It’s a fact that every single one of us encounters wood every day! Whether it be the desks we write on, the doors we open, or the buildings that shelter us, it’s clear that wood is important. Wood is important in green chemistry because it follows a number of the 12 principals. Wood is “natural, renewable, energy efficient and biodegradable.” Most people have probably noticed that these wood items we encounter every day seem to remain unchanged. Have you ever stopped and wondered why though? Without special wood preservatives, most of the wood we encounter on a daily basis would probably rot due to the growth of microbes, fungi and insects.
Wood preservatives come in many forms. Chromated copper arsenate (CCA), Organotin, and Creosote, are just a few common ones, all of which are very toxic but mainly to small organisms. Generally the toxicity is limited to smaller organisms which destroy wood; however, their have been cases of wood preservatives being toxic to humans. Australia has recently banned all pine timber in children’s playgrounds treated with wood preservatives. Australian authorities have linked a special wood preservative to cancer.
Green chemistry focuses on the production of less hazardous materials (in this case wood preservatives). Safer alternative wood preservatives are compounds containing boron. Borate ions form covalent bonds with some woods to form borate esters which are good, safe wood preservatives. Borate esters are known to target functional chemical groups present in most microbes, fungi and insects and kill them. The only drawback is that under wet conditions such as rain, the borate esters can be washed away. A solution to this problem is simply mixing the borate esters with hydrophobic compounds.
Green chemistry also focuses on limiting dangerous chemical products in the environment. Wood treated with potentially dangerous preservatives have to be properly disposed of. Preservatives treated with boron compounds are almost entirely benign and do not require such harsh disposal techniques.
Both types of wood preservatives have their positives and negatives. When it comes to green chemistry however, it is clear which type of preservative is the winner: those that form borate ions.
http://www.future.org.au/news_2005/may/green.html
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2 comments:
And I forgot to add a title to this post so I will call it: Green Preservatives. Sorry, I've been suffering from a cold that is making me delirious.
As my senior project in high school I made a bench out of wood. I coated it in a wood preservative and it's been sitting, more or less unchanged, in my backyard for the past three years. I wonder if mixing borate ester with a hydrophobic compound really keeps water from washing it off. Because if not I think it would defeat the whole purpose.
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