It'd been one of the worst kept secrets, or best rumors, in the cleantech biz to date.

But yesterday, Imperium Renewables, which has been working to scale biodiesel production to hitherto unimagined levels, officially filed to go public.

Some question its science. Others question its feedstock supply. And Imperium's mass production facilities have not yet proven themselves. But this is clearly a deal to watch.

That said, don't let the deal distract you from considerable other important goings-on in deals this week.

This week in cleantech/greentech dealflow:

• Imperium Renewables filed a registration statement with the U.S. Securities and Exchange Commission announcing its intention for a proposed initial public offering of up to $345 million of its common stock. UBS Securities is acting as lead manager, and Jefferies & Company, Piper Jaffray & Co. and Calyon Securities (USA) Inc. are acting as co-managers. Headquartered in Seattle, Imperium operates a 5 million gallon per year facility through its subsidiary, Seattle Biodiesel, and is currently the largest producer of biodiesel on the West Coast. The company is constructing a 100 million gallon per year facility in Grays Harbor, Washington that is scheduled to open in July 2007, and has plans to build additional facilities. Read all of Cleantech.com's coverage of Imperium here.
• Earlier this week, France's Veolia Environnement announced final terms of a €1 billion bond, scheduled to close today. The notes are to offer 5.125 percent interest, and will be due May 2022. Veolia Environnement is a global company offering the wide range of environmental services in water, waste management, energy and transportation sectors.
• Petra Solar of Green Brook, New Jersey, a developer of power electronics for solar systems, raised a $14 million Series A round, led by DFJ Element and BlueRun Ventures. National Technology Enterprises Co. also participated. The investment will be used for product development and global market expansion. Petra focuses on increasing efficiencies and reducing the cost of installed solar electric systems through innovative power electronics.
• Tri Alpha Energy Inc., a Foothill Ranch, California-based nuclear fusion research company, raised $40 million in Series C-2 funding, according to a regulatory filing. Backers include Goldman Sachs, Venrock, Vulcan Capital, Enel Produzione SpA and PIZ Signal. Directors include Dick Kramlich of New Enterprise Associates.
• Transonic Combustion, a Camarillo, California-based developer of fuel injection systems that enable conventional internal combustion engines to operate at higher efficiency, raised an undisclosed amount of second-round funding. Venrock led the deal, and was joined by return backers Rustic Canyon and Khosla Ventures. The company's technology appears to radically increase conventional engines' fuel efficiency. As an investor described at a conference yesterday, the company plans to demonstrate its effectiveness by driving a Volkswagen diesel Jetta from Los Angeles to Washington, D.C. on a single tank of gas.
• Evergreen Solar, already traded on the Nasdaq, priced an additional public offering of 15,000,000 shares of its common stock. The price of $8.25 per share is to result in gross proceeds of $123.75. Evergreen also granted underwriters a 30-day option to purchase up to an additional 2,250,000 shares. The company plans to use the proceeds for manufacturing expansions, to secure the supply of key raw materials, including silicon, as well as for general corporate purposes.
• Evergrid, a Menlo Park, California-based provider of resource management software for data centers, has raised $10 million in Series B funding. Menlo Ventures led the deal, and was joined by return backer Acartha Group.
• Dutch company fluXXion B.V., a producer of micro filtration technology, received a EUR 6.4 million (US$ 8.6 million) financing round to fund its global expansion. The financing was led by Emerald Technology Ventures (formerly SAM Private Equity) and included investments from Capricorn Cleantech Fund and WHEB Ventures as well as from existing investors Koninklijke Philips Electronics NV and S. L. Hui. Founded in 2003, fluXXion designs, assembles and sells micro filtration modules which provide improved liquid bulk filtration.
• General Electric confirmed it has agreed to sell its GE Plastics division to chemical company Saudi Basic Industries for approximately $11.6 billion in cash. GE will receive after-tax proceeds of around $9 billion. Other bidders had included Apollo Management and Dutch plastics company Basell. See GE gets out of plastics business, sells it to Saudi company.
• MBA Polymers of Richmond, California, a company recycling discarded plastics, secured a $20 million funding round co-led by Doughty Hanson Technology Ventures and Benchmark Capital. MBA will use its new funds to further expand the number of factories it operates in Europe and Asia, it says.
• Struggling CIGS thin film solar maker DayStar Technologies entered into a commitment letter with an existing investor to provide up to $4.0 million of bridge financing to the company. DayStar recently took drastic product and organizational measures, some of which were contingent on new financing. See Cleantech.com's DayStar trims staff, refocuses.
• SunLink of Larkspur, California, a provider of solar mounting systems for the commercial market, raised an undisclosed amount of Series B funding led by Clean Pacific Ventures.
• Nexterra of Vancouver, Canada received a further $720,000 CDN in funding from the Canadian government and Ethanol BC. The money is to support Nexterra's product development program to directly fire boilers and lime kilns with syngas produced from wood residue. For more on Nexterra, see Funding to promote paper industry wood waste gasification.

Rumors? Insight into other deals? Contact us.

Browse other dealflow roundups here.