Greenware is the brand name of a 100% corn based cups produced by Fabri-Kal.

It is used to provide a plastic cup that can be composted.

I'm wondering what externalities might exist for this product and whether on the whole using such products is sustainable or just a step better than using regular plastic? Are there any downsides to including these products in your composting efforts?

  • Greenware isn't compostable in your home compost pile. As with most compostable plastic, it can only be composted in industrial composting facilities (see also remark at bottom of this webpage or this question)
    – THelper
    Feb 28 '14 at 8:37

The biggest downside is that it is still a consumable; a nontrivial amount of energy needs to go into growing and harvesting the corn, shipping it to the manufacturer, producing the cup, shipping the end product to a retailer, and then getting it to the consumer.

With respect to composting, I don't know specifically about this brand, but I have heard that other "compostable" products (e.g. those noisy Sunchip bags) do break down, but over a fairly long period of time -- possibly as long as a couple of years.

  • Right, why not just use a cup that you can keep for a lifetime?
    – clweeks
    Jan 30 '13 at 14:58
  • 2
    If this is PLA we are talking about, it's more like hundred years. It is compostable, but under well controlled conditions. The main advantage is that it's not from fossil materials, which means it does not contribute directly to mining more carbon from the earth. Nov 18 '19 at 16:03

Here in The Netherlands a lot of organic fruits and vegetables and some magazines are wrapped up in corn-based plastics. A while ago, on a television program they showed what happens with the plastics when you throw them in the separate garden, fruit and vegetables wastebin (these are collected and dealt with separately here). In the communal decomposing factory everything is composted. This process takes about 10 weeks if I remember correctly. However, the plastics take much longer to decomposes so after 10 weeks all left-overs, including the plastics, are filtered out and then incinerated.

  • So, just to summarize, where you live, the corn-based plastics are theoretically biodegradable, but because of the process used, wind up being burned instead?
    – Nate
    Aug 8 '13 at 20:35
  • @Nate correct. Even the compostable plastics (as opposed to biodegradable plastics) are burned.
    – THelper
    Aug 8 '13 at 21:11
  • So, if the leftovers from the first round of composting were left for the next round of composting wouldn’t more of it degrade? After all, we filter out rocks. Could the leftovers be left to function for drainage and soil structure along with the rocks?
    – Bonnie
    Dec 5 '20 at 20:25
  • @Bonnie if you leave the compostable plastics I'm sure more would degrade, but AFAIK most waste processing facilities just remove (and incinerate) the plastics because 1. it's hard to distinguish between compostable plastic and non-compostable plastic and 2. the amount of compostable plastic is not large enough to make an effort and change way waste processing is set up. There is little point in using the plastics in your backyard, because there they do not decompose.
    – THelper
    Dec 6 '20 at 12:15

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