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Overview

When garden waste is recycled it is transformed into nutrient-rich soil conditioner. This can then be used in a range of different applications, such as for agriculture, land reclamation and as an ingredient in some multipurpose composts you can buy at a garden centre.

Most types of garden waste can be recycled, including bark, flowers, grass and hedge cuttings, leaves, plants, small branches, twigs and weeds. If you are unable to compost at home, you can take it to your local garden waste recycling point or put it into your garden waste collection scheme, if you have one, where it will then be taken to a central composting facility to be processed. Check with your council to see if you can recycle garden waste locally.

Did you know

• Garden waste makes up 14% of the average household bin (WRAP, 2002).
• Around 94% of local councils collect garden waste.
• Adding compost to soil increases the nutrients and improves the soil’s structure to help plants grow.

How is it recycled?

Garden waste collected at the kerbside is taken to a composting site where it is turned into a nutritious soil conditioner.

When the garden waste arrives at the composting site any material that is not compostable is removed, the remaining waste is then shredded and then laid out in a long pile to decompose, usually in the open air.

The process at a composting site is similar to that that takes place in home compost bin, but is actively managed to speed up the process. However, due to the amount of material the temperature reached is a lot higher than in a normal household compost bin. Temperature can reach up to 60°C. This higher temperature means that the enzymes and bacteria are quickly put to work resulting in finished compost in just a few weeks.

The material is turned frequently to provide much needed oxygen to micro organisms that help decompose the material. High temperatures kill off any harmful microbes, weeds and plant diseases.

The final part of the process involves screening the compost to remove any remaining contaminants and to grade the material for various end uses. Any compost that is still oversized or hasn’t decomposed enough, can then be put back through the process until it has composted down sufficiently.

The whole process takes between 8 and 16 weeks, depending on the final use for the compost.

Problems and issues

In 2008/9, a total of 5.1 million tonnes of material was composted or digested  in the UK, of which approximately 90% was garden waste. Nearly ¾ of this material was composted at sites that operate to the national composting specification (PAS100), which controls the quality of the process and compost produced.

Although composting sites have measures to remove contamination, it is important that garden waste collected for composting is as clean as possible and that plastics and large stones are kept to a minimum, in order to ensure that a quality product can be made. It is also important that grass cuttings where herbicides have been used aren’t put in the recycling bin.

Open air windrow composting is generally used for garden waste materials only, and cannot accept catering or animal wastes (such as food from household kitchens). Garden wastes containing these other types of material have to be processed using methods such as in-vessel composting (IVC) or anaerobic digestion (AD) in order to comply with the Animal By-Products Regulations. Other methods are also available.