Everyone I know (maybe I need to get out more) wants to be environmentally responsible, especially about climate change. After all, I live in Berkeley and work at a university. I know more about this than many people, so I wind up in conversations about how one could walk this talk, and I wish mightily for a 4×6 card like Harold’s financial summary, or Michael Pollan’s wonderful “Eat food. Mostly plants. Not too much.” But I keep using phrases like “you might think” and “actually, not always, it’s complicated”.

For example, take today at work, where we have finally driven bottled water off the menu for events and have containers for compost, trash, containers, and paper waste. In the kitchen was a new stock of this product. 

“Wow, that’s one of the nicest PLA cups I’ve ever seen,” I thought; “biodegradable plastic is improving”. I looked at the bottom, and found it clearly marked PETE. Ooops. Polyethylene terephthalate (1 in the little triangle) is not biodegradable/compostable; it’s recyclable, just like almost any hard plastic, which means it can be melted down and made into something like a polyester schmata or another bottle or your new deck (in fact, this cup is 20% recycled PETE). This saves landfill space and reduces litter, but doesn’t matter for climate.

I carried one around and asked people, “would you put this cup in the compost, or the trash, or the recycle bin?” Five out of five said “compost”, reasonably, because after all it has nice green leaves on it, and there are a fair amount of bioplastic cold cups in use, and biodegradable is good, right?

Here is where it starts to get complicated. This cup, made from oil, has three possible futures. It can be burned as fuel, in which case its carbon goes into the atmosphere; or recycled into something, (with the use of more fossil fuel to haul it around and process it); or put into a landfill where it will stay more or less forever. Which do we like on climate grounds? If we burn it, it’s just a fossil fuel, an energy source that puts carbon into the air instead of underground.Recycling into product is good, but it just puts off the issue for another cycle or two. A little less than a third of US PET containers are recycled, so after two cycles 90% of the original material gets burned or landfilled anyway. And polyester fabrics go to landfills or the flame when they die, not recycling.

What if it really were biodegradable? Then it could have another future, being metabolized by God’s natural little critters in a compost pile–into CO2 that goes into the atmosphere.


Biodegradability is a feature for plastic that will otherwise be littered into the landscape or the ocean, but a bug for materials captured in the solid waste system that can be landfilled. Unless you care more about landfill capacity than climate; at this point, I do not.

So for the most of it that isn’t practically recyclable into new products, burning and at least getting some energy out of it is better than composting, and unless you’re going to burn coal to make up for what you give up as fuel, landfilling is best from a climate perspective. In California, where our electric grid is pretty low-carbon, the landfill is the best future for that cup (and putting it into the compost stream just messes up the system).

Bioplastics are generally biodegradable; this is what Solo wants us to think about this cup. And it’s better to make plastic out of plants than fossil fuels, because the carbon comes out of the air where we want less of it, right? This last can be true, but it depends a lot on what plants, grown how, where, are used as feedstock. Wood from a sustainable forest operation can become fairly green rayon or cellophane. Wood from tropical deforestation, not so much. And the hot bioplastic these days is PLA, which comes from row crops and sugarcane. By the time we account for the N2O (a potent greenhouse gas) released from fertilizing these, and the diesel to drive the tractor, and the forest burned to make room for the crops, bioplastics are often not much less fossil-carbon intensive than plastic from oil and natural gas.

But at least they’re biodegradable, right? Again, this is either a feature or a bug just as it was for the petroleum plastic, and without reference to the original source of the carbon. In fact, the planet would be well served by non-biodegradable biomaterials (pace the question about their real life-cycle carbon intensity)that would take carbon from the air, do something useful with it along the way, and then hold that carbon underground.

There’s no excuse for Solo’s tacit greenwashing of this product, but it’s not at all clear that the thing they want us to think it is is actually more sustainable than what it really is.

[Cross-posted at The Reality-Based Community]

Michael O'Hare

Michael O'Hare is a Professor of Public Policy at the University of California, Berkeley.