Landfilling is the most common MSW disposal practice in the
world likely because it is most economical and does
not required skilled operators. As a result, it is particularly suited
for developing countries where low capital and maintenance cost
depression or closed mining sites are commonly used for landfills
. In the US, modern landfills are wellengineered facilities that are designed, operated, and monitored
in compliance with federal regulations. Some new landfills collect
potentially harmful landfill gas (LFG) and convert the gas into
energy.
Although landfilling is of low cost, it poses serious threats to the
environment. Landfilling is a process in which MSWs is transferred
from one place to another, rather than be used as a resource. The
biodegradable fraction of MSW is slowly biodegraded in the landfills, resulting in liquid leachate and landfill gas. Liquid leachate
will cause severe contamination of groundwater, while landfill
gasses composed largely of methane and carbon dioxide, if not captured, will aggravate greenhouse effect and bring stench to surrounding environment. The number of U.S. landfills has steadily
declined, which may be attributed in part to the stringent EPA regulations regarding MSW landfills. In some countries or cities whose
land resources are restrained, landfilling is gradually replaced by
other approaches.
In the US, governments at all levels are encouraged to decrease
the generation and increase recycling of MSWs. Regulations are
enforced to ensure safe disposal and require operators to provide
final cover and post-closure care of landfill facilities. Some landfill
facilities collect the biogas (mainly methane) generated from the
landfill wastes to generate electricity or heat. The estimated biogas
generated globally is 57 million tons but only 10 or less is collected
and used in 2000 (Themelis and Ulloa, 2007). Attempt to use
microbial fuel cells to generate electricity from landfill leachate
has also been reported