The fish farms provide both a source of income and a source of fertilizer, which reduces overall carbon emissions, since producing and using fertilizer is ordinarily a major source of carbon emissions in biofuels production. The mangrove forest also sequesters carbon dioxide in its root system. Most biofuels are at best carbon neutral, emitting as much carbon dioxide when they’re produced and burned as the biofuel crops take in as they grow. One of the key parts of the Masdar research project is determining just how much carbon can be economically sequestered.
A version of the system has already been demonstrated in the north African country of Eritrea by Carl Hodges, the founder and chairman of the Seawater Foundation. (He’s acting as a special advisor to the Masdar project.) In that project, the salicornia and leaves from the mangroves were used as animal feed, and some of the oil from the seeds was converted to biodiesel. That project ended as a result of political upheaval in that country, Hodges says, but it demonstrated that the integrated approach could work.
The effort to avoid using fresh water and land that’s used for food “should be applauded,” says Mark Schrock, a professor of biological and agricultural engineering at Kansas State University. But he says it will be important to quickly develop a mechanized means of harvesting the salicornia. This could be a challenge because, although it can be harvested with existing equipment, the plant has high salt levels that could damage these machines, says Wayne Coates, a professor at the Office of Arid Land Studies at the University of Arizona.
It will also need to compete with other biofuels crops. Per acre yields of oil are on par with soybeans (which provide additional economic value from non-oil products), but are just one-eighth the yield of palm oil. The saltwater system, however, has the advantage of not requiring expensive land and water, and it produces its own fertilizer. Kennedy says that initial estimates suggest that fuel produced from salicornia could be competitive with petroleum-based fuels, but warns that detailed studies still need to be done.