Algae might have eclipsed corn as the next great source for biofuels, but some leading venture capitalists aren’t buying it … literally.

That’s what Vinod Khosla, John Doerr and Bryant Tong said when asked about their interest in algae-based fuel ventures during last week’s ECO:nomics conference in California.

The Business Insider reports that Khosla, managing partner of Khosla Ventures, said he’s investigated more than 100 algae-focused firms so far but won’t yet invest in them. That’s because algae-based biofuels aren’t yet competitive without subsidies in today’s crude oil prices, he said.

Doerr, partner at Kleiner Perkins Caufield & Byers, and Tong, managing director of Nth Power, went further, expressing doubts beyond economics about the viability of algae-based biofuels. Doerr pointed out that the highest yields now come from expensive bioreactors versus less-costly open-air ponds.

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