Economic conditions have not favored cleantech companies intending to launch Initial Public Offerings on Nasdaq this year. But those that have gone public, and those registered but still waiting in the wings, point to uncertainties in the clean energy industry.

An Ernst & Young’s report, Global IPO Trends 2011, showed that there were 150 companies in the US that had filed S1 forms for their initial public offering this year, the highest level since 2007, which would raise around $40 billion. Small high-tech and energy companies were behind this trend, it said.

Advanced biofuels may have reached a stage of maturation, while investors hesitate to reveal an appetite for riskier technologies. So far, 2011 has seen a cautious continuation of last year’s trend, which saw the introduction of biofuels companies such as Amyris and Codexis.

Amryis, backed by the Bill and Melinda Gates Foundation, has been as close to a clean tech overnight success as we’ve seen since its flotation in September last year. Its share price was initially priced at $16 and has peaked at $33.66 and deals with Total and Nikko chemicals have followed since for the company’s yeast-based technology that turns sugars into hydrocarbons.

But as with many cleantech companies the costs of reaching commercial scale are enormous, and as Solyndra’s collapse illustrated, sometimes unbearable. Amryis’s second quarter losses for 2011 were $42.6 million compared with $19.9 million in the same quarter of 2010 – figures which overshadow revenue increases for the second quarter in 2011 of $32 million versus $12.7 million in 2010.