Raised veggie bed's frame; is composite lumber safe to use?

[Carolyn252]

Using untreated pine lumber for vegetable beds' frames is fine, but will only last for about 5 years as it will rot in contact with the earth, water, etc. Treated lumber will last "forever" but I won't risk toxicity leaching into the soil. Cedar and redwood will last longer than pine but I'm thinking of using man-made boards. They're usually used for constructing decks and porches; they're a composite of plastic and wood fibers; very strong, will stay good-looking for years, and won't rot. One well-known brand is Trex. But, are composite boards safe to use for a vegetable-bed's frame?

I've read lots of opinions stating both yea and nay, but would like some independent study's factual conclusions. Anyone have the facts? I've put a call into Trex and their tech dept will call me back in a few days, but I wonder if anyone on this forum has already researched the topic. I've surfed the web for some documented assessments, but only can find biased "facts" or best guesses. It's difficult to know who to believe, anyway. The federal government's lobbied pronouncements? The Trex company's vested interest? Still, maybe some university or cooperative extension has done some analysis of composite lumber's ability to leach contaminants into the soil. (and from the soil, into the vegetables.) Anyone know of such studies? I haven't been able to find any so far.
Thanks.
-Carolyn252@aol.com

 

[CARS]

I would have used composite if I could afford it. I just used landscaping 3x3's and will replace them when needed.

I don't have the detailed info you want to hear, but I can't imagine that a thermo-set plastic composite can do anything to your soil or veggies. In fact, I would believe that real wood would harbor more disease than a non porous plastic.

One could argue that it is not a "green" product, but then again if it lasts 100 years, you are saving a few trees by not replacing boards every 5 years.

I would do it in a heartbeat next time I need to replace my timbers.