Ask the Eco Geek: Is #7 PLA plastic safe?

I just purchased a bottle of \"Primo\" brand bottled water. On the bottle it says that the plastic is made from plants, not crude oil, but there is #7 PLA on the bottom. Is it safe to drink?
I just purchased a bottle of "Primo" brand bottled water. On the bottle it says that the plastic is made from plants, not crude oil, but there is #7 PLA on the bottom. Is it safe to drink?
CD, Toronto, Ont

Dear CD,
These cups are safe to drink since they are made from polylactide biodegradable corn (PLA). Corn goes into one end of a complex one of a lactic-acid plants and white pellets come out the other end that is PLA plastic.

It's being touted as the of plastic in a post-petroleum world. But there are a few problems.
Chances are the cups originate from NatureWorks, the largest lactic acid producer in the States. PLA has caused a lot of excitement in the packaging field because according to a study commissioned by NatureWorks, it does use 65 percent less energy than producing conventional plastic and generates 68 percent fewer greenhouse gases.

PLA is said to decompose into carbon dioxide and water in a "controlled composting environment" in fewer than 90 days. There's the rub – the controlled composting environment is not going to be your backyard composter or your local municipality's composter.

PLA will decompose when it's been torn into plant scraps being digested by microbes and needs to reaches 140 degrees for ten consecutive days. Very few of us have access to composter that are as efficient. There are only 113 currently in operation in the States.

There is also some concern that putting PLA into the regular recycling bins can cause problems for those doing PET recycling. There are worries also that PLA will also lower the market value that PET currently brings on the market.

It doesn't look like there is any way out of the disposables dilemma.