In-vessel solutions: the people's choice

In-vessel composting is a cost-effective, proven technology that is gaining
prominence in the UK. Alexander Maddan explains why

Today's hi-tech UK composting industry is playing an increasing part in helping local authorities achieve their targets for recycling and diverting waste from landfill. For many years the composting industry was a relatively low-tech, small-scale niche market. But times are changing.

Technological developments, customer demand, legislative pressures and changes in public attitude are all combining to strengthen and transform the industry. New and innovative technologies are emerging from this re-energised industry.

In-vessel composting (IVC) - the system of producing compost from organic waste contained within specially designed tunnels - is one of the key technologies that has been adopted by LAs. Although a new technology in the UK, IVC systems have proved their worth in providing large-scale diversion from landfill in continental Europe for over a decade.

In the UK each year we currently process some 2 million tonnes of compost. This figure needs to increase rapidly if we are to meet the target of 12 million tonnes in ten years, set under the landfill allowance trading scheme (LATS).

The Composting Association, for example, estimates that we would need some 600 facilities to meet these targets. Yet less than 2% of this number have so far been built that are both compliant with the Animal By-Products Regulations (ABPR) and are of commercial size.

Greater need for diversion
Obliged to meet these rising LATS targets and anxious to avoid fines, LAs are looking to the compost industry for more efficient and cost-effective solutions. New technologies, such as IVC, are helping to increase the speed and consistency of the composting process, while allowing a larger proportion of the waste stream to be composted.

IVC is now featuring in many LA waste strategies. Those bold enough to build IVC plants a few years ago are now reaping the benefits - with most IVC plants with ABPR certification currently running at full capacity. The majority are considering expansion.

What is driving this increase in interest in IVC? One reason is that IVC represents proven technology - an important factor in most LA waste plans - having been tried-and-tested across both Europe and America. Speed and ease of construction and implementation are other significant factors.

Although IVC plants need to be highly engineered, they can be built quickly and are often up and running within six months from the start of construction.

In a sector where planning permission can be a challenge, 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, therefore, are often achieved within shorter timescales.

Though the capital investment required for IVC plants should not be underestimated, IVC can represent good value for money for LAs. Their capital costs certainly compare well with rival technologies that are often commercially viable only on a larger scale. IVC operational costs are also generally lower than most other technologies.

Popular with the public
LAs are being encouraged to consult more widely with their local population. And research shows that the public favours recycling and composting over other solutions, which are viewed as wasteful of 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. Many would say that composting solutions are the 'people's choice'.

All organic matter breaks down through the action of micro-organisms, but 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 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 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 (PAS 100).

Alarmist comment that there is no market for the product is simply unfounded. Good quality product is in high demand by the agricultural sector, which can provide sustainable markets for the foreseeable future.

Despite its advantages, in-vessel composting is a solution only for the biodegradable element of the waste stream. It is likely that most LA waste strategies will adopt a mix of technologies for a sustainable and cost-effective solution to waste management.
But 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's no wonder that IVC is featuring more prominently in an increasing number of LA waste plans.

Alexander Maddan is managing director of Agrivert

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