On compost

Biodegradable cutlery

Don’t you dare throw that in the trash.

At Ensia (formerly Momentum), Bill Chameides tackles compost, or our lack of it.

The thing that really caught my attention was a report on the results of a series of student dumpster dives around campus. After collecting and sorting all the garbage, they found that about three-quarters of Duke’s so-called non-recyclable trash destined for area landfills was compostable—things like food scraps, napkins, paper towels, etc. Based on calculations fromgovernment data [pdf], the national average is closer to 50 percent, but that’s still a lot of compost mostly headed for a landfill.

While I agree with the gist of his post – we should stop sending so much compostable material to the landfill, it makes good dirt – he reaches, what seems to me, a somewhat troubling conclusion (bold emphasis mine):

Right now we send a lot of compostable materials to landfills. If you’ll pardon the pun, that’s a waste. Instead of being treated like trash, compostable items can be converted into organic-rich soil for growing crops. And that could even help slow climate change. The anaerobic decay that occurs in landfills produces methane, a greenhouse gas that can escape into the atmosphere if a gas-capturing system is not installed. Composting, which is primarily an aerobic process, generates very little methane.

But the real challenge in making a compost economy is moving our compostable trash toward 100 percent. Let’s replace recyclable, petroleum-based plastics with nontoxic, cellulosic, compostable plastics. In addition to making compostable products, let’s make the packaging compostable too.

Now, in that first quote he says half our of current trash is compostable.  That seems to me to indicate that our trash is already fairly compostable, and we aren’t doing anything about it.  It seems our real challenge(s) is/are:

  1. Make sure compost collection is available (far from standard across the country, and certainly not in Minnesota).
  2. Education/coercion (get people to throw it in the right bin).  No small task.
  3. Make sure that ability to process compostable material is available.  This is not a minor issue.  Consider that in the Twin Cities metro, there is one location that processes organic compost.  Many items collected through composting collection regimes can’t simply be thrown on a compost pile, they need specific temperature, moisture and material mixtures to break down properly.  Processing needs to expand if we’re going to get that other 50% composted.

My other issue is with Bill’s conclusion: let’s turn all our disposable products into compostable products.  This is backwards.  If collection isn’t available OR people don’t separate their compostable material properly (and just about universally), the results (for the climate, at least) could be worse.

Consider work done by David Allaway at the State of Oregon’s Department of Environmental Quality.  They looked at the lifecycle impacts of different water delivery systems (water bottles), including PLA (compostable) and PET (oil-based, recyclable) water bottles.  As Bill notes, in a landfill, compostable materials produce methane, which when combined with the upstream impacts of making the water bottle, are worse than just using a regular, oil-based recyclable bottle.


Green bar – 62% of PLA bottles are diverted from the landfill and composted, the rest go to landfill, where they produce methane during decomposition.

The scenario above, represented by the green bar, shows that even if you’re successful at collecting and composting 62% of compostable bottles entering the waste stream, the emissions from the landfill of the remaining 38% offset any benefits.  This includes “upstream” emissions, like making each bottle.

And this assumes a collection regime is in place.  Every time I see a Twin Cities restaurant trying to up their green cred by offering “compostable” cups or flatware, I check their waste disposal area.  Nine times out of ten there is no “compost” container available.

So, is promoting a conversion of “throw away” products like flatware and packaging to compostable materials a good idea?  At best, maybe.  At worst, well, it could make things worse. I think much more analysis needs to be done, and certainly more collection infrastructure and a highly-effective education campaign about sorting need to be in place.  Of course, composting food waste that’s already in the waste stream is a no-brainer, but let’s take a closer look at compostable products.

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