Carbon storage in harvested wood products: implications of different methodological procedures and input data—a case study for Portugal

Abstract

This study aims to quantify the contribution of the harvested wood products (HWP) to the carbon removals/emissions by the agriculture, forestry and land-use sector (hereafter referred to as HWP contribution) using the tier 1 method proposed by the Intergovernmental Panel on Climate Change (IPCC) in the 2006 Guidelines (hereafter referred to as GL tier 1 method) and to compare it with the results obtained with the tier 2 method proposed by the IPCC in the Good Practice Guidance for Land Use, LandUse Change and Forestry (hereafter referred to as GPG tier 2 method). The HWP contribution was calculated for three approaches: stock change, production and atmospheric flow. Another objective was to perform a sensitivity analysis in order to identify the calculation procedures and the input data that have the largest impact on the HWP contribution estimates. An uncertainty analysis was also carried out with Monte Carlo simulation. The case study of Portugal was analysed in this study. The HWP contribution obtained with the GL tier 1 method ranged from 150 to 1,240 Gg C year-1, for the period from 1990 to 2004. These results are similar to those obtained with the GPG tier 2 method, except for the production approach, since the GL tier 1 method underestimated carbon accumulation in solid waste disposal sites (SWDS) under this approach. The most influential calculation procedures and input data were the algorithm used to calculate the change in carbon stocks for the pools that follow a first-order decay, the procedure to estimate the input of carbon to the pool of HWP in SWDS, the procedure to determine the change in carbon stocks of HWP in SWDS for the production approach, the type of carbon stocks considered in SWDS and the conversion factor for wood-based panels.