There is something pristine about new crates and wooden pallets, although of course this doesn't last forever. After years of service, they degrade to the point where they can no longer be used for their intended purpose. Some of these crates and pallets can be re-purposed into craft projects. Yet some will not even be suitable for this. If you're considering picking up some old crates or pallets to use as firewood, there are a few things you need to consider, since burning some types of crates or pallets can be unwise:
Have you heard of methyl bromide? It's a pesticide used to treat wood in order to eradicate bugs and other parasites. It's not particularly environmentally friendly and has been linked to the depletion of the ozone layer. Its use has been outlawed in many parts of the world, but it's still in use in some crates and pallets in Australia. It was scheduled to be phased out across Australia by 2005, but these plans never came to fruition.
When burned, there is a concerning level of toxicity in the resulting smoke, so this is why you need to carefully inspect any old wooden crates and pallets for a stamp that simply reads: MB, indicating that the wood has been treated with methyl bromide. Such a stamp means that the wood should not be used. It's also wise to remember that the stamp might have rubbed off when it comes to particularly old crates and pallets. Do not use the wood if you should have any doubts.
When you find an old crate or pallet that lacks the MB label, it is safe to use once other contaminants have been ruled out. You might see additional stamps, such as HT or KD. These amount to about the same thing, since HT means heat treated, and KD means kiln dried. This means that the wood has been heated to kills bugs and other parasites without the use of chemicals. Do not be concerned with these particular stamps as nothing toxic has been added to the wood.
Paint and Oil
An additional inspection of the wood is required. Look for paint and potential oil stains. This does not mean that you cannot use the wood, but any stained sections should be discarded when the wood is split into smaller pieces. Again, the existence of these compounds can result in added toxicity when the wood is burned.
There's no reason why old wooden crates and pallets cannot be used for firewood, just as long as you know what to look for.