues:

“Orange peels need more of the pectinase enzyme, while wood waste requires more of the xylanase enzyme. All of the enzymes Daniell’s team uses are found in nature, created by a range of microbial species, including bacteria and fungi. Daniell’s team cloned genes from wood-rotting fungi or bacteria and produced enzymes in tobacco plants. Tobacco was chosen as an ideal system for enzyme production because it is not a food crop and it produces large amounts of energy per acre. Producing these enzymes in tobacco instead of manufacturing synthetic versions could reduce the cost of production by a thousand times, which should significantly reduce the cost of making ethanol, Daniell said.”

I’m sure that tobacco growers are thrilled with Daniell’s research. It should be pointed out, however, that even though tobacco is not a food crop, the acreage upon which it’s grown could be used to grow food crops. One of the reasons that I favor algae as feedstock for biofuel is because it can be grown in places that can’t be used for food crops (for more on algae-based bio fuels, read my posts entitled The Potential of Pond Scum and Biofuel from Algae). George W. Huber and Bruce Dale, chemical engineers at the University of Massachusetts Amherst and Michigan State University, respectively, are also working on creating biofuels from non-food crop sources [“The Fuel of the Future Is Grassoline,” Scientific American, 9 April 2009]. Huber and Dale write:

“Civilization is not about to not stop moving, and so we must develop a new way to power the world’s transportation fleet. Biofuels, or liquid fuels made from plant material, remain the most technically promising alternative. Biofuels can be made from anything that is, or ever was, a plant. First-generation biofuels are made from edible biomass such as corn or sugarcane. Although we already possess the technology to convert these feedstocks into fuels (as evidenced by the nearly 200 refineries currently processing corn into ethanol in the U.S.), there is simply not enough corn, sugar cane or vegetable oil to provide more than about 10 percent of the liquid fuel needs of developed countries such as ours. These first generation biofuels also compete for farmland with crops used for human food and animal feed, which complicates the calculations of the environmental costs and benefits associated with them. We need biofuel raw materials that are cheap, abundant and that do not interfere with food production. The winner in all three categories is cellulosic biomass—woods, grasses and inedible stalks of plants. Fuel made out of this biomass—what we’ll call ‘grassoline’—could come from dozens, if not hundreds, of potential sources, from wood residues such as sawdust and construction debris, to agricultural wastes such as corn stalks, to ‘energy crops’—fast-growing grasses and woody materials that are grown expressly for their energy content.”

Huber and Dale report that a study by the U.S. Department of Agriculture and Department of Energy claims that “the U.S. can produce at least 1.3 billion dry tons of cellulosic biomass every year, and all without decreasing the amount of biomass available for our food, animal feed or exports.” That amount of biomass translates into a potential of “more than 100 billion gallons per year of grassoline, or about half the current annual consumption of gasoline and diesel in the U.S.” They go on to report that globally available amounts of biomass contain “an energy content equivalent to between 34 billion to 160 billion barrels of oil per year, numbers that exceed the world’s current annual consumption of 30 billion barrels of oil.” Not only is the potential amount of biofuel available impressive, but, they claim, “unlike biofuel made from corn, cellulosic biomass can be converted to any type of fuel—ethanol, ordinary gasoline, diesel or even jet fuel.” Potential availability of biomass, however, is just that — potential. In order to convert it into biofuel, waste material must be gathered and transported to refineries. That is probably easier to do in developed countries than it would be in developing countries where infrastructure remains limited. Cellulosic biomass also presents another challenge, unlocking its potential. Huber and Dale explain:

“Growing the cellulosic biomass isn’t the problem (or, at least, isn’t yet the problem—as the industry grows, agricultural techniques will become increasingly important). Because cellulose is so strong, it can be very difficult to extract the energy stored within. Many approaches have been attempted, but only now are scientists and engineers beginning to understand how we might scale grassoline production up to industrial levels. Successfully doing so may be the most important technical and environmental challenge our civilization now faces. Cellulosic biomass has been designed by evolution to give structure to a plant. It features rigid scaffolds of interlocking molecules that provide support for vertical growth. It also stubbornly resists biological breakdown. Scientists must find a way to defeat nature’s highly effective design.”

After explaining several techniques for refining biomass, they conclude:

“The ‘best’ pathway is one that converts the maximum amount of the biomass energy into a liquid biofuel at the lowest costs. We don’t know yet which pathway(s) will be the most economical. It may be that different pathways will be used on different cellulosic biomass materials. High-temperature processing might be best for woods, whereas grasses may work better at low temperatures. The most technically developed pathway to biofuels is the route that runs through the high-temperature gasification process to produce syn-gas. Syn-gas is a mixture of carbon monoxide and hydrogen that can be made from any carbon containing material. Syn-gas can be transformed into diesel fuel, gasoline or ethanol using a process called Fischer-Tropsch Synthesis (FTS) that was developed by German scientists in the 1920s. The Third Reich used FTS during World War II to create liquid fuel out of Germany’s coal reserves. Most of the major oil companies still have a syn-gas conversion technology that they may introduce under the right economic conditions.”

One of the continuing problems related to the production of biofuels from cellulosic biomass is cost. Huber and Dale explain:

“Though the technology is well understood, [gasification] reactors are expensive. An FTS plant in Qatar to convert natural gas into 34,000 barrels per day of liquid fuels was projected to cost $1 billion to 1.5 billion. To pay off these high capital costs, a biomass gasification plant would have to consume around 5,000 tons of biomass per day, every day, for a period of 15 to 30 years. There are significant logistic and economic challenges with getting this amount of biomass to a single location, and so research in this area focuses on ways to reduce the capital costs.”

Not only are capital costs high, but the refining process is not particularly environmentally friendly. Huber and Dale explain that all gasification processes require heating the biomass. Obviously, the more heat that is required the greater the cost and the less environmentally friendly the process. They are working on a process that involves both heat and chemical engineering. They explain:

“Researchers are also figuring out ways to process biomass using the chemical engineering equivalent of one-pot cooking—converting the solid biomass to oil then the oil into fuel inside a single reactor. The research group of one of us (Huber) is developing an approach called catalytic fast pyrolysis that would do just that. The ‘fast’ in fast pyrolysis comes from the initial heating—once biomass enters the reactor, it is heated to 500 degrees C in a second. This heating breaks down the large biomass molecules into smaller molecules. Like eggs and 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. The entire process takes just two to 10 seconds. Already the startup company Anellotech is attempting to scale this process up to the commercial scale. Its first test plant is expected by 2014.”

Huber and Dale report that most investments in biomass (and most of the public attention) have been in “traditional” approaches that “unlock the sugars in the plant, then ferment these sugars into ethanol.” They point out that unlocking the sugars in plant materials is not easy because most plants have developed strong structures that resist being broken down. According to the authors, “scientists have studied literally dozens of possible ways to break down cellulose. You can do it mechanically, using heat or gamma rays. You can grind the material into a fine slurry or subject it to high-temperature steam. You can douse it with concentrated acids or bases, or bathe it in an appropriate solvent. You can even genetically engineer biological organisms that will eat and digest the cellulose.” The approach that will eventually garner the most support won’t use “use toxic materials or require too much energy input to work” and it “must be cheap.” They continue:

“The most promising approaches right now involve subjecting the biomass to extremes of pH and temperature. One approach that uses ammonia—a strong base—is being developed at a laboratory run by one of us (Dale). In the ammonia fiber expansion (AFEX) process, biomass plant material is cooked with hot concentrated ammonia under pressure. When the pressure is released, the ammonia evaporates and is recycled. The treated biomass gives high sugar yields of 90 percent or more following a final conversion by enzymes. This approach minimizes the side effect of sugar degradation that often occurs in acid or high temperature environments. The AFEX process also is ‘dry to dry’: biomass starts as a mostly dry solid and is left dry after treatment, undiluted with water. It thus provides high ethanol at high concentrations. It also has the potential to be very cheap: a recent economic analysis showed that, assuming biomass can be delivered to the plant for around $80 a ton, AFEX pretreatment can produce cellulosic ethanol for around $1.40 per gallon. If we project to a future where a streamlined agricultural infrastructure exists, and assume a ‘mature’ process in which the processing costs are about 30 percent of the overall grassoline production costs (as it is in the oil refining business today), grassoline will be delivered to the pump for around $2 per gallon.”

The big question, of course, is whether all this research will ever amount to anything. Is there really a future for biofuels? Huber and Dale believe there is:

“Grassoline … enjoys two major advantages over fuels from petroleum. First, the raw feedstocks that go into making the fuel are far less expensive than raw crude. This should help keep costs down once the industry gets up and running. Second, new analytical tools and computer modeling techniques will let us build better, more efficient biorefinery operations at a rate that would have been unattainable to petroleum engineers just a decade ago. We’re gaining a deeper understanding of our raw feedstocks and the processes we can us to convert them into fuel at an ever-increasing pace. The government’s support for research into alternative forms of energy should help this process to accelerate even further. Indeed, if we maintain our current national commitment to move beyond oil, we will see an explosive growth in cellulosic biofuels over the next five to 15 years as biomass conversion technologies move from the laboratory to commercial scale. This move towards grassoline will fundamentally change the world. It is a move that is now long overdue.”

It shouldn’t surprise anyone that scientists working on biomass projects are optimistic about their research. Moving processes from the laboratory to the real world, however, is not easy. In the case of biomass to biofuel processes, an entirely new logistics chain needs to be established. As noted above, this will be easier for developed countries than developing countries where money to develop infrastructure is difficult to find. If the technology does progress sufficiently to make the biomass to biofuel sector profitable, it may open up a new source of revenue for some emerging market countries. With the number of drivers in China and India increasing at a rapid rate, the need for fuel will not diminish anytime soon. I doubt we’ll ever see the day when we can strap a Mr. Fusion model fusion generator onto to our cars, throw in some coffee grounds and orange peels, and head out on the road; but we may find ourselves driving cars that use gasoline derived from trash.