The climate change mitigation effect of bioenergy from sustainably managed forests in Central Europe

Abstract

We compare sustainably managed with unmanaged forests in terms of their contribution to climate change mitigation based on published data. For sustainably managed forests, accounting of carbon (C) storage based on ecosystem biomass and products as required by the United Nations Framework Convention on Climate Change is not sufficient to quantify their contribution to climate change mitigation. The ultimate value of biomass is its use for biomaterials and bioenergy. Taking Germany as an example, we show that the average removals of wood from managed forests are higher than stated by official reports, ranging between 56 and 86 mill. m3 year−1 due to the unrecorded harvest of firewood. We find that removals from one hectare can substitute 0.87 m3 ha−1 year−1 of diesel, or 7.4 MWh ha−1 year−1, taking into account the unrecorded firewood, the use of fuel for harvesting and processing, and the efficiency of energy conversion. Energy substitution ranges between 1.9 and 2.2 t CO2 equiv. ha−1 year−1 depending on the type of fossil fuel production. Including bioenergy and carbon storage, the total mitigation effect of managed forest ranges between 3.2 and 3.5 t CO2 equiv. ha−1 year−1. This is more than previously reported because of the full accounting of bioenergy. Unmanaged nature conservation forests contribute via C storage only about 0.37 t CO2 equiv. ha−1 year−1 to climate change mitigation. There is no fossil fuel substitution. Therefore, taking forests out of management reduces climate change mitigation benefits substantially. There should be a mitigation cost for taking forest out of management in Central Europe. Since the energy sector is rewarded for the climate benefits of bioenergy, and not the forest sector, we propose that a CO2 tax is used to award the contribution of forest management to fossil fuel substitution and climate change mitigation. This would stimulate the production of wood for products and energy substitution.

A regional assessment of land‐based carbon mitigation potentials: Bioenergy, BECCS, reforestation, and forest management

“…This occurs because decreases in wood product storage (−53 Mt C), immediate and delayed energy substitution (−41 and −14 Mt C, respectively), and material substitution (−119 Mt C) outweigh additional carbon uptake in vegetation and soils (+128 and +9 Mt C, respectively; Figure ). Similar results have been reported by Klein et al (), Klein and Schulz (), and Schulze et al (). The finding that managed forests are superior climate mitigation options than unmanaged forests sounds surprising in view of a recent study emphasizing the need of tropical forest renaturation rather than tree plantations for climate protection (Lewis et al, ).…”

Recognizing the importance of unmanaged forests to mitigate climate change

“…We find several assumptions and conclusions in the Opinion piece by Schulze et al. (2020) inaccurate or questionable.…”

“…The most effective means for keeping carbon out of the atmosphere to meet climate goals is to protect primary forests (Mackey et al, 2020) and continue growing secondary forests to accumulate additional carbon (proforestation; Moomaw, Masino, & Faison, 2019) while reducing emissions from all sources including bioenergy. We find several assumptions and conclusions in the Opinion piece by Schulze et al (2020) inaccurate or questionable.…”

It’s time to stop pretending burning forest biomass is carbon neutral

“…The opinion piece “The climate change mitigation effect of bioenergy from sustainably managed forests in Central Europe” by Schulze et al (2020) argues against putting forests into conservation, concluding that managed forests can help mitigate climate change more effectively than unmanaged forests mainly due to the potential to use end of life wood products as fuel. This is alleged to produce “emission savings” by substituting diesel or other energy use.…”