A four-year patent battle over a promising corn-based alcohol called isobutanol ended Monday, boosting prospects for the world's only producer in Luverne, Minn.

Gevo Inc., a small, struggling company that owns the Minnesota plant, and competitor Butamax Advanced Biofuels announced they settled multiple lawsuits over patents to produce isobutanol, which is used as engine fuel and in making green chemicals and plastic.

Under the agreement, Gevo, based in Englewood, Colo., and Butamax, a Wilmington, Del., venture of BP and Dupont, have cross-licensed their technologies. The royalty structure gives each company explicit incentives to expand separate market segments for isobutanol — for the benefit of both companies.

"That is the strange thing about this and the world of business — they are now our friends," Gevo CEO Pat Gruber said of his competitor in an interview. "We wish them success. Go, Butamax, go, and develop the marketplace. That makes more markets for us."

Isobutanol is a chemical cousin of ethanol, and is produced using fermentation. It can be blended with gasoline at up to a 16 percent ratio for use in engines, and does not have the same issues as ethanol in boat motors and small engines. It also can be turned into jet fuel, solvents and other chemicals such as paraxylene used to produce plastic pop bottles.

The agreement calls for Butamax to take the lead winning regulatory approvals to open up markets for isobutanol-blended gasoline in on-the-road vehicles. Meanwhile, Gevo will develop the jet fuel market. Gevo has sold isobutanol-based jet fuel to the U.S. military, and has won marine-industry endorsement of isobutanol-blended gasoline. No royalties will be paid by either company for the first 30 million gallons produced annually by each company or for any sales as off-road vehicle fuel or to make solvents.

Both companies have been suing each other, mostly in U.S. District Court of Delaware, since early 2011. At one point, Gruber said, more than 10 lawsuits were underway. He said litigation accounted for 30 percent to 40 percent of Gevo's monthly cash burn, and even more during trials, although the exact figure hasn't been disclosed.

Now that the legal expenses have ended, "it is the equivalent of putting money on our balance sheet that we can use for other things," Gruber said.

He said Gevo plans to invest in distillation columns at Luverne to achieve continuous isobutanol production. Until now, the product has been fermented in batches in Luverne and distilled elsewhere. Gevo has a Texas facility to convert isobutanol to jet fuel.

Butamax has a demonstration plant in United Kingdom, but has not begun commercial-scale isobutanol production. When Highwater Ethanol, a farmer-owned ethanol plant in Lamberton, Minn., installed equipment to separate corn oil last year, it chose technology from Butamax. Neither Highwater nor Butamax on Monday would discuss whether further investment is planned to begin isobutanol production.

But Highwater CEO Brian Kletscher, who is president of the Minnesota Biofuels Association, said the settlement is good for the industry.

"It is good to see two companies working together," he said. "I hope it will be a good thing and get us out of the development stage and into new biofuels in the country."

Gevo acquired the Luverne ethanol plant in 2010, installed its technology and expected to be producing 500 million gallons of isobutanol annually at multiple sites by now. But making commercial quantities proved to be a challenge. Two years ago, Gevo resumed making ethanol in the Luverne plant but continued to work on isobutanol production.

In the meantime, Gevo has accumulated a deficit of $325 million, including $22 million in net losses in the first half of this year. It had $22.5 million in cash at the end of June, and said it would seek to raise more investment to keep going.

Gevo's stock, which had briefly slipped to less than $2 per share earlier this year, rose 4 percent Monday, closing at $2.38 per share.

David Shaffer • 612-673-7090 • @ShafferStrib