Sustainable timber can be
carbon positive over the life-cycle of its production and distribution to market – even when transported long distances by sea – a New Zealand forest industry emissions study claims. The study also concludes that sustainably-produced wood compares well in
carbon footprint comparisons with other construction materials such as steel, concrete and aluminium.
The study, by Daniel MacCallum for timber producer Nelson Forests, used a life-cycle analysis (LCA) of
greenhouse gas emissions across the supply chain at the company’s Kaituna sawmill. It considered the carbon and non-carbon greenhouse emissions of log and lumber production at each step from forest to market, using relevant ISO standards.
The analysis shows that even in the case of distribution to export markets thousands of miles away over sea, the supply chain remains carbon positive. Crucial to the positive net emissions outcome, however, is the counting of carbon stored in the wood products and assumptions on the life of those products. It also counts the woody biomass fuel to power drying kilns in lumber processing as a renewable, carbon-neutral fuel source.
“When stored carbon is included … all lumber products are net stores of carbon, storing between 6 to 243 kg CO2e/cubic metre, even after all down stream emissions associated with the production and extraction of raw materials, processing and distribution have been accounted for,” the study concludes.
The biggest contributor to emissions across Nelson Forests’ log supply chain is ocean freight of export logs - 41 per cent of the total on average. Harvesting emissions accounted for 28 per cent, followed by road transport, 20 per cent, transport from harvest to mill, 8 per cent, and other forestry operations 2 per cent.
The emissions associated with the wood products after they reached the market until the end of their life weren’t calculated in the study. Consideration of possible end-of-life scenarios for lumber products, however, suggested that the majority of likely disposal or re-use options would not increase their full cradle-to-grave carbon footprint.
The study also concluded that there is scope for reducing emissions across both the log and lumber supply chains by 16 to 25 per cent. Reduction measures included greater use of woody biomass for fuels in processing, greater fuel efficiency through education of log truck drivers and harvest crews, and increased use of coastal shipping and rail for distribution to domestic markets.
The country’s Southern Wood Council says the Nelson Forests study shows that wood exports can compete on a carbon-friendly basis with those of other countries. New Zealand is being forced to defend its exports in the debate over ‘
food miles’ and ‘wood miles’. Green groups say the country’s produce comes with a high carbon footprint due to the transportation emissions associated with the huge distances they travel by sea to markets in Europe and North America.
The study highlights the big difference in emissions profiles between road freight and bulk sea transport based on tonnage-per-kilometre measures. It showed, for example, that it is just as carbon efficient for the company to ship timber products across the Tasman Sea to Australia as it is to truck them by road 225 kilometres from Nelson to Christchurch on New Zealand’s South Island.
Analysis such as the Nelson study add to the growing body of work that will be useful to forest carbon project developers and standards providers in afforestation and reforestation for sustainable harvest. The forest carbon sector is only beginning to come to terms with accounting for the carbon stored in harvested wood products in the calculation of net emissions reductions for offset credits. Uncertainties over what happens to wood at the end of its life, however, still make full LCA accounting difficult.
More:
Download the full study at NZwood.co.nz [PDF 440KB]