Have you got any sources for the usually?
Any ex landfill I've seen just has vents to the open air, and mentions of landfill gas never give the impression its mainstream.
But as others have been saying, it makes much more sense to simply bury the food in your garden. Or collect food waste on a municipal level, which has, for example, been the law in Germany since 2015.
The "dry fermentation" system used in Munich is a particularly good example. They collect food waste in the city, compost and ferment it in a big sealed hall near the soccer stadium, wait 12 weeks for the bacteria to work, collect the resulting biogas to put into their gas network (or power garbage trucks), and sell the leftover organic compost and fertilisers to local residents and farmers. A closed and sustainable cycle.
https://www.youtube.com/watch?v=HF0gU9ljHo4
https://www.awm-muenchen.de/fileadmin/PDF-Dokumente/awm/Fold...
You might make your distributed practices even more efficient with vermicompost / bokashi; by selecting an organism with known beneficial outputs to metabolize the waste you'll end up with a higher conversion to usable nutrients and beneficial microbes for your plants.