Making Gasoline from the Sun

A Louisville, Colorado, company says it has perfected a solar-energy technology capable of producing 100 million gallons of synthetic gasoline annually from corn stalks and wood chips.

Sundrop Fuels Inc., which has constructed a 60-foot tower rising above a nearly 3,000-mirror solar array near Highway 7 and Interstate 25 in Broomfield, Colorado, already has proven it can generate synthetic gas using the sun’s heat.

Now it wants to raise between $100 million and $150 million to build the world’s first solar-powered biorefinery. That demonstration project could make 7 million to 8 million gallons of gas a year.

“We want to use the sun to make renewable fuel,” said Wayne Simmons, Sundrop’s CEO. “We’re going to convert the sun’s energy into liquid fuel using concentrated solar power to gasify biomass, then convert the biomass into gasoline or diesel.”

The new technology has the potential to revolutionize the biofuels industry, experts say, because it removes one of the long-term cost hurdles to creating fuel from organic waste.

The company blasts organic materials, such as wood chips and straw, with superhigh temperatures gathered from sunshine. The heat tears the material apart on a molecular level, adds the sun’s heat energy in the thermo-chemical reaction, and creates a synthetic gas that can be formed into gasoline or diesel fuel.

“They’re using solar power in conjunction with biomass-to-energy, and really, no one else is doing that,” said Jim Lane, editor of the online Biofuels Digest, a leading biofuels-industry daily newsletter that has 15,000 subscribers.

Sundrop’s solar reactor, near the top of the tower, operates at temperatures of 1,200 to 1,300 degrees Celsius (2,200 to 2,400 degrees Fahrenheit) using the heat reflected from the mirrors.

By comparison, concentrated solar-power plants, which use the sun’s reflected heat to generate steam for electricity, typically operate at around 500 degrees Celsius (more than 900 degrees Fahrenheit), Simmons said.

Biofuels are a growing area of interest because they offer what’s essentially an above-ground oil reservoir that can be located in the United States. When vehicles burn biofuels made from plants, they’re relatively carbon-neutral.

That means there’s little or no net gain in carbon-dioxide emissions from cars using the synthetic fuel, because the CO2 comes from the biomass grown in the last year or so, rather than from fossil fuels formed millions of years ago.

And biofuels can act as a hedge for large oil companies worried about unstable foreign regimes or their ability to find more oil, Lane said.

Sundrop’s reactor can use any kind of biomass, including plants grown specifically for their energy content. The organic biomass material is dropped into the reactor; the high temperatures vaporize it in seconds. The molecules are torn apart and recombined to form a synthetic gas (syngas), made up of hydrogen and carbon—which can be turned into gasoline, diesel, plastics, or chemicals, Simmons said.

Gasification of organic material to make synthetic gas has been done. But traditional gasifiers burn a large percentage of the biomass, or a fossil fuel such as natural gas, to reach operating temperatures above 1,000 degrees Celsius (1,832 degrees Fahrenheit). Sundrop’s process uses the free sunshine as its fuel source, and—as a plus—picks up some of the sun’s heat energy in the chemical process, he said.
As a result, Sundrop can produce 100 to 125 gallons of fuel per ton of dry biomass, about twice what conventional gasification plants are getting. It also needs just a half gallon of water—and its hydrogen molecules—to produce a gallon of fuel, compared to six gallons or more needed by traditional gasification technology, Simmons said.

The high temperatures also mean not producing tar as a waste byproduct, which happens with traditional gasification processes, he said.

The bottom line, according to Simmons, is that Sundrop’s technology can produce fuel that’s cost competitive, with unsubsidized production costs of under $2 per gallon. Meanwhile, oil prices have ranged between $70 and $80 per barrel for the last few months.

“This is a renewable, thermal-chemical sledgehammer; because of the temperatures that we operate at, it’s possible to handle all kinds of feedstocks,” said Alan Weimer, a University of Colorado chemical engineering professor and Sundrop consultant acting as its chief technology officer. Weimer co-founded Boulder-based Copernican Energy Inc., a company pursuing the use of solar-fired reactors, which Sundrop bought in June 2008.

Weimer also is executive director of the Colorado Center for Biorefining and Biofuels. The center is a consortium involving CU, the National Renewable Energy Laboratory in Golden, Colorado State University, and the Colorado School of Mines.

The Broomfield tower has its roots in technologies coming out of CU, NREL, and the Los Alamos National Laboratory. Scientists at the three institutions have spent years working on using the sun’s heat to tear apart molecules.

“We’re trailblazing an area,” Weimer said. “It’s very unique and novel, and people don’t think of it in terms of conventional fuel production. What we do is at the interface of a couple of technologies. You have concentrated solar thermal using mirrors and towers to heat water to make steam to drive a turbine to make electricity. And on the other side you have people doing standard biomass conversion.

“We operate at the interface of those two areas.”

Sundrop is focusing on producing gasoline or diesel from its syngas because transportation fuels are a large, existing market that Sundrop’s fuel fits in with, Simmons said.

The fuel is identical to petroleum on a molecular level and can be shipped in existing pipelines, pumped in existing fuel pumps, and burned in existing vehicle engines—no new infrastructure is needed, he said.

Sundrop flipped on the tower’s solar reactor in late September. Simmons figures the company has another 18 months to two years of research work there before the tower no longer is needed.

But the next step is to raise those millions to build Sundrop’s next phase, a demonstration, commercial-scale gasifier and refinery.

Simmons said the plant—a 564-foot tower surrounded by 100 acres of mirrors and linked to a pilot-scale biorefinery—probably would be located in the sunny deserts of Arizona, New Mexico, Nevada, or Southern California. The plant should be near a rail line, so trains can haul biomass to the plant, and a pipeline, to ship the fuel to market, he said.

Construction on the demonstration plant is expected to start this year. A full-scale commercial plant, with a tower surrounded by mirrors and an expanded biorefinery, capable of producing 100 million gallons of fuel a year, is planned for completion in 2015.

Colorado will remain home for Sundrop’s headquarters and research work, and the state also could play a role in growing crops destined for the gasifier, Simmons said.