Hi Temp Landfills

Is that a typo or do you really mean 2500 F?

I'm not seeing anything over 250 F.

Do you have a link to what you read? This sounds interesting.

Here is the link:

https://www.solidwaste.com/doc/eref-and-nwra-unveil-resource-for-elevated-temperature-landfill-information-and-research-0001?vm_tId=2057837&user=7d4f7b08-6058-4f34-8f72-b837ca3c0c26&utm_source=et_6214354&utm_medium=email&utm_campaign=SOL_03-23-2018&utm_term=7d4f7b08-6058-4f34-8f72-b837ca3c0c26&utm_content=EREF+And+NWRA+Unveil+Resource+For+Elevated+Temperature+Landfill+Information+And+Researchised I too was surprised at the elevated temperatures claimed in this link.

I read several possible sources of this heat,including exothermic,endothermic,pyrolysis,and bacterial but no one seems to completely understand the process.

Our landfills may one day become a crude oil source.

I could only find that one reference to 2500F. Possibly it's a typo in the original article. I'm pretty sure there is no biology that operates at those temperatures. It would be nice to have reference to some actual data taken at some site.

Energy released from a chemical reaction with high enough thermal insulation can result in high temperatures when the generated heat has no place to go. I have seen huge piles of wood chips that have caught fire from "spontaneous combustion".

Agreed. If 2500F is not a fire then what is? I think this is a typo in that article or "fake news".

I just read that the autoignition temperature for methane is 600C or 1112 F. Since there's methane produced by decomposition in landfills, it stands to reason it'd be flaming hearty at temps of 2500 F.

Only if there is oxygen present, and the methane concentration is in the flammable range, about 3 - 15% v/v for methane in air if I remember right.

"Only if there is oxygen present..."

What about the presence of other oxidizing material?

What do you have in mind? Nitrates, chlorates? As biogas is formed in a reducing environment it's unlikely oxidants will be produced at the same time.

But it raises an interesting question - if methane (or biogas) is put in a vessel with some potassium nitrate (say) and warmed, at what temperature would it explode?

I wasn't thinking of formation of other oxidants, but improper disposal of same.

Please feel free to experiment on that one and, should survival of the explosive event have happened, the results will prove interesting to readers here.

Would that be dangerous? I'd never have guessed.

Instead of coming out with smart remarks, it would be good if you'd respond when appropriate. On a recent thread about design pressure for a thermal deaerator I disagreed with one of your posts. I can only assume you accepted I was right, or you would have reaffirmed your position. An acknowledgement would have been in order, if only for the sake of the OP, to give him a clear answer.

https://cr4.globalspec.com/thread/118226/Deaerator-Pressurization

There can be a massive amount of O2 in your typical landfill; this is why conscientious landfill operators do two things: #1. vent the pile with deep wells, if the pile is big and deep enough capture the biogenic gases, separate the methane, and produce electricity onsite. #2. Move the active dumping drift points about the pile so the captured oxygen can self ventilate prior to deep burial and the biogenic methane production.

About the super hot piles:Wood and paper waste are substantial components of your typical Class D Landfill. Wood starts to smolder at +/- 500 Fahrenhite; it is big challenge at wood mulch and sawdust recycling centers. Glass becomes molten at +/- 1500 Fahrenhite and steel at 2500 Fahrenhite. With even a minimal amount of O2 in the pile at those temperatures something is going to be burning. As prior postings have said it's either fake news or a severely bad typo. Given that Copy Editors and fact checking have been replaced by "spellcheck" and not at all, I vote typo.

But what is a massive amount? Does it give rise to a flammable mixture?

Biogas is often extracted from these dumps using vacuum pumps, Nash used to push it in their ads, don't know whether they still do. I'm surprised that is safe, as I'd have expected a risk of drawing in atmospheric air leaking through the waste, apart from any oxygen in the gas to start with, risking a flammable mixture. But it doesn't seem to be an issue as far as I know. Maybe they have gas analysers to warn of a potential problem.

( 50,000 ppm/v = Lower Explosive Limit (LEL) of Methane (CH₄) );

( 150,000 ppm/v = Upper Explosive Limit (UEL) of Methane );

If LEL < [CH₄] < UEL , then a spark, in the presense of enough O₂, can ignite the Methane, otherwise, it won't...

That is how it can burn-off once it reaches open air... and doesn't burn-off if it can't reach open air...

Sufficiently open air can be available at variable depths below the surface of landfills, as the photos attest...

In the absence of appropriate instrumentation, the hazard can be mitigated by carefully (emplacing) more burn-off vents...

Methane is 2 to 4 times worse than carbon dioxide CO₂ for global warming, and CO₂ is produced in the combustion of CH₄, but more O₂, H₂, H₂0, etc., are also produced in that process, thereby benefiting the atmosphere, over all...

Some of the reactions are not biological in nature.They may be chemical,such as the hydration of calcium from industrial processes,aluminum-iron oxide(Thermite?) reactions,ash hydration,acid-base reactions,etc.

You said, "I read several possible sources of this heat,including exothermic,endothermic,pyrolysis,and bacteria."

I'm having a problem believing that an endothermic reaction can produce heat.

Endothermic process - Wikipedia

Our local landfill recovers methane gas and uses it, or sells it.

You are correct.Endothermic reactions do not directly produce the heat.The endothermic process in this case is one step in the heat production. Some endothermic reactions,such as iron-to iron oxide, produce hydrogen,which feed bacteria which produce heat.It is an intermediate step in the process.

Can any bacteria survive 2500F?

The bacteria are not the final stage,they are the beginning stage of the process.The bacteria are everywhere,and in certain areas,all of the ingredients combine to produce a self sustaining reaction even after the bacteria are destroyed.

Under pressure,with the right amount of leachate (which picks up chemicals on the way down) a witches brew sometimes occurs that is in the Cinderella range to promote such reactions.

Corrosion of iron absorbs heat,but produces hydrogen.Corrosion of aluminum produces heat.

The hydrogen is eaten by some bacteria and produce a low-level heat,which accelerates other reactions.It is a very complicated problem,which is hard to replicate exactly in the lab,and is not fully understood.

Due to the varied mixture of wastes in a landfill,there are areas of high temperature where these processes are at work.Hot spots are scattered throughout,and makes them hard to predict or utilize.

I have discovered a link that explains the present state of the knowledge.:

http://www.waste360.com/landfill-operations/diagnosing-and-understanding-elevated-temperature-landfills-part-3

Apparently that link is bad.Try this one:

http://www.waste360.com/landfill-operations/diagnosing-and-understanding-elevated-temperature-landfills-part-3

You are correct,the high temps from the original link must have been a misprint.

Those dang zero's and decimal points will get you in trouble all the time.

I have found no other references to temperatures of this magnitude.

2500 degrees? It sure sounds like it's on fire. Can you provide a link?

It's forming a black hole?

Why not direct bury a bunch of (pex) tubing and pull the heat out for industrial or residential use.

Imagine being able to say you own a home heated by a big steaming dump.

Here you have it: landfill heat pump.

https://www.sciencedirect.com/science/article/pii/S1876610216312541

Well landfill fires are common for several reasons, but spontaneous combustion fires occur mostly in poorly managed landfills in third world countries...

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

In order for enough heat to be generated decomposition has to occur, this requires oxygen...and 500° F is certainly possible, enough to start a fire, or explosion in some cases....There is a problem in some third world countries with kids losing legs and even being killed from these explosions as they hunt through the trash dump for certain commodities that can be sold...It's like walking on a minefield....

http://www.toxicsites.org/Explosions_And_Fires_At_Dumps.pdf

http://etd.fcla.edu/CF/CFE0002589/Moqbel_Shadi_Y_200905_PhD.pdf

Now I don't know how hot an underground coal fire gets, but it's probably pretty hot....

..."Coal seams can be set on fire by spontaneous combustion or contact with a mine fire or surface fire. Lightning strikes are an important source of ignition. The coal continues to burn slowly back into the seam until oxygen (air) can no longer reach the flame front. A grass fire in a coal area can set dozens of coal seams on fire. Coal fires in China burn an estimated 120 million tons of coal a year, emitting 360 million metric tons of CO₂, amounting to 2–3% of the annual worldwide production of CO₂ from fossil fuels. In Centralia, Pennsylvania (a borough located in the Coal Region of the United States), an exposed vein of anthracite ignited in 1962 due to a trash fire in the borough landfill, located in an abandoned anthracite strip mine pit. Attempts to extinguish the fire were unsuccessful, and it continues to burn underground to this day. The Australian Burning Mountain was originally believed to be a volcano, but the smoke and ash comes from a coal fire that has been burning for some 6,000 years."..

There are at least 24 coal fires burning at this time....

http://atpeacewithpink.blogspot.com/2015/04/australias-eternal-flame-about-coal.html

From SE “Now I don't know how hot an underground coal fire gets, but it's probably pretty hot”

You are in to the 1000°C range.

Unfortunately one of our coal fines stockpiles caught fire despite all the care we took to seal the air out. Normal practice is to roll the coal to exclude air and push moisture out, the final top seal is bitumen. Temperature probes driven in to the core monitor the temperature and control nitrogen injection.

18 months of N₂ and CO₂ cooling and it was under control. Out of 35,000 Tonnes we recovered 10,000 Tonnes contaminated with ash and to our plants, unusable.

Thank you for that info Tony, so it's not hard to imagine that with an air supply and an exhaust outlet, that a thermally driven air supply might develop ...and that could boost the temp up to 2500°F....for a coal fire anyway....and I might add that with a network of tunnels, nearly impossible to extinguish...

Flames rise from an underground coal seam fire in Dhanbad district of Jharkhand state in northern India.

"The 108-acre French Gulch Fire, a coal seam fire burning about 5 miles east of the Parks Highway near Healy, Alaska."

http://wildfiretoday.com/tag/coal-fire/

Centralia, Pennsylvania has been burning for over 50 years,and has been almost totally abandoned.

Here is a link:

https://www.huffingtonpost.com/entry/this-abandoned-pennsylvania-town-has-been-on-fire-for-53-years_us_55df6490e4b08dc09486d4a0https://www.huffingtonpost.com/entry/this-abandoned-pennsylvania-town-has-been-on-fire-for-53-years_us_55df6490e4b08dc09486d4a0

About 35 years ago I visited what was left of Centralia. That was weird. The steam plumes out of the ground were bizarre.

I visited Centralia about 5 or 6 years ago and there was no steam then. I found some vent stacks in the woods that were cold and abandon roads and foundations but nothing that told me this place is on fire.

Yes this fire was started by firemen burning the town dump to reduce the amount of landfill, unfortunately they neglected to completely extinguish the fire afterwards and it spread to an open coal seam that reached the surface...

Just one <...country...> or does this apply to other landfills across the globe as well?

Good catch. It's one reason why I use degF or degC in my writing.

The latest link above does a pretty good job of explaining the current understanding of the HTLF problems,and will answer a lot, but not all questions about the processes at work.

There is a great Doc. on Showtime about the Bridgeton, MS landfill that covers Hi Temp and radiation bleeding to the ground water and air. They store regular waste at the landfill, and are miles from a nuclear waste site on the other side of the county landfill.

Both sites were deemed "safe" by the EPA Oops here we go again!!!!

https://www.bloomberg.com/news/features/2017-09-28/fighting-the-toxic-nightmare-next-door

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

If there is enough water in the landfill, and/or, if enough water could be introduced into the landfill, then theoretically, resultant steam could be enough to be harnessed in the same manner as geothermal energy is harnessed...

The local landfill ( Lamb Canyon ) uses a system where gasses are collected via underground plastic pipelines. Then that is sent to a burner. There is a very basic system where condensate is collected . Leachate is collected in a settling pond and anerobic agents are added. There does not appear to be a system in place to collect the gasses to produce reusable energy. The landfill relies on outside power for it's energy requirements.

One type of solution to this type of problem has been to, in effect, install a row of closely spaced gas wells, as a sort of gas collection curtain, along the landfill boundary to intercept the migrating soil gases before those soil gases leave the landfill property...