but if garbage dumps fail to facilitate decomposition due to the lack of an oxygen rich environment, why wouldn’t the waste managers bore columns to pump in oxygen and good bacteria to compensate ?
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What could go wrong with piles of hot trash and metric tonnes of O2? Certainly not a trash fire.
Ok, so you have a hole… In a solid pile of trash. You have added a tiny bit of surfave to a tiny amount of the total pile.
To do what you’re imagining, the trash would have to be porous like a sponge. And that’s just not doable.
A lot of facilities have started doing this. But it is not as simple as just blowing air into the ground. There is a big risk of fire at these facilities, even the heat from the microbes can start fires and once a fire start it is very hard to extinguish under ground. Adding to this you would get a lot of smell from the decomposition if you do not have enough oxygen, which they almost never have. And they need to reduce the amount of smell and even toxic gasses that gets released. There is also a big problem in that a lot of trash do not allow air to flow through it. So if you blow air down in one part of the landfill it may not get to all areas. So it is a very technical and expensive operation to make sure you get a nice controllable amount of air into the landfill without any of the issues with this.
Modern landfills are constructed to be permanent storage for a toxic stew of no-longer-wanted items. They’re expensive to build and maintain. They are most definitely not designed to compost because the compost one gets out would be so heavily laden with toxic compounds that it would be a crime to add it to any clean soil.
As such, landfills are built to hold as much as possible before filling up. Therefore everything inside is compacted as much as possible and then sealed off in individual cells from the outside world to prevent infiltration of things like rainwater which would then have to be collected and treated. (This stuff is known as leachate and it’s some of the nastiest stuff going.) Anyway, this is the exact wrong way to build something if you were looking to pump air through it.
The idea that landfills compost was just what some civil engineers assumed would happen, because it was convenient to tell the residents at the time. Nobody ever actually studied it for decades, until some dude decided to go check on the progress and actually mined down into one of the original NYC landfill sites. What they found was that instead of composting, the landfills were PRESERVING the trash.
The issue here is that not all trash is suitable for this kind of processing. And not all landfills are built to decompose trash. Mostly it’s just kicking the can down the road for a few centuries if we can.
What you are describing is known as an air sparging system. It’s used to clean up a variety of chemical spills that have entered the water table. Usually stuff thar is normally a vapor but is just dissolved in the water.
Air is injected into the ground. It’s stirs up the water and aerosolizes the vapors. Shakes the junk out of the water. Then you have a vacuum system sucking the air in the ground out. This can be done with a buried tube covered in fabric connected to a vacuum.
You can also use this system to inject nutrients to bacteria, as you say. A common gas to I just is actually propane. This is used when the chemical involved doesn’t have carbon in it. Normal bacteria can eat chemicals to rip carbon off them to make more bacteria. So propane is added to give the bacteria carbon to grow, while also eating the harmful chemical.
Regular air can be injected into the ground also. However, some chemicals break down into more dangerous ones in the presence of oxygen. So sometimes it is more practical to just bury it and let it degrade slowly over time.
Source: I went to school for environmental remediation. This is literally something I’ve studied.
I designed landfills for a couple years. It is less about air or oxygen, and more about water. You want anarobic decomposition, which creates carbon dioxide and methane. You can collect the gasses and burn them to generate electricity. The old philosophy was called “dry tomb” landfilling. Keep it dry and stable to prevent water migration. The water from landfils (leachate) is tough to treat. The more modern design philosophy refers to a “bioreactor” type landfill. Water gets recirculated to promote degredation and gas generation. The down side is more leachate, les surface and slope stability, since the waste shrinks as it decays.
You’re thinking along the lines of composting, which is good. The reason you think like this is because waste doesn’t exist. In other words, nature doesn’t acknowledge the human concept of waste. A landfill has different objectives than composting. New landfills are constructed with thick plastic on the bottom and top that is ultimately welded together and only allows for anaerobic decomposition and the drainage of leachate. The plan is to leave the problem for the population to deal with in 7 generations or until seismic activity engulfs our shameful time capsules in a smelly termination of magma.
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