BAN Waste Select Committee evidence

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Phase 1 Day 7 2001-10-22 Mr Stephen Wise (Composting Manager, SITA)

written evidence submitted in advance


Composting is the oldest and most natural form of recycling organic material. Natural biological processes breakdown organic material in aerobic conditions into stable compost. Compost as a product has many uses including land restoration, enhancing soils and acting as a direct growing media for plants.

Composting is the biological decomposition and stabilisation of organic substrate under conditions that are predominantly aerobic and that allow the development of thermophilic temperatures as a result of biologically produced heat. For the biological process to work effectively, sufficient quantities of carbon, nitrogen and oxygen are required. The microbes utilise the carbon and nitrogen as sources of food. By-products of this process are carbon dioxide, water and heat. The heat generated by the microbes kills off unwanted pathogens, weed seeds and bacteria. When the microbes have used the available carbon and nitrogen they start to decline in numbers and the heat being produced is reduced indicating the end of the active composting process. To produce high quality compost curing is required. Curing allows the compost to stabilise, which helps to prevent nitrate leaching and reduces the electrical conductivity, high levels of which can damage soil structure. The longer the period for curing the more soil like the compost will become.

Composting in the UK is still a relatively new industry and has lagged behind the industry in continental Europe. The higher price of landfill, less void space and more socially responsible attitude to recycling has enabled the European composting industry to develop more rapidly. The industry has developed from the traditional open windrow systems composting green waste to sophisticated in vessel systems that are able to process a wide range of materials using advanced real time monitoring to control environmental conditions and monitor a wide range of parameters. The industry has developed more slowly here in the UK due to lower landfill prices and less need to develop recycling options.

The Composting Association has calculated that over one million tonnes of compost are produced annually in the UK. The size of facility ranges from small on farm composting units to large centralised facilities that process over 30,000 tonne of material each year. The technology used encompasses the entire spectrum ranging from basic open windrow facilities on soil through to the sophisticated in vessel systems that are able to compost the most putresible of materials. However, at present the predominant methodology used in the UK is open windrow systems composting green waste derived from either civic amenity sites or collected from households.

Increasingly stringent legislation including the landfill directive and the statutory recycling targets are now leading to more rapid growth in the industry in terms of tonnage being composted, the width of materials being processed and the technology used. Composting is not a cheap option, as the materials being composted need intensive treatment and management. The increasing costs for landfilling of materials is making the use of composting using more advanced technology and processing wider waste streams more economically and environmentally viable.

Until recently compost produced from 'waste materials' has not been subjected to a marketing approach. Developing a marketing approach is even more important than the processing of the material. Without marketing there is no final customer for the compost and therefore no need to process it in the first place! This area has been greatly neglected and has led to the general view that compost is of poor quality and not effective within the marketplace. Recent efforts by the Composting Association to stimulate marketing and the forward thinking of one or two compost producers who have adopted a marketing led approach have started to see compost enter the large commercial markets of bagged retailers and landscaping professionals. Without adopting an effective marketing approach this is not possible.

Allied to this approach is ensuring that consistent high quality of the compost product is maintained. The standards being introduced by the Composting Association, Soil Association and HDRA are helping to achieve this and keep out those organisations that have no interest in producing quality compost.

SITA believes that composting is going to play an increasingly important role within the waste management and recycling industry. We are therefore continually developing our knowledge and operational experience of all types of composting systems. This knowledge has been developed from our experience of using a whole range of composting technologies to compost all types of 'waste streams' in facilities located around the world. Within the UK SITA has experience of composting using both in vessel and open windrow systems. Within the UK composting industry SITA has been one of the pioneering organisations adopting a marketing approach, introducing quality standards, developing integrated composting management tools and developing successful sustainable markets for high quality compost

We believe that composting is not just a method for processing waste but an integral part of ensuring that a sustainable future can be achieved.