Biodiesel giant Imperium Renewables is looking to get $345 million in investments in an initial public offering. You might remember Imperium from our previous posts about how the Seattle-based company is building a 100 million gallon a year refinery (Feb. 2nd) – one of the biggest in the nation – and how it secured a record $214 million investment (Feb. 21st) and how building the big refinery on the West Coast is helping that area’s economy (March 8th).

This story in the Seattle Times says the company is continuing to grow and will have more than 400 million gallons of production capacity by the end of next year:

In a regulatory filing today, Imperium also said it has a contractual commitment from one large industrial user to buy at least 18 million gallons of biodiesel annually for approximately five years. It said that is “the single largest long-term biodiesel sales contract to an end user in the U.S.”

Biodiesel consumption is growing rapidly in the U.S., but so is production capacity. Use increased from 500,000 gallons in 1999 to an estimated 250 million gallons last year, according to Imperium’s filing with the Securities and Exchange Commission.

The stock is going to be sold under the proposed ticker symbol IMPR. Morgan Stanley, Lehman Brothers, and UBS Investment Bank will underwrite the offerings.