Wood substitution potential in greenhouse gas emission reduction–review on current state and application of displacement factors

Abstract

Background Replacing non-renewable materials and energy with wood offers a potential strategy to mitigate climate change if the net emissions of ecosystem and technosystem are reduced in a considered time period. Displacement factors (DFs) describe an emission reduction for a wood-based product or fuel which is used in place of a non-wood alternative. The aims of this review were to map and assess DFs from scientific literature and to provide findings on how to harmonise practices behind them and to support coherent application. Results Most of the reviewed DFs were positive, implying decreasing fossil GHG emissions in the technosystem. The vast majority of the reviewed DFs describe avoided fossil emissions either both in processing and use of wood or only in the latter when wood processing emissions were considered separately. Some of the reviewed DFs included emissions avoided in post-use of harvested wood products (HWPs). Changes in forest and product carbon stocks were not included in DFs except in a few single cases. However, in most of the reviewed studies they were considered separately in a consistent way along with DFs. DFs for wood energy, construction and material substitution were widely available, whereas DFs for packaging products, chemicals and textiles were scarce. More than half of DFs were calculated by the authors of the reviewed articles while the rest of them were adopted from other articles. Conclusions Most of the reviewed DFs describe the avoided fossil GHG emissions. These DFs may provide insights on the wood-based products with a potential to replace emissions intensive alternatives but they do not reveal the actual climate change mitigation effects of wood use. The way DFs should be applied and interpreted depends on what has been included in them. If the aim of DFs is to describe the overall climate effects of wood use, DFs should include all the relevant GHG flows, including changes in forest and HWP carbon stock and post-use of HWPs, however, based on this literature review this is not a common practice. DFs including only fossil emissions should be applied together with a coherent assessment of changes in forest and HWP carbon stocks, as was the case in most of the reviewed studies. To increase robustness and transparency and to decrease misuse, we recommend that system boundaries and other assumptions behind DFs should be clearly documented.

The Missing Limb: Including Impacts of Biomass Extraction on Forest Carbon Stocks in GHG Balances of Wood Use

“…However, both the concept of payback time (e.g. [20,37,38]) and the concept of the displacement factor (synonym substitution factor; [39,40]) conflate the individual GHG balances of a wood product and a non-wood product into one indicator. As a result, there is a loss of transparency.…”

“…The displacement factor compares the GHG balance of wood and non-wood products and correlates the result to the wood used. In their recent review on the concept, Myllyviita et al [40] noted that very few studies included changes in forest and product carbon stocks in displacement factors. This finding highlights that the CSBF is currently mostly ignored in studies, yet also confirms that its integration into the displacement factor is possible.…”

Required displacement factors for evaluating and comparing climate impacts of intensive and extensive forestry in Germany

“…These values represent average DFs for 2019 and result from meta studies. Since the underlying system boundaries were not always consistent (Leskinen et al 2018), they are subject to considerable uncertainties (Tanja Myllyviita et al 2021). Volume shares of wood usage, was used as weight for calculating averages (Table 1).…”

“…"Where GHG n on − wood and GHG w ood are the GHG emissions resulting from the use of the non-wood and the wood alternatives, respectively, expressed in mass units of carbon (C) corresponding to the CO 2 equivalent of the emissions, and WUwood and WUnon-wood are the amounts of wood used in the wood and non-wood alternatives, respectively, expressed in mass units of C contained in the wood" (Sathre and O'Connor 2010). A vast variety of DF estimates exist in the literature but there is a lack of coherence, transparency and robustness in thos estimates (Tanja Myllyviita et al 2021). Therefore we refrain from calculating climate impacts with fixed DFs in this study.…”

Study on the Estimation of Forest Volume Based on Multi-Source Data

“…As an important part of the global ecosystem, the forest landscape plays an important role in maintaining the global carbon emission balance and curbing global warming, in which context forest volume is one of the important indicators [ 1 , 2 ]. In order to actively respond to climate change, take the path of green and low-carbon development, and achieve sustainable development, China has proposed to achieve the goal of carbon neutrality and zero emissions by 2060, and increasing forest volume is an important means to achieve this goal [ 3 , 4 , 5 , 6 ].…”