What is Cellulosic Ethanol and how do you produce it?
Cellulosic ethanol is an alternative fuel made from stalks and stems of plants and a variety of non-food plant materials, including:
Agricultural Residues (rice, corn stover, wheat straw)
Agricultural Wastes (sugar cane bagasse waste, rice husks, citrus pulp)
Forestry Wastes and Wood Wastes (including willow and poplar)
Municipal Solid Wastes (including paper pulp and sawdust)
Dedicated Crops (switchgrass, miscanthus)
Cellulosic ethanol has great potential as a future alternative fuel for helping to reduce our dependence on petroleum.
Which cellulosic sources offer more benefits, i.e, are less expensive to process, more plentiful, generate less greenhouse gas emissions in the processing, etc?
The pros and cons of the various feedstocks and the pre-treatment processes of the feedstock, (the first step before you use a similar process for making corn ethanol today) are all being evaluated in various research efforts that are underway and in six U.S. Department of Energy Cellulose pilot plants.
The Biomass Conversion Research Laboratory at Michigan State University, under the direction of Professor Bruce Dale, has performed research for more than 30 years on pathways to use cellulose as a feedstock to produce ethanol. Dales work on pretreating biomass for cellulosic ethanol (from corn stover, grasses, wood, and other biodegradable material) using ammonia is patented.
This technology has been licensed by BMI International (Lansing) and is being scaled up by them for use in one of the recently selected U.S. Department of Energy Cellulose pilot plants. This facility will use corn stover as the basis for making cellulosic ethanol. The plant may be the first to use MSUs patented cellulose pre-treatment process. Five additional companies in five states have been identified by the U.S. Dept. of Energy for the production of cellulosic ethanol by various processes.
When production is launched at these plants in 2008, the cellulosic sources and the pre-treatment processes will be quite comprehensively evaluated. Here’s what’s being said about some of the feedstocks.
|Agricultural Residues (rice, corn stover, wheat straw)||
· Probably less costly than most forest residue. It’s renewable.
· New source of revenue (farmers, and rural preprocessing industries that may spring up to handle material.
Currently, agricultural waste is
composted, plowed back into the soil,
thrown away, or burned.
· Potentially higher yields per acre than corn.
· Potential market for animal feed.
· Existing harvest equipment, storage systems are immature. For example, combines are designed to pluck an ear of corn and leave the rest of the corn plant in the field. A new machine is needed to harvest the corn stalk, in addition to the corn kernels.
· The current high costs for recovering most agricultural residues, contribute to preventing their wide use for energy purposes. (Still more expensive than harvesting corn.)
|Wood fibers – (forestry wastes and wood wastes)||
· Widely used source of renewable energy 44 percent of the total (in the U.S.).
· Substantial source of renewable energy. In the year 2030, more than 7 percent of the country’s energy needs could be met by woody biomass resources.
· Current infrastructure and natural resources already exist.
· Reduces sulfur dioxide and nitrogen dioxide in biomass processing versus coal or oil.
· Use of forest waste helps decrease fire hazards associated with deadwood.
· Wood chips could become too expensive to compete; wood costs <$60 per bone dry ton to be competitive (others cost an estimated $35-60).
· There are competing demands for wood fiber and these may drive up prices up.
|Energy Crops (switchgrass, miscanthus)|| |
· Native to North America.
It requires little water or fertilizer to
grow. Like the grass in your yard, it
comes back year after year without
· Thrives in places unsuitable for most crops.
· Growing 5 “ 9 tall, this gangly plant yields twice as much ethanol per acre as does corn.
· Switchgrass is a “captive energy source.” It has no competing use other than energy.
· Switchgrass helps prevent soil erosion.
· Broader range of adaptability to poorer soils, and drought tolerance, which would allow energy crops to be grown in regions that cannot support large-scale food crop production.
· It’s a perennial and will take 2-3 years to get to full yield.
· Enzymes needed to break the cellulose down are expensive. DOE and private investors are working diligently to solve this problem.
· Provides a local solution to waste accumulation by allowing managers to dispose of materials with a 30-50 mile radius of their generation point.
· Disposal is safe and permanent, requiring no burning.
· Establishing MSW-to-ethanol plants in rural communities directly improve economic welfare by creating hundreds of construction jobs and permanent operational positions.
· Producing fuel from MSW provides a viable solution to multiple environmental problems.
· Converting compostable waste to ethanol may divert efforts for recycling paper products. However, ideally, ethanol production from MSW will only add to the percentage of garbage reused, rather than draw away from the material that is currently recycled.
How do you make cellulosic ethanol?
It takes three steps to make it:
Pre-treatment of the cellulosic feedstock
Use of enzymes to make the sugars needed for ethanol
What are the benefits?
Reduces our dependence on petroleum. Ethanol, (grain and cellulosic ethanol) could replace 30 “ 50 percent of the nation’s demand for energy, according to biomass researchers.
We can grow our own. We have the potential to produce more ethanol with cellulosic feedstocks than we are currently able to produce through corn alone.
U.S. Department of Energy study estimates annual biomass potential at 1.33B tons by 2030, with an ethanol potential of 90-97.5B gallons
It’s good for the environment. Both grain-based ethanol and biomass ethanol reduce greenhouse gases “ 29 percent for ethanol and 86 percent for cellulosic ethanol according to Argonne National Labs.
Promotes energy diversity and provides consumers a choice. Biofuels, such as ethanol, give consumers a real choice at the pump “ a choice beyond “regular,” “mid-grade” or “premium.” GM believes that advanced technologies and widespread use of ethanol are key to achieving energy diversity independence.
It will eventually provide savings for consumers. Using technology first demonstrated in WWII for cellulosic ethanol, we could produce cellulosic ethanol today for about $2.50 per gallon.
What are the six U.S. BioEnergy plants underway to produce cellulosic ethanol? What will be their total capacity for ethanol production when complete?
Kansas: Abengoa Bioenergy Biomass. Capacity to produce 11.4 million gallons of ethanol annually and enough energy to power the facility, with any excess energy being used to power the adjacent corn dry grind mill. The plant will use ~700 tons per day of corn stover, wheat straw, milo stubble, switchgrass, and other feedstocks. (bio/Thermo)
LaBelle (Hendry County), Florida. ALICO, Inc. Capacity to produce 13.9 million gallons of ethanol annually using ~770 tons per day of the yard, wood, and vegetative wastes and eventually energy cane. (Thermo/fermentation)
Southern California. BlueFire Ethanol, Inc. is Sited on an existing landfill, with the capacity to produce 19 million gallons of ethanol annually using ~700 tons per day of sorted green waste and wood waste from landfills. (bio)
Emmetsburg (Palo Alto County), Iowa. Capacity to produce 125 million gallons of ethanol annually (~25% will be cellulosic ethanol) using ~850 tons per day of corn fiber, cobs, and stalks (bio)
Shelley, Idaho. Iogen Biorefinery Partners, LLC. Capacity to produce 18 million gallons of ethanol annually using ~700 tons per day of agricultural residues including wheat straw, barley straw, corn stover, switchgrass, and rice straw (bio)
Soperton (Treutlen County), Georgia. Range Fuels (formerly Kergy Inc.). Capacity to produce 40 million gallons of ethanol annually and 9 million gallons per year of methanol, using ~1,200 tons per day of wood residues and wood-based energy crops. (Thermo)
Courtesy of General Motors