Aurora Biofuels, an Alameda, Calif. startup with plans to produce algal biofuels, has raised a substantial second round of funding to speed development.

Like most of the other algae companies that have publicly announced their plans, Aurora intends to use its oily charges to produce biodiesel, a near-copy of petroleum-based diesel fuel.

However, there are few other details on Aurora. Algae is typically grown in water, but the specifics of what kind of water and whether anything is used to feed the algae are also of some importance.

Other companies playing in the space include Solazyme, which has partnered with Chevron, Cellana, a company that is working with Shell, and independents LiveFuels and Sapphire Energy, whose $50 million funding and plans to make “green crude” we recently covered.

The $20 million investment into Aurora was uncovered by VentureWire, which reports that only existing investors took part. Oak Investment Partners led, with Gabriel Venture Partners and Noventi participating. Aurora’s first round of $3.2 million took place a little over a year ago.