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Liquid fuels from wood - ethanol, methanol, diesel
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ALCOHOLS AND THEIR PRODUCTION

here are various fuel alcohols that may be made from wood. Those most commonly proposed are ethanol and methanol.

Fuel ethanol has been made from wood, but generally at a noncompetitive cost.

During World War I, two plants made ethanol from wood using a dilute sulfuric acid hydrolysis process. The plants closed after the war because of a decreased supply and increased cost of wood residues used as raw material for the process.

Moreover, the cost of blackstrap molasses, also used for alcohol production, decreased.

During World War II, the War Production Board constructed a dilute sulfuric acid wood hydrolysis plant for the production of ethanol at Springfield, OR.

The plant. was completed under sponsorship of the U.S. Department of Agriculture in 1947. Production trials indicated that the plant could be modified to operate, and it was leased to two different companies, but was not operated successfully by either.

Also constructed during World War II was a plant for the production of ethanol from the fermentation of sugar obtained as a byproduct of a sulfite pulpmill in Bellingham, WA.

In this plant , which is still operating, the spent sulfite pulping liquor is treated to remove sulfur dioxide and lignosulfonate byproducts, and the sugars are fermented to ethanol.

About 25 gallons of 95 percent ethanol are produced per ton of sulfite pulp. Similar plants have been and are now operating in other countries.

Other than fermentation of sugars from sulfite waste liquor, the process that has been most successful for conversion of wood to ethanol is dilute acid hydrolysis. Such plants operated in Germany and Switzerland during World War II, and similar plants are still operating in the Soviet Union. Another type of process is concentrated acid hydrolysis.

This type plant operated in Germany during World War II, but was less competitive than dilute acid hydrolysis because it required the use of much more acid, and the acid could not be recovered effectively.

An advantage of concentrated acid over dilute acid hydrolysis is that cellulose from wood could be hydrolyzed to glucose, as needed for fermentation to alcohol, in much higher yields.

Several types of dilute acid hydrolysis processes have been used. The World War I process was a single-stage batch type. It produced 20 gallons of ethanol per ton of dry wood.

Later research at the Forest Products Laboratory and in Germany led to development of a percolation process known as the Scholler process.

During World War II, this process was modified by the Forest Products Laboratory and the Madison process was developed. Compared with the German Scholler process, hydrolysis by the Madison process was accomplished in less time because the sugars produced by the hydrolysis were removed more rapidly.

This process produced 64.5 gallons of 95 percent ethanol from a ton of dry, bark-free Douglas-fir wood waste.

This process is similar to the one used in plants that are operating in Russia, and the technology has recently been used in the operation of a new alcohol-from-wood plant in Brazil.

I hope that we can learn more about the present-day aspects of alcohol from wood from the Brazilian plant. More recent research at the Forest Products Laboratory is aimed at an improved dilute acid hydrolysis process for use with hardwoods.

It is a two-stage process in which the hemicellulose is hydrolyzed at mild conditions first, and the residue from this process is then subjected to stronger hydrolysis conditions that are needed to hydrolyze the cellulose. A pilot plant is now being built by TVA to further test this process. The costs of production of alcohol by dilute acid hydrolysis are difficult to estimate.

Ultimately, in an actual plant, the costs of alcohol production will likely be reduced through production of byproducts, since only a portion of the wood, the cellulose and possibly some hemicellulose, can be converted to ethanol.

Because of different ways of handling byproduct credits, and assumption of different feedstock costs, the estimated costs for ethanol made from wood vary widely.

I believe it is reasonable to assume this cost to be $1.50 to $2.50 per gallon of ethanol.

METHANOL.

The other major possibility for production of alcohol from wood is methanol. Methanol was once made from wood and was, in fact, known as wood alcohol. However, methanol was made as a byproduct from pyrolysis processes which were designed primarily to produce charcoal. To make methanol as a primary product would require a different approach. Wood might be gasified to produce mixtures of gases, from which carbon monoxide and hydrogen could be separated and combined in the correct proportions to produce methanol. Cost estimates for production of methanol from wood through intermediate synthesis gas, or syngas, range around $1.00 per gallon or less.

Although ethanol has been the preferred fuel for blending with gasoline, some methanol is used to accomplish octane enhancement because it is cheaper than ethanol. If methanol is used above a certain percentage in gasoline, cosolvents such as methyl-tertiary-butyl ether, tertiary butanol or ethanol
are needed to prevent phase separation.

 Another approach could be to use methanol as a neat fuel.

AS long as natural gas supplies are not considered a problem and natural
gas prices don’t double compared to other materials, there probably will be
little incentive to make methanol from any other feedstock.

 But, in my experience, there have been repeated shortages of natural gas with curtail-
ments, cutoffs, and price escalations. When such crises occur, there is
always much concern about alternatives to gas as a feedstock for methanol.

Coal is usually considered first, and wood as an afterthought.
Wood has some distinct advantages over coal as a source of methanol.

Because wood doesn’t have significant amounts of sulfur or heavy metals,
is easy to pyrolyze, and has a low ash content, it can be shown that for
plants of the same capacity it is cheaper to make methanol from wood than
from coal.

On the other hand, coal has advantages of being available in many
places in high concentrations at low moisture content and high energy density.

However, a case could be made to favor wood over coal because of environmental
and safety concerns.

The main advantage always claimed for coal is economy of scale.

Thus a plant using 20,000 tons of coal per day would be more economical on a per
gallon of methanol basis than a plant using 1,000 tons of wood per day.

With coal concentrated in large deposits, supply of a methanol plant close to a
mine site with 20,000 tons per day should be possible, but supplying the
equivalent in wood per day would be extremely difficult, if not impossible.

However, investment in a large coal-to-methanol plant would require such
a large investment that a private company would be unlikely to risk putting
it into operation.

No plants have been built for the gas to methanol from wood process, but
plants have been proposed in Canada and Brazil.

There is at least one coal to methanol plant in the United States, this located at Kingsport, TN

I believe the most likely wood-to-alcohol plant for competing in today’s market with the Federal and State subsidies that are now in place would be a dilute acid hydrolysis plant.

Such a plant might use 1,000 dry tons of wood per day to produce 25 million gallons of ethanol per year. Sixteen of these plants could produce about as much ethanol as we are now getting from corn

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