PNNL algae study sets baseline for available US land, water

For anyone looking for a piece of land to start an algae production site, Mark Wigmosta from the Pacific Northwest National Laboratory might be the person to speak with. Wigmosta and a team of researchers have completed a study titled, “National microalgae biofuels production potential and resource demand,” which outlines the best regions throughout the lower 48 U.S. states for algae biomass growth potential given both land and water footprint concerns. “We were hoping,” Wigmosta told Biodiesel Magazine, to produce a baseline study with “scientifically defendable estimates of the amount of land and water required to achieve a certain level of production.”

To do that, the team compiled a number of factors into their modeling system, and the result is a study that Wigmosta said shows that the 17 percent of the country’s imported oil used for transportation can be replaced by algae-based biofuel. The study was based on the notion that algae production would happen through the open pond method, and the team started by screening out areas that would require land excavation to flatten the land, and areas that may compete with other food-based agriculture, national parks or any other sensitive areas. “That got us down to 5.5 percent of the land areas in the lower 48,” he said. “At those potential sites we wanted to get an estimate of production potential and water demand.”

At those sites, the team then looked at the local climate. “We used 30 years of hourly meteorological data and drew an open pond temperature evaporation model.” After that, the team combined water temperature information at a given site with incoming solar radiation in a biophysical pond growth model to estimate hourly biomass production. Based on that modeling, Wigmosta said, “We identified roughly 90,000 potential suitable areas,” and based on climate analysis, “we had potential production levels and water demand at each site.”

While the study does show that algae oil could replace a significant amount of fossil oil, the team also pointed out in the study that the freshwater amounts required to do so would be high, nearly a quarter of what the country currently uses for irrigated agriculture. The best areas in the U.S. that would provide both growth potential and would not require as much freshwater in comparison to other regions, according the study, are in the Gulf Coast, the Eastern Seaboard and the Great Lakes region. The team was able to identify those areas based on the flexibility of the study. “The flexibility of the approach we took is you could have a production target and then try to optimize to try and reduce the water or the land footprint.”

Like most studies, Wigmosta said that there are a number of questions still unanswered by his study, and that he is already working to complete a similar study that would look at saline water locations for algae production, as well as the potential resource availability for nutrient-rich locations that could provide CO2 for the growth of the algae biomass. But, even with future studies already in the works, he also said that this study shows the theoretical maximum any area in the U.S. would be able to produce and how much water would be available at each location. The theoretical maximums were calculated by using incoming solar radiation, and the algae’s ability to turn that sunlight into biomass. While certain efficiencies could change that maximum in some cases, he said, “If production numbers are showing up higher than they are in a particular region, they are kind of questionable.”

Overall, Wigmosta said the study shows that there is potential to meet a significant portion of some of the renewable fuels targets, but that it will come with a significant land and water requirement if an open pond system is used.

“It’s been really interesting and enjoyable work,” he said, “and valuable for this country. We have some energy issues we need to deal with.”

The study was published in the journal of Water Resources Research.