A landfill is made up of several basic parts. Each part provides a solution to potential problems. Federal regulations govern much of the location, design, operation and monitoring of landfills. This is to ensure that the landfills do not contaminate nearby groundwater or emit harmful gases into the air.
The typical "dry tomb" landfill was designed to eliminate open dumping of solid waste. The bottom liner system keeps trash separate from groundwater. Trash is stored in the old and new cells. Rainwater that falls on the landfill is collected in the storm water drainage system. Contaminated substances mix with the water to form "leachate" that can drip through the landfill, and the leachate collection system collects the contaminated water. When trash breaks down it produces methane gas, so there is a methane collection system to gather the gas. Finally, there is a cap that covers the top of the landfill and seals it.
A bioreactor landfill makes decomposition go more quickly than it does in a traditional dry tomb landfill. Because moisture is the most important element in helping to quickly decompose solid waste, the idea behind bioreactor landfills is to add liquids when necessary to keep the moisture content consistently high. This can produce more methane gas sooner, but decomposes materials more quickly and cuts down on leachate disposal [source: EPA]. The Environmental Protection Agency is working with other agencies and industry partners to determine how to improve operations of landfills, including bioreactor landfills.
The good news is that methane can be converted to energy and in communities like Polk County, Fla., bioreactor landfills are capturing the methane produced by the decomposing garbage and using it to power homes [source: Buie]. This is important, because controlling greenhouse gas emissions is now a critical part of landfill management, along with protecting water systems. One approach is biocell mining, which stabilizes waste quickly using the bioreactor technique, but then mines portions of the composted waste to extract recyclable and composted materials. The landfill space can be reused instead of being closed [source: Hettiaratchi].
Nearly all landfills must have groundwater monitoring systems in place that operators use to periodically collect and monitor groundwater samples for contamination. Bioreactor landfills like the one in Polk County are recycling rain water and leachate back into the landfill to help wet and decompose the garbage. There also are standards in place to help communities carefully close dry tomb landfills when they are full so that the garbage causes minimal impact on the environment. Some are finding creative ways to reuse or redevelop the land.
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