I have been doing some more research into using pallets for construction. Pallets are being thrown out all the time, and present a tempting source for free lumber. I always have a lot of projects on the go that require lumber, from potato towers, raised beds and cold frames to compost boxes, pallet gardens and frames to hold rain barrels. I'd recieved some information stating that pallets were safe for construction, and others saying they all were dangerous and treated with harmful chemicals. It turns out that some are okay to use while others aren't.
All pallets are treated with heat and pressure, to kill things like pine beetles that you don't want to ship internationally. Many countries also treat their pallets with something called methyl bromide which is used as an insecticide. It is a potent neurotoxin and carcinogen. Methyl bromide has the potential to 'gas off' as elemental bromine, after which it acts as a serious ozone depleter. I'm not sure if methyl bormide or its products enter food, compost or soil but exposure to it is dangerous and the effects are cumulative. During the Montreal Protocol talks, in which substances causing ozone depletion were banned, methyl bromide got an exemption when the pallet undustry argued that it was necessary to their trade and to prevent the spread of harmful species. 1 All except Canada, who still doesn't treat their pallets with anything except pressure and high temperatures. 2
Most pallets will have a country code. The HT stands for Heat Treated. It was illuminating for me to see from how far away pallets really came, from Germany and India to Mexico to the US. 3
Good to use
Also not good
Different pallets have different specs depending on what industry they are used as well. Pallets used in the food industry can be contaminated with e-coli 4 , but are probably still the most suitable to use. E-coli does not survive for very long outside of the gut of an animal, a matter of weeks to months, and you could easily keep pallets around for that length of time before having them be in contact with your finished produce. 5 Pallets that have been used to carry paint or hazardous chemicals might be avoided by the more careful.
This is a guide with specs for pallets used for different industries 6. One might avoid pallets used for telecommunications/paint, drums, military/cement, automotive, drums/chemical, and Military 1/2.
You can read more at my blog, http://barefootpermaculture.dreamwidth.org
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