Short answers, pulled from the story.
Systematic burial of waste with daily covers began only after World War II ended. Before this decade, waste simply sat in piles or was thrown into open pits known as middens by archaeologists.
This process drops pH levels from approximately 7.5 down to 5.6 during the third stage. Acid formation begins hydrolysis of solid waste fractions leading to rapid accumulation of volatile fatty acids in leachate.
About half the volumetric concentration of landfill gas is methane while slightly less than half is carbon dioxide. Landfills rank as the third largest emitter of methane worldwide according to United Nations data.
Estimated duration spans several decades up to eternity with costs exceeding 20 million euros per site in the Netherlands. Some countries consider long-term aftercare requirements extending indefinitely due to liner lifespans.
Permitting generally takes five to seven years and costs millions of dollars. U.S. regulations require state agencies to establish minimum guidelines not falling below EPA standards.