 |
|
|
|
|
|
|
|
|
 |
 |
 |
 |
|
||||
|
||||||||
|
||||||||
 |
 |
|
||||||
|
||||||||
 |
|
|||||||
|
||||||||
|
||||||||
 |
|
|||||||
|
||||||||
|
||||||||
 |
|
|||||||
 |
 |
|||
 |
|
|||
Clearing the air |
||||
| UGA biorefinery reduces build-up of greenhouse gases | ||||
| By Cat Holmes |
||||
The abrupt and cataclysmic
weather that was portrayed in the movie The
Day after Tomorrow is
UGA scientists are developing a biorefinery that will be an environmentally sound alternative to crude oil refineries. The biorefinery processes biomass, such as agricultural waste and biofuel crops, to produce fuel. And, it’s beneficial for the environment. “Obtaining our energy through a biorefinery instead of depending on fossil fuels doesn’t just reduce carbon dioxide emissions,” says K.C. Das, a bioconversion engineer for UGA’s College of Agricultural and Environmental Sciences. “It actually sequesters carbon.” That means a potential source of carbon dioxide is transformed into a form of carbon that’s harmless. “It could remain in the soil for a long time, away from the atmosphere where it would contribute to global warming,” Das says. The scientists began the project with a simple idea: The chemical difference between hydrocarbons, such as coal and oil, and carbohydrates, found in plants, is small. “We realized that all we’re missing is a process that can mimic nature’s conversion of biomass to fossil fuel,” Das says. Pyrolysis, an old technique that creates charcoal, can do this. Pyrolysis transforms biomass and agricultural waste products into a fuel and chemical feedstock called bio-oil. One byproduct of pyrolysis is hydrogen, a much cleaner fuel and a substance used to make ammonia fertilizer.
“You basically take peanut hulls and heat them to 450–500 degrees Celsius,” Das says. “In the absence of oxygen, the cellulose pyrolizes and forms oil. It looks a lot like engine oil, but it’s a little more viscous.” One of the most exciting aspects of the technology is that it also generates carbon char, a solid form of carbon. Unlike carbon dioxide, the analogous byproduct of crude oil refineries and a major environmental problem, the char is harmless and even beneficial. Eprida, a private company and partner with the UGA team, has developed a process that turns char into a slow-release nitrogen fertilizer. Studies show that char in this form restores soil fertility and increases crop yields. “Char is unique because it is quiescent—it just stays there,” Das says. “With fossil fuels, carbon dioxide that has been in the soil for millions of years is used up in a few years, producing large amounts of carbon dioxide that end up in the atmosphere. This pyrolysis technology actually sequesters the carbon while adding ammonia to the char so that we can put it back in the soil as a fertilizer.” Since the biorefinery uses agricultural waste like peanut hulls, poultry litter and other byproducts, the technology also turns an environmental obstacle into an environmental advantage. While the technology is very promising, there are still challenges to work on. A major challenge is that bio-oil is unstable and reactive, which makes it more difficult to work with. “There are around 300 compounds in bio-oil,” Das says. Engines must be modified to work with a fuel that has different properties, or else the fuel must be modified. The team is also looking for new applications for both the technology and its byproducts. Other useful byproducts discovered so far are glues, which Das says are “a very high-value product. Paper mills have a lot of wood waste and manufacture plywood, which uses a lot of glue. Setting up a wood waste biorefinery on-site would be ideal.” Pyrolysis products can also be used to flavor food, in products like liquid smoke. Finally, the scientists are working to make the process more efficient, which will make it more economical. “It is a complex process,” Das says. “The typical process is to make something and throw away the ‘trash.’ The difference in a biorefinery is that everything is used for something else, everything has value.” |
||||
