Grow Your Own Energy: A NASA-Backed Experiment Harvests Algae for Oil, Releases Fresh Water
by Jonathan Trent (Slate) …Algae are single-celled organisms that thrive globally in aqueous environments and convert CO2 into carbohydrates, protein, and natural oils. For some species, as much as 70 percent of their dry weight is made up of natural oils. Through transesterification (the process of adding three molecules of alcohol to one molecule of natural oil), the algae oils can be transformed into renewable fuels.
…But there are big unsolved problems at which governments should be throwing funds and brainpower as if we were involved in a Manhattan project. For example, since few species of microalgae have been domesticated, we don’t know how to grow them reproducibly or economically. At what scale will algae farming be efficient? To put this in perspective, U.S. planes use 80 billion liters of fuel per year. To supply this fuel from microalgae at the lower end of the estimated production rate would take 4.2 million hectares—twice the area of Wales.
Luckily, there may be a good way to cultivate this much algae while solving the ethical problem of producing biofuel without competing with agriculture. Freshwater algae can be grown in wastewater (effectively, water with fertilizer), or marine algae can be grown in a blend of seawater and wastewater. In both cases, wastewater provides a growth medium and the algae clean the wastewater by removing nutrients and pollutants from it. So there’s no competition for fresh water needed elsewhere, no reliance on synthetic fertilizer, and the environment benefits.
…For coastal cities, we should try a system I call OMEGA: Offshore Membrane Enclosures for Growing Algae. Some 40 to 60 percent of Earth’s population lives near a coast, most of the biggest cities are near a coast, and nearly all coastal cities discharge wastewater offshore.
