Cellulosic Ethanol Fights for Life

The Abengoa cellulosic ethanol plant near Hugoton, Kansas, will start production this year.

ENERGY included in the country’s fuel supply. In its early years, the law emphasized the production of corn ethanol, considered ripe for early commercialization. Cellulosic ethanol Yet corn ethanol comes with problems. It offers only modest savings in greenhouse-gas emissions compared to petrol (see Nature 499, 13–14; 2013). Production is vulnerable to poor fights for life harvests and can contribute to increased food prices because the maize must be grown on land that would otherwise be used for food. Pioneering biofuel producers hope that US government Tapping the storehouse of biomass left after largesse will ease their way into a tough market. the harvest is much less controversial. Ethanol made from corn stover produces at least 60% less greenhouse-gas emissions than petrol, and BY MARK PEPLOW by DuPont). The industry has long promised making it does not require any extra farmland. that this second-generation biofuel will cut Brewing such cellulosic ethanol, however, n the flat plains of Kansas, a stack greenhouse-gas emissions, reduce US reliance is hard. Producers must dismember large, of gleaming steel towers and pipes on imported oil and boost rural economies. Yet indigestible molecules such as cellulose and stretches 16 storeys into the sky. More just as the fuel is on the cusp of making it big, hemicellulose to yield fermentable sugars. Othan 1,000 construction workers toiled to market forces and government policies could The process requires the biomass to be ground complete the ethanol plant near the town of choke its progress. “This is going to be a very up and pretreated with acids. A cocktail of Hugoton, and its owners expect it to join a critical year,” says Zia Haq, a chemical engi- enzymes must then be applied to chop up the fermented-fuel revolution. neer and senior analyst at the US Department tough biological polymers inside — all before But unlike most ethanol factories, in which of Energy, which has the yeast is added to the resulting sugars. yeast feeds on sugars in foodstuffs such as helped to fund the “We don’t Hence the scale of Abengoa’s processing facil- maize (corn) kernels, the Hugoton facility plants. The challenges have room ity, much larger and more expensive than any will make use of what has been, until now, have already pushed for any more corn-ethanol plant. According to the RFS, agricultural waste: cellulose. Thousands of some researchers and ethanol.” commercial production of cellulosic ethanol tonnes of corn stover — the leaves, stalks and companies towards was meant to start around 2010, but that did husks left over after the maize harvest — are an alternative approach that converts cellulose not happen. With patchy investment backing, already waiting, stacked in square bales, at the into hydrocarbon fuels using chemical rather many companies have fallen by the wayside. 1.6-square-kilometre site. By June, the plant than biological processes. will begin processing the stover into ethanol, With more than 200 operating plants, the BLEND WALL which will be blended with petrol and end up corn-ethanol industry is well established in Part of the problem is that the ethanol mar- in vehicle fuel tanks. the United States. Its dramatic growth has ket is already saturated. In 2012, the industry The plant, which is owned by multinational been driven by tax credits and the Renewable produced more than 50 billion litres of corn company Abengoa of Seville, Spain, is one of Fuel Standard (RFS), created by law in 2005 ethanol, comprising 10% of US transportation three US facilities that should start commercial and extended in 2007. Administered by the fuel — enough to completely satisfy demand production of cellulosic ethanol in the next few US Environmental Protection Agency (EPA), for the E10 petrol blend that most vehicles now months (the others are both in Iowa, one run by the standard mandates annual increases burn (see ‘Hitting the wall’). This ‘blend wall’ POET-DSM Advanced Biofuels and the other in the volumes of various renewable fuels puts an upper limit on the amount of ethanol

that the market can absorb. And it is closing in: demand for petrol has actually fallen, and 38 Methanol CANADA Biological

(AEC, 2012) (AEC, there is growing interest in alternatives such as battery-powered cars. Cellulosic ethanol may ENEKEM POET-DSM DUPONT Thermochemical now be arriving, but its timing is terrible. “We Edmonton, Alberta Emmetsburg, Iowa Nevada, Iowa don’t have room for any more ethanol,” says Feedstock: Municipal • Corn stover • Agricultural residues solid waste • Online mid-2014 • Online late 2014 Wallace Tyner, an agricultural economist at Status: online mid-2014 Annual capacity Purdue University in West Lafayette, Indiana. (Millions of litres) Corn ethanol is now slightly cheaper than UNITED 75 Ethanol 4 petrol, but cellulosic ethanol is more expen- STATES Ethanol sive than both. A cellulosic-ethanol plant’s capital costs are roughly twice those of a corn- ABENGOA INEOS BIO ethanol plant, says Tyner, and enzymes raise Hugoton, Kansas Vero Beach, Florida operational costs further. Unable to undercut • Corn stover and other • Agricultural or 95 49 municipal solid waste its rivals, cellulosic ethanol will be heavily agricultural residues • Online mid-2014 Ethanol Petrol/ • Online 2013, currently dependent on the RFS to clear its path to the diesel o ine for upgrades pumps. Yet its delayed arrival has prompted

CELLULOSIC BIOFUELS INDUSTRY PROGRESS REPORT 2012–2013 REPORT PROGRESS INDUSTRY BIOFUELS CELLULOSIC the EPA to reduce the amount of cellulosic KIO POWER PLANTS Columbus, Mississippi Three out of six commercial cellulosic plants in ethanol that refiners are required to blend into • Woody biomass North America are using thermochemical 30 SOURCE: their petrol. • Online 2013, currently Ethanol processes rather than biological enzymes to o ine for upgrades The RFS plan for this year originally called convert waste feedstocks into fuels. for 6.6 billion litres of cellulosic ethanol. But in November, the EPA proposed that the man- date should be reduced to 64 million litres, a of chemical catalysts, both can be turned into Producing syngas also gives the company a mere trickle in comparison. A final ruling is hydrocarbons such as petrol, diesel and jet fuel. lot of flexibility. If there are changes to policy expected in March or April. Groups working Crucially, these ‘drop-in’ fuels, named because mandates or the market, the system could on renewable fuel, who say that producers will they can replace normal fuels with no adjust- be switched to making hydrocarbon fuels or easily make more than 64 million litres once ments to engines, have no blend wall to vault. higher-value chemical products. Enerkem they get going, have cried out. “We think the Thermochemical routes can also use lower- plans to build similar plants in Mississippi EPA underestimated the capacity of the indus- quality feedstocks, tearing through anything and Quebec next year, and it is partnering try,” says Christopher Standlee, executive vice- from wood chips to municipal solid waste. with Waste Management in Houston, Texas president of global affairs for Abengoa. The Enerkem, a company in Montreal, Canada, is — the biggest US landfill operator — to take expensive excess ethanol might have to be sold starting its first commercial-scale plant to turn its waste. at a loss on the open market, potentially crip- solid waste into syngas, in Edmonton. By April Research funding, too, is shifting to thermo pling the fledgling industry. or May, it will be able to transform the syngas chemical methods, says Haq. “That doesn’t into methanol. Next year, it plans to convert mean we’re abandoning cellulosic ethanol,” he CAPACITY PROBLEM the methanol into ethanol, and it says that will says. “But certainly, going forward, we’re look- Cellulosic-ethanol producers have several be cheaper than corn ethanol. ing more seriously at hydrocarbon pathways.” options to increase their market. First, they This is mostly because the feedstock is Last year, an energy-department project to could break through the blend wall. All US cheap. US landfill fees for solid waste are about supply the US Navy with advanced biofuels vehicles produced in the past decade can run $44 per tonne, not including transportation, so provided funding for four facilities that will on a 15% ethanol–petrol blend — but consum- municipalities are keen to get companies such all use thermochemical methods to make ers and distributors are mostly unconvinced, as Enerkem to take the waste off their hands, drop-in fuels. Thermochemical processes are perhaps spooked by car-industry studies says Marie-Hélène Labrie, the company’s vice- also key to the first two commercial cellulosic claiming that the fuel damages engines. president for government affairs and commu- plants in the United States, which opened last Another way over the wall might be exports nications. “Generally, we’re being paid to take year: KiOR in Columbus, Mississippi, and to the European Union, which aims to make the feedstock.” INEOS Bio near Vero Beach, Florida (see 10% of its transportation fuel renewable by ‘Power plants’). (Both plants are currently idle, 2020. And cellulosic ethanol could get cheaper pending upgrades.) Haq thinks that longer- with more efficient stover harvesting, beefier HITTING THE WALL lived catalysts will further reduce the costs of enzymes and cheaper pretreatments. The There is already enough corn ethanol to satisfy US thermochemically produced cellulosic hydro- SOURCE: EIA demand for a widely used 10% ethanol–petrol blend, industry has already cut costs from as much as in part because petrol consumption is declining. carbons in coming years. US$9 per gallon ($34 per litre) five or six years But Standlee says that biology can still com- ago to close to $2 today, says Thomas Foust, 600 pete, by tackling ever-cheaper feedstocks. His director of the National Bioenergy Center, part company is betting that a new generation of of the National Renewable Energy Laboratory 500 enzymes can turn municipal waste into etha- in Golden, Colorado. Demand for petrol nol, and last July it opened a demonstration (billion litres) US petrol use US petrol is falling But Tyner says that this approach can be 400 plant near Salamanca, Spain, to do just that. squeezed only so far. He and others see more Abengoa hopes that this technology will even- promise in a different approach to breaking 12 tually allow it to expand its US operations 10% blend wall up cellulose — a brute-force combination of 8 beyond the ‘corn belt’. temperature, pressure and chemistry. These Standlee says that, as long as the cellulosic 4

thermochemical methods can produce either (%) share industry is given time to mature — just as corn

a crude bio-oil or a stream of carbon mon- Ethanol market ethanol was — it can get back on the trajectory 0 oxide and hydrogen known as syngas. After 2004 2006 2008 2010 2012 2014 set out by the RFS. “If,” he adds, “the EPA sticks further treatment and refining with the help with the programme.” ■