Forests provide many essential ecosystem services. In Sweden, roundwood assortments and residual biomass are vital feedstock sources. Swedish forestry is slowly replacing conifer monocultures with mixed conifer-broadleaf forests to enhance climate resilience. This study evaluates the economic returns of managing mixed forest stands comprising 0.25 ha patches of individual species compared to larger Norway spruce and silver birch monocultures. Specifically, we investigate (1) harvesting silver birch as energy biomass in the first thinning and timber in the final felling and (2) determining thinning timing based on stand basal area versus species-specific criteria. We used the Heureka forest growth and development modelling software to simulate various stand types and management strategies based on experimental forest data. Group-mixed stands were simulated by integrating separate species’ monoculture data. Results indicate that incorporating energy thinning into birch-spruce mixed stands can generate positive net revenues, supporting the economic viability of biomass harvesting. Strengthening birch biomass and timber markets, optimising thinning logistics, and refining harvesting methods will promote sustainable birch management. Expanding these strategies could significantly enhance the economic and ecological resilience of mixed and broadleaf-dominated forests in Sweden.

The transition to sustainable transportation fuels requires investment in emerging biomass-to-liquid production pathways under uncertain market and policy conditions. This study applies a real options analysis framework to evaluate the economic viability and timing of investments in biomass- and power-to-liquid pathways by identifying conditions where an investor should invest, defer, or abandon investments. The analysis is conducted for Sweden, reflected by its large biomass base and well-developed forest industry and ambitious defossilization policies. Results indicate that large price gaps between feedstock and produced fuels are not by themselves sufficient to trigger investment; in volatile markets, investors may still defer because the option to wait has economic value. Thus, even at identical price levels across scenarios, outcomes range from commitment to inaction depending on volatility. Moreover, when investments do occur, they are consistently deferred until the final year of the investment window. While modest subsidies may suffice under stable price conditions, volatile markets with high drifts require significantly greater support to counteract the incentive to defer investments. Electricity cost structures and carbon pricing must be targeted to support the transition toward electrified fuel production pathways. The insights from this study can inform the design of policy instruments that align investor incentives with global transition goals.

Transitioning to biofuels is crucial for reducing greenhouse gas (GHG) emissions in transportation, but limited biomass availability requires maximizing carbon efficiency. This study evaluates Fischer-Tropsch liquid (FTL) production from biomass, focusing on the impact of partial electrification and carbon capture and storage (CCS) on efficiency and flexibility. Five configurations—ranging from a biomass-intensive base case to a fully electrified process—are simulated and assessed through techno-economic and GHG evaluations under fluctuating energy prices. Full electrification achieves the highest carbon efficiency, increasing carbon-to-liquid fuel conversion from 37 % to 91 %, but faces challenges due to high electricity demand (up to 2.5 MWh per MWh of fuel) and reliance on low-carbon grids. Partial electrification offers a cost-effective alternative, reducing production costs by up to 40 % compared to fully electrified cases, while maintaining a carbon efficiency of around 60 %. CCS enables net-negative emissions, though its viability hinges on sufficiently strong carbon pricing incentives. Compliance with sustainability mandates, such as Renewable Fuels of Non-Biological Origin (RFNBO) requirements, depends on access to decarbonized electricity. Overall, partially electrified BtL pathways enhance carbon utilization, reduce emissions, and offer resilience to market fluctuations. These pathways provide a promising balance of environmental and economic performance, outperforming both traditional BtL under high biomass prices and fully electrified e-fuels in terms of cost. Their advantages make them attractive from both investment and policy perspectives—especially in markets supported by stable electricity prices, carbon incentives, and sustainability-driven regulation.

This study investigates hydrothermal carbonisation (HTC) of pulp-and-paper mill sludge to produce hydrochar and enable industrial symbiosis with steelmaking in Sweden. The assessment combines life cycle assessment (LCA) and techno-economic analysis (TEA) to evaluate environmental impacts, production costs, and national-scale implementation potential. The results show that HTC-derived hydrochar reduces the climate impact compared to use of fossil coal in electric arc furnace (EAF) steelmaking, particularly in mill-integrated scenarios that exploit onsite energy and wastewater treatment synergies. Economic viability, however, hinges on CO₂ pricing and hydrochar quality. Without a significant cost penalty for fossil CO2 emissions, hydrochar can be costlier than its fossil counterpart due to lower carbon content. Several pulp mills or mill clusters, in mid- and southern Sweden could support industrial symbiosis arrangements with local steel industries. The nationwide hydrochar production potential, estimated at less than 15% of the projected future carbon demand in Swedish EAFs, indicates a limited role, amplified by substantial regional variations in both supply and demand. Overall, the findings highlight that the suggested industrial symbiosis concept can help mitigate pulp and paper industry waste issues while contributing to reduced fossil coal dependence in steelmaking, forming part of a defossilisation strategy. However, strategic policy frameworks, multi-feedstock approaches, and further optimisation of hydrochar quality will be crucial for realising large-scale adoption.

Sustainable aviation fuel (SAF) is a key component for the defossilization of the aviation sector. The economic feasibility of SAF production is typically evaluated through techno-economic assessments (TEA), with the Minimum Jet Fuel Selling Price (MJSP) serving as the key economic performance indicator. Comparing MJSP values across different SAF pathways is challenging and potentially misleading due to differences in modelling assumptions, estimation methods for key variables, and their underlying relationships. This study aims to contribute to a more comprehensive understanding of the economic feasibility of four prominent SAF pathways: Hydroprocessed Esters and Fatty Acids (HEFA), Pyrolysis-to-Jet (PTJ), Alcohol-to-Jet (ATJ), and Fischer-Tropsch (FT). We employed qualitative and quantitative methods, including meta-analysis and variable harmonization, to analyze a wide range of TEA studies from the literature and investigate the factors contributing to MJSP variation for these pathways. Our findings reveal that feedstock cost is a primary driver of MJSP variability across all pathways. Moreover, regression and harmonization analyses uncovered complex interdependencies among economic variables often underexplored in individual TEAs. Key sources of MJSP variability include methodological differences in by-product credit valuation, process design choices, capital cost estimation approaches, and financial assumptions. Recognizing and addressing these factors offers strategic opportunities to improve the techno-economic performance and comparability of SAF pathways. Notably, the PTJ pathway emerged as a promising alternative for non-food feedstocks, and all pathways demonstrated improved economic outcomes when integrated with existing industrial infrastructure. The analytical findings of this study provide a robust empirical foundation that can be leveraged by future studies aimed at policy analysis, as well as for project budgeting and investment decisions in sustainable aviation fuels. 

The iron and steel industry is a major emitter of carbon dioxide globally. To reduce their carbon footprint, the iron and steel industry pursue different decarbonization strategies, including deploying bio-based materials and energy carriers for reduction, carburisation and/or energy purposes along their value-chains. In this study two potential roles for biomass were analysed: (a) substituting for fossil fuels in iron-ore pellets induration and (b) carburisation of DRI (direct reduced iron) produced via fully hydrogen-based reduction. The purpose of the study was to analyse the regional demand-driven price and allocative effects of biomass assortments under different biomass demand scenarios for the Swedish iron and steel industry. Economic modelling was used in combination with spatial biomass supply assessments to predict the changes on relevant biomass markets. The results showed that the estimated demand increases for forest biomass will have significant regional price effects. Depending on scenario, the biomass demand will increase up to 25 percent, causing regional prices to more than doubling. In general, the magnitude of the price effects was driven by the volumes and types of biomasses needed in the different scenarios, with larger price effects for harvesting residues and industrial by-products compared to those of roundwood. A small price effect of roundwood means that the incentives for forest-owners to increase their harvests, and thus also the availability of harvest residues, are small. Flexibility in the feedstock sourcing (both regarding quality and geographic origin) will thus be important if forest biomass is to satisfy demands in iron and steel industry.

This project has targeted utilisation of infrastructure for organic waste treatment in Sweden, in particular sewage sludge, to achieve increased production of high-value materials and energy carriers, reduced use of primary resources, and improved economic performance. We have investigated the sewage sludge management system as a socio-technical system facing a change, with integral connections to the energy and waste systems.

In conclusion, there is no silver bullet for the future of sewage sludge management. Indeed, it would have to be a full clip of silver bullets, as we found that a mishmash of different barriers –technical, economic, legal, and related to public perception – creates uncertainty that hinders progress regarding both sustainable long-term strategies and technological advancement. The Swedish sewage sludge management is largely fragmented, highlighting the need to shift directionto a more holistic approach. This can help actors address common issues rather than focussing solely on activity-specific problems. Introducing new legislation could be a key step, as the current specific legislation on sewage sludge has a seemingly insignificant role for today’s sludge management, compared to other legislation and the voluntary certification.

We have formulated six overall research highlights, to outline both published results and meta-conclusions based on combined insights. Each highlight is described separately in this report.

Sewage sludge management is torn between a desire for pollution prevention and reuse of a valuable resource. Reconciling these interests in sustainable management is a challenge for researchers. This study focuses on how research on sewage sludge management practices has evolved and scrutinizes how this research is interlinked with concerns and societal issues such as contaminants, economic efficiency, and legislation. Based on published academic papers on sewage sludge management between 1971 and 2019, this study found four trends in research focused on sewage sludge management: a decreasing interest in disposal (landfilling and sea dumping), a dominant interest in land application, a growing interest in sewage sludge as product, and a stable interest in energy recovery. Research on disposal focuses on increasing sludge volumes, legislative changes, and economic challenges with an interest in waste co-treatment. Research on land application concerns nutrient use and contaminants, mainly heavy metals. Research on sewage sludge as a product focuses on the extraction of certain resources and less on use of sewage sludge specifically. Research on energy recovery of sewage sludge focuses on volume reduction rather than contaminants. Two-thirds of the papers are detailed studies aiming to improve single technologies and assessing single risks or benefits. As management of sewage sludge is multifaceted, the narrow focus resulting from detailed studies promotes some concerns while excluding others. Therefore, this study highlights potential gaps such as the combination of nutrient use and disposal and energy recovery and nutrient use. 

Hydrothermal carbonization (HTC) can mitigate the disposal costs of sewage sludge in a wastewater treatment plant. This study analyzes the impact of integrating HTC with anaerobic digestion (AD) and combustion from a combined energy and economic performance perspective. Net energy balance and investment opportunity are investigated for a number of technical scenarios considering i) different combinations of the technologies: AD + HTC, AD + thermal dryer + combustion, and AD + HTC + combustion, ii) different options for HTC process water treatment: wet oxidation (WO) + AD, and direct return to AD, and iii) different products: heat-only, heat and electricity, hydrochar, and phosphorus.

The results show trade-offs between investment cost, self-supplement of heat, and output electricity when WO is used. In AD + HTC, net heat output decreases compared to the reference plant, but avoided disposal costs and hydrochar revenue result in profitable investment when the process water is directly returned to the AD. Although HTC has a lower heat demand than the thermal dryer, replacing the thermal dryer with HTC is only possible when AD, HTC, and combustion are connected, or when WO covers HTC’s heat demand. HTC may impair the electricity production because of the necessity for a high-temperature heat source, whereas the thermal dryer can utilize a low-temperature heat source. In conclusion, energy advantages of HTC in AD + HTC + combustion are insufficient to provide a promising investment opportunity due to high investment costs of HTC. The investment opportunity improves by co-combustion of hydrochar and external sludge.

Mitigating the climate impact from aviation remains one of the tougher challenges in adapting society to fulfill stated climate targets. Long-range aviation cannot be electrified for the foreseeable future and the effects of combusting fuel at high altitude increase the climate impact compared to emissions of green-house gasses only, which further limits the range of sustainable fuel alternatives. We investigate seven different pathways for producing aviation biofuels coupled with either bio-energy carbon capture and storage (BECCS), or bio-energy carbon capture and utilization (BECCU). Both options allow for increased efficiency regarding utilization of feedstock carbon. Our analysis uses process-level carbon- and energy balances, with carbon efficiency, climate impact and levelized cost of production (LCOP) as primary performance indicators.

The results show that CCS can achieve a negative carbon footprint for four out of the seven pathways, at a lower cost of GHG reduction than the base process option. Conversely, as a consequence of the electricity-intensive CO₂ upgrading process, the CCU option shows less encouraging results with higher production costs, carbon footprints and costs of GHG reduction. Overall, pathways with large amounts of vented CO₂, e.g., gasification of black liquor or bark, as well as fermentation of forest residues, reach a low GHG reduction cost for the CCS option. These are also pathways with a larger feedstock and corresponding production potential. Our results enable a differentiated comparison of the suitability of various alternatives for BECCS or BECCU in combination with aviation biofuel production. By quantifying the relative strengths and weaknesses of BECCS and BECCU and by highlighting cost, climate and carbon-efficient pathways, these results can be a source of support for both policymakers and the industry.