Microplastics in our garden soil

Did you know that microplastics are a threat to more than just our oceans and beaches? There are worrying levels of microplastics in the air as well as in freshwater ecosystems. Studies are also shedding light on the concerning levels of microplastic in the world’s soils. And these concentrations will just keep rising. What does this mean? Should we be concerned about microplastics in our soil? And, what can we do to minimize microplastics in our garden soils?

What are microplastics?

To understand more about microplastics in our gardens, let’s first think about what microplastics are. Microplastics are small, barely visible pieces of plastic. They are not one specific type of plastic. Instead they are defined as any type of plastic fragment that is less than 5mm in length.

Microplastics are categorized into primary and secondary microplastics. Primary microplastics are plastic fragments that are less than 5mm in dimension when they enter the environment. Things such as microfibers from clothing, and microbeads from body washes and facial scrubs. Secondary microplastics, on the other hand, are created when larger plastic products are broken down in the environment. Sources of secondary plastics include water bottles, fishing nets, and plastic bags that degrade over time.

The problem of microplastics in soil

Research into microplastics in our soil is very limited and the impact of microplastics in our soils is not fully understood. However, the scale of the problem is beginning to emerge. Microplastics have been found in the digestive systems of earthworms and other soil biota. And eating plastics appears to be bad for earthworms. Some worms experience stunted growth, and others die. These worms and biota are crucial to the health of our soil (Earthworms: Why your garden needs them). As gardeners and composters, we spend a lot of time producing ideal environments for these soil biota to thrive, so keeping microplastics out of our soils is another way we can keep our soils healthy and productive. Plus, anything that eats these worms (birds, frogs, skunks etc) will also ingest microplastics and, in turn, risk experiencing these same negative effects.

Research has yet to show any effects of microplastics on soil microbes or plants. However, there are concerns that if microplastics continue to break down into smaller and smaller fragments they could become nanoplastics. Plants can absorb nanoparticles and they can reach as far as a plants leaves. This obviously raises concerns of plastic being able to enter our food chain through agriculture.

Lots more research is needed to confirm (or, hopefully disprove) this concern. However, there is no denying that plastics are foreign to our natural environment. The less plastic in our garden soils, the better.

How to manage the problem of microplastics in our soils

Removing plastic pollution from our oceans is posing a significant challenge. Removing plastic from our soils is even harder. Why? Because of worms. Worms are nature’s tillers. They are very good at mixing and churning up soils. This is crucial for mixing in organic matter and aerating our soils. But, not so good for microplastics. By mixing plastics through our soils they then become virtually impossible to separate. The problem of microplastics in our soils is only going to get bigger and is going to be very hard to control. Therefore, the best (and possibly only) way to control microplastics in your garden soil, is to stop the addition of new microplastics to your soils, sooner rather than later.

Top 3 ways to reduce microplastics in your garden

1. Compost at home

Adding food waste to bokashi composter

Making your own compost at home is the biggest way that gardeners can control and prevent microplastics from entering their gardens. Compost is a potentially significant source of microplastics.

Many studies are showing high concentrations of microplastics in compost; particularly compost produced from curbside collection programs. Plastic contamination of organic matter from household collections is fairly problematic, think plastic bags, food wrappers, plastic fruit and vegetable labels etc. Although the compost is screened and filtered, smaller microplastics cannot be removed from the finished compost. Anyone who has bought compost made from organic collection programs will likely have found large visible pieces of plastic in their compost along with lots of smaller pieces of plastic bags and other contamination. If these visible pieces of plastic are making it to the final sol compost product, it is worrying to think how many invisible microplastics are also mixed into the compost. Microplastics are also being discovered in bagged and pellet composts.

So, how do you avoid adding microplastics along with your compost? Create all the compost you need at home. That way you can take the time to ensure no plastic enters your compost.

Common plastic contamination in food waste:

  • Plastic fruit and vegetable stickers: Remove all stickers before adding the vegetable and fruit skins to your compost. Ideally, choose fruits and vegetables without stickers. And, better still, grow unlabeled fruits and vegetables at home!
  • Teabags: Most teabags contain some plastic within the net bag. Even those made of silk and cotton often have plastic netting in them to add strength. If you are adding teabags to your compost make sure to use certified compostable teabags. Alternatively, rip the teabags and empty only the tea leaves into your compost, or use loose leaved tea and skip the bags completely.
  • Butchers paper: Paper used to wrap fish and meat may be waxed paper, though it often has a thin plastic film on one side. You can tell the difference if you tear it carefully and watch for the layer of plastic. Likewise, scratch it with your fingernail; the wax layer will sometimes scrape off. If in doubt, best to leave it out of your compost.
  • Paper coffee cups: The same is true with paper coffee cups. These may be waxed or lined with paper. Sometimes coffee cups will be marked compostable. This often means that they are lined with a thin layer of compostable plastic. But beware, as this plastic will often only compost in industrial composting facilities. Again, best to keep these out of the compost.
  • Drier lint: Some people choose to collect and compost lint from their driers. Whilst this may seem preferable to putting it into the garbage, don’t forget that many clothes contain plastic. The lint in tumble driers will therefore contain plastic microfibers and should not be added to your compost unless all of your clothes are purely natural materials.
  • Household dust: Similarly, sweepings from the floor and the contents of your vacuum cleaner will contain plastic microfibers from clothing, carpets and soft furnishings, as well as other airborne microplastics. Avoid adding household dust and sweepings to your compost.

Plastic garbage: microplastics

2. Remove litter and garbage

Litter and garbage can  blow into your garden, particularly at fence and hedge lines. Simply remove any windblown garbage to prevent the plastic becoming incorporated with your soil. Take particular care to remove garbage from raked leaves.

3. Avoid using plastic garden products

Another key way to prevent microplastics getting into your garden soil is to avoid using plastics in your garden. Common sources of plastic in the garden are:

  • Plastic plant labels: There are lots of alternatives to plastic plant labels; wooden labels, rocks and metal labels are all readily available and can look great in any garden.
  • Sod: Most turf sod contains fine netting. Avoid this by sowing lawn from seed or searching for a local supplier of no-net sod.
  • Netting and garden twine: Most netting and garden twine are plastic, or contain plastic. Again, try to find alternatives, such as wooden trellising and natural twine made from 100% jute fiber.
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