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.
If value is applied to the degradation and GHG abatement, some groups might find it worthwhile.
There very well may be, but adding pipes to burn off excess methane is way easier than generating and transporting electricity.
If you eliminated all gasoline cars tomorrow, there isn’t enough infrastructure to support electrics. When cars first came out, you didn’t have to convince people to use them by taxing horses: cars were more efficient than horses.
You don’t have to artificially make something worse to encourage something better. The something better should just naturally be better, making a switch obvious.
If you use energy efficient appliances, you save money on your utilities. Given the same quality, more efficient (and lower cost) is always preferred and a rational actor will choose the lower cost option that solves his need at the level he wants it solved.
That “green” stuff is more expensive is an engineering problem. If someone develops an electric car that costs the same or less than an ICE car and has the same or better performance and quality, people will naturally buy them — and the company that can do that stands to win big. But making everything else worse/more expensive to prop up tech that isn’t as good or affordable is trading what’s best for the individual for what’s best for the owners/employees of the less efficient producer.
I am in favor of government funded basic science, research, innovation (it brought us NASA after all,) however I oppose funding that by the selective targeting of industries in order to artificially boost the viability of a new tech. We didn’t have to kill horses to get people into cars. We won’t have to kill ICE cars to get people into better alternatives. We are already producing less CO2 emissions and the relevant tech is already getting cheaper and better. The market is slowly working and it didn’t take a tax to do it. And when it comes to markets, slow is good; it minimizes the negative effects of economic reallocation.
The way carbon tax is implemented in Canada is to return the tax to folks at the end of the year, keeping none of it, but correcting that imbalance.
A carbon tax would not eliminate all petrol cars tomorrow, would it? It would increase the price of fuel, which would encourage some to make their next vehicle an EV in place of ICE. It would inevitably encourage cities and petrol stations to add EV infrastructure too.
Not entirely sure how the US taxes vehicles, but personally I would put some combination of fuel (carbon) tax, increasing monthly well in excess of inflation and a vehicle tax that cost some combination of vehicle weight and emissions. The combination effect of which would be to discourage ICE, pickups and 4x4s whilst encouraging smaller EVs.
Many landfills do harvest methane from the combined heap of trash. However, after methane production ends we are still left with compost with tons of plastic.
Overall result is many homeowners now have a plastic wheelie bin they never use any more, and organic waste goes in the landfill bin. Putting us in a worse place than before we started.
Tory party is busy promoting how environmental they are in their electioneering ...
(This was new to me until I talked with one of the managers at the plant one year ago)
Getting rid of non-organic packaging would help even more. Dealing with packaging materials is one of my biggest frustrations when trying to get rid of boxes. However, this is very much a "long tail" sort of problem.
As other comments in this thread have pointed out, people are resistant to "fixing" their waste stream. I think this is a serious lack of personal responsibility. There is nothing about consumption that absolves the consumer of proper disposal. Sure, we want local government to make it as easy and efficient as possible, but best practices are leaning toward sorting, and I think every person has to step up to the practice.
That is also common for US landfills.