Biofuels, based on non-food feedstocks, are huge right now, and bound to get bigger. There are certainly not without issue, as many don't seem to be very resource efficient, but if they can be brought to a reasonable point of their net energy consumption and cost, they may prove to be one the most efficient ways to harness the sun's energy for use in applications like cars and airplanes. From the Green Car Congress Website:

"California-based Cobalt Biofuels has raised $25 million in equity to accelerate the commercialization of its cost-effective biochemical process for biobutanol production. Cobalt says that the advantages of its process are based on advances in microbial strain improvement, fermentation reaction management, and separation technology.

The Series C equity round was co-led by LSP and Pinnacle Ventures and included both new and existing investors. The Series C round had strong participation from Cobalt Biofuels’ existing institutional investors, including Pinnacle Ventures, Vantage Point Venture Partners, The Malaysian Life Sciences Capital Fund and @Ventures. New investors included LSP and Harris and Harris. Fouad Azzam, General Partner of LSP, will be joining the Board."