Bioenergy from boreal forests managed for productive purposes (e.g., pulp, timber) is commonly held to offer attractive options for climate change mitigation. However, this view has been challenged in recent years. Carbon balances, cumulative radiative forcing, and average global temperature change have been calculated for a variety of bioenergy management regimes in Swedish forests, and the results support the view that an increased use of forest biomass for energy in Sweden can contribute to climate change mitigation, although methodological (e.g., spatial scales) and parameter value choices influence the results significantly. We show that the climate effect of forest-based bioenergy depends on the forest ecosystems and management, including biomass extraction for bioenergy and other products, and how this management changes in response to anticipated market demands; and on the energy system effects, which determine the fossil carbon displacement and other greenhouse gas (GHG) mitigation effects of using forest biomass for bioenergy and other purposes. The public and private sectors are advised to consider information from comprehensive analyses that provide insights about energy and forest systems in the context of evolving forest product markets, alternative policy options, and energy technology pathways in their decision-making processes.

Studies report different findings concerning the climate benefits of bioenergy, in part due to varying scope and use of different approaches to define spatial and temporal system boundaries. We quantify carbon balances for bioenergy systems that use biomass from forests managed with long rotations, employing different approaches and boundary conditions. Two approaches to represent landscapes and quantify their carbon balances -expanding vs. constant spatial boundaries -are compared. We show that for a conceptual forest landscape, constructed by combining a series of time-shifted forest stands, the two approaches sometimes yield different results. We argue that the approach that uses constant spatial boundaries is preferable because it captures all carbon flows in the landscape throughout the accounting period. The approach that uses expanding system boundaries fails to accurately describe the carbon fluxes in the landscape due to incomplete coverage of carbon flows and influence of the stand-level dynamics, which in turn arise from the way temporal system boundaries are defined on the stand level. Modelling of profit-driven forest management using location-specific forest data shows that the implications for carbon balance of management changes across the landscape (which are partly neglected when expanding system boundaries are used) depend on many factors such as forest structure and forest owners' expectations of market development for bioenergy and other wood products. Assessments should not consider forest-based bioenergy in isolation but should ideally consider all forest products and how forest management planning as a whole is affected by bioenergy incentives -and how this in turn affects carbon balances in forest landscapes and forest product pools. Due to uncertainties, we modelled several alternative scenarios for forest products markets. We recommend that future work consider alternative scenarios for other critical factors, such as policy options and energy technology pathways.

No abstract

Biomass co-firing with coal is a near-term option to displace fossil fuels and can facilitate the development of biomass conversion and the build-out of biomass supply infrastructure. A GIS-based modeling framework (EU-28, Norway, and Switzerland) is used to quantify and localize biomass demand for co-firing in coal power plants and agricultural and forest residue supply potentials; supply and demand are then matched based on minimizing the total biomass transport costs (field to gate). Key datasets (e.g., land cover, land use, and wood production) are available at 1,000 m or higher resolution, while some data (e.g., simulated yields) and assumptions (e.g., crop harvest index) have lower resolution and were resampled to allow modeling at 1,000 m resolution. Biomass demand for co-firing is estimated at 184 PJ in 2020, corresponding to an emission reduction of 18 Mt CO 2 . In all countries except Italy and Spain, the sum of the forest and agricultural residues available at less than 300 km from a co-firing plant exceeds the assessed biomass demand. The total cost of transporting residues to these plants is reduced if agricultural residues can be used, as transport distances are shorter. The total volume of forest residues less than 300 km from a co-firing plant corresponds to about half of the assessed biomass demand. Almost 70% of the total biomass demand for co-firing is found in Germany and Poland. The volumes of domestic forest residues in Germany (Poland) available within the cost range 2-5 (1.5-3.5) €/GJ biomass correspond to about 30% (70%) of the biomass demand. The volumes of domestic forest and agricultural residues in Germany (Poland) within the cost range 2-4 (below 2) €/GJ biomass exceed the biomass demand for co-firing.Half of the biomass demand is located within 50 km from ports, indicating that long-distance biomass transport by sea is in many instances an option. K E Y W O R D Sagriculture, bioenergy, CO 2 emissions, co-firing, European Union, forestry, geographic information system, residues

No abstract