[DoctorBeaver (OP)]

Is there anything that can burn that didn't start its life as a plant or tree? Coal, oil, natural gas, paper, wood, etc - all were once plants or trees.

[another_someone]

Most metals will burn (even if the ignition temperature may be higher than for carbon).  The other problem is that in our oxidising environment, few metals (least of all those most likely to combust) naturally exist in unoxidised form, so you first have to reduce them (which requires energy, often from combustion of carbon) in order to obtain their reduced metallic form, which then allows them to oxidise again by burning in air.

Similarly, hydrogen (although that might be regarded as a metal) will burn, but is naturally already found in an oxidised state - namely water.

Phosphorous will burn (although historically, primary source of phosphorous often tended to be from things that were once living - e.g. bones, or urine).  White phosphorus is even self igniting in oxygen.

[dentstudent]

Non-cellulose based plastics?

[another_someone]

Non-cellulose based plastics?

But most plastics are produced from oil, which is assumed to have originated as plant matter.

[dentstudent]

OK, perhaps what I meant was fully synthetic plastics.

[another_someone]

OK, perhaps what I meant was fully synthetic plastics.

Please explain what that means?

Almost all carbon we use was once plant matter, so any carbon based plastic will at some time most likely have been plant matter.  It is theoretically possible to obtain carbon from extraterrestrial sources, and this carbon is unlikely to have ever been plant matter, but it is not a source of carbon that is presently readily or cheaply available.

Ofcourse, not all plastics need be carbon based - there are also silicon based plastics - but they are not normally combustible.

[DoctorBeaver (OP)]

So basically the answer to my question is no. That's what I thought.

I first considered this when I started a cooking fire at the stables the other day. I started thinking about what material was normally used for fires & I couldn't think of any that weren't originally plant material.

[another_someone]

So basically the answer to my question is no. That's what I thought.

I first considered this when I started a cooking fire at the stables the other day. I started thinking about what material was normally used for fires & I couldn't think of any that weren't originally plant material.

The point is that in our environment, anything that can be easily oxidised has already been oxidised; so in order that we can obtain something that is not in an oxidised state, it needs to have gone through some chemically reducing process.  The only common chemical reducing process that naturally occurs is photosynthesis.  So, the only naturally occurring materials materials that are not already in an oxidised state, and are capable of oxidation, are likely to have gone through a process of photosynthesis - i.e. they were plant material at one time.

Maybe the only exception to this might be at submarine volcanic vents, where hot reduced matter might be vented, and not having access to air, do not get a chance to oxidise (I am thinking here maybe about sulphur, or hydrogen sulphide).

[dentstudent]

I remember from school chemistry that we had strips of magnesium which would burn very readily. Does this qualify? Also sodium, which reacted strongly in water? Or do both of these have to be reduced as George said earlier?

[another_someone]

I remember from school chemistry that we had strips of magnesium which would burn very readily. Does this qualify? Also sodium, which reacted strongly in water? Or do both of these have to be reduced as George said earlier?

You would not get either as raw metals in the natural environment (Sodium exists in numerous salts, most significantly as Sodium Chloride, which can be reduced to Sodium; and magnesium would I suspect exist predominantly as oxides or sulphates).

[eric l]

Is there anything that can burn that didn't start its life as a plant or tree? Coal, oil, natural gas, paper, wood, etc - all were once plants or trees.

Your phrase "didn't start its life" confirms the general impression that all our fuels are of organic origin.  But not all of vegetable origin.
I remember reading that the Inuit (Eskimo) use(d) cod liver oil and similar substances as fuels, there are probably other fuels of animal origin.  Other example :  bee wax for candles.  But I would qualify the famous buffalo chips as of vegetable origin because ultimately they come from grass.

[DoctorBeaver (OP)]

Good thinking, Eric. Unfortunately, we don't get many walruses or seals here in central England so blubber is a non-starter for me.

[ukmicky]

Methane hydrate ,then again no as it use to be organic plant material

[DoctorBeaver (OP)]

Doesn't methane ultimately derive from plant material?

[ukmicky]

quite right ,You got in before i got my edit finished

[DoctorBeaver (OP)]

That's made me look stoopit!  []

[Soul Surfer]

There are a few that I can think of. 

Firstly there are truly mineral sources of carbon, that is graphite and diamonds.  both are found in meteorites.

Sulphur is also found native and this will burn in air.

Some metals like iron are also found native for example meteoric iron and these will burn if finely divided.

[DoctorBeaver (OP)]

Do they burn?

[Soul Surfer]

All will burn in air. sulphur is the easiest to ingnite.  It is possible to make sulphur candles.  These are used for fumigating greenhouses.  Graphite needs to be heated quite hot before it burns but once it starts it will burn quite fiercely.  The windscale reactor fire was a graphite in air fire.