We had our first dump of snow last night and I was reminded of last February when my chain fell off at minus 30 degrees. Here's a quick and simple diy heater that takes two minutes to make. I liberated a old candy? tin from the kid's room and cut down a empty soup can so it stands about one inch higher than the base. I packed some fiberglass insulation around the soup can then added around two ounces of denatured alcohol and I was done. It lights easily and will bring a small pot of water to a boil in six minutes. You could easily make a smaller version out of a empty cat food and a vienna sausage tin. I'm going to pack a heater when I take my bike ice fishing and build another one for the car. Obviously it's for outdoor use only and will consume oxygen in a enclosed space.

Wouldn't it just be easier not to ride too far from civilization at -30C?

Also, you generally have to dress more warmly for biking than you do running, if you're really in danger, ditch the bike and run to the nearest house. You'll stay plenty warm.

I can't think of a situation where I'd be far enough from civilization to need an "emergency" heater while biking.

I'm not knocking your thing, I think it's cool, I'm just stumped as to why you'd need it. (And wouldn't it just be easier to bring an actual furnace with propane/butane fuel if you're doing something like ice fishing?)

I like this but this means you have to carry this stuff with you!

You have a valid point on using a LPG stove or catalytic heater but a micro stove suitable for hiking starts around 50 bucks and this cost me nothing. It has no moving parts and guessing it weighs about 100 grams. LPG can be tempermental at really low temps but alcohol or HEET gas line antifreeze always burns.

I could see using this out in the woods doing some trail riding in the winter cold.

I think that using fibreglass insulation as the wick is brilliant. I had not come across this idea before.

The one issue is that alcohol stoves work on vapor pressure, which is a lot lower at colder temps. So while that stove can boil water in 6 minutes, it will double or triple or not work at all if the temps are low enough. Make sure you know alcohol stoves' limitations before relying on them (though they are cheap and light!).

Not necessarily. Here's the stove I've used for backpacking which cost me $7. Flame is nicely adjustable from a simmer to a roar and it includes the piezo-electric spark lighter so you don't need matches.
https://www.amazon.com/Ultralight-Por...s=orange+stove
Of course if you end up using it any significant amount you'll end up spending far more for fuel than for the stove whether alcohol or butane/propane.

What about a can of Sterno? It adds a sealed lid to contain everything and uses gelled alcohol so it will not spill. 3 cans cost about $6 I believe, an in a pinch you can use it to keep food warm at Thanksgiving! Granted it is more expensive than free, but still pretty cheap and probably safer to transport.

Where is your spirit of adventure!

Actually, I suspect most people that could benefit from one of these had no plans at all to be in a survival situation miles away from help, but an accident or wrong turn put them in the place where this might have been a lifesaver in severe weather conditions...

Tuna can packed with rolled up corrugated cardboard. Fill with melted paraffin. Light like a candle, burns for 2-3 hours. Works like a champ.

I used to work in the arctic ,every one of our vehicles had a metal coffee can ,a roll of toilet paper and can of air brake antifreeze ( alcohol ) .Stick the bum wad in the can ,pour the alcohol in the can and light it and you will have about 7 hours of heat .