Why crush algae when you can incinerate it?
That's one way to describe a shift in strategy at Genifuel. The company, which started out as an algae biodiesel company, has obtained a license from Pacific Northwest National Labs for a process to turn algae into natural gas.
It works like this. Algae is grown in ponds and, while it is still wet, is it placed in gasifiers with a chemical catalyst that allows it to cook at relatively low pressures and temperatures, said president Jim Oyler. It cooks at 350 Celsius versus 700 Celsius.
The cooking produces a synthetic gas that is 65 percent methane, or CH4, and 35 percent carbon dioxide along with some other trace materials. The carbon dioxide is then pumped into algae ponds as food. It will be more expensive than natural gas pulled from the earth, but it will require lower subsidies than liquid algae fuel to be competitive with its fossil fuel equivalent. It yields 0.55 liters of gas per gram of dry material, Oyler claimed.
The process has distinct advantages over making liquid fuels with algae, he said, as well as making methane with biological digesters. First, gasification lets fuel producers use the entire organism – the carbohydrates, the protein and the lipid oils. Algae fuel producers only want the lipid material, which naturally is only about one-third of the organism by mass. Boosting the oil content has forced algae fuel producers to genetically modify their strands. Some hope to devise creatures that are 70 percent lipid. Even if the oil content is boosted, algae fuel makers have to figure out what to do with the leftover biomass. Most claim they will sell it for animal feed, which could even turn out to be more profitable.
Monocultures are also not required for gasification-mixed species of algae can be roasted together without hurting the consistency. Most importantly, the algae go in wet. Algae biofuel makers have to separate the water from the algae to make fuel, an arduous process. Although pond water can look green, there can be 1,000 liters of water for every liter of algae. Separating out that water has prompted companies to devise growing techniques that don't include water (Solazyme, who seems to be ahead of the rest of the pack) or techniques for shaking oil out of them (OriginOil).
"Water is an integral part of the process," he said. "We started out to make liquid fuel but we concluded that it was in the category of 'too difficult.' "
Digesters – in which microbes turn manure and biomass into methane – work in the same manner but can take weeks. "This is almost instantaneous. There is nothing left over and there are higher yields."
But, like nearly everything else in green, Genifuel is in need of money to get off the ground. It is currently trying to build a prototype plant and raise money for larger prototypes.