Seattle-based Imperium Renewables took time out of its quiet period today to open a new 100 million gallon per year biodiesel plant in Grays Harbor, Wash.

Imperium, which filed for a $345 million initial public offering in May, now takes the top spot in size with the largest biodiesel facility in the U.S.

"Imperium Grays Harbor really brings, I think, a commercial, industrial scale to this industry - ratchets it up to the next level of energy production," John Plaza, founder and president of Imperium, told the Cleantech Group. [1]

See how big the plant really is right here >> [1]

The company has already made a deal to sell 15 million gallons of biodiesel this year to Royal Caribbean Cruises (NYSE: RCL [2]), which holds a 7 percent stake in the new plant.

The cruise line company has agreed to buy 18 million gallons for the next four years with an option for a three-year extension, according to Imperium's filing.

Imperium plans to use $10 million from the expected proceeds of its IPO to buy back Royal Caribbean's 7 percent stake.

The company said the feedstock agnostic plant is capable of storing up to 17 million gallons of biodiesel and feedstocks, the oil that is used to produce biodiesel, at any one time.

"You have to be capable of taking various inputs and producing a single high-quality out the other end," said Plaza.

If you're wondering where Imperium is going to get all that feedstock, the company is set for the rest of 2007 and 2008 with supplies from Canola oil.

"Canada, Washington and the Pacific Northwest are really where most of the Canola is grown in the North American continent, so obviously we're pretty close to all three of those," said Plaza.

He said that in the company's other planned facilities Imperium will be looking for similar low cost, high quality opportunities that suit the locations.

The company has three more big plants in development in Hawaii, Argentina and Pennsylvania.

Founded in 2004, Imperium didn't just leap into the 100 million gallon business. The company has been running a pilot 5 million gallon per year plant in Seattle for almost two and a half years, working out the kinks in the technology before tackling its bigger project.

"It's been as much an education facility as it has a production facility," said Plaza. "We were producing fuel for many customers throughout the region. It's going into the local city bus fleet for King County Metro, the City of Seattle, individual consumers, a variety of outlets."

Plaza said the new plant will serve additional markets, as well as fulfilling the company's current supply.

"You could buy a 2008 Volkswagon Jetta diesel that's going to be coming out this fall and fill it up with 100 percent biodiesel, and no modification to the vehicle itself and it'll work just great," said Plaza.

King County Metro's hybrid buses from General Motors currently use a 20 percent biodiesel, 80 percent diesel mix, and Plaza said "there was no modification required from the manufacturer to do that."

While Imperium doesn't have any competition in the States at the 100 million gallon per year level, it still faces other established biodiesel groups.

Earlier this week, Houston-based Nova Biosource Fuels (AMEX: NBF [3]) announced a biodiesel sales agreement for ConAgra Trade Group to market and sell fuel and manage logistics for Nova at a Mississippi refinery (see Nova, ConAgra in biodiesel sales agreement [4]).

The 20 million gallon per year plant was designed and constructed by Nova but is owned by Scott Petroleum. Nova has a deal to obtain 50 percent of the biodiesel and glycerin production from the refinery at a specified cost.

And California's SE Energy has thrown its hat into the ring to try for a bigger-than-big 320 million gallon per year biodiesel refinery in Chesapeake (see Will startup build world's biggest biodiesel plant? [5]).

The startup recently boasted that it plans not just one, but two super-sized facilities at that same location.

Imperium's more modest aspirations, made real with today's plant opening, are backed by Technology Partners, Nth Power, BlackRock Investment Management and others (see Imperium Renewables lands $214 million [6]).