Now that's green
Pond scum. It sounds too good to be true. The plan is to grow millions of acres of algae in large open ponds filled with wastewater and then harvest oil from the algae and turn it into biodiesel fuel. Energy crisis solved. Global warming eliminated. Energy security ensured. What could be more simple?
One problem with our new instant information age is that every new idea, great or small, harebrained or valid, innovative or crackpot, seems to demand its 15 minutes of fame. I'm not saying that using algae to produce biodiesel fuel is harebrained or crackpot; in fact, some really excellent research work is taking place and perhaps someday in the future we might actually get useful energy to fuel our vehicles out of algae. No, what strikes me is the desperation with which we grab onto anything-any wild idea or fanciful concept-that might provide a solution to the energy problems we are facing. Just this past week I learned that the world was going to be saved by sunlight focused on molten salt, doping trees with nitrogen fertilizer, marine power from tidal generators, geothermal energy, electric cars, clean coal, arctic methane ice, and smoke and mirrors placed in the sky to reduce the amount of sunlight hitting the earth. It was a busy week. We're willing to grasp at almost anything in the hope that it will be a life ring, ignoring the fact that much of what is offered to us could end up being an anchor.
Not that algae is anything new. Commercially, algae has been used for centuries as a fertilizer to grow crops and condition soil. Algae is used as animal feed and, especially in China and other parts of Asia, as a food source for humans. It can be used to soak up nitrogen fertilizer from fields and as a pigment in cosmetics. It's pretty useful stuff, and, as nearly 30,000 different species of algae and hundreds of thousands of different types have been identified, more uses are found almost daily.
Algae has been around pretty much since day one of life on Earth and is in fact the source of the crude that we refine into oil and gasoline. The prevailing theory among geologists is that oil and natural gas result from fallout of organic materials from tiny plants and algae and microorganisms onto the seafloor. These tiny algae plants once captured and stored solar energy when they were living organisms. The fallout formed layers of sediment rich in organic materials. Later, thanks largely to movement of the tectonic plates forming rift zones where the plates separated, these organic sediments were buried deep within the earth. Those buried deep enough (7,500 feet would be deep enough) were raised to a temperature of around 175 degrees F, where the long chains and rings of organic carbon broke down into smaller pieces. Those smaller chains with five to twenty carbon atoms became liquid crude oil. Those with fewer than five atoms formed natural gas. This is a simplification of course; actual crude oil contains thousands of different hydrocarbon chains and rings. Exactly how this takes place remains a mystery, but typically millions of years of heat and pressure are involved. The process didn't suddenly end millions of years ago; it's still taking place today, but the time required to complete it is so long that waiting for recently buried organic matter to become oil isn't practical.
So if we don't have time to wait around for tens of millions of years, how about speeding things up? It turns out that some of the hundreds of thousands of different types of algae contain up to 75 percent oil. From 1978 to 1996, the Department of Energy (DOE) funded a program with the National Renewable Energy Laboratory (NREL) called the "Aquatic Species Program." The program's initial focus was to sequester carbon dioxide emissions from coal-fired power plants, but when researchers discovered that some algae had high oil content the emphasis shifted to growing algae to produce biodiesel. Because of their extremely fast growth rates and high oil content, NREL suggested that 7.5 billion gallons of diesel fuel could be produced from roughly a half-million acres of algae grown in desert land covered with algae ponds. More recent research has suggested that around 15,000 gallons of oil can be obtained annually from an acre of land cultivated with algae, compared with about 20 gallons of oil if that acre were planted with corn that was then processed into biodiesel fuel. If that's true, we would need about 9.5 million acres-an area roughly the size of Maryland-to grow enough algae to replace our current oil consumption.
Great! Let's do it! Except, even though we've had more than a dozen years of continued research since the end of the NREL program, making oil from algae isn't quite ready for prime time yet. Finding the right strains of algae, learning how to grow them and stress them so that they produce the maximum amount of oil, and learning how to extract that oil has taken significant research, but is fairly well understood in the laboratory. The problem comes in scaling things up. Questions like how deep to make the ponds (light only penetrates about six inches in an algae-filled pond), how many different strains of algae, how to avoid contamination from bacteria or other invasive species, and how to keep your oil-producing algae from escaping and invading the local environment are all details that need to be worked out.
"None of this makes any sense until we get to the farm level," says Clayton McNeff, Chief Science Officer for Ever Cat Fuels, a Minnesota company that's building a prototype processing plant to harvest oil from algae. "It's the scale-up," he adds. "A lot more research needs to go into the area-we need more funding. We need to get out of the laboratory, do some bigger ponds with the ideas we currently have and see if they work on a larger scale." McNeff indicates that they will be doing this in the next few years, but there is a lot of work that still needs to be accomplished. "It depends how much resources are put into it. If we have the willpower, I think it can be done in the next ten years." Growing the algae, developing the commercial systems, and figuring out the best methods of extraction all need to be worked out.
Clearly, you won't be filling your TDI's tank with pond scum biodiesel anytime soon. As with so many promising alternative fuels, this one isn't ready quite yet despite what you might have read or heard. Replacing the 390 million gallons of gasoline we use in the U.S. every day with something made from pond scum seems the very edge of credibility. You know what they say about things that sound to good to be true...