Carbon dioxide, sun, and secret ingredient are firm’s fuel recipe

The company will today unveil a new process for making alternative fuels that it calls helioculture, chief executive Bill Sims said.

In the process, sunlight and the greenhouse gas carbon dioxide, considered to be a factor in global warming, are captured in a converter that resembles a solar panel. Inside the converter, suspended in brackish water, are the company’s highly engineered, proprietary organisms. They absorb the gas and light, and produce the fuel ethanol, hydrocarbons, and petroleum-derived chemicals, Sims said.

Although they say it’s something that exists in nature, neither Sims nor Joule cofounder David Berry would disclose what kind of organism the company modified to make fuel.

There are companies that currently make so-called biofuels from grass, algae, and other materials. Sims said the Joule process is different.

“We do not require an intermediary algae. No grass. None of that stuff that has to be grown or harvested,’’ he said. “If I tell you what the organism is, I’m inviting everyone else to take part in a transformational, evolutionary, game-changing technology.’’

At the Union of Concerned Scientists, headquartered in Cambridge, Margaret Mellon, director of the organization’s Food and Environment Program, said it sounds like Joule is working with some sort of plant.

“The question is what kind of plant they’ve got,’’ she said.

Mellon added that Joule’s real innovation appears to be that it has engineered an organism that can secrete ethanol - meaning that the company’s fuel-making process is probably more efficient than others.

Although the company’s reluctance to name the organism it is using is understandable, she said, that decision will make it harder for Joule to combat the usual skepticism about alternative fuels as it tries to break into the market with an untried product.

“There are many, many [renewable energy] products that work on the bench, but are difficult to scale up. And there are many products that even if you scale them up in the marketplace, there are other people that do it better or cheaper,’’ Mellon said. The issue for Joule and its process, she added, will be “just how well they’ve really done it, and whether their product is ready for prime time.’’

Sims said Joule has started testing its technology outside the laboratory and intends to have a pilot facility, possibly near a power plant that emits carbon dioxide, operating by early next year. If the company stays on schedule, a commercial-size plant could be making SolarFuel by 2012. Joule estimates it can generate 20,000 gallons of fuel per year from every acre of solar converter panels.

The company estimates that SolarFuel will cost about $50 a barrel, as much as today’s fossil fuels.

Ian Bowles, secretary of the state’s Executive Office of Energy and Environmental Affairs, said his office has been talking with Joule about possible sites for its pilot plant.

“I think, big picture on this, that there are several companies that are trying to use carbon dioxide as a feedstock to interact with organic products, with energy from the sun, to produce biofuels,’’ Bowles said. “This is a general area that is very important as a potential solution for re-purposing CO{-2} for benign purposes.’’

Erin Ailworth can be reached at eailworth@globe.com.