Short answers, pulled from the story.
The first modern sanitary landfill appeared in the 1940s. This era transformed chaotic open pits into engineered biological reactors that utilized systematic burial with daily, intermediate, and final covers.
A landfill undergoes five distinct phases of decomposition over decades including the initial adjustment phase, anaerobic conditions, acid formation phase, methane fermentation, and final maturation and stabilization. These phases ensure waste breaks down into simpler compounds while the process can take centuries to fully complete.
Leachate forms when precipitation falls on open landfills or water is released from waste breakdown and percolates through the refuse. This liquid contains heavy metals and organic contaminants with nitrogen reaching concentrations upwards of several thousand milligrams per liter.
About half of the volumetric concentration of landfill gas is methane which has a global warming potential of 29.8 relative to carbon dioxide over a 100-year period. Landfills are the third largest emitter of methane worldwide making them a significant source of climate change.
The aftercare stage can last for several decades up to eternity once a top liner or cap is placed on a filled landfill. The estimated duration of aftercare has been calculated to cost more than 20 million euros per landfill in the Netherlands.
Countries like Germany, Austria, Sweden, and Switzerland have banned the disposal of untreated waste in landfills. The European Union requires individual states to enact legislation to comply with the European Landfill Directive leading to a shift away from traditional landfilling.