Some states(US) cap landfills with large sheets of plastic (the new ones have plastic on the bottom, making a "giant bag") and punch holes for venting methane and other exhaust gasses. They vent because the gas is flammable and having it build up under a sheet of plastic is risky. Landfills catch on fire frequently. 
Some sites collect the gas and burn it, but it isn't common.
You can see the venting tubes on this photo of liner repair after lightning strike...
Map of composting facilities in California: https://www.biocycle.net/2018/03/12/california-composting/
We can speculate what punnerud meant, but I would point out that Norway has some kind of a landfill ban. IIUC, they have (almost) no classical mixed-use landfills, and nearly all landfilled organic waste is actually in an anaerobic digestion or composting "facility".
Why is parent comment saying Norway captures the methane for electricity generation while you're going we need to vent the methane because it's dangerous.
Same gas. Same landfill setup (by the sounds of it).
...why is the conclusion so different?
Does methane work differently in Norway?
Either way, it has to be collected and burned off.