The National Renewable Energy Library (NREL, Washington, DC / USA; www.nrel.gov), part of the US Department of Energy (www.doe.gov), has developed what it says is an environmentally friendly route to ethylene production. The process based on photosynthesis, which does not release CO₂, is said to be an improvement on technology discovered 10 years ago in Japan.

Unlike fossil fuel-derived ethylene stemming from photosynthetic organisms that captured the sun’s energy millions of years ago, the NREL process is based on “new photons” that are currently hitting plants, algae and bacteria capable of producing fuels directly, explains NREL’s principal investigator, Jianping Yu.

While scientists at Japan’s Sojo University were able to leverage the cyanobacterium “Synechoccus 7942” to produce ethylene, by the fourth generation these bacteria were defunct, says Yu. The US team employed the cyanobacterium “Syneechocysits 680” to convert CO₂ and water to ethylene. As the DNA sequence of the bacterium was successfully manipulated, it can survive for four months.

According to Jim Brainard, director of NREL’s Biosciences Center, the new method is “much more efficient than the standard separation technologies used in industry.” The ethylene could be produced in an enclosed photobioreactor containing sea water enriched with nitrogen and phosphorous. The ethylene gas would rise and be captured from the reactor’s head space, from where it could be converted via a catalytic polymer process to fuels and chemicals. The continuous production system is said to improve energy conversion efficiency and thus reduce operating costs.

NREL is now initiating talks with potential technology partners in industry to help take the process to industrial scale.