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Carbon storage in agricultural soils is an important measure to mitigate climate change. As the soil management techniques can greatly influence the amount of carbon stored in agricultural soils, the influence of different managements was analyzed in a literature review for northern Europe and Sweden. With a unique dataset, the temporal development of soil organic matter, and in a case study the influence of SOM on crop yield in Sweden was examined, as well as the relationship of SOM towards clay content and pH level. For northern Europe, organic amendments in form of manure and sewage sludge application and crop residue incorporation as well as nitrogen fertilization and diverse crop rotations indicate a positive impact on soil organic carbon. The influence of reduced tillage was found to be less impactful. Detailed development of SOM in Swedish agricultural fields remains unclear due to data restraints and scarcity, but for the Skåne region the data analysis suggests a stable SOM content for the time period analyzed. The relationship of SOM to crop yield remains unclear but indicates that SOM can have a positive effect on crop yield. More research is needed to understand underlying mechanisms of development, management influence and yield response on soil organic carbon for northern Europe.

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För klimatet spelar skogen en viktig roll eftersom den binder in koldioxid från atmosfären. Genom fotosyntes binds kolet in i biomassan och när organiskt material bryts ned bidrar det till kolinlagringar i marken. Idag finns det många studier om skogens kolinlagringar, men de undersöker endast nettoinbindningen av kolet i skogen och få studier visar hur mycket kol som totalt är inlagrat i en skog. Det finns inga studier om hur det ser ut i Sverige och det finns få studier som visar på skillnaden i kolinlagring mellan en produktionsskog och en urskog. I den här litteraturstudien presenterar jag hur mycket kol som är inbundet i den svenska skogen och hur det skiljer sig mellan produktionsskog och urskog. Genom att applicera data från en studie som undersökte hur mycket kol som är inbundet i skogen i Kanada på den svenska skogen kom jag fram till att det finns totalt mellan 5 413 och 6 798 miljoner ton kol inlagrat i den svenska skogen, men mer kol skulle kunna lagras. Medelåldern för när träd slutavverkas är i Sverige 101 år. Jag kom fram till att det lagras in ungefär 53 till 75 ton mer kol per hektar i en skog som är äldre än 140 år än i en skog som är mellan 101 och 120 år. Resultatet visar att det binds in mer kol i en urskog än i en produktionsskog och att det är viktigt att bevara de urskogar som idag finns för att kunna möta de klimatproblem vi står inför. / For the climate, the forest plays an important role because it binds carbon dioxide from the atmosphere. Through photosynthesis, carbon is bound into the biomass and degradable organic material contributes to carbon storage in the soil. There are many studies on the forest carbon deposits, but they only examine the net binding of carbon, and few studies show how much carbon is stored in total. There are no studies on what carbon storage looks like in Sweden and few studies that show the difference in carbon storage between production forests and old-growth forests. In this literature study, I present how much carbon is bound in Swedish forests and how it differs between production forest and old-growth forest. By applying data from a study that examined how much carbon is bound in Canadian forests on Swedish forests, I concluded that there is a total of between 5 413 and 6 798 million tonnes of carbon stored in Swedish forests, but more carbon could be stored. In Sweden, the average age for when trees are felled is 101 years. I concluded that approximately between 53 and 75 tonnes more carbon per hectare is stored in a forest that is older than 140 years than in a forest that is between 101 and 120 years. The results show that more carbon is bound in an old-growth forest than in a production forest and that it is important to preserve the old-growth forests to reduce the climate problems we face.

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The warming of our planet is a direct consequence of anthropogenic emissions with carbon dioxide as the main driver. A need to mitigate carbon emissions is urgent and forests can be a part of the solution since they sequester and stock carbon during their lifetime This study has shown that production forests can sequester carbon to a higher degree since they consist of younger trees which are better at sequestration than older trees. But the study also show that older forests keep sequestering carbon and might not be carbon neutral as previously thought. Old growth forests contain higher carbon stocks than younger production forests since they often remain unmanaged and can continuously accumulate carbon into living and dead biomass as well as the soil. Production forests also accumulate carbon, but it is not nearly the same amount as in old growth forests. With regard to meeting the 1,5-degree goal set by the IPCC, i.e., cutting emissions with half until 2030 and having net zero carbon dioxide emissions until 2050. Harvesting with clear-cutting was found to be worse compared with harvesting at a lower frequency which causes less emissions but still supplies wood products to the industry. The result also show that we must protect more old growth and unmanaged forests that can sequester and stock carbon longer to be able to succeed with the 1,5-degree goal. The debate climate in Sweden is heated and opinions often differ. The difference may depend on the time frame or how results are interpretated.

On the fourth of November 2016, The Paris Agreement entered into force, stating that nations worldwide should pursue efforts to limit the global temperature increase to 1,5 °C. Since then, the Intergovernmental Panel on Climate Change has specified that carbon dioxide removal, such as biochar sequestration, is necessary to achieve this goal. Biochar is a solid and porous material, rich in carbon, produced when biomass undergoes a process called pyrolysis and can, if buried in soil, sequester carbon for hundreds or even thousands of years while at the same time acting as a soil amendment. When biomass is pyrolyzed to produce biochar, a pyrolysis gas is also produced, which can be used to generate both heat and electricity. This thesis investigates if constructing and operating a plant, called a combined pyrolysis and CHP plant, which combines biochar production with heat and electricity generation, could be economically feasible and thus be an effective method for carbon dioxide removal. The findings show that constructing and operating a combined pyrolysis and CHP plant can be economically feasible. However, the economic feasibility is greatly affected by the price of biochar as a soil amendment product. The biochar market is also an undeveloped market, making price estimates of biochar far from accurate. Another factor that could significantly affect the economic feasibility of the plant is the fraction of carbon in biochar, which can be accounted for as sequestered. A higher fraction means that significantly more governmental support can be given to provide financing of the plant as well as potential revenue from carbon credits could increase. The capital cost of constructing the plant is also a factor with high uncertainty, which has a substantial effect on the economic feasibility. From this thesis, it is concluded that more research regarding the biochar market, as well as the capital costs of constructing the plant, is needed. More research could further ascertain whether or not the plant could be economically feasible and thus, an effective method for carbon dioxide removal. / Den fjärde november 2016 trädde Parisavtalet i kraft vilket uppgav att länder över hela världen ska sträva efter att begränsa den globala temperaturökningen till 1,5 grader Celsius. I enlighet med detta mål har FN:s mellanstatliga klimatpanel, IPCC, specificerat att koldioxidavlägsnande åtgärder, såsom kolinlagring genom produktion av biokol, är nödvändigt. Biokol är ett fast och poröst material, rikt på kol, som produceras när biomassa genomgår en process som kallas pyrolys. Om biokol blandas ner i jord kan det binda kol i hundratals eller tusentals år samtidigt som det fungerar som jordförbättrare. När biomassa pyrolyseras produceras också en pyrolysgas som kan användas för att generera värme och elektricitet. Det här examensarbetet undersöker om det kan vara ekonomiskt genomförbart att bygga och driva en anläggning, benämnd en kombinerad pyrolys- och kraftvärmeanläggning, som kombinerar biokolsproduktion med värme- och elproduktion för att avlägsna koldioxid från atmosfären. Resultaten från arbetet visar att det kan vara ekonomiskt genomförbart att bygga och driva en kombinerad pyrolys- och kraftvärmeanläggning. Den ekonomiska genomförbarheten påverkas dock i hög grad av priset på biokol som jordförbättringsprodukt. Marknaden för biokol är dessutom outvecklad vilket gör att priset för biokol osäkert. En annan faktor som i hög grad skulle kunna påverka den ekonomiska genomförbarheten för anläggningen är andelen kol i biokol som kan anses vara lagrad. En högre andel innebär att betydligt mer statligt stöd kan ges för att finansiera anläggningen samt att potentiella intäkter från kolkrediter kan öka. Kapitalkostnaderna för att bygga anläggningen är också en faktor med hög osäkerhet som har stor effekt på den ekonomiska genomförbarheten. Från detta examensarbete dras slutsatsen att mer forskning kring biokolsmarknaden samt kring kapitalkostnaderna för att bygga anläggningen behövs. Detta behövs för att ytterligare fastställa den ekonomiska genomförbarheten hos en sådan anläggning för att avlägsna koldioxid från atmosfären.