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Operation of a Downdraft Gasifier Fueled with Source-Separated Solid Waste
Author: Samuel A. Vigil, D.A. Bartley, R. Healy, George Tchobanoglous
Date: 6/205
Reprinted from the American Chemical Society Symposium Series, No.130, 1980

The disposal of solid waste is a critical problem faced by most communities. It is also costly in terms of capital and energy resources. In 1971, 109 million metric tons of solid waste were collected in the United States at a total cost of $2.64 billion for collection and disposal. By 1985, this quantity is expected to increase to between 150 and 200 metric tons per year with an annual cost between $4.02 to $5.06 billion. (1). Although the composition of municipal solid waste varies greatly both geographically and by season, an analysis of data from many cities in the United States shows a remarkable similarity. Typically, municipal solid waste in the United States contains about 40 percent combustible material by weight. Although resource recovery and recycling are receiving considerable attention today, most solid waste is still disposed of in a sanitary landfill. Even though it is widely recognized that placing solid wastes in a landfill is a misuse of potentially valuable resources, this practice will continue until economic and environmentally acceptable alternatives are found. One such alternative, the gasification of the paper fraction of solid waste is considered in this report. Recently, interest has developed in pyrolysis, thermal gasification, and liquefaction (PTGL) processes for the recovery of energy. The PTGL processes offer the advantage of producing a usable fuel (gas or liquid) from the combustible portion of solid waste. Jones, (2), provides an overview of the many processes currently under consideration. Unfortunately, most of these processes have one characteristic in common. They are more complex than conventional incineration systems. They are also very capital intensive. For example, on such system, the PUROX Process, developed by Union Carbide Corporation, is economic only in capacities ranging from 363 to 1814 metric tons per day of solid waste (3). The corresponding size of cities vary from about 200,000 to 1,000,000 in population. Because of the cost and complexity of such systems, they are not cost-effective for smaller cities.