[acomjean]

I worked for a time designing and building landfills. Nothing really rots in them typically as it’s really dry and don’t have good access to oxygen. Modern landfills are like giant plastic bags. This is to protect ground water.

Decomposition as noted releases methane. Some landfills gather it in pipes and “flare” it )burn. They have to vent the gas as a full landfill is covered by a plastic cap to prevent water infiltration.

We dug up trash from the 70s to extend the landfill out. It was in remarkably good shape.

https://planetliner.com/landfill-cap/

[tonypapousek]

Thanks for the share, crazy that 1-2mm polyethylene is all it takes to cap a landfill.

Practical Engineering put out an excellent video on landfills a couple years back, well worth the watch for the visualizations alone.

https://youtu.be/HRx_dZawN44

[zahlman]

> Some landfills gather it in pipes and “flare” it )burn.

Can useful energy be recovered from this?

[bluGill]

Yes, any landfill of any size is going to clean this up a bit and run it through a generator. They can get contracts from the utility to use so much power per week (whatever the tank capacity iso and since the utility controls when it is on (that is when other renewables are low) they get a higher price. The details are complex, but thus is very valuable green renewable (we can debate how green and renewable eslewhere) energy to a utility.

[hommelix]

At some sites, the methane is burned in gas engine to generate electricity. Some sites build a CHP and resales the heat for district heating. The engines may need more maintenance due to silicate in the gas.

[pseudohadamard]

There used to be a huge flare at a landfill near here but at some point they redirected it to energy generation, around 200-250kWe from gas that was just going to waste before then.