The natural solution

With the waste industry facing stricter landfill regulations, increasing numbers of local authorities are turning to in-vessel composting. Alexander Maddan reports

The composting industry can play a crucial role in meeting the UK's biodegradable municipal-waste challenges.

The government threw down the gauntlet when it introduced the Landfill Directive to increase levels of recycling and recovery, along with its regulatory tool, the Landfill Allowance Trading Scheme (Lats) to reduce the amount of biodegradable waste going to landfill. This makes sense when you consider that 25% of the UK's methane emissions were released from landfill sites in 2001. This gas is 20 times more potent than CO2, and represents 2% of the UK's greenhouse gas emissions.

And added to the recent landfill regulatory changes are the Animal By-products Regulations (ABPR).

It is now the industry's responsibility to come up with practical, sustainable and economic solutions for diverting waste towards more integrated, high-tech schemes. And the industry is responding.

The composting market is seeing unprecedented changes and growth in the UK. We are now producing around 2M tonnes of compost each year. The danger is that the market is immature. There are only a few companies that have any experience in operating composting technology - and, even more importantly, technology with a proven track record.

The growth of the industry is largely being driven by local authorities, which are increasingly looking to invest in biodegradable waste treatment plants in order to hit their Lats targets. This is leading to new technology, as the pressure to achieve compliance encourages composting companies to widen their expertise. Some technologies have proved to be effective, but others are yet to do so. And only time will tell.

So how can composting help to improve waste flow? There is huge potential for growth and technological development in the future. But the industry needs to think carefully about how to maximise this potential and how to overcome problems.

Planning permission is one of the major stumbling blocks, although composting plants are often viewed with more favour at the planning stage than Energy from Waste (EFW) or Mechanical Biological Treatment (MBT) plants. Planning permissions for composting plants, therefore, can sometimes be achieved within shorter timescales.

Plants need to be built close to the communities they serve in order to keep travelling times to and from the plants and collection points to a minimum. Realistically, we need a huge number of plants if we are to significantly reduce current volumes of municipal waste going into landfill. There are about a dozen in-vessel composting (IVC) plants of commercial size in the UK today. And, according to the Composting Association, we need around 600 sites to meet the Lats target of 12M tonnes of compost in ten years' time.

So it's crucial that we have high-tech, proven facilities which are ABPR compliant and capable of effective odour management to allow harmony with the local population.

Having established that it is uneconomic to have isolated plants operating alone, what we need is an integrated network of composting facilities around the country. In this respect, the industry is reliant to a large extent on co-operation between local authorities to work together more closely.

This is where IVC can play a key role in helping local authorities to achieve waste minimisation and reuse targets to divert waste away from landfill. Some have already taken advantage of this system of producing compost from organic waste contained within specially designed tunnels.

This emerging technology is relatively new to the UK but it is tried and tested in Europe. A proven technology is almost always an important factor in local-authority waste plans.

LondonWaste selected a technology supplied by Agrivert which has been deployed in some 30 plants across Europe for the past 12 years. It processes 750,000 tonnes of organic waste each year, which proves its ability to provide large-scale waste diversion.

IVC can help to increase the safety, speed and consistency of the composting process, at the same time producing high-quality end products.

Essentially the system accelerates what nature would have done anyway, with the added assurance of producing a consistently high-grade end product. This provides stability, environmental considerations, such as odour control, and a wide application of use in areas such as agriculture, horticulture, turf, land restoration, amenity use and retail.

The speed and ease of construction and implementation is also a significant factor in choosing the IVC route. Although plants need to be highly engineered to meet ABPR requirements and to withstand the harsh environment created during composting, they can be built quickly. And they are often up and running within six months from the start of construction.

For instance, Agrivert's Edmonton plant, part of LondonWaste's EcoPark, was completed in just five months. It serves seven North London boroughs, and has a capacity to divert 30,000 tonnes of waste a year from landfill. This is due in part to the modular design of the plant, an arrangement that, incidentally, lends itself to expansion, if required.

The North London composting centre is operated on behalf of LondonWaste by Agrivert, which receives an operating fee per tonne of waste handled, with a minimum guaranteed tonnage. LondonWaste recoups its costs through gate fees.

The primary feedstock for the plant is green waste and kitchen waste. The ratio of green to kitchen waste is currently around 70:30. But the latter is rising steadily as the local population begins to appreciate the benefits.

Up to 140 tonnes of waste is processed at Edmonton each day, with each of the boroughs it serves running its own collection system. Some collect single waste streams and some organic and dry recyclable simultaneously, in dual-collection vehicles. Officially opened in March 2006, LondonWaste hit operational capacity in its second week, and has been working at this level since.

Although the capital investment required for an IVC plant should not be underestimated, it can represent good value for money for local authorities. The capital cost compares well with rival technologies that are often commercially viable only on a large scale. Operational costs are also generally lower than most other technologies.

It is a time when local authorities are being encouraged to consult their population more widely. And research is showing that the public favours recycling and composting over other solutions which can be viewed as wasting precious resources. Dest separation of waste allows high recycling rates of dry recyclables, while the organic fraction is composted to produce a high-grade product.

All organic matter breaks down through the action of micro-organisms. IVC plants accelerate the process, ensuring that decomposition occurs in a controlled and managed environment.

Waste is first blended and shredded to produce optimum conditions for composting. It is then composted in specially designed tunnels, or vessels, where the temperature and oxygen availability are carefully controlled, before being placed on a maturation pad.

The compost is screened to produce a pure, high-grade compost with excellent nutrient value and high soil-conditioning qualities. As with all waste-management processes, the quality of the IVC end product partly depends on the quality of the input streams.

With low levels of contamination in the waste streams, there is no reason why ABPR-compliant IVC plants should not produce a high-quality product, fully compliant with the British Standards Institution's Publicly Available Specification for Composted Materials.

Although there has been some alarmist comment that there is no market for the end product, this is simply not true. Good quality compost is in high demand by the agricultural sector, which can provide sustainable markets for the future.

Despite its many advantages, however, IVC is a solution only for the biodegradable element of the waste stream. It is likely that most local authority waste strategies will adopt a mix of technologies to provide a comprehensive, sustainable and cost-effective solution.

With the Lats clock already ticking, IVC offers a proven technology that can be delivered quickly, with relatively

low capital requirements and comparatively low planning risk. It is therefore no surprise that IVC is featuring more prominently in an increasing number of local authority waste plans.

Alexander Maddan is managing director of Agrivert. Visit www.agrivert.co.uk

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