Researchers at Rochester Institute of Technology, N.Y., are using microalgae grown in wastewater to product biodiesel. They say the process is “doubly green” because the algae also consume pathogens — nitrates, phosphates — and reduce bacteria and toxins in the water. Unlike conventional biofuel sources like corn or soybeans, algae are easy to grow, don't require vast tracts of land, and use photosynthesis to convert sunlight into energy.