When Your Compost Becomes My Compost

My homemade composting system at the edge of our yard.

I started a garden to be closer to my food source. As an Environmental Health Scientist, one who studies pathways of pollution in our environment and how it ends up in our bodies, I am particularly privy to the many opportunities for contamination in food supply chains. A backyard garden felt like the best way to (eventually) control every step of the process and protect my household from pesticides, plastics, and other pollutants. 

Seven yards of raised-bed mix—beautiful, except for the plastic.

The sunniest spot in my tree-filled yard requires raised beds. So I purchased a blend of soil and compost from a local supplier to fill my 8 beds before planting my first year of seeds. The delivery truck came and nine yards of sweet, musty smelling earth tumbled out onto my driveway, forming a mountain of rich, chunky soil. It was beautiful. I couldn’t wait to dig into what I thought was the clean, nutritious “black-gold” beginning for my new garden. 

The first piece of plastic I picked out of this gorgeous pile of earth didn’t alarm me. I expected a little contamination. Then I saw another piece, then another, and another. After four hours of shoveling soil into my garden beds, my pockets were bursting with dirty trash: bits of plastic film, tines of bioplastic forks, stickers from produce, shards of rigid plastic and sharp glass, broken plant tags, and bottle caps, to name a few. I was slightly disgusted, but planted my seeds and tried to move on. Then a couple of weeks later, it rained—hard—and up came more plastic. Hundreds of buried fragments floated to the surface in each flooded bed and swirled around my seedlings. I was aghast at the sheer amount of plastic hidden in my raised bed soil. And I knew there was more where I could not see. 

I know plastics. Plastics can contain chemicals linked to cancer, infertility, hormone disruption, and other unwanted health effects; chemicals including phthalates, paraffins and flame retardants. Most of these chemicals are able to migrate from their plastic “host” into other mediums like food, water, soil, skin, oils, air—whatever it is they are touching[1]. This soil-compost-plastic blend was not what I envisioned for my “organic” backyard veggie garden. 

Plastics, both macro- and micro- in size, can have impacts on soil. It can affect soil microbial communities, soil structure and water percolation, and introduce pollutants which can be taken up by the plants that I intend to eat[2],[3]. I have also observed songbirds swooping down to grab pieces of colorful plastics and glimmering glass out of my raised beds—and that can’t be good. 

Admittedly, I am biased. I harbor a rooted fear and loathing of plastic—even if most of the nasty chemicals have already leached out into someone else’s environment. I was irritated having just paid good money for unwanted plastic sprinkles in my soil, but I also felt saddened by the realization that Vermont’s commercial compost is so contaminated. 

Why don’t people take stickers off their avocados and oranges before chucking them into the compost? Why are people fooled by greenwash marketing claiming disposable products are biodegradable when, in fact, they are not? Plastics will not decompose in our lifetime. Most bioplastics do not biodegrade either—not completely—and not within the time they spend in the commercial composting process[4],[5]. With statewide composting mandates approaching, I fear that the widespread lack of understanding around what actually composts in our commercial composting facilities will lead to dirtier compost for us all. 

Purchasing contaminated compost is not for me, so I made the switch to home composting after taking the online Master Composter course. In 2020, I hope to apply my own compost—a cleaner compost—to my raised beds and other perennial gardens. And while I am sure to be stuck picking plastic from my garden beds for years to come, I hope to find a way to support cleaner composting efforts in my community. Commercial composters need our help to produce cleaner compost. Composting is a good thing. But good things are only good if they’re done well. 

[1] Hahladakis, J. N., Velis, C. A., Weber, R., Iacovidou, E., & Purnell, P. (2018). An overview of chemical additives present in plastics: migration, release, fate and environmental impact during their use, disposal and recycling. Journal of hazardous materials, 344, 179-199.

[2]  Cattle, S. R., Robinson, C., & Whatmuff, M. (2020). The character and distribution of physical contaminants found in soil previously treated with mixed waste organic outputs and garden waste compost. Waste Management, 101, 94-105.

[3]  Esan, E. O., Abbey, L., & Yurgel, S. (2019). Exploring the long-term effect of plastic on compost microbiome. PloS one, 14(3). 

[4]  Narancic, T., Verstichel, S., Reddy Chaganti, S., Morales-Gamez, L., Kenny, S. T., De Wilde, B., ... & O’Connor, K. E. (2018). Biodegradable plastic blends create new possibilities for end-of-life management of plastics but they are not a panacea for plastic pollution. Environmental science & technology, 52(18), 10441-10452.

[5]  Muniyasamy, S., Ofosu, O., John, M. J., & Anandjiwala, R. D. (2016). Mineralization of Poly (lactic acid)(PLA), Poly (3-hydroxybutyrate-co-valerate)(PHBV) and PLA/PHBV Blend in Compost and Soil Environments. Journal of Renewable Materials, 4(2), 133-145.