[UDDYBUDDY]

Hey there,
     This is my first post on here, so apologies in advance for any mistakes. I have a relatively simple question that I'm having trouble finding information about online. (Perhaps my googlefu is lacking) Regardless, I hope anyone on the forum can help me out. Thanks in advance by the way.

Question: What liquid fuel has the longest burn time per gram? (Caveat: the fuel must be nontoxic, or at least safe to burn without PPE, inhaling nasty fumes doesn't sound fun)

I'm looking to use whatever said fuel is for backpacking, where weight is critical. More as an "accelerant" for fire starting rather than a sole heat source.

The idea came to me when thinking about the necessary "3+ methods of fire starting". Most lighters start with a ferrocerium striker, using the liquid fuel as a heat source. In my mind that seems to equate to using a larger ferrocerium rod and striker with an accelerant. The lighter is essentially a "small fire" that is completely redundant to already carrying a full size ferro rod and striker as most backpackers do. Thus, hopefully with this information I can eliminate a piece of superfluous equipment on my next trip.

What I have been able to dig up shows that alcohol burns less efficiently compared to white gas which is inferior to kerosene. I've been able to find some info about OSHA classified combustibles but not much beyond that. I would prefer something that's stable. I don't need spontaneous  combustion happening in my pocket if I put this in a small bottle.

Thanks again for your help.

[ATMyller]

Diesel has the highest energy density per mass (J/g) of fuels suitable for camping stoves. It might require preheating the burner and it produces a lot of soot. I prefer kerosene, it has only slightly lower energy density per mass, but better energy density by volume (J/L). Also it burns more cleanly and ignites easier.

[Borek]

Not that long ago box of matches was everything you ever needed to start a fire I understand why you may prefer to replace matches with the ferrocerium (I admit I don't have much experience with using it, I started just a few fires this way, as compared to hundreds started with just matches and whatever I was able to find around), but every other addition is not really necessary.

[Enthalpy]

What kind of fuel is so difficult to light: thick wood, coal...?

An excellent backpacking fuel is hexamine, aka hexamethylene tetramine. It's a benign solid, easy to light with matches or a lighter but not too easy, it burns quietly for very long without melting, which helps keep the fire under control, and without smoke. Hexamine is so good that it's a standard answer, widely available in special shops and on the Internet including eBay. Often used as the main fuel because a solid is safer, it can also serve to light more restive fuels.

Slightly less heating power than a hydrocarbon but you save the liquid's container.

[UDDYBUDDY]

All,
    Thank you for your help thus far.

ATMyller, Diesel sounds interesting. However it doesn't have to be suitable for a camping stove. I'd be using it more as an accelerant, dumping it on wet tinder and spark with the ferro rod to make fire starting in wet conditions easier. As long as I don't get cancer from breathing it and it won't explode in my pocket, I'm all ears.

Do you happen to know the burn time per gram for diesel? I would think energy density and burn time would be related but I'm unsure. My chemistry knowledge is limited to a high school level course. Whatever level of heat produced is likely enough to start fires in any scenario I can think of, burn time is more important due to the dampness of fire starting materials. Additionally ignition of the accelerant isn't the difficult part as ferro rods make sparks in excess of 2000 degrees F.

As for mass vs volume weight is more important in this scenario. I'm more likely to carry too much heavy stuff than I am too bulky stuff.

Borek, believe me I see the merit in matches. I intend to bring both and have done so previously. in terms of most efficient to carry (i.e. which one starts more fires for less weight) ferro rod wins! I've started fires with everything from a bow drill kit to a lighter and aerosol can (fun times at scout camp...). Partially due to scouting's "be prepared" mindset, I've always found good wisdom in bringing multiple fire starting implements as a contingency for the failure of one or the other. (i.e. it's too cold so the butane lighter won't work, your matches are soggy and won't burn, etc.). In most cases, I agree it's not necessary, however, I intend to do some backpacking in tough terrain (think Canada/Alaska) in the future and refuse to be caught without a "multi layer" fire starting kit.

Enthalpy, The fuel is not so much a problem as the tinder. Of course bringing along cotton balls makes life easy, but I much prefer to carry less and use natural tinder or process my own in the field. Often times this method is made more difficult by weather, thus the need for fire starting aids like I'm proposing here.

Hexamine is good, and I've used it before, however as a solid fuel the best I've found is a product called "livefire" it comes in a little tin and is orangish-yellowish in color and burns far longer than hexamine partially due to the tin. I use this as a "last resort" in a situation where everything has gone completely bad, I keep a pack of this in my pocket and use it when I can't get a fire started any other way or I need one NOW for fear of hypothermia or other issues.

It occurs to me while writing this that mayhaps it would be better to simply carry more livefire? A solid is more dense than a liquid by nature... Each tin weighs .9 oz total, so 25.5 g. with a burn time of 30 minutes the burn time per gram figures to be ~1.18 min/g. I wonder how Kerosene and Diesel compare...

Thank you all for your help

[Enthalpy]

That's clearer.

First, if a spark must ignite the chosen stuff, bye-bye to all safe fuels. I didn't try, but hexamine is unlikely then - give it a try? I couldn't light Diesel oil with a lighter, so burning metal chips are unlikely too - you can check. That may leave kerosene maybe, but variants of kerosene exist, some have a "flash point" below the room temperature hence are easier to light, others above the room temperature hence are difficult to light, and I have big doubts in Alaska.
https://en.wikipedia.org/wiki/Flash_point
Among oil distillates, gasoline catches fire at cold too, but I feel it really dangerous. If they weren't sensitive to humidity, I'd recommend cotton balls, sure.

Burning time... It depends on too many conditions to be defined just by the fuel. In the proper lighter, gasoline burns for long. But if you spread the same amount on a big concrete area, it's burnt quickly. The heating power is a fuel caracteristic, and to a decent approximation, oil distillates are excellent and equal from propane to heavy heating oil.

[ATMyller]

Yes diesel is not good for something like that. If you are just going to dump the fuel on some tinder and twigs it needs to be quite volatile, like gasoline or petroleum ether.

I think solid fuels are the better choice here, they burn longer and are safer to carry, even the flame is not as intense as with liquid fuels. Hexamine tablets, petroleum jelly cotton balls or good old egg carton dipped in candle wax should do the trick.