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The forest industry is a significant emitter of CO2 and thus it needs to transform toward​ a more sustainable operation in order to contribute to tackling climate change. This paper looks at the progress, tools, possibilities, and barriers of Finnish and Swedish forest industries in achieving deep decarbonization. Finland and Sweden have set ambitious national targets to reach net negative greenhouse gas emissions. The role of the forest industry in reaching national targets in these countries remains unclear even if significant fossil CO2 emission reduction and efficiency improvement has occurred. If the forest industries in these countries fulfill their planned future visions, their contribution to meeting the targets will be substantial. This study identified the largest CO2 emitting sectors in the forest industry. They are for both countries, arranged by size, transport including non-road mobile machinery, on-site energy production, fossil fuel use in processes (lime kilns and dryers), and purchased electricity. Viable decarbonization measures exist for key fossil CO2 emissions sources, but several technical, economic, and political barriers are hindering their implementation. Fuel switching from fossil energy sources to bio-based alternatives is the main tool in the decarbonization of the forest sector in both countries, but also electrification of e.g. transport, provides emission reduction opportunities. The forest industry has a high and sustainable potential to become carbon-negative by investing in bioenergy with carbon capture and storage (BECCS) but achieving net-zero emissions might not be realistic without changes in policies and suitable incentives.

Of the various waste and side streams created in a kraft pulp mill, the biological sludges from the wastewater treatment plant are some of the most problematic to handle. Incineration is becoming a common solution as landfilling is no longer permitted by legislation in many countries, but this is also problematic due to the high moisture content, poor drying characteristics, and high ash content in the solids. This study evaluates the technical potential of mild hydrothermal carbonization (HTC) at 160 °C for 3 h to improve the energy efficiency of on-site incineration as a biosludge handling method. HTC treatment transforms wet organic substrates into a hydrophobic carbonaceous material (hydrochar). The heating value and elemental composition of both the sludge and the hydrochar product were analyzed. Based on this, a hydrothermal carbonization model developed earlier was adjusted for the feedstock, and process integration modelling performed to evaluate the performance impact on the power and heat generation at the mill. The results indicate that if the alternative is combustion in the power boiler, HTC pre-treatment could allow a significant increase in power generation. If the sludge is combusted in the recovery boiler, a practice often avoided in order to not introduce non-process elements to the chemical recovery cycle but sometimes necessary due to, e.g., absence of a power boiler, a much smaller increase is obtained. The increase is smallest if the freed evaporator plant capacity cannot be utilized for increasing the firing liquor dry solids content.