According to the Environment Agency, the space currently approved for landfill in the UK is set to run out in 10 years’ time at best – at worst in five.

Furthermore, the UK government is struggling to meet its obligations under the European Union Landfill Directive, to cut biodegradable waste by 3.5 million tonnes by 2010 and by a further 3.7 million tonnes by 2013. Local authorities in England alone are set to miss these targets by 270,000 tonnes and 1.4 million tonnes respectively – and the European Commission could impose a fine for non-compliance on the UK of up to £180m per year (nearly £500,000 per day).

Climate change

How we as a nation manage our wood waste has a significant role to play in this and there are good scientific reasons why we should minimise the volume of wood waste going to landfill. The Intergovernmental Panel on Climate Change estimates that up to 20% of the carbon in wood will decompose in landfill, of which 50% will be emitted as methane (CH4) – as a greenhouse gas, this is more than 20 times more potent than CO2.

CH4 is produced by anaerobic micro-organisms that are able to exist in an oxygen-free environment. Unlike human respiration, which is aerobic (using oxygen and releasing CO2), anaerobic respiration releases CH4. Municipal waste in particular contains a high proportion of biodegradable material and this is commonly broken down by anaerobic bacteria in a landfill environment. Landfill gas is typically in the order of 60% CH4 and 35-40% CO2.

So what is the scale of the problem? In 2004 the Waste Resources and Action Programme (WRAP) identified estimates for UK wood waste as between 1.9-7.5 million tonnes a year, but revised this a year later to as much as 10.5 million tonnes/year.

The volume recycled is at present only 15-20%, depending on which figures you use.

Wood waste can be broadly categorised under three main headings:

  • 48% construction/demolition (48% of the UK total wood waste);
  • 42% commercial/industrial (of which 40% arises from panelboard and furniture manufacture);
  • 10% municipal (mainly civic amenity and household collection).

For companies and organisations handling or generating wood waste there are also sound economic reasons for minimising the proportion going to landfill. To help in the quest for diversion from landfill, UK government has introduced punitive increases in landfill tax. Ten years ago it cost a mere £7/tonne to dump waste in landfill. Last year this had more than doubled to £18/tonne and is expected almost to double again to £35/tonne in the medium to long term.

Diversity

Part of the problem with wood waste is that it is not a homogeneous entity, ranging from ‘clean’ to ‘highly contaminated’ or even ‘hazardous’. The UK is likely to follow Germany’s lead and introduce a grading system. The Environment Agency, working with WRAP, has proposed a UK protocol, which could be published in March 2007. A grading system will help to align each category of wood waste with specific markets, thus the protocol will encourage a shift of emphasis from waste to resource.

This diversity is one of the main obstacles to recycling wood waste. Wood-based panels such as chipboard, MDF, OSB and plywood do not lend themselves to recycling back into panelboard products, although much of the manufacturing off-cuts are incinerated by the industry’s own boilers rather than being sent to landfill.

The wood waste generated by many sources may be mixed with other materials – including paints, laminates and fixings – or contaminated with stones, dust or plastic. Many wood recyclers are, however, able to clean and thus improve the quality of this waste by the use of technologies such as: magnets to extract ferrous metals, eddy-current separator (rotating drum with magnets of alternating polarity) for non-ferrous metals, wind sifting or suction to remove lighter materials such as paper, cardboard and plastic.

Clean wood, on the other hand, is available in adequate volumes for certain end uses. There is a relatively small but growing market for animal bedding and high quality mulches, which have high value but also high specification – wood must have minimal physical and chemical contamination. By far the largest market for recycled wood is for feedstock, a useful outlet for the panelboard industry, which currently uses a million tonnes per year.

The collection of clean wood, however, is often not economically viable (too small volumes spread over a large area, for example) and for small manufacturers with limited space and resources, storage and segregation on site can be difficult.

For wood treated with CCA and creosote there are additional problems, as this waste is officially classified as hazardous, so the options both for disposal and for reuse are very limited. An additional issue is that, as the large volumes of CCA-treated timber used over the last few decades reach the end of their useful life, this waste stream is expected to grow significantly over the next 50-60 years.

Technological advances

On the positive side, technological approaches to panel recycling are being developed. The Fibresolve process uses a temperature/vacuum/pressure cycle to produce fibre from MDF and chipboard and has been demonstrated at pilot plant scale, while FIRA owns a patent for a Microrelease system, which uses water and microwaves to separate MDF and chipboard fibres. This is under development.

Similarly, work is being done to find technological solutions for remediating hazardous waste, but nothing commercially viable is on the horizon, certainly not in time to make an impact on the 2010 landfill directive targets. There are, however, some advanced thermal technologies such as pyrolysis, where organic materials are degraded by heat in a low oxygen environment, which show promise.

Other solutions which might be more effective in the shorter term for non-hazardous treated wood waste include composting or combustion, especially for electricity generation: an industry spokesperson estimates that by 2009, three power stations will be using 500,000 tonnes of recycled wood and by 2016 biomass intake will be larger than for panelboard production.

One thing is certain. Wood recovery through reuse, recycling or energy recovery will continue to grow – simply because it has to.