Assessing the contribution of harvested wood products under greenhouse gas estimation: accounting under the Paris Agreement and the potential for double-counting among the choice of approaches

BACKGROUND: There are multiple approaches for estimating emissions and removals arising from harvested wood products (HWP) based on differences between when and where a given carbon stock change is calculated. At this moment, countries are free to use any HWP approach to prepare their annual greenhouse gas (GHG) inventory and determine emission reduction targets for their Nationally Determined Contributions (NDCs), although under the Paris Agreement (PA), the production approach is used for standard reporting in GHG inventories. Global double-counting and non-counting of HWP might occur depending on the HWP approach each country uses; however, the impact of such double-counting and non-counting has not been thoroughly evaluated. RESULTS: We identified all cases of global double-counting and non-counting of HWP for combinations of the six HWP approaches: 'instantaneous oxidation', 'stock-change', 'production', 'stock-changes approach for HWP of domestic origin (SCAD)', 'simple-decay' and 'atmospheric-flow' approaches. In Intended Nationally Determined Contributions (INDCs), forest land is often partly or completely excluded, especially by developing countries. In such cases, HWP approaches that require comprehensive national data on wood harvesting and trade are not suitable for estimating HWP contributions. In addition, most developing countries apply the 'instantaneous oxidation' at the time of harvesting. Recent GHG inventories from Annex I countries show the averaged contribution of annual HWP emissions or removals to national total emissions is nearly 1%; therefore, the potential contribution of HWP to the accounted emission reduction volume is assumed to be a smaller value. CONCLUSIONS: Instantaneous oxidation remains a pragmatic approach for countries in which wood production is not a dominant part of the economy. The combination of 'instantaneous oxidation' with the 'production', 'SCAD' or 'simple-decay' approaches could be a practical solution to realize a global HWP accounting approach the eliminates double-counting. Regardless of how global double-counting and non-counting occur, the amount is not large. To improve the accuracy of the global assessment, it is important to reduce the uncertainty of estimation regarding when and how much HWP-related emissions occur at national level.