The other day Tim brought home some food in a container that claimed to be made of corn and therefore compostable. I was intrigued by this, since I remember going to street parties and Christmas markets in Germany where the disposable plates were grain-based and even edible (not that people usually did eat them) but haven’t seen them here. So I looked into it a bit more.
The container was made out of something called PLA, which is made from starch. The label said not to microwave it, which had me puzzled – isn’t corn safe to microwave? What would happen? Would it melt? I tried microwaving some water in the container and nothing untoward happened, so I poked around on the website for the company (NatureWorks LLC, a subsidiary of Cargill) to find out more.
The website didn’t give any details that I could find as to why not to microwave the container, so I emailed them. And got back a rather mixed reply. Some breathless marketing prose (new, revolutionary, bridges the gap between natural and synthetic products), the actual answer in the middle, a somewhat odd paragraph about how all the technical info they’re prepared to disclose is on the website (if the answer to the microwave question had been there, I wouldn’t have emailed them). Anyway, the answer is supposedly that PLA has a low melting point, so the containers might leak in the microwave.
So if this container is compostable, where can one compost it? The store has a big bin to take them back, but what about the Vancouver compost facility? Or indeed my compost bin? The cashier said “oh, just throw it in your compost bin.” “Are you sure?” “Yes, absolutely”. According to the PLA brochure, you need
140ÂºF and humidity between 80% and 90% for extended periods of time. So that rules out my compost bin. And the Vancouver City compost facility as well, unfortunately, since they use an open windrow process. I emailed the relevant people in the Vancouver City engineering department, and they pointed out not only would it not compost, if I put the plastic in the yard waste bin, it might encourage other people to put unsuitable plastic containers in there. So it’s back to the store with the containers; fortunately it’s not a big deal since it’s one of the local stores we shop at anyway.