For GSS Energy Use chapter 9. Excerpt: Plants take energy from the Sun, and use it to make sugar. We ...extract the sugar, and ferment it to make fuel. That’s the process for ethanol and cellulosic biofuels in a nutshell. ...Kef Kasdin... is executive at Proterro, a company that has taken a different approach to biofuels. Proterro cuts out plants entirely, instead using cyanobacteria to produce sugar directly. ...Kasdin and Proterro cofounder John Aiken ...were drawn to the idea of engineering cyanobacteria to make sugar. Cyanobacteria get all the energy they need from the Sun, and live on water and carbon dioxide. ...Irrigation-grade or even waste water can be used. And depending on how they are grown, they can produce considerably more sugar per acre of land than sugarcane can. ...[Proterro's] bioreactor sits in a field in Florida, a 5-meter-long white cylinder suspended in black netting. ...Proterro hopes this outdoor bioreactor replicates the success of its greenhouse demonstration, .... If this bioreactor does as well, they will replicate it 100-fold. And ...the next step would be a commercial plant. Ideally, such a plant would be hooked up directly to an ethanol fermenter, Kasdin says. Proterro would take the CO2 exhaled by the fermentation yeast in the ethanol vats and pump it through the bioreactors. The cyanobacteria in the bioreactors would take the carbon dioxide and make sucrose. The sugar water from the cyanobacteria’s bioreactors could then be pumped right back to the ethanol refinery and fed to the yeast. “That sounds pretty easy, a pretty tight little loop ...eliminating the traditional costs of transport, harvest and storage for biomass. Once implemented, the process would sharply increase the energy return on energy investment (EROEI) compared to conventional ethanol production, according to Proterro’s Kasdin.... http://scitation.aip.org/content/aip/magazine/physicstoday/news/10.1063/PT.5.5010. Kim Krieger, Physics Today.
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