PetroAlgae and Gevo, two alternative fuel and chemical companies, hope to fire up the tepid IPO waters. PetroAlgae, which produces biocrude from duckweed, has not generated any revenue yet, and has just filed to go public. The Florida-based renewable energy company, which has traded over-the-counter under an inactive shell corporation, hopes to raise $200 million. The underwriters of the offering are Goldman Sachs; UBS Investment Bank, and Citi.

PetroAlgae licenses and deploys a biomass production platform it believes will result in commercial scale, economically viable production of drop-in fuel products to replace fossil fuels and high quality digestible protein products for animal use. The company says it has lined up five prospective customer licensees representing up to 18 license units.

Colorado-based Gevo also added itself to the IPO runway. The company produces isobutanol from biomass but has not yet generated any revenue yet. The company hopes to raise $150 million in an initial public offering that will be underwritten by UBS Investment Bank, Goldman Sachs, and Piper Jaffray. Burrill & Company, publisher of The Burrill Report, is an investor in Gevo.

Gevo is also commercializing biobased alternatives to petroleum-based products using a combination of synthetic biology and chemical technology to produce isobutanol that can then be converted into a variety of plastics and fuels. Gevo has partnership agreements with French oil giant Total, United Air Lines, and Toray Industries among others. Gevo just acquired a 22 million gallon-per-year ethanol production facility in Minnesota which it will convert to its process.

Both companies hope to fare better than their sector predecessor, Codexis. The California-based developer of catalytic enzymes went public in April at $13 per share, and is currently trading below $8 per share.

Competitor Amyris filed a $100 million initial offering in June.