Four Dirty Truths: My Deep Dive into the Compost Bin

With natural disposable diapers made from plastic, words like "renewable", "biodegradable", and "compostable" are everywhere. But are these so-called compostable plastics really...compostable? The short answer is no. 

NO commercially available disposable diaper is fully compostable or biodegradable. And there are 4 dirty things even I had to learn for myself (which I'm sharing here). But first. What do these words even mean?


BIODEGRADABLE: The ability of something to be broken down by microorganisms into the building blocks of life (water, carbon dioxide, biomass, and other elements). For something to be “biodegradable” it must be broken down naturally. With or without exposure to air.

COMPOST: Compost is recycling for food and plants. Generally, food and plants, including yard waste like grass clippings and fallen leaves, are considered “organic” material, meaning they were once alive. The beauty of organic material is that it can be decomposed and recycled into usable organic material to enrich the soil and help more plants grow. Compost is a specific type of biodegradation. 

DISINTEGRATION: The process of coming to pieces. Biodegradation might look like disintegration under certain conditions.

ORGANIC MATERIAL: Something that was once alive and can be broken down into usable materials like oxygen and biomass.

HUMUS: Not “Hummus”! Decayed organic material used as a soil conditioner. Humus is the outcome of a good composting process. It is sold to farmers, landscapers, home gardeners, and anyone looking to improve their soil.

 Compost cycle with inputs

The 4 Dirty Truths

 1. Without time and heat, composting won’t happen.

Decomposition of food waste takes time and generates a LOT of heat. In large composting operations, compost is organized in rows and “turned” or mixed at a regular interval to speed up the decomposition. Turning compost can get the heat up to a level that significantly speeds up the process from one that could take three months on its own to one that takes about a month from start to finish. But turning too frequently can cause the humus to have less organic material in it, so industrial composters have to balance quality and speed

One thing to note: compostable plastics only “biodegrade” under those high temperature conditions available in composting. They are just like normal plastics at room temperatures: they will last for a LONG time if heat is not applied!

 2. A lot of compostable plastics, including packaging, are destined for landfills.

Just because something *can* theoretically be composted does not mean it will be. Compostable plastics are only compostable if a composter is willing to take them. They need to sell the humus they produce, so it has to be a quality product that actually benefits customers’ soils. When composted, plastics like PLA degrade into H2O and CO2. While this is great because it leaves nothing behind, PLA also contributes nothing to the quality of compost. So an industrial composter needs another incentive to compost plastics.

The decision for a composter to accept plastics depends on how much other “good stuff” (nitrogen, phosphorus), like salad remnants or food scraps, comes with the plastics.

 3. “Biodegradable” items are only biodegradable under certain conditions. 

All those things we buy labeled “95% biodegradable”? I almost don’t want to breach that topic because it is so loaded. But for complete transparency, I have to share this: things are only biodegradable under specific conditions. 

For example, wood is biodegradable. It can reliably be expected to decompose if it is wet and covered in leaves, like when a tree falls in a forest and decays. But what about houses built of wood that are still around after four centuries? Even if the outside of those homes have been replaced, the dry structural timbers don’t biodegrade. Those timbers were set up to last by keeping them out of the wet conditions that cause degradation -- just like garbage in a landfill

In general, I think companies could do a better job of avoiding “greenwashing” by specifically calling out the conditions under which their claims of “compostable” or “biodegradable” are true. 

 4. That bin labeled “compost” might not actually be composted (but this isn’t necessarily bad).

Sometimes composting is not the best or most economical option for “biowaste.” An example of an alternative to composting is a process called anaerobic digestion, which is used by our Kudos founder’s hometown of Cambridge Massachusetts. Even though food waste is placed into bins labeled “compost,” the food is actually consumed in a totally different process, with a totally different output of methane fuel and “digestate,” which is an organic soil additive used for landscaping.

Still, composting is a win!

Let’s do more of it please! Overall I feel really optimistic about trends toward recycling biowaste such as food or plant-based materials. When composting is set up correctly, it is a no brainer to recycle “used” organic material into usable organic material.

Whether that's garden composting at home, purchasing compostable products, or simply using the correct 'compost' bin at Whole Foods -- composting is worth doing.

I am already applying what I’ve learned about composting and biodegradability as we develop a sustainable baby diaper at Kudos. I hope you’ll join Kudos as we keep developing products that are great for baby, great for parents, and great for Momma Earth!


About the author

Mom of 3 and an engineer-by-trade. Emily is leading up diaper engineering at Kudos and pushing the industry to be more sustainable. Whether the topic is diapers, babies, or Mama Earth, she's on a mission to find and share the best info there is to offer. Engineer and mama by day. Blogger by night.

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