NOVELTY - Production of biofuel from algae comprises: cultivating a carbohydrate-producing algae by autotrophic growth in a first stage; shifting growth from autotrophic growth to heterotrophic growth by inducing stress in the carbohydrate-producing algae in a second stage; extracting carbohydrates from the starch-producing algae; and utilizing the carbohydrate as a component of biofuel production.    USE - The process is useful for producing biofuel from algae (claimed), where the biofuel is biodiesel or bioethanol.    ADVANTAGE - The process: utilizes algae that produce lipids (oil) which are readily converted into biodiesel and is grown, energy stores are extracted and converted into useable fuels, and byproducts of the fuel production are either sold directly or fed back as inputs into algae growth and fuel production stages, where this integrated system uses a minimum of external inputs other than sunlight, water, and carbon dioxide from the air; produces biodiesel, which is similar to but superior to petroleum diesel fuel in many respects; is highly efficient and energy-positive, meaning the energy produced in the form of fuels is far in excess of external input energy, because very little fossil energy is used; allows algae growth that requires none of the heavy machinery, expensive fuels, or chemical fertilizers and pesticides required by conventional agriculture and algae to be processed near the growth ponds, thus eliminating transportation costs; and produces biodiesel lacking aroma, having a flash point near 150 degrees C, thus safer to store and handle, containing less or no sulfur, thus reducing sulfur emissions even compared to ultra low sulfur petroleum diesel, producing 20% carbon monoxide and less soot, reducing particulate emission by up to 75% and nearly eliminating black smoke often associated with diesel engine exhausts, exhibiting better combustion efficiency, burning more efficiently resulting in smoother-miming engine, thus noticing power drop rarely, having higher lubricity so fuel injection systems and other engine components can have a longer life, having higher equivalent cetane number, thus reducing diesel noise and knock, and that is atmospherically carbon-neutral, breaks down about four times faster in the environment, so spills are less enduring, and can be mixed with petroleum diesels during the transition to 100% biodiesel fuels. Most of the energy of the sugar ends up as useful fuel, rather than suffering the fermentation losses which occur during the production of alcohol, e.g. in the form of heat and carbon dioxide emissions.