Can composting save the world?

I explain why having abundant biodegradable polymers is only half of the equation for a circular bioplastic economy.

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In the News:

John Schwartz for The New York Times recently published an excellent article about biodegradable containers. In summary, just because it says biodegradable doesn’t mean that it is good for the environment and that there is more than meets the eye when it comes to biodegradable plastics, paper products, and those fiber/paper type bowls you might get a Chipotle.

Schwartz touches on poly(lactide) or poly(lactic acid) or PLA as a biodegradable polymer that has a problem. PLA initially was a big deal for medical devices because there was finally a polymer that the body could breakdown and absorb. If you have ever gotten a surgery where the surgeon says “these stitches will eventually dissolve and you will be healed” then you’ve experienced the work of PLA based technology.

In fact thyssenkrupp recently announced expansion of PLA capacity in China with an additional 30,000 tons of PLA capacity per year. Their first plant was to supply China’s largest food and beverage company COFCO with material and has since been a success. Natureworks and Total Corbion have also announced capacity expansions on PLA this year. Sounds good right?

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How does PLA work and what is the problem here?

The degraded pol(lactide) yields lactic acid, which is a common acid found in the human body after strenuous exercise. Poly(lactide) or poly(lactic acid), which is referred to by many as PLA, can easily get confused with other plastics and can be thrown into recycling streams or be thrown into the trash. If PLA is thrown into the trash it goes into a landfill and generates methane and takes decades to degrade just like all the other plastics out there. If PLA is thrown into a mixed use recycling stream then it can hinder recyclers being able to separate out what they actually want, which is typically polyethylene, polypropylene, polystyrene, and polyethylene terephthalate. As a science experiment this fall try putting some PLA into a backyard compost pile and see how long it takes to biodegrade.

The label says it is compostable, but as pointed out by the New York Times this means under industrial compost conditions which are hotter, more humid, and containing special microbes, which cannot be achieved in a backyard compost pile. Once PLA was able to be made at scale by Natureworks in 2002 there was a lot of hope that a revolution would happen where compostable single use plastics would take over. There was a slight problem though in that in 2002 PLA was significantly higher in price than its competitors and most people didn’t care. Corbion has an excellent white paper about how many feedstocks there are for PLA, which are all related to food production.

Global PLA capacity is growing and this means we will have more availability and lower prices for this biodegradable polymer. The only problem is we do not have a robust industrial composting infrastructure to biodegrade all this plastic.

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Compost: Nature’s cleanup crew

Composting is growing in certain areas of the United States such as the Northeast where a consumer can pay to have their compost (food scraps, paper, PLA, etc) collected and processed at an industrial composting facility. The two companies that operate in my neighborhood are Garbage to Garden and Black Earth Compost. For about the price of Netflix our compostable waste is collected once a week and composted for us. We then have the option of obtaining bags of that compost for our garden. The sheer weight of compost that we put out every week is staggering. What these companies have access to are industrial composting facilities where even PLA can be broken down.

What is Industrial Composting?

The main difference between composting at home and industrial composting are the temperatures. Industrial composting typically reaches 122–140 °F (50–60 °C) with high humidity and microbes capable of surviving those temperatures. The microbes help degrade the organic matter into soil and a final process of over 140 °F helps obtain a more sterile compost. Industrial compost enables faster turnaround times on organic waste in and nutrient rich soil out. An industrial composting cycle can last 3–6 months and the final compost can be inspected for unwanted microbes or unwanted materials before it goes to the customer. More basics on composting can be found here and here.

The popularity of these composting programs could lead to further installation of industrial compositing capacity in the future and one thing that the large capacity can introduce is reduced costs. Compost is nature’s way of getting key nutrients to plants and its possible that massive industrial composting could be an alternative to dousing fields with fertilizer. Composting can also create jobs, about 4x the amount of jobs than a trash incinerators.

This means that composting can do the following:

  1. Create local economic success
  2. Produce high quality soil as an alternative to traditional fertilizer
  3. Sequester carbon in the soil
  4. Give new biodegradable polymers a place to biodegrade
  5. Enable people to help make the world a better place.

Living through 2020 has taught me that it is very easy to feel powerless. We started composting this year and until I wrote this I didn’t fully understand how important composting is to the future of our planet.

Do you want us to have more plastics that can biodegrade and cause less harm? We need more composting. Do you want to help sequester carbon out of the air and help improve soil health? We need composting. Do you want to help create jobs within your local economy while also doing good for the planet? Compost.

Our composting infrastructure is still in its nascent phase and as it develops costs will come down, more plastics that can biodegrade will be available, and many of the problems we currently have with plastic waste and landfills will start to get better.

You can’t pack an ethylene cracker on a spaceship to Mars, but you could pack some freeze dried microbes that can eat and produce plastic and grow themselves.

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All of the opinions are my own and do not reflect the views of any of my employers nor are they investment advice.

I’m still experimenting with what I want this to be. I’m thinking of twice a week. Fridays = more topical and Tuesday = deeper dives.

Written by

Writer of The Polymerist newsletter. Talk to me about chemistry, polymers, plastics, sustainability, climate change, and the future of how we live.

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