Cellulosic waste processing

A hydrolysis step is involved in the pulp industry in order to concentrate the cellulose from wood. This uses large-scale processes whereby a liquid fraction, the lignocellulose, is formed as a by-product in the process, and contains high levels of phenolic components and their derivatives. These compounds also constitute an environmental problem due to their possible introduction into rivers, lakes, and/or seas. Chlorophenols from the cellulose bleaching process have traditionally attracted most of the interest in the analysis of industrial waste because of their high toxicity. 

Cellulosic Materials. Over 900 x 106 metric tons of carbohydrate-containing cellulosic wastes are generated annually. The technology for converting this material into ethanol is available, but the stoichiometry of the process is disadvantageous. Even if each step in the process of the conversion of cellulose to ethanol proceeded with 100% yields, almost two-thirds of the mass would disappear during the sequence, most of it as carbon dioxide in the fermentation of glucose to ethanol. This amount of carbon dioxide leads to a disposal problem rather than to a raw material credit (209). 

In addition to the variations in the LHC composition that occur from species to species, each species has its extractives, which include resins and waxes. These constituents are capable of interfering with cellulose hydrolysis because of their hydrophobic nature. Tannins and other highly reactive materials are constituents of some woody species. When LHC is obtained from nonwoody (herbaceous) species, the range of interfering constituents increases greatly. Sugars, starches, dextran, carotenoids, and many isoprenoids are to be found. Operators of a cellulose hydrolysis process that uses municipal solid waste as its biomass resource may experience seasonal variations in composition and chance inclusion of crankcase oil and other products that inhibit enzymes or kill yeast. 

Cellulosic wastes have great potential as a feedstock for producing fuels and chemicals. Cellulose is a renewable resource that is inexpensive, widely available and present in ample quantities. Large amounts of waste cellulose products are generated by commercial and agricultural processes. In addition, municipal facilities must treat or dispose of tremendous quantities of cellulosic solid waste. 

Research to improve ethanol fermentation has also focused on the development of a high solids, continuous feeding process as well as improved yeast strains. Other related developments include processes for the use of biomass feedstocks, such as cellulosic waste material.40"44 The Genencor-NREL collaboration funded by the U.S. DOE has (a) put in place the tools required for continual improvement of biomass-derived cellulases, (b) built a suite of enzymes with enhanced thermostability and improved specific performance at elevated temperatures, (c) developed an improved production strain for the enhanced cellulase components and demonstrated an enhanced production process. Therefore, plans are in place to provide a developmental product(s) in support of continued industry development. 

Our plans for this technology in the very near future include the process design, procurement, fabrication, construction and operation of a 50-ton/day cellulosic waste conversion facility, followed by a commercial scale facility... 

This section describes several new building blocks available from renewables, and how those building blocks can be converted by chemical processes into other materials. The contributions by Moens and Olson describe new uses for levulinic acid, an important renewable building block available inexpensively from cellulosic wastes (17), Kiely s paper on carbohydrate diacids describes approaches to selective glucose oxidation, the preparation of new polymers made from oxidized glucose, and where these materials might find use in the chemical industry. Witczak overviews uses of levoglucosenone, an... 

Cellulose materials. These are the most promising raw materials for ethanol production. These materials include crop stalks, forest logging and wood processing residues, straws, paper mill and sugar-containing-cellulose wastes, and parts of solid waste. 

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