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Severn Waste Services has been composting green garden waste for some 10 years. The resultant product is a composted soil conditioner marketed under the brand name 'Greengrow®'.
Composting is seen as a key component in the government's drive towards more sustainable waste management, and in the Joint Municipal Waste Strategy for Worcestershire and Herefordshire. In addition to the waste management benefit, there is the 'win-win' effect of having a valuable product at the end of the process, as a reward for our efforts. Using composted materials in the garden improves soil fertility without the use of chemical or peat-based products, and really 'closes the loop' in recycling our waste into new plants. Of course, we encourage people to compost their own kitchen and garden waste at home and there is plenty of help and information around to tell people how to do it. For useful links, see end of the page. However, for people with larger gardens or only limited capacity for home composting, we provide a service to deal with big volumes green waste.
At our Hill
and Moor composting site near Pershore* we receive thousands
of tonnes of green garden waste per year. Most of this comes
from the public delivering material to our household waste sites. At Hill and Moor we shred the waste and place it into long piles called 'windrows.' Then we just let nature do its stuff. We monitor the temperature and moisture content in the windrows, and we irrigate them and turn them over regularly to provide good oxygen supply and to maintain the correct conditions for uniform decomposition. (For more information on the science of composting go to The Composting Association) After about 14 weeks the composted material is screened using a rotating drum sieve. Most of our product is supplied at less than 10mm size although we can provide coarser material at less than 25mm. Screening removes any 'woody' material that can be re-introduced into the windrows. It also removes any bits of plastic or other contrary material that has escaped the eagle eye of our operatives. *We are looking to set up new composting facilities for green waste in north Worcestershire and in Herefordshire. Properties of Greengrow We call our composted product a soil conditioner rather than a compost, so as not to confuse it with branded growing media - mainly peat-based - that you see in garden centres. Greengrow improves soil fertility; releases plant nutrients slowly and encourages vigorous plant root systems. It is a good source of essential trace elements and supports the activity of soil micro-organisms that convert soil nutrients into forms available to plants. Applications of composted green waste soil conditioner improve soil structure and its ability to hold water. Laboratory studies have shown that it can give effective control of economically important crop diseases, such as club root on brassicas, white rot on onions, stem canker and black scurf on potatoes. Typical properties of a composted green waste soil conditioner are shown below. For sources of further information see the links below.
Other
parameters Electrical conductivity - Around 770 µS/cm (Measures concentration of soluble salts) Bulk Density - About 0.6 kg/litre or 1.6m³ per tonne Loss on Ignition - About 20% (Measures organic matter content) Carbon: Nitrogen (C:N) ratio - About 12 A good quality composted green waste soil conditioner may contain the odd piece of glass, plastic or other contaminants. These are likely to amount to less than 0.2% by weight in total. The composting process should eliminate all weed seeds (measured as Viable Seeds or vs per litre). A count of 1 or 2 vs per litre is considered acceptable. The availability of nitrogen in the product is relatively low compared to say animal manure, but this is important in areas of the country where groundwater is susceptible to infiltration of excessive nitrate (Nitrate Vulnerable Zones as expressed by the Environment Agency). Our product is analysed on a regular basis, and we have forged strong links with technical experts, the Henry Doubleday Research Association (HDRA) and ADAS Consulting, who provide us with scientific and technical support. Applications and availability
We have supplied Greengrow for a host of users and applications, like:
Keen organic gardeners may have visited the Ryton Organic Gardens near Coventry and seen the 'Vegetable Kingdom' exhibition and garden opened by HRH the Prince of Wales in 2003. We were proud to supply 100 tonnes of Greengrow for the new vegetable demonstration plots. Greengrow is certified by the Soil Association as suitable for use in organic growing systems.
For all users of Greengrow composted green waste soil conditioner, please note the following HYGIENE ADVICE: 1. Wear
gloves when handling compost or soil. There is a lot of ongoing development work and field trials demonstrating the advantages of using composted green waste soil conditioners. See links below. Severn Waste Services and its forebears has funded a number of research projects in the field of green waste composting, through the Landfill Tax Credit Scheme. This research has looked at:
Key contacts for further information are: The Composting
Association - www.compost.org.uk |
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local
authorities and engineering companies. The
following sections explain:
It
is estimated that some 60% of all waste generated by households
in the UK can be composted. Composting organic materials like
green garden waste, vegetable peelings and scraps makes a substantial
contribution towards diverting waste from landfill, and avoiding
the potential for environmental pollution. 
Composting
is a natural biological process in which micro-organisms present
in organic waste break it down into a stable organic material
that can be easily stored, handled and spread on land. Any harmful
micro-organisms or weed seeds that may be present are killed
by heat generated during the composting process (nominally around
60°C) 
