496. UNT FOUR ENVIRONMENTAL HEALTH AND SAFETY Today, about 73% of all municipal waste goes into landfills. However, the number of existing landfills in the United States has declined from approximately 20,000 in 1978 to fewer than 6,000 in 1991. At this rate, only one of every six land fills that was operating in 1979 will still be open in the year 2000. This means that (1) it will be more costly to use existing landfills in the future because of supply and demand, (2)new sites for landfills will be needed, and 3)alternative means of waste disposal must be developed Incineration Incineration, or the burning of wastes, is the second major method of refuse dis- posal. The passage of the Clean Air Act of 1970 severely restricted the rights of ind iduals and municipalities to burn refuse because most could not comply with the strict emission standards. Today only about 14% of all municipal waste is inciner- ated. Most of the nearly 200 municipal incinerators are waste-to-energy (Wte) plants. That is, they are able to convert some of the heat generated from the incin- waste-to-energy eration process into steam and electricity to operate municipally owned equipment (WTE) Plants incinerators that are or to be sold to a utility. Some high-tech waste-to-energy plants also include the sep- able to convert som. aration of waste prior to incineration so that glass and metals can be recycled the burning of trash Incineration greatly reduces the weight and volume of solid waste. generally, am and volume is reduced by as much as 90% and weight is reduced by as much as 80% While incineration might seem to be the ultimate solution to the solid waste dis posal problem, it is not without serious drawbacks. First of all, large commercial incinerators are cxpcnsive. Start-up costs can approach a quarter of a billion dol- lars. Some environmentalists feel that there are too many unanswered questions about incinerators to invest that type of money. One of their questions is about air quality. While most modern incinerators use filters to reduce harmful emissions they do not eliminate them entirely. A second environmental concern has to do with the remaining ash. The ash may be toxic, particularly when plastics have been incinerated, which occurs with increasing frequency. a third concern is that least 10% of the volume(20% of the weight) of the original wastes remains to be dealt with. Most of this ash enters landfills, but because of its toxicity poses a threat to local groundwater. Also, it now appears that future restrictions on items placed in landfills may prohibit the disposal of the ash Finally, since incinerators require large amounts of wastes to operate effi ciently, there is concern that the existence of community incinerators migh impede the development of recycling and source-reduction programs. However, it would seem logical in these times that incineration and waste reduction could Recycling is the collection and reprocessing of a resource so that it can be reused nond for the same or another purpose. This process yields three major benefits. First, it resoure aer use o conserves resources. If we recycle paper, we do not need to cut down as man i can be reused for trees to generate new paper. Second, recycling conserves energy. It takes less putpose energy to recycle an aluminum soft drink can than it does to create a new one Third, recycling conserves sanitary landfill space that can be used for the disposal of nonrecyclable waste. 3