During the last 3 years the use of compost derived from organic waste by gardeners has increased considerably in the UK. The main reason is that the extraction of natural peat deposits, previously used as garden and potting compost, has been banned by the end of 2023 to save the peatland ecology and protect the wildlife of dwindling natural peat bogs.
Composted organic waste has thus become an increasingly significant source of commercial compost products bagged and sold in garden centres and supermarkets and a great alternative source of plant growing media for a nation of gardeners.
Biodegradable waste is big business. Some 60% of all waste generated by households in the UK can be composted. * This can and should be treated to produce a product grade compost that serves both amateur gardener and agricultural business – as well as reducing the amount of waste to landfill where is would create hugely environmentally harmful methane gas.
But how green is organic waste?
The use of this recycled compost, created from residential organic waste helps improve soil fertility but if not managed properly in the treatment process can also be a source of microplastics that are present after the composting process.
Microplastics are tiny plastic particles that result from the breakdown of larger plastics and as a pollutant can be harmful to the environment and animal health. Generally, microplastics are plastic debris less than five millimetres in length, or about the size of a sesame seed.
The problem, however, starts at the very beginning of the waste journey where the plastic waste goes in the wrong bin.
To reduce microplastics the whole supply chain needs to contribute to ensuring that the compost produced, which is then spread onto the land, is clean and free of plastics.
This clearly starts with the householder doing their bit and continues with the local authority tightly regulating the collections. The waste operator then must play an important role in removing the unwanted plastics and other materials still present in the waste, prior to and during the composting process.
It is both time consuming and costly to remove the contamination from the waste once it gets this far down its journey. Contamination often enters the treatment site in the form of plastic bags, plant pots, plastic ties, labels, bulb nets, and other such items thrown in with kitchen waste, hedge, and grass cuttings. They are not always easy to spot and the composting process often causes disintegration of larger plastic items into smaller microplastics.
At Wastewise we use a range of methods that involve trommels and screens as well as hand-picking to reduce plastic contamination. Despite these interventions, it is not possible to capture and remove every scrap of plastic.
The ideal solution is a comprehensive approach that must start with Educating the householder and reminding them to be vigilant with organic waste content. Next this approach involves improved waste collection practices and increased efforts to reduce plastic waste at its source. As waste processors the final piece of the puzzle is continued improvements in plastic removal and clean up technology on site and continued vigilance. We hope that on-going and improved collaboration will help reduce the microplastic content further.