Figures 5 and 6 below show the mixture of renewable and non-renewable primary energy quoted by each manufacturer (including renewable energy from burning waste wood on-site). The ICE database does not provide an energy breakdown with its carbon factors. However, the Wood for Good (2013) EPDs, which formed part of the ICE database study and represented a 2013 UK industry average, has been used to give an indicative energy mix for the study period. Several observations can be made:
- Less energy is typically used by each manufacturer to produce 1m3 of mass timber compared to the Wood for Good analysis
- Less non-renewable energy is typically used by each manufacturer to produce 1m3 of mass timber compared to the Wood for Good analysis
- The A1-A3 embodied carbon factors correlate to the non-renewable energy component quoted by each manufacturer
Based on industry engagement, primary contributing factors also include varying transport distances during production, the energy mix of the country of manufacture and the utilisation of the factories studied.
It is also useful to compare the new embodied carbon factors derived to the value for conventional sawn and dried softwood timber.
The softwood value given in the ICE database and the IStructE guide is 0.263 kgCO2e/kg – very similar to the new values for CLT and glulam proposed. A review of current EPD data from Europe’s largest sawn and dried softwood timber producers suggests that this value may also warrant reduction, and further work by the industry in this space is suggested.