By Cat Holmes

University of Georgia

The abrupt and cataclysmic weather portrayed in “The Day After
Tomorrow” is pure Hollywood drama, but the overwhelming
consensus among scientists who study the atmosphere is that
global warming is real. It’s primarily caused by a build-up of
greenhouse gases, mostly the result of burning fossil fuels
like coal and oil.

University of Georgia scientists are developing a bio-refinery
that will be an environmentally sound alternative to crude oil
refineries. The bio-refinery processes biomass such as
agricultural waste and biofuel crops to produce fuel. And, it’s
beneficial for the environment.

“Obtaining our energy through a bio-refinery instead of
depending on fossil fuels doesn’t just reduce carbon dioxide
emissions,” said 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 said.

The researchers began 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 said.

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.

Unfortunately, most hydrogen ammonia/nitrogen fertilizer
producers commonly use natural gas (a non- renewable resource)
in production which creates large amounts of greenhouse gases.
Agricultural waste is a renewable resource and is net-zero in
emitting greenhouse gases.

“You basically take peanut hulls and heat them to 450-500
degrees Celsius,” Das explained. “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 said. “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 bio-refinery 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 said. Engines
must be modified or the fuel must be modified to work with a
fuel that has different properties.

The team is also looking for new applications for both the
technology and its byproducts. Other useful byproducts
discovered so far are glues, “a very high-value product,” Das
said. “Paper mills have a lot of wood waste and manufacture
plywood, which uses a lot of glue. Setting up a wood waste bio-
refinery on-site would be ideal.” Pyrolysis products can also
be used to flavor food in products like liquid smoke.

Finally, they’re working to make the process more efficient,
which will make it more economical.

“It is a complex process,” Das said. “The typical process is to
make something and throw away the ‘trash.’ The difference in a
bio-refinery is that everything is used for something else,
everything has value.”