Ethanol from wood

Slow pyrolysis, also called carbonization, is characterized by a high charcoal yield and is not considered for hydrogen production processes. The slow pyrolysis of wood (24 h typical residence time) was a common industrial technology to produce charcoal, acetic acid, methanol, and ethanol from wood until the early 1900s. 

Material and Energy Balances in the Production of Ethanol from Wood... 

Interest in renewable resources as raw materials for chemicals and energy has intensified in recent years as a result of anticipated shortages of petroleum and natural gas ( 1, 2, 3). A significant part of this effort has been devoted to the production of alcohols, particularly methanol and ethanol, from wood ( - ) Methanol is the main constituent of "wood alcohol", made for a great many years by the destructive distillation of wood, especially hardwoods W. From a ton of hardwood, one could expect about 60 lb, that is 7.5 gallons of methanol, along with a variety of other chemicals. Wood alcohol is no longer made. The processes discussed in recent reports, are quite different,... 

The situation with regard to ethanol is much clearer there is long industrial experience in the manufacture of ethanol from wood, by fermentation of the sugars in the waste effluents of pulp mills, or of the sugars made by wood hydrolysis ( ). In the years following World War II, wood hydrolysis plants have been unable to compete economically with petroleum-based ethanol synthesis, mainly by hydration of ethylene, and they have been shut down in most countries. However, in the Soviet Union, we understand, there are still about 30 wood hydrolysis plants in operation (10). Many of these are used for fodder yeast production (11) but the wood sugars are also available for ethanol production. 

While ethanol from wood sugars has not been part of that program, the successful substitution of ethanol for gasoline commercially has raised the prospect of a large market outlet, and the rapidly increasing price of gasoline here suggests that the economics, if not favorable now, may become so in a foreseeable future. 

Alcohol recovery from the fermentation brews was less than complete in most cases, which may be attributable to less than ideal conditions. The best yields, 60 to 97% of theory, were obtained with sugars obtained by hydrolysis of cellulosic residues of the autohydrolysis-extraction process. Unextracted pulps, or the hemicellulose solutions, gave poor ethanol formation, which suggests inhibition. In the calculation of material and energy balances which follows, we have assumed 95% yields of ethanol from wood sugars, which is readily achieved in industrial practice and which we believe to be achievable with our wood sugars as well. 

Brazil has produced ethanol as a fuel since 1930. Table II shows that productivity of methanol from wood is better than ethanol from sugar cane and much better than ethanol from wood. This fact plus the convenience of not being dependent on just one crop and the possibility of using poor lands for reforesting indicated that the production of methanol from wood should be more deeply evaluated. 

Because of high oil prices, Brazil (most of whose sugars are produced from sugarcane) took the dramatic step of shifting to a much greater use of fuel alcohol. One wood hydrolysis plant was constructed, but it was uneconomical to operate and was shut down. However, Brazilian experience has demonstrated that fermentation ethanol (95 percent ethanol and 5 percent water) is a perfectly satisfactory motor fuel. At least 500,000 Brazilian automobiles operate on undried alcohol continuously, and most of the rest of their fleet operates on this fuel on weekends when only alcohol is available at the gas stations.36 A number of methods can be used for the production of ethanol from wood, as described below. 

The process described by Burton et al. (1984) uses proven technology and demonstrates the point that the production of ethanol from wood is likely to be viable only when integrated as a multiproduct operation. The obvious areas for improvement are in increasing the ethanol yield and in encouraging fermentation to continue as the concentration of ethanol builds up in the solution, whieh would significantly reduce the cost of distillation. 

Tubs and vats reflected the state of art before World War I. Agitation vessels with active aeration were used in the production of yeast (M. Rohr [2]). In World War II, mixing and stirring posed serious problems in mass production of ethanol. The German plants for the production of ethanol in Tornesch, Holz-minden and Dessau never got beyond 70% of the planned output. One ton of wood yielded 160 kg of ethanol only. In peace time and after careful scrutiny of their economic viability, these plants were closed. In Switzerland, the production of ethanol from wood could not cover the investment and running costs. Ten years after the war, the Swiss voters decided to withdraw government subsidies from the plant in Ems, which led to its closure. 

While corn yield per acre has a steadily increasing trajectory, there is a long-term interest in the use of hgnocellulosic biomass for the production of fuel ethanol. Acid-mediated depolymerization of saw dust (and other materials) into sugar was noted in 1819 by Braconnot [15, 16]. This acid-mediated hydrolysis and subsequent fermentation came to be known as the Classen process [17, 18], and by 1910 there were reports of economically successful production of ethanol from wood waste [19, 20]. But interest in these processes waned and they were largely forgotten, as evidenced by the fact that the 2013 opening of a facility... 

Eig. 15. Eurfural, phenols, and ethanol production from wood in a multiproduct process biomass chemical plant (52). Wood (qv) is ca 50% cellulose (qv),... 

More recently, interest has developed in the use of enzymes to catalyze the hydrolysis of cellulose to glucose (25—27). Domestic or forest product wastes can be used to produce the fermentation substrate. Whereas there has been much research on alcohol fermentation, whether from cereal grains, molasses, or wood hydrolysis, the commercial practice of this technology is primarily for the industrial alcohol and beverage alcohol industries. About 100 plants have been built for fuel ethanol from com, but only a few continue to operate (28). 

Eighty-seven percent of the ethanol produced in the United States conies from corn. The remainder comes from milo, wheat, food wastes, and a small amount from wood waste. In Brazil, the largest pro-... 

Wood chips can also be utilized as such to produce bioethanol. The cellulose and hemicellulose material is hydrolyzed in the presence of acids (H2SO4, HCl, or HCOOH) or enzymes to yield glucose and other monosaccharides [16]. Lignin is separated by filtration as a solid residue and the monosaccharides are fermented to ethanol, which, in turn, is separated from water and catalyst by distillation. Ethanol can be used not only as energy source but also as a platform component to make various chemicals, such as ethene and polyethene. Today green acetaldehyde and acetic acid from wood-derived bioethanol is manufactured by SEKAB Ab, at the Ornskoldsvik Biorefinery of the Future industrial park. 

The advances made in enzymatic hydrolysis of cellulosic materials (14) are also of interest. This technology involves only moderate temperature processes in simple equipment which promises to be of significantly lower capital cost than the pressure equipment associated with conventional acid wood hydrolysis processes. All of these considerations combined to lead us to study processes for ethanol production from wood, especially in an effort to obtain data for material and energy balances, and possibly for the economics. 

Yields of ethanol from aspen wood are 70.7% and 83.4% of theoretical where acid hydrolysis and enzymatic hydrolysis were employed. These were, respectively, 58.4 gallons and 68.9 gallons of 95% ethanol per ton of aspen wood. In addition 426 lb lignin with heat of combustion of 11,100 BTU/lb were obtained. 

Includes energy from wood and wood-derived fuels municipal solid waste from biogenic sources, landfill gas, sludge waste, agricultural byproducts and other biomass (through 2000, also includes non-renewable waste such as municipal solid waste from non-biogenic sources, and tire-derived fuels) and fuel ethanol and biodiesel consumption, plus losses and co-products from the production of fuel ethanol and biodiesel. 

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