May 22, 2013
Pond Scum As Biofuel? Researchers Explore Algae As Green Energy
April Flowers for redOrbit.com - Your Universe Online
The land and water resources of the US could likely support the growth of enough algae to produce up to 25 billion gallons of algae-based fuel a year, according to a new study from the Department of Energy´s (DOE) Pacific Northwest National Laboratory. That amount of fuel would satisfy one-twelfth of the country´s yearly needs.
An in-depth look at the water resources needed to grow significant amounts of algae in large, specially built shallow ponds led to the findings, published in a recent issue of the journal Environmental Science and Technology.
"While there are many details still to be worked out, we don't see water issues as a deal breaker for the development of an algae biofuels industry in many areas of the country," said Erik Venteris of Pacific Northwest´s Hydrology Technical Group
The best sites to produce algae are hot, humid and wet — the Gulf Coast and the Southeastern seaboard are especially promising.
"The Gulf Coast offers a good combination of warm temperatures, low evaporation, access to an abundance of water, and plenty of fuel-processing facilities," said hydrologist Mark Wigmosta.
Algae are rich in natural oil, and several research teams and corporations are searching for ways to improve the creation of algae-based biofuels. Such ways might include growing algae composed of more oil, creating algae that live longer and thrive in cooler temperatures, or devising new ways to separate out the useful oil from the rest of the algae. The first challenge, however, is simple — the algae must grow. The biggest requirements are sunlight and water. Clouds, shortage of water and evaporation are the chief antagonists to large-scale algae growth.
The same team previously studied the demand for freshwater that such algae farms would create and demonstrated that oil based on algae have the potential to replace a significant portion of the nation´s oil imports.
The focus of the new study is on actual water supplies. It examines a range of possible water sources, including fresh groundwater, salty or saline groundwater, and seawater. The estimate of 25 billion gallons of algal oil is an increase of 4 billion gallons from the previous study. While the new estimate is enough to fulfill the nation´s oil needs for one month of every year, the scientists are careful to stress that it is exactly that — an estimate based in part on assumptions about land and water availability and use.
"I'm confident that algal biofuels can be part of the solution to our energy needs, but algal biofuels certainly aren't the whole solution," said Wigmosta. However, the cost of making the fuel far currently exceeds the cost of traditional petroleum-based products currently.
Many ponds with water about six to 15 inches deep would be needed for each algae farm. Smaller algae farms have been built by a few companies, and these farms are just beginning to churn out huge amounts of algae to convert to fuel. One such company sold algae-based oil to consumers in California. Algae-based biofuels are attracting the attention of a wide variety of players, from Exxon-Mobil, which launched a $600 million research effort four years ago, to this year's teenage winner of the Intel Science Talent Search, who was recognized for her work in developing algae that produce more oil than they normally do.
THE WATER DEMANDS OF ALGAE BIOFUEL
In the adoption of broad-scale production of algal biofuel, the availability of water has been one of the biggest concerns. Biofuels created from algae would use a great deal more water than industrial processes used to harness energy from oil, wind, sunlight, or most other forms of raw energy, the scientists estimate. To create the full 25 billion gallons, the process would potentially require the equivalent of about one-quarter of the amount of water that is now used annually in the US for the entire agriculture industry. The team notes that while this is a huge amount of water, it would come from a multitude of sources: fresh groundwater, salty groundwater and seawater.
The team limited the amount of freshwater that could be drawn in any one area to perform their analysis, assuming that no more than five percent of a given watershed´s mean annual water flow could be used in the production of algae. The five percent is a starting point, says Venteris. He notes that this is the same percentage the US EPA allows power plants to use for cooling.
"In arid areas such as the Desert Southwest, 5 percent is probably an overstatement of the amount of water available, but in many other areas that are a lot wetter, such as much of the East, it's likely that much more water would be available," Venteris explained.
"While the nation's Desert Southwest has been considered a possible site for vast algae growth using saline water, rapid evaporation in this region make success there more challenging for low- cost production," he added.
The pros and cons of various water sources were weighed by the team, who noted that freshwater is cheap but in limited supply in many areas. Saline groundwater is widely available, making it attractive, but is usually found at a much deeper depth, requiring more equipment and technology to bring it to the surface and make it suitable for algal production. Seawater is the most plentiful, but requires even more infrastructure, including the creation of pipelines to move the water from the coast to the processing plants.
The estimates of water availability could be affected by special circumstances, such as particularly tight water restrictions in some areas or severe drought or above-average rainfall in others.