Conventional Ethanol vs. Cellulosic Ethanol

Ethanol has long been hailed as a more environment-friendly and renewable fuel source than gasoline, and furious research is on the way in our modern world to make it more viable and economical. Traditional ethanol and cellulosic ethanol are actually one and the same product, because the final product is chemically identical. The difference lies in the raw material or feedstock they are made from, and the processes used to produce them. The advantages and disadvantages of either are related to these two basic factors.

Conventional ethanol is produced using grains like corn and wheat or soybeans. The most important and widely used ingredient for conventional ethanol is corn or sugarcane, and it is processed either through dry or wet milling. Cellulosic ethanol, on the other hand, can be produced from a wide variety of cellulosic substances such as agricultural plant wastes like corn stover, cereal straws, and sugarcane bagasse. Also included on the cellulosic feedstock list are plant wastes from industrial processes like sawdust, paper pulp as well as switchgrass.

The comparisons are immediately apparent. While conventional ethanol needs to have grain or sugarcane (which could serve as food) for its raw material, cellulosic ethanol actually uses wastes, which are typically disposed right now using costly methods like landfills or burning. Wastes like sawdust and paper pulp are especially useful, because they are already processed to a degree and eliminate a step from the cellulosic ethanol production process, saving cost. The usage of agricultural plant wastes mean that these are no longer a waste, but are value propositions for the farmers. There is a huge untapped potential in this area.

Cellulosic ethanol production prevents the danger that food cropping will turn into more lucrative fuel-cropping. The supply of raw material is also more abundant than corn-based ethanol production. The use of fertilizers and watering essential for corn for ethanol production is also not required to such an extent for cellulosic ethanol. Important as well is the fact that traditional ethanol uses fossil fuels as part of it manufacture, whereas cellulosic ethanol uses only lignin, which has energy content equal to coal. Lignin is a bi-product of the conversion process from bio-mass to ethanol, and does not need to be procured extra. Thus, no expensive fossil fuel is required for the cellulosic manufacturing process, and best of all, the amount of harmful CO2 produced while using the lignin is totally compensated by the absorption from the original plants in photosynthesis. The environment also does not have to suffer from the greenhouse emissions that are usual in the production of traditional ethanol.

The usage of the perennial switchgrass for cellulosic ethanol also bodes well for the environment and efficiency. This grass has a deep root system which helps prevents soil erosion and contributes toward soil fertility. Since it is a species native to the U.S., it is the best adapted to the climate and soils, using water efficiently and needing less pesticides and fertilizers. It can be grown in land which is unsuitable for any other sort of cash crops. New research is looking towards substituting soybeans with switchgrass for production of animal feed proteins, because one can grow more switchgrass per hectare than soybeans. This would make switchblade grass a popular option for farmers as it will have double value in terms of ethanol feedstock and affordable production of animal feed, because switchblade grass production is still to be incorporated into the U.S. agricultural system.

The only disadvantage of cellulosic ethanol lies in the difficulty with which it is presently extracted from the feedstock. The cellulosic feedstock in process consists mainly of cellulose, hemicellulose and lignin, and the idea is to extract fermentable sugars in order to synthesize into ethanol. But these sugars in cellulose and hemicellulose are bound in complex carbohydrates called polysaccharides, and separating these complex structures into simple sugars is not easy. This leads to longer process time, and low yield per unit of feedstock, making cellulosic ethanol somewhat less economic to produce than conventional ethanol at the present moment.

Comprehensive research is required to increase the efficiency and quantity of production. The success of countries like Brazil in producing affordable conventional ethanol is encouraging, and needs to be adapted with changes to suit the vastly different U.S. scenario, where cellulosic ethanol would be more viable given the cost of producing traditional feedstocks like corn. Brazil has the most extensive domestic cellulosic ethanol industry based on sugarcane, and almost all its cars can run on ethanol. Countries like Pakistan, India, China, Colombia, Australia, Thailand and Japan have also stepped into ethanol production to offset gasoline demands, though they still do not have significant production and delivery infrastructure. In Thailand, more than 4000 stations serve E10, a 10% blending of ethanol into 95 RON gasoline, and the country is now trying to boost cassava and sugar cane for ethanol production. Pakistan is also producing ethanol and making it available in the bigger cities, as are India and more recently, China.

The current use of ethanol and its production in the U.S. is mainly based on corn. Archer Daniels Midland is presently the largest producer of ethanol, and ethanol is available in about a 1000 gas stations in the U.S. As of today the U.S. can produce about 5.01 billion gallons of ethanol, and is gearing up for another 3.28 gallons which will become functional after construction. About 5 million cars in America are capable of running on both gasoline and ethanol, and given research trends, the smartest thing for a car buyer right now is to look at the flex-fuel option, keeping the future in mind. Research is under way to make the manufacture and distribution of cellulosic ethanol more viable so as to enable mass production within the next two years, and companies like Wal-mart are showing an interest in retailing cellulosic ethanol.

Cellulosic ethanol and conventional ethanol have some challenges in common: development and availability of fuel-efficient cars using ethanol and an efficient infrastructure of raw material collection, processing and delivery. But in the long term given adequate research into developing efficiency and infrastructure, cellulosic ethanol appears to have the better potential for economy, environment-friendliness and waste management.

Author: Mike Conkey with EthanolConsultants.com

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