Third Generation Biofuels Are Closer Than You Might Think
Considering the problem we have with the accumulation of atmospheric carbon dioxide, it makes sense to try and turn it into energy, for which we have a great appetite and a diminishing supply. If we could only convert the CO2 to energy, then we wouldn’t need to burn the fuel that produces so much of it. But can that be done?
As any schoolchild knows, green plants do exactly that every day. So it makes sense that an engineered biological process should be able do it too. Developers of algae-based fuels and researchers have been exploring this possibility, using various approaches such as genetically modified organisms at the University of Georgia and artificial photosynthesis at MIT. Still, success seems a long way off.
But a joint venture of British and American companies is developing a process that can do this to commercial scale in a just a few years.
Naturally Scientific of Nottingham, England, and Sweetwater Energy of Rochester, N.Y., have designed a process that produces oil for biodiesel and such byproducts as bio-chemicals directly from carbon dioxide.
Unlike algae-based systems, which use CO2 to feed the growth of oil-rich algae in a photo-bioreactor, Sweetwater’s process is based on an embryogenic cell culture (similar to a stem cell) that produces oil directly without requiring sunlight, according to Dr. Sarad Parekh, Sweetwater’s CTO. This also means that the process of expressing oil, from seed or from algae, is no longer necessary.
“This is a unique novel concept for converting waste gases. We are slowly converting into a carbon company, where carbon is sequestered and used as a feedstock and converted into valuable chemicals,” he said.
There is a big opportunity for carbon reduction in biofuels, according to Parekh. In ethanol production, the starch or cellulose in the crops and plants convert to sugar. As microbes feed on the sugar, ethanol and carbon dioxide are generated. If that carbon could be captured and utilized immediately, it would be tremendously useful, he said.
“Sweetwater is working very closely with Naturally Scientific,” said Parekh. ”They use a two-stage biological process. In the first stage they use a chloroplast cell which uses a photosynthesis-type process that converts the carbon dioxide to carbonic acid which ultimately gets converted into intermediate precursors in the form of glyceraldehyde or C3 sugars. This can be done at room temperature. That glyceraldehyde is then fed into a specific cell culture known as an embryogenic culture.”
The cell component that the team has isolated has the sole function of producing oil. “So what we do is basically take that embryogenic culture and propagate it in the second stage, and it expresses oil that can be easily recovered,” Parekh said.
Sweetwater’s expertise in producing sugars is a great fit here, as the second stage of this process can take C3 sugars or can take the C5 and C6 sugars that Sweetwater is already producing. “So the flexibility of this process is that you can convert sugars into oil,” said Parekh. “This is totally different from the conventional seed processing where you have to grow the seed, cultivate, harvest, dry, crush, extract and refine. The beauty of this process is that it eliminates many of these steps, just as plants will do in the field, but we are doing it in a contained tank.”
The process requires a relatively small amount of land and is very simple to scale up, Parekh said.
“It can also be applied to corn ethanol plants that are always emitting CO2 anyway,” he said. “So this can maximize the efficiency with a wraparound process that can recover the carbon that was being wasted and convert it into more valuable product. At the same time, it is helping to control emissions.
“These oils can be converted into biodiesel, or specialty chemicals that are even more valuable. Right now, some ethanol plants are maxed out because of emissions. This can help them expand their nameplate capability.
“People who are developing ethanol plants would also like to diversify their portfolio to include not only ethanol, but distiller’s dry grain (DDG) and now they can convert their CO2 and make oil from it.”
Using this embryogenic cell culture approach, all that’s needed from the plant is a specialized batch of cells to begin the process, like a starter for yoghurt. This can then be propagated, feeding on the C3, C5 and C6 sugars which Sweetwater’s process can derive from the CO2.
The $250 million joint venture between the two companies will yield a production plant that will produce oils from cell cultures derived from oil producing plants.
This is new business for Sweetwater, which has been developing second generation cellulosic biofuels.
Biofuel production has traditionally been vertically integrated, with refiners taking in biomass, breaking it down, converting it into sugars and then converting those sugars into ethanol through some kind of fermentation process. Sweetwater has proprietary knowledge in the first part of the process, starting with the pretreatment of the cellulosic biomass and ending up with monomeric C5 and C6 sugars.
They saw a business opportunity in this stage, becoming a producer of sugars and a producer of sugar production technology that could directly feed into the current biofuel supply chain.
Their process utilizes non-food agricultural wastes such as wood chips, and corn stover and turns them into simple, high quality sugars suitable for conversion into ethanol. Their proprietary process includes a way to gently cook the cellulosic materials in a way that does not release agents that act as inhibitors to fermentation, which are often present in more conventional bio-refinery operations. Once the sugars have been extracted in a two step process, it is concentrated to levels suitable for their intended end use (25 to 30 percent for ethanol, 50 percent for bio-plastics). Because of their process efficiency and the low cost of agricultural residue, their sugar can be used to supplement the more expensive feedstocks such as corn. You could think of it as a kind of biomass equivalent to hamburger helper.
Sweetwater’s intention is to replicate and scale this process and move it out to areas near where the feedstocks are available. The company plans to have two commercial-scale sugar production facilities in operation within the next two years.