Polaris Venture Partners will be represented on GreenFuel’s Board of Directors by Dr. Robert Metcalfe, a Polaris General Partner. Bob Metcalfe helped build the Internet and invented Ethernet—the dominant local-area networking (LAN) standard on which he shares four patents.

The GreenFuel system takes in a continuous stream of flue gases directly from the base of the stack. The algae in the reactor use the available carbon dioxide and water to grow new algae, giving off pure oxygen and water vapor in the process.

The organisms also absorb nitrogen oxide and sulfur dioxide, which contribute to acid rain. GreenFuel estimates that a single pass through the GreenFuel system strips flue gas of up to 40% of its CO₂ on average, and 86% of the NO_x.

When the algae die and drop to the bottom, the slurry is harvested, dried and used as biomass fuel, or further processed into biodiesel.

GreenFuel uses an implementation of an air-lift reactor (ALR), which is a type of pneumatic contacting device in which fluid circulation takes place in a defined cyclic pattern through channels built specifically for this purpose.

The process, called photomodulation, rotates the algae in and out of the sunlight, rather than bringing the sunlight to the algae, as in a competitive system being designed by GreenShift. (Earlier post.)

The GreenFuel bioreactor consists of a riser tube or channel, a gas separator, and a downcomer tube or channel, applied in a triangular configuration. The difference in the apparent fluid densities between the riser and downcomer provides the driving force for liquid circulation.