Bruce Dannenberg is a big fan of cyanobacteria – the ancient lineage of organisms you may remember from high school as blue-green algae. Turns out cyanobacteria aren’t algae after all; hence the name change. But what Dannenberg likes about cyanobacteria isn’t what they are, it’s what they do: photosynthesis.
Photosynthesis is the process by which organisms use carbon dioxide from the atmosphere combined with energy from sunlight to make the sugars that fuel their growth. And you may remember that oxygen is a byproduct of this process. Billions of years ago, cyanobacteria began photosynthesizing, and in so doing, created the oxygen that supports animal life as we know it.
“Cyanobacteria is the first organism on Earth that developed photosynthesis – it’s responsible for our breathable atmosphere,” Dannenberg said. “It’s the most efficient photosynthetic organism on Earth. It has additional pigment and structure within the cell that allow it to utilize more of the light spectrum and be a more efficient photosynthetic engine.”
Dannenberg plans to harness that photosynthetic engine to produce marketable quantities of industrial chemicals and fuels.
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Butanol, not sugar
All it takes is a little bioengineering. In 2009, Dannenberg founded an Asheville-based company called Phytonix, which, with the help of its scientific partners, has already developed two types of engineered cyanobacteria that use carbon dioxide and sunlight to produce n-butanol instead of sugar.
“Photosynthesis is a fantastic biochemical process,” he said. “It’s very efficient at converting carbon dioxide into (various) target chemicals.”
N-butanol, often simply called butanol, is a type of alcohol used as an ingredient in plastics, solvents and a wide range of products, from processed foods to cosmetics. It can also be used in place of gasoline in a car engine. Dannenberg says the worldwide market for butanol is large and growing.
Current methods of producing butanol use petroleum as a feedstock and emit carbon dioxide in the process. Because the Phytonix approach uses carbon dioxide as a feedstock, it removes carbon dioxide from the atmosphere.
“Our route is about as green or sustainable as you can get,” he said. “It reduces carbon dioxide significantly so it has substantial benefits for slowing down climate change.”
In the process of producing a gallon of butanol, the engineered cyanobacteria remove about 16 pounds of carbon dioxide from the atmosphere and give off about 16 pounds of oxygen. If that gallon ends up being burned in a car engine, the chemical reaction would release the 16 pounds of carbon dioxide back into the atmosphere.
“If you use it as fuel, it’s net zero and you have that 16 pounds of oxygen to boot,” Dannenberg says. “There’s no other technology that can do that.”
Because the cyanobacteria need a source of carbon dioxide, Dannenberg envisions Phytonix facilities being located near sources of carbon dioxide, such as ethanol refineries, oil and gas production plants, cement factories or breweries.
What would it look like? Well, imagine an ethanol refinery in the cornfields of the Midwest, surrounded by large enclosed soft-sided “tanks” filled with water and cyanobacteria – essentially giant fluid-filled bags “like IV bags, if you will,” said Dannenberg.
Carbon dioxide from the ethanol plant would be directed into the bags, where it would dissolve into the water. Sunlight shining into the bags would give the cyanobacteria the energy to convert the carbon dioxide into butanol, which could then be separated out from the water.
Just add water...
Each gallon of butanol would require about 40 gallons of water to produce, but about 38 of those gallons would be recycled. In addition, the water doesn’t have to be clean to start with, but it will be clean after the cyanobacteria get through with it.
Dannenberg predicts each acre of the giant bags could produce 20,000 gallons of butanol per year. By 2021, Phytonix aims to have four facilities, each producing 25 million gallons of n-butanol a year.
“Phytonix is also working to be a leader in biosafety,” Dannenberg said. “These are not inherently dangerous organisms, but you never know.”
The first line of defense is using enclosed tanks rather than open ones. In case of a leak or rupture, Dannenberg said the organisms wouldn’t be able to survive because they are engineered to grow in water that is 3 percent to 4 percent carbon dioxide, a concentration much higher than what exists in rivers, lakes, or the Earth’s atmosphere. The two cyanobacteria already engineered are freshwater species that would not be able to survive in the ocean. Another safety guard is that once they achieve a certain density, the engineered cyanobacteria stop replicating.
Phytonix is targeting the industrial chemical market first, because it’s a large and high-value market. “We believe we can produce n-butanol in volume for about $1.35 a gallon,” Dannenberg said. “Current production (methods) cost $4 to $5 per gallon.”
Eventually, Dannenberg would like to see Phytonix selling butanol as an additive or replacement for gasoline in cars. Butanol burns more cleanly than gasoline because its combustion products are carbon dioxide and water – there are no emissions of sulfur oxides, carbon monoxide or hydrocarbons such as methane.
“Butanol is much safer than gasoline because it’s less evaporative, less explosive, and less toxic,” Dannenberg said. “It has 50 percent more energy per gallon than ethanol, and it can be used directly, unlike ethanol.”
He said butanol can be used in older cars with no modifications, whereas new cars with fuel injectors would require an adjustment to the fuel-air ratio.
Phytonix is also working on engineering a cyanobacteria that can produce pentanol, a type of alcohol that has even more energy per gallon than butanol. Pentanol has similar uses to butanol, and it could also be used as a fuel.
In addition to producing butanol and pentanol, the Phytonix business plan calls for licensing some of its patented technology, including biosafety technology that might be useful to other companies that are engineering microbes.
So far, Dannenberg is the sole employee of Phytonix, which also has a five-member board of advisers.
“We have a distributed business model,” he said. “We don’t build labs. We find the best scientists in the world and best labs to do pieces of our development.”
Scientists at South Dakota State University and the Ångström Laboratory at Uppsala University in Sweden, among others, are working with Phytonix to design the engineered cyanobacteria, the soft-sided enclosed tanks and the biosafety technology.