Bill Gates' Cascades Investments has backed algal biofuel maker Sapphire Energy, bringing the total amount raised by the startup to over $100 million.

The San Diego, Calif., company is one of a slew of startups developing processes for harvesting fuels from algae. In May, the one-year-old company said it had raised over $50 million from Arch Venture Partners, the Wellcome Trust and Venrock.

Sapphire CEO Jason Pyle told the Wall Street Journal Wednesday that the company plans to build a production plant capable of generating 10,000 barrels of algal oil a day.

Biofuel is not a new field of investment for Cascade, which put money in Pacific Ethanol, a public company in Sacramento, Calif.

But the investment firm sold all of its shares in Pacific earlier this year after the company reported losses and suspended construction of a planned ethanol plant (see Biofuel Forecast Buoys a Bit).

Pacific Ethanol said it was on track to complete a new plant last month even as it posted further losses