I remember the first time I was introduced to garbage bag composting. A neighbor down the street (in Sacrament CA) bagged up all his grass clippings and set the bags in the garage next to his 911 Porsche, two days later the bags exploded, burning down the garage and the Porsche. They were in the backyard around their swimming pool. I was driving down the street and their garage door flew out into the street behind my GTO.
Garbage bags work great at creating a hot/humid environment when green cuttings are added. Just be sure to prop the bag end open so the heat doesn't collect to the point of spontaneous combustion.
I have used the technique several times, I still use it to make leaf mold in a hurry. I use the giant Industrial size, really thick black Contractors Bags. These are not treated in anyway. I built a heavy wire triangle and set this into the end of the bag, some clips hold the bag opening to this triangle and away I go filling it up, if I don't have any green stuff to add, I spray in some
water. The triangle allows me to fold the opening over to build heat and distribute humidity but still be able to open it up so it won't over heat.