[paul.fr]

Hi all, just wondering what you think of an idea i have been musing on lately.
We have just been informed by the local council that we need to do more in the way of recycling or be hit with large government fines and that the fines will be passed on in the "poll tax", they also say that we are running out of landfill space. This set me thinking....

Now i may be wrong here but, don't landfill sites produce methane gas? in the region of yorkshire that i live in we have over 100 disused coal mines that also produce methane gas.

Is it possible to "back fill" the thousands of miles of mine shafts with the landfill wastse? thus creating a super source of methane gas which could then be used as an energy source.

i have the idea that the methane could be used to heat a series of water tanks and the hot water then piped into homes or offices to both supply hot water and heating, central heating is commonly just hot water pushed through radiators after all.

Having listened to every podcast i have never heard this mentioned, maybe that tells me the answer but iput it out there any way.

Paul

[chris]

Hi Paul

interesting idea, and you're quite right about the methane production from landfill. Methane makes up about 50% of the gas oozing out of a rubbish tip and it's produced by bacteria breaking down the organic components of the debris under low oxygen (anaerobic) conditions.

It can pose a considerable explosive risk, so some sites are capped and the gas drawn off for flaring (burning off), or fuel.

However, and I'll need to check this, I think from an energy perspective it would be more cost-effective and probably more environmentally-sound, to merely burn the rubbish and extract the energy that way.

Indeed, at the hospital where I work rubbish from the city is burned in the site incinerator and the heat produced warms the hospital and generates electricity.

I think your idea of packing rubbish into disused coalmines would be costly in terms of energy and infrastructure, it would be technically difficult and it could well be dangerous.

What does everyone else think?

Chris

[paul.fr]

Hi Chris, and thanks for the reply.

i agree the idea of using disused coal mines to deposit landfill would be costly. but a lot of government and EU funding already goes into coalfield regeneration. This could help offset some of the costs.

I found this on the net this morning, http://www.greenhouse.gov.au/ggap/envirogen1.html

It tells of the Tahmoor Power Station in New South Wales where "The power station is mainly fuelled by waste coal mine gases including methane, which previously escaped to the atmosphere as the coal was mined. Methane has a global warming potential 21 times greater than carbon dioxide. Methane vented from coal seams accounts for 4 per cent of all greenhouse gas emissions in Australia. Envirogen's GGAP projects will bring a sizeable reduction to these emissions"

I'm not sure how the mines in Australia compare with those in the UK, but we do have hundreds of disused mines, some of which must be viable for this kind of operation.

paul

[daveshorts]

I think back filling coal mines would be very difficult as they are all the wrong shape - long and thin, so it would be very expensive, also you couldn't collect methane while you were filling them as you would have to ventilate them very well while you were working in them to avoid explosions.

I think it is probably easier to build a rubbish dump next door and seal it with polythene and collect the released gas, or burn the rubbish directly as was previously mentioned.

[science_guy]

speaking of methane, another possible source for collection would be cattle farms.  cows do release a lot of methane...

[daveshorts]

Although the aparatus to collect it would be... interesting

[paul.fr]

also you couldn't collect methane while you were filling them as you would have to ventilate them very well while you were working in them to avoid explosions.

Ah, i never thought of that. Oh well back to the drawing board...

[DoctorBeaver]

Although the aparatus to collect it would be... interesting

The mind boggles!

[JimBob]

They require catchers for horses in town here so why not cow sealer diapers?

BTW, abandoned coal mines would be VERY dangerous - it is the last idea I would consider in a long list (as a geologist -  I are uno geologer, paul.fr)