The comparison between incineration and recycling is more complex. When looking at energy consumption,
incineration with energy recovery tends to be more favourable than recycling. The picture is more balanced
regarding the contribution to climate change since the environmental impacts of recycling and incineration are of
a similar scale. The final conclusion depends on the type of recycling which determines the avoided material
production and the type of energy recovery (electricity, heat or both). This result is again influenced by
assumptions regarding the sustainable nature of forestry activities (see following section).
Carbon storage
Being a renewable resource, the organic carbon contained in the wood is of biogenic origin. This carbon is stored
all along the product lifecycle. Then during the end-of-life stage the available options differ regarding what
happens to this biogenic carbon. In the case of sustainable forestry practices, the input and output of biogenic
CO2 may be in equilibrium. Per tonne of wood, this equates to a flow of 1.4 tonnes CO2 equivalent.
In the case of incineration or landfill disposal, the biogenic carbon is released. If the wood is burned, this carbon
will be released as CO 2. However, as this carbon is of biogenic origin, these CO 2 emissions are not accounted for
global warming since the quantity of CO 2 emitted corresponds to the quantity absorbed during the growth of
trees. When wood waste is landfilled, the carbon is released as methane and thus there is a significant
contribution to global warming if the landfill gas is not collected.
In the case of recycling and reuse, the biogenic carbon is not released but remains stored in the wood. This
property provides benefits in the event that wood wastes are recycled into products with a long lifetime such as
particleboard or medium density fibreboard which can be incorporated in buildings or furniture. This allows the
carbon storage period to be extended for several decades.
Supply and demand
Recycling and reuse also bring environmental benefits via the associated avoided manufacture of products from
virgin wood. Reducing the use of virgin wood is especially interesting for a country like the UK which imports
most of its wood products. For example in 2008, UK production accounted for around one-third of the UK
sawnwood market and around half of the UK woodbased panel and paper markets (Forestry Commission, 2009).
While sawn softwood, particle particleboard and fibreboard are mainly imported from EU countries, UK imports of
plywood commonly come from countries outside of the EU, such as China, Brazil and Malaysia (Forestry
Commission, 2009). Importing wood from these countries raises the issue of forest sustainability, as wood
exploitation in these areas contributes to deforestation. However, as mentioned in section 4.2 about paper and
cardboard, deforestation is rather driven more by the need for extra land for agricultural purposes than
by the need for wood. Therefore the link between wood recycling and forest use is not straightforward
even though wood recycling and reuse can to some extent contribute to the reduction of wood importation from
unsustainable forests.
In addition, in order to expand recycling and reuse, adequacy is needed between supply and demand for recycled
products. The main constraint is that wood recycling can require certain quality criteria for the wood waste,
depending on the recycling channel. For instance panel manufacturers require clean woodchips uncontaminated
by preservatives, glues or metals (Magin, 2001). Items such as railway sleepers or telegraph poles are therefore
unsuitable for panel manufacture. Such constraints limit the proportion of wood waste arisings suitable for the
given recycling option and make the wood recycling market more complex by creating different submarkets
depending on the wood waste quality. It makes it harder to ensure the adequacy between supply and demand
for each submarket and to guarantee the sustainability of the wood recycling industry.
The potential of energy from waste
The studies have highlighted that the comparison of incineration and recycling is very close. Energy recovery is
particularly promising with regard to the energy and resource depletion aspects, when wood waste is used in
combined heat and power plants.
Another option that has not been assessed in this review but that is currently developing in the UK as mentioned
earlier is the use of wood waste in dedicated biomass energy plants. Compared to incineration, this option
presents the advantage of a better efficiency but also requires certain quality criteria and is not suitable for all
wood types (contamination issues). For instance, some restrictions apply to preservative-treated wood that may
produce toxic emissions when burnt (Magin, 2001).