Fuel of the Future?

Algae gave us life. Thanks to photosynthesis, algae created an atmosphere on our planet that allowed “higher” life forms to develop. Algae (with help from anaerobic bacteria, time and pressure) also gave us fossil fuels, which ironically could be our eventual undoing.

As America tries to reduce its importation of fossil fuels, we have largely turned to corn-derived ethanol. This looks to be a win-win situation on the surface. There is a well-established system for producing corn, the economic benefits fall largely on the heartland where we live and we import less oil. When you look a little deeper, however, there are some downsides to corn ethanol. For one, a lot of water is used to produce ethanol from corn. Estimates range from 3 to 6 gallons of water for each gallon of ethanol produced. That could drop ground water tables, requiring deeper wells to get at what little water is left. Not only is a lot of water used, but about 12 gallons of solids are left over after a gallon of ethanol is made. While the solid waste can largely be used as animal feed, it has to be transported, which requires fuel. Further, corn ethanol is not particularly efficient to produce, yielding only 1.3 units of energy for each unit used to manufacture it. Some estimates of the energy yield are higher while others are considerably less.

Another issue with making ethanol from corn is the environmental impact. Corn requires intensive agricultural practices, including repeated land disturbance, fertilizers and pesticides. These land practices have a negative effect on water quality, several of which the LMVP volunteers monitor by measuring sediments, nutrients and algae. Finally, there is the issue of using food as fuel. Thanks to the laws of supply and demand, corn prices will continue to escalate. Higher costs for basic human and animal food are to blame for the recent riots in Mexico over tortilla prices.
Alternatives to corn exist. One example, switchgrass (Panicum virgatum), has a natural range that extends from Central America to southern Canada, making it a native Missouri plant. It has the potential to more than double the ethanol production of corn per acre while using a fraction of the pesticides and fertilizers and requiring no tilling after it is established. It can also be grown in soil that is not suitable for corn production.

Another familiar crop doesn’t get as much media coverage; algae. The Department of Energy began researching algae as an energy source in 1978. Initially, research was focused on using algae to produce hydrogen. In the early 1980s emphasis was redirected to biofuel production (particularly ethanol) until the DOE eliminated the funding in 1996. There has been a resurgence of attention to algae lately, as crude oil prices approach the $100 per barrel mark.

Here’s how it might work. Carbon dioxide from a coal burning power plant would be directed into a series of ponds or chambers rather than emitted to the atmosphere. The CO2 would be used by algae as a carbon source. Municipal waste effluent might be added to the ponds for nutrients and, given enough sunlight, algae could flourish. Algae would be encouraged (or engineered) to produce more lipids, or fats, that would be extracted and processed into liquid fuel. The remaining solids could be compressed and burned as a solid fuel or given to animals as a feed supplement. Much of the water used to grow the algae could be recyled.

Power plants could offset their carbon footprint by as much as 40%, fewer nutrients would go into our waterways, food crops could feed people and animals, and we could gain some independence from oil imports. And, lowly algae might get the respect they deserve.

This image shows how algae might be farmed for fuel. Research is still in its infancy, but biodiesel derived from algae grown in wastewater has already powered an automobile in a demonstration. Hydrogen and lipid production can theoretically be maximized by tweaking the nutrient content of the water.

Sources:

The National Renewable Energy Laboratory's Report (pdf ~3MB)
National Geographic Article "Green Dreams"
Popular Mechanics article on the subject
Popular Science article on the subject
Wikipedia article on the subject

 

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