The document discusses using microalgae to produce biodiesel as a renewable alternative fuel. Microalgae have advantages over other biodiesel feedstocks like seed oils in that they do not require arable land, can use brackish or saline water, and absorb more CO2. While open ponds are commonly used, they have issues with contamination, evaporation and land use. The aim is to use microalgae for high and cost-effective biodiesel production to address declining fossil fuels and global warming without competing with food supplies.