THE ADVANTAGES OF A THERMOCHEMICAL PROCESS FOR
PRODUCTION OF ETHANOL
Ethanol blended gasoline is being used worldwide as countries are looking for solutions for their growing energy needs using sustainable resources. Many countries have already mandated the percentage of ethanol in all gasoline:
• US - 5%
• Brazil - 23%
• Canada - 5% by 2010
• India - 5%
• China - 10% in Heilongjian, Jilin, Liaoning and Henan provinces
• Bolivia - 10%
Ethanol demand in the U.S. will continue to rise with the introduction of the Energy Independence and Security act (EISA) of 2007. With this bill, the U.S. government has now ensured the need for an increasing supply of alternative fuels in order to reduce greenhouse gases and reduce dependence on foreign oil. EISA requires the use of 36 billion gallons of renewable fuels annually by 2022.
At the same time, the production of ethanol has become an increasingly controversial with the food for fuel debate continuing. The use of corn, wheat and sugar cane to produce ethanol has been blamed for the rising costs of everything from corn tortillas to meat, poultry and even soda pop. Fears have been expressed that this trend will result in hunger, malnutrition and urban riots.
Even the compelling argument that the use of ethanol will reduce greenhouse gas (GHG) emissions which contribute to global warming has been the subject of contention. Instead the claim has been that using land to grow crops for fuel leads to destruction of forests that are sequestering large amounts of carbon.
The solution is to produce ethanol using a thermochemical process which can utilize a wide variety of waste cellulosic biomass. The use of cellulosic feedstock to produce ethanol has been shown to reduce greenhouse gases by the largest percentage over ethanol derived from other feedstocks such as corn, wheat and sugar cane.
Current Ethanol Product
Currently, the world's ethanol supply is produced through fermentation of crops such as corn, wheat and sugar cane in much the same manner that our favorite liquor is made. The starch component of the feedstock is combined with water and enzymes are added to convert the starch to dextrose, a simple sugar. Yeast is added to begin the fermentation process which takes about 40-50 hours. Once the fermentation is complete, the mixture is then distilled and dehydrated to concentrate the ethanol to fuel standards.
According the Renewable Fuels Association's Annual Report, in the U.S. there are 139 ethanol biorefineries capable of producing 7.9 billion gallons per year (bgpy) with a further 61 under construction and expected to come online in 2008 for a further 5.5 bgpy. Of the more than 13.4 billion gallons of ethanol that will be produced in 2008, only 0.42 billion gpy do not use corn or wheat as the feedstock. The anticipated 2008 production is about double the 6.5 bgpy produced in 2007.
In 2006, corn prices were approximately $2 per bushel but during 2007, prices rose to nearly $4 per bushel. This sparked many discussions regarding the use of food for fuel and the debate continues since the ethanol production from corn and wheat in the U.S. is expected to double in 2008 and the price of corn is still rising. According the Chicago Board of Trade, corn futures for December 08 are now at $6.18 a bushel.
The continuing increase in the price of corn impacts every aspect of a grocery bill. Corn is used in breakfast cereals and corn syrup is used as sweeteners in soft drinks. The majority of the impact is indirect in areas such as increases in retail cost of milk, chicken, ham, eggs, yogurt, ground beef etc. since feed grains are a major cost contributor in raising chickens, cows and pigs. The increase in retail cost of food will affect everyone but will be more keenly felt in developing countries where 70 percent or more of their budgets are (or, budget is) already spent on food.
One of the compelling arguments for producing ethanol irrespective of the process is the need to reduce greenhouse gas (GHG) emissions that contribute to global warming. According to the United States Environmental Protection Agency, corn ethanol reduces GHG's by about 21.8%. However, this claim for the reduction of GHG has been the subject of contention. The rising price of corn has created a chain reaction. Soybean farmers in the U.S. have converted their crop production to corn so soybean farmers in Brazil are increasing their production by utilizing cattle pastures to meet the soybean demand. The cattle farmers have relocated to the Amazon and are responsible for 60-70% of the deforestation. The result of this deforestation means that huge amounts of carbon is no longer sequestered and instead, has entered the carbon cycle and contributed to the very global warming that ethanol use is supposed to reduce.
The Solution
Thermochemical conversion of biomass into fuels is the solution that will be able to allow countries to meet the ethanol demand while not placing stress on food resources or land use. Thermochemical conversion process has three main steps:
1. Gasification - the biomass is dried, reduced in particle size and mechanically fed into a gasifier. It then heated to a high temperature in an oxygen-limited steam environment to produce synthesis gas which is then scrubbed to remove trace elements. The resulting syngas is comprised primarily of carbon monoxide (CO) and hydrogen (H2).
2. Catalysis - the cleaned syngas is passed over a catalyst in a fixed bed reactor; the unique Syntec catalyst converts syngas into an alcohols mixture of methanol, ethanol, propanol, butanol, and water.
3. Purification - the alcohol mixture is dehydrated, and the water is recycled. The alcohols are then separated to specification purity for different uses, including liquid fuels.
The use of gasification allows many types of waste biomass to be used as a feedstock since it is reduced to its basic components. Waste biomasses such as forestry residues, mill residues, agricultural waste, MSW, etc. are considered to be ideal feedstocks since essentially the same syngas is produced from all of them. The use of garbage generated by current ongoing processes to produce fuel solves not only disposal issues, but also produces the needed fuels without resulting in deforestation of large tracts of land.
The ethanol produced via a thermochemical route produces the mandated cellulosic ethanol which reduces greenhouse gas (GHG) emission. The method of ethanol production and feedstock choice greatly changes the GHG reduction percentage. Cellulosic ethanol reduces total lifecycle greenhouse gas emissions by as much as 90%, significant improvement over corn-based ethanol and the fermentation process. Added to this is the impact of leaving forests intact to sequester carbon from the carbon cycle.
Cost of Production
According to information supplied by the Chief Economist, USDA, March 2007, the cost to produce a gallon of corn based ethanol is $1.65. However, due to the rising costs of corn, over $6.00 a bushel, the price of the feedstock component has increased from
$1.17 per gallon to $2.25 per gallon, resulting in an overall cost of $2.73 per gallon. It is no longer economically viable to produce ethanol at this cost.
In contrast, the production cost of a gallon of alcohol produced using a thermochemical route is $1.07 based on a feedstock cost of $35 per ton. This is expected to drop to under $1.00 per gallon as performance of the gasification process and catalyst is improved and optimized.
Meeting the Need
The world wide demand for ethanol will continue to increase - driven by programs to increase use of ethanol blended fuels as one solution to reducing the greenhouse gases that have led to global climate changes and as a solution to meeting the energy needs of the world. Corn ethanol is used at this time to meet the immediate demands but the future of ethanol production is the use of thermochemical conversion of waste biomass to ethanol. Waste biomass as a feedstock eliminates the need to use food to produce fuel, is globally available and maximizes reduction of greenhouse gas emissions without placing stress on food supplies, food prices or land use.
2008
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