At this time of year, everybody is thinking about tidying up the garden ready for the winter. Summer flowering bedding plants need to be removed, it is time to deadhead roses, prune climbers and ramblers, cut back hardy herbaceous plants and trim hedges; and a supply of good rich compost is needed to lay the foundations for next year’s vegetables.

So, what can you do with all this unwanted garden material?

The simple answer is to compost it. All you have to do is separate kitchen waste such as vegetable and fruit peelings, add to your garden waste, and find space for a compost heap, container or bin.

Traditionally, owners of large gardens and allotments have dealt with their biodegradable waste in this way; vegetable peelings, egg shells, and other kitchen waste is composted with grass cuttings, bedding plants and waste from the vegetable garden. Woody garden cuttings can be shredded and added to the compost heap. Explains Wickham GP, Dr Stephen Smallwood, "Everything goes into my compost bins, kitchen waste, grass cuttings, weeds and woody material - this is a practical solution, and also the best environmental option. I don’t use chemicals and the compost is ready for use on flower beds and vegetables after about six months." Dr Smallwood, who is also a keen angler adds, "A ripe compost heap also provides a good source of worms for bait."

Composting is a biological process in which bacteria and other microorganisms break down organic material, using oxygen from the air. This process produces carbon dioxide, water vapour, and a much less bulky residue, compost. Most importantly, the material must be kept well aerated as it rots. The microbes also need a source of nitrogen and phosphates, which come from fresh green vegetable material, or can be added in the form of an activator such as manure or fishmeal (or even urine!) if necessary. The temperature in the heap increases and needs to reach 60° C to kill seeds and spores unwanted by gardeners.

Kitchen waste, grass cuttings and other soft garden waste can be treated in a plastic home composter (preferably made from recycled plastic). Contact your local district council or unitary authority recycling officer, to see if composters are being offered at a bargain price in your area; about 70,000 composters have been given away or sold at subsidised rates in Hampshire. Biodegradable waste is introduced as it is produced and, as it rots, the carbon dioxide released disperses into the air and is absorbed by the surrounding plants. Some people prefer to use a wormery which works on the same principles, but as well as the bacteria which rot the waste, worms are introduced and the organic matter is broken down more quickly. The worms help aerate the composting material as well as aiding the decay.

People with small gardens, who live in flats, or who have large amounts of bulky garden waste may wish to make use of Hampshire’s central composting facilities. Some district councils collect garden waste from residents by supplying either a specific bin or bags for residents to fill, and then collecting them, sometimes for a small charge. Garden waste that can not be collected or home composted may be taken to a Household Waste Recycling Centre. There are 26 of these throughout Hampshire, run by contractors on behalf of Hampshire County Council and Southampton and Portsmouth unitary authorities; dedicated recycling bins for many different types of recyclable material, including garden waste, are provided. This is then transported to various sites throughout the county where it is shredded and composted on a large scale, to produce Pro-Grow.

A new site at Down End has recently been approved for this purpose, and another, in Chilbolton is proposed; these will join the site at Little Bushy Warren, near Basingstoke, where green garden waste is currently composted. The compost is turned using hydraulic excavators which both aerate and mix to expose all parts of the mound to the elevated temperatures needed to kill seeds and spores. The final product is approved by the Soil Association, for organic use. Chemical activators are not used, but a final 10mm-screening of the compost leaves a residue containing all the decomposing microbes, and this is added to the next batch of fresh green waste to act as an activator and speed up the process.

Peter Mills, Composting Manager at Hampshire Waste Services, which produces Pro-Grow, comments, "The product is called Pro-Grow, but a lot of people call it ‘Miracle Grow’. To make a recycled product successful, you have to produce something of inherent quality, or people won’t buy it. The whole process is geared to getting a saleable end product - this is the primary motive, because we are competing with producers of peat and other composts. We produce a product which is organic, humus rich and has good nutrient levels, by a reliable process; the fact that it uses recycled materials and is sustainable is a bonus."

The introduction of an Anaerobic Digestion plant is another possible way of dealing with putrescible waste, and is a method under discussion as part of Hampshire’s integrated waste strategy, Project Integra. It would provide a means of disposal for biodegradable waste in towns and cities; issues of cost, collection and separation are being investigated.

The answer to this is … air! If you bury large amounts of the material in a landfill site and cover it with layers of mixed waste it will rot, but without air, anaerobic bacteria decompose it. Instead of the local small quantities of carbon dioxide and water vapour produced in home composters, large quantities of methane and carbon dioxide are produced from organic waste buried in a landfill site. If these gases are released into the atmosphere, they potentially increase global warming and contribute to the greenhouse effect. Release of landfill gas can be controlled but prevention is better than cure. All material going to a landfill site is weighed and landfill tax has to be paid from your council tax, another reason to avoid sending your waste - garden or other - to landfill, if you possibly can.

And after all this, nobody can get at the buried compost to use it to fertilize next year’s vegetables … what a waste of a valuable resource!

More information about Hampshire’s integrated waste strategy, can be found on the Project Integra website www.integra.org.uk.

1 October 1999