Microplastic particles in soil

This blog is the second of two on the problem of plastics in teabags and microplastic particles in the soil resulting from composting.

In the past the main concern when composting teabags was based on the fact that uncomposted teabags spread on the garden, which had passed through the composting process are unsightly but now the main problem relates to the presence of microplastic resulting from degradation of plastic in the teabags and other plastic-coated items in the soil and in drainage water.

A recent study* has shown that earthworms can be play a significant role in transporting microplastics in soils by means of their casts, burrows, etc with the smaller particles being carried to a deeper depth which may increase the risk of the microplastic entering groundwater. As composting an area tends to attract worms should be borne in mind when choosing teabags and the subsequent treatment after use.

 Other research* has shown that polyethylene microplastics in plant litter deposited on the soil surface resulted in reduced worm growth and higher mortality. Would the same results be seen if a mulch of compost contaminated with plastic microparticles from a significant “plastic” teabags was used.

But it is not just teabags there are other plastic-coated items that might find their way into the compost bin or council waste stream that can produce microparticles. Check the label, do not confuse home compostable products with those compostable at an industrial site.  Compostable products such as those containing PLA (poly-lactic acid) do not contain petroleum-based plastics and will decompose to form healthy compost.

*“Microplastic transport in soil by earthworms” by Matthias C. Rillig, Lisa Ziersch & Stefan Hempel Scientific Reports volume 7, Article number 1362(2017)  

 ** Earthworms on a microplastics diet Julia Fahrenkamp-Uppenbrink     Environ. Sci. Technol.10.1021/acs.est.5b05478 (2016).http://science.sciencemag.org/content/351/6277/1039.1/tab-article-info

Plus

The Environmental Hazards Inherent in the Composting of Plastic-Coated Paper Products WILL BRINTON1 , CYNDRA DIETZ2 , ALYCIA BOUYOUNAN2 , DAN MATSCH2  http://www.ecocycle.org/files/pdfs/microplastics_in_compost_white_paper.pdf