A modern landfill is an engineered method for depositing waste in specially constructed and protected cells on the land surface or in excavations into the land surface. Despite the fact that an increasing amount of waste is reused, recycled or energetically valorized, landfills still play an important role in waste management strategies. The degradation of wastes in the landfill results in the production of leachate and gases. These harmful gases are the potential threats to the human and animals’ health as well as degraded the natural environment. The leachate from landfill is rich in organic, inorganic and suspended particles which may cause threat to ecosystem. Engineered method landfill gas consists mainly of methane and carbon dioxide, both important greenhouse gases. This chapter recommends an engineered landfill design helpful for landfill gas generation which replaces the fossil fuel as a compressed natural gas or liquefied natural gas. Finally, the impact of these released gaseous emissions has been analyzed completely and this review is complemented with suggestions to minimize the environmental burden of landfills and to re-introduce the buried resources to the material cycle.