[ethagnawl]

It's recently occurred to me how "valuable" today's trash is likely to be considered in the future. I'll focus on organics here but I think the plastics will be equally valuable, too.

I have no idea what % of American households compost or live in places which offer municipal compost pickup but I imagine it's in the single digits. As evidenced by this article, compost is/can be an incredibly powerful agent of change: food production, habitat restoration, etc. However, most of us are putting organics into refuse streams where they're likely to be burned or buried in a way that's actually harmful because they release methane when they decompose under those conditions. It can be a bit gross and tedious to compost at home but there is a certain satisfaction which comes along with it.

[acomjean]

I worked for a time designing and building landfills. Nothing really rots in them typically as it’s really dry and don’t have good access to oxygen. Modern landfills are like giant plastic bags. This is to protect ground water.

Decomposition as noted releases methane. Some landfills gather it in pipes and “flare” it )burn. They have to vent the gas as a full landfill is covered by a plastic cap to prevent water infiltration.

We dug up trash from the 70s to extend the landfill out. It was in remarkably good shape.

https://planetliner.com/landfill-cap/

[tonypapousek]

Thanks for the share, crazy that 1-2mm polyethylene is all it takes to cap a landfill.

Practical Engineering put out an excellent video on landfills a couple years back, well worth the watch for the visualizations alone.

https://youtu.be/HRx_dZawN44

[zahlman]

> Some landfills gather it in pipes and “flare” it )burn.

Can useful energy be recovered from this?

[bluGill]

Yes, any landfill of any size is going to clean this up a bit and run it through a generator. They can get contracts from the utility to use so much power per week (whatever the tank capacity iso and since the utility controls when it is on (that is when other renewables are low) they get a higher price. The details are complex, but thus is very valuable green renewable (we can debate how green and renewable eslewhere) energy to a utility.

[hommelix]

At some sites, the methane is burned in gas engine to generate electricity. Some sites build a CHP and resales the heat for district heating. The engines may need more maintenance due to silicate in the gas.

[pseudohadamard]

There used to be a huge flare at a landfill near here but at some point they redirected it to energy generation, around 200-250kWe from gas that was just going to waste before then.

[schrectacular]

The thought occurred to me some 25+ years ago that today's landfills will be tomorrow's mines. I hope it isn't true but taking the very long view I'm afraid it will be.

[6510]

A british inventor created a setup with two long vibrating plates with ferrofluid in between. A flaky powder made from garbage was dumped in on one side and came out the other end beautifully separated in many layers by density. (with one mixed layers in between that went back in at the beginning) Innitially he "knew" it was silly to use something as expensive as ferrofluid but planned to try other substances if it worked. It turned out the process produced a lot more ferrofluid than it used.

No one was interested in further research.

edit: I see some research is now happening.

[mlyle]

We already mine landfills -- mostly for land reclamation but sometimes to recover resources.

In the longer run, when there's been more compaction, settling, and densification (and changes in what things are valuable), and more need to reclaim land that was previously landfilled, we will do this more.

[PaulHoule]

People sometimes build stuff on top of landfills.

[dekhn]

Example: Shoreline Amphitheater, near Google HQ in Mountain View. Built on top of a landfill. For a while in the 80s, there were occasionally small fires during shows when people lit cigarettes. Google also harvested the methane and used it to power some stuff, although I can't find an authoritative article with details.

[pseudohadamard]

Several schools I know of have part of their playing fields on reclaimed land that's former landfill. You can't build on it because you have no idea what sort of gases and possibly toxins will work their way up from below, but wide open fields with free air movement that aren't round-the-clock occupied are fine. The only downside is that for an initial period you need to re-cap places with soil every few years as the fill underneath settles. There was one place where they'd paved over it rather than leaving it as soil to create tennis courts and after a few years it was a sort of dune landscape since they couldn't backfill the dips with soil. It was quite picturesque actually, a sort of post-apocalyptic look with miniature ponds with reeds growing in them and occasional visits from ducks. Sure, they'd lose a kid in one from time to time, but being a large school they didn't have a shortage of those.

[PaulHoule]

This shopping center was built on a landfill

https://www.wskg.org/regional-news/2025-08-08/binghamton-off...

when I first saw it in the 1990s it was kinda on the outs, like K-Mart was already failing (as a business) and the parking lot was visibly wavy because of subsidence. Funny the New York Pizzeria mentioned in that article is run by my relatives.

[rootusrootus]

Indeed, sometimes big things. The landfill we used when I was growing up is now beneath a Home Depot, which was built over the top of it almost 25 years ago. The landfill in this case was unlined, too.

[mlyle]

Yup. It is a little undesirable for various reasons, and not every landfill is suitable for construction on top (seismics, sealing/capping technique, materials, etc).

[salad-tycoon]

Like ski courses!

[kleinsch]

Today’s landfills are already used for natural gas generation.

[PaulHoule]

See https://www.floridatrend.com/article/14356/trashed-plan-to-u...

St. Lucie County wanted to use a plasma torch that would have converted plastic and other carboniferous waste to energy. Like many other plans to do the same, it fell through

https://en.wikipedia.org/wiki/Plasma_gasification

[pstuart]

Yeah, reminds me of Changing World Technologies -- so much hope, so little reality: https://en.wikipedia.org/wiki/Changing_World_Technologies

In a more civilized civilization we'd be investing in making these processes work. Likely there was more money to be made by stakeholders to scuttle these endeavors.

[PaulHoule]

Well, a plasma torch -> energy system is basically a chemical factory attached to a plasma torch and the thing about a chemical factory is that quality inputs lead to quality outputs. Poor quality inputs lead to poor quality outputs or maybe something blowing up. Any kind of "circular economy" chemical factory has the problem that it has to run on whatever inputs are available that day and that kind of thing will have Chem-E's pulling their hair out.

If you are throwing in nothing but rubber tires a thing like that will yield a lot of energy, if it is nothing but concrete rubble from buildings it will consume a lot of energy. To keep it happy it really wants every bite you feed it to have the perfect mix of ingredients and it's not easy to get that out of municipal waste.

[robotnikman]

Apparently that same technology is being used on newer US Navy ships for waste management.

[IncreasePosts]

These machines are currently too expensive for widespread adoption, but I love the electric composter I bought that I keep in my garage.

There's no grossness or work involved. You just dump stuff in it and it cooks it down to something dirt-like(nearly but not quite compost ready) in less than a day.

I have municipal compost, but it's only picked up every 2 weeks, so that meant I needed to keep food scraps around for two weeks before pick up, so they either would get super gross and smelly, or I had to use my chest freezer to store them and make that gross and smelly and dedicated to just compost.

[bdcravens]

For those who can't or find dealing with compost a challenge, there are also other options to recycle biowaste. It's a bit of pricey subscription, but we have a Mill which processes most food waste into chicken feed (you do have to mail the processed food to them for further processing).

[makr17]

California has a low-double-digit percentage of the US population, and mandates organic waste separation/collection.

https://calrecycle.ca.gov/Organics/SLCP/collection/

[ChrisMarshallNY]

For anthropologists and archaeologists, trash/sewage is gold.

[roboror]

Proud to report residential composting is now mandatory in NYC.

[IG_Semmelweiss]

Please elaborate. From what i know based on prior research, most metro (including NYC) recycling is effectively a scam. How do you mandate composting in NYC ? Are you implying that all buildings have now must build a 3rd chute specifically for compost ? And who's picking up that compost ? NYC Trash collection ?

I've seen compost vending machines in my visits to NYC and a few other places, but i've yet anyone using them

[rayiner]

> most metro (including NYC) recycling is effectively a scam. How do you mandate composting in NYC

Also a scam.

[ethagnawl]

In what way?

[rayiner]

Most municipalities collect recycling and then just landfill it: https://www.earthday.org/plastic-recycling-is-a-lie/.

I find it very difficult to imagine that composting is actually legit.

[ethagnawl]

You can't just label a program like this "a scam" on the basis of ... your feelings? Intuition? Biases? In other contexts, that's libel.

It looks legit to me, based on a few minutes of web searching: https://www.nyc.gov/site/dsny/what-we-do/programs/compost-gi...

[ethagnawl]

It's doubtful that'll ever happen in Dutchess County but I can dream.