Algae may become The Greenest Green Fuel — if researchers can get it to work:
Algae seems a strange contender for the mantle of World’s Next Great Fuel, but the green goop has several qualities in its favor. Algae, made up of simple aquatic organisms that capture light energy through photosynthesis, produces vegetable oil. Vegetable oil, in turn, can be transformed into biodiesel, which can be used to power just about any diesel engine. (There are currently 13 million of them on American roads, a number that’s expected to jump over the next decade.)Algae has some important advantages over other oil-producing crops, like canola and soybeans. It can be grown in almost any enclosed space, it multiplies like gangbusters, and it requires very few inputs to flourish — mainly just sunlight, water and carbon dioxide. “Because algae has a high surface-area-to-volume ratio, it can absorb nutrients very quickly,” Sears says. “Its small size is what makes it mighty.”
The proof is in the numbers. About 140 billion gallons of biodiesel would be needed every year to replace all petroleum-based transportation fuel in the U.S. It would take nearly three billion acres of fertile land to produce that amount with soybeans, and more than one billion acres to produce it with canola. Unfortunately, there are only 434 million acres of cropland in the entire country, and we probably want to reserve some of that to grow food. But because of its ability to propagate almost virally in a small space, algae could do the job in just 95 million acres of land. What’s more, it doesn’t need fertile soil to thrive. It grows in ponds, bags or tanks that can be just as easily set up in the desert — or next to a carbon-dioxide-spewing power plant — as in the country’s breadbasket.
How to make fuel from algae:
As the colonies mature, starve them of nitrogen [2]. The cells react to the low nutrient supply by entering survival mode and producing extra fats. When they’ve created enough fat, collect the cells and break them apart [3]. Filter out the large organelles and cell membranes, and then use solvents like methanol to separate out the fats from the water-soluble proteins and sugars [4]. Purify the collected fats, and evaporate the solvent [5]. Finally, put the fats in a chemical reactor to transform them into biodiesel (a process called transesterification) [6].