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MAFES to turn waste into fuel
By Charmain Courcelle
MISSISSIPPI STATE -- A search for alternative fuels may uncover an additional source of income for Mississippi farmers and provide a solution to the waste disposal problems encountered by the state's agricultural industry.
Biobased fuels have been in use from the time man first set fire to wood for heat. But they account for less than 1 percent of energy generated worldwide today due to the cost of production and the need for improved manufacturing processes. The Mississippi Agricultural and Forestry Experiment Station has joined Oklahoma State University in an initiative to make production of biofuels more efficient and economically feasible.
"Our goal is to develop technologies that will make plant-biomass-derived fuel competitive with conventional fuel and to produce crops that may be more energy-efficient than fuel," said Nancy Cox, MAFES associate director.
Biobased fuels are derived from biomass, which includes plant material, wood and agricultural residues, solid municipal waste and animal waste. Examples of biofuels are ethanol, methanol and biodiesel.
Current U.S. ethanol production exceeds 1.5 billion gallons every year. Low petroleum prices have limited widespread use of ethanol as a fuel in the past, but pressing environmental concerns and the need for energy self-sufficiency have stimulated the search for a more cost-effective means to produce biofuels.
"The most common way we make ethanol for fuel is by traditional fermentation of corn. It's a very simple and well-known technique," said Mark Zappi, Mississippi State University chemical engineer. "However, of the whole crop of corn, we only use parts of the kernel for ethanol production. The protein, fiber and oil present in the kernels, leaves and stalks of corn cannot be fermented, so you can imagine how much of the plant is actually wasted. Also, more than 70 percent of the earth's biomass cannot be processed to ethanol using this technique."
In addition to traditional fermentation of crops, there are four primary ways to make ethanol. MAFES researchers will use biotechnology and engineering advances to improve one of these methods -- the conversion of synthesis gas into ethanol.
Synthesis gas, or "syngas", a mixture of hydrogen, carbon monoxide and carbon dioxide, is made when feedstock is combusted at a high temperature. These gases are bubbled into a fermenter containing bacteria that are able to convert the gas to ethanol. One area of research supported by the initiative examines the impact the type of feedstock has on the composition of synthesis gas.
"We know from literature that different materials that are used as feedstock can yield different syngas compositions," said Jerry Gilbert, MAFES agricultural and biological engineer. "We need to know the gas composition that's going into the fermenter because it can affect the conversion efficiency of gas to product.
"MAFES scientists will evaluate biomass from waste streams that are common to Mississippi, such as wood waste, cotton gin trash and poultry waste, as potential sources of feedstock for ethanol production. We're also going to look at cultured grasses, such as switchgrass and other tall grasses, for biomass feedstock production," Gilbert said.
Gilbert added that these sources of feedstock have the potential to lower the cost of ethanol production because they are relatively inexpensive. Using waste biomass would also help solve the disposal problems facing the Mississippi agricultural and forestry industries.
Synthesis gas composition is also affected by the gasifier, or high-temperature furnace, used to combust feedstock. Engineers involved with this project will identify gasifier technology and fine tune it to match the type of feedstock and fermenter that will be used.
In addition, MAFES researchers will look for ways to improve current fermenter design and operation.
Gilbert and Zappi both noted that the technologies developed for conversion of biomass and waste biomass to ethanol could also be used for producing other valuable products. Synthesis gas can be combined to produce at least eight chemical compounds.
"The production of ethanol and other products from 'waste' biomass sources allows for the beneficial use of these resources and the development of a new industrial base in Mississippi," Zappi said.
The U.S. Department of Agriculture is funding the MAFES-Oklahoma State University biomass-based energy research initiative.