Ever since 1997, when the government signed the Kyoto Protocol and committed the UK to drastic reductions in its greenhouse gas emissions, the pressure has been mounting to find less environmentally-damaging ways of procuring public sector building projects. And because this is a national commitment, the public sector has to be seen to lead the way.

In their pursuit of sustainable procurement strategies, public sector clients are turning to one of the oldest and most familiar building materials: wood. A renewable resource when grown in sustainably-managed forests, wood has excellent insulating properties which helps achieve warm, low-energy buildings, thus conserving fossil fuels.

This is one of the reasons why timber-frame construction is the fastest-growing ‘modern method of construction’ (MMC) in the UK today. Development and use of MMCs are actively encouraged by the government for their speed and efficiency of construction. Most are manufactured off-site and their high levels of thermal insulation mean that buildings erected using MMCs are highly energy-efficient.

Oriented Strand Board (OSB), Medium Density Fibreboard (MDF) and particleboard, are widely used in all sectors of the industry, especially housebuilding. OSB in particular is a primary component of most timber-frame systems, but all of these products are also used extensively within traditional brick-and-block houses.

Steve Roebuck, Norbord’s Environment, Health and Safety Director, is unequivocal about the environmental benefits of using wood: “Wood has one unique characteristic – it is the only sustainable building material. You cut down one tree, plant another and it grows,” he says. “Admittedly, this is only true if the wood in question is grown in a proper, sustainably-managed forest”, he adds.

“Timber must come from independently verified sources if it’s to be truly sustainable. You can be sure that the timber products you use are from a sustainable source if they carry either PEFC [Programme for the Endorsement of Forest Certification] or FSC [Forest Stewardship Council] certification”, says Steve.

“Sustainable forestry has an important role in countering carbon emissions. Trees absorb CO2 as they grow and that CO2 is locked away in the timber when the tree is harvested. It remains locked away in the products we make. Meanwhile, new trees are planted to replace the ones harvested. The process is a continuous cycle,” he adds.

The production of engineered wood-based panels makes efficient use of raw materials. Forest thinnings, the small immature trees harvested to make space for larger specimens to grow properly, provide the wood fibre used to make OSB and MDF. Particleboard also uses thinnings, but very little of its raw material is virgin timber.

“About 80% of the material used to make Caberboard chipboard is recycled, or ‘post-consumer’ wood waste” says Steve. There is a whole industry devoted to the recovery and re-use of post-consumer wood, and most of this goes into the production of board products. “Our industry recycles around one million tonnes of wood every year” explains Steve.

Even wood residues – the small proportion of wood fibre that is for whatever reason unsuitable for inclusion in board manufacture – are not wasted but are used as fuel in the manufacturing process. “We get 80% of our energy requirements from wood residues” says Steve.

Residues are burned to provide heat for the production line as well as heating oil to heat the presses. “Until the mid 1990s, there was very little regulation about emissions from this combustion process,” says Steve. “But these days we are required by law to adopt ‘best available’ techniques to clean that up. The definition of ‘best available’ is a moveable feast and we have to keep up with technological advances,” he adds.

At present, this involves the use of Wet Electro-Static Precipitation (WESP) equipment to remove particulates and chemical pollutants from the combustion fumes. What emerges from the factory chimney is therefore practically pure water vapour. “The pollutants form a strong liquor which is mixed with wood dust, which soaks it up. You then centrifuge this mixture to remove the water and you’re left with a dry crumb. That is then fed back into the combustion cycle,” says Steve.

Like many other energy-intensive industries, the wood board products industry is subject to heavy taxation. This can be mitigated by signing up to one of two carbon emissions trading schemes: the UK Climate Change Agreement Scheme (CCA) and the European Union Emissions Trading Scheme. Although these operate slightly differently, the aim is the same: reduce your carbon emissions or pay high taxes. “The UK scheme is supposedly voluntary, but in practice it’s mandatory. If we did not participate the tax penalty would be enormous,” explains Steve.

“Environmental good practice provides a very strong argument in favour of using timber in construction,” continues Steve. “Timber frame systems are among the most popular and effective Modern Methods of Construction and the material’s inherently low conductivity makes it ideal for warm, highly insulated structures. This is precisely what we should be aiming for: a low-energy production process leading to a low-energy, low-carbon built environment”.