The aim of this project was to study the leakage of CO2 in a Geological Carbon Sequestration (GCS) system. To define the GCS system, a tool that is known as an FEP database was used. FEPs are the features, processes and events that develop scenarios for the goal of the study. Combinations of these FEPs can produce thousands of scenarios. However, among all of these scenarios, some are more important than others for leakage. The FEPs that were used as scenario developers were the formation of the liquid flow, the salinity of the formation liquid, diffusion as a process for gas bubble transport and the depth of the reservoir layer. In this study, the leakage path is considered as the presence of a fracture in sealed caprock. The fractures can be modeled using various approaches. Here, I represented the influence of fracture modeling by applying the Equivalent Continuum Method (ECM) and the Dual-Porosity and Multi-continuum methods to leakage. This study suggests that considering groundwater in the aquifer would reduce the leakage of CO2 and that a shallower formation leads to higher leakage. This study can be expanded to future studies by including external FEPs that are related to the FEPs that were used in this study.

A forest’s ability to sequester carbon dioxide depends on factors such as periodic disturbance regimes, land-use change, the composition and productivity of the vegetative community, and the location and age of forested stands. However, one of the driving forces that contributes to changes in forest carbon dynamics include climatic factors, such as changes in temperature and precipitation, as well as atmospheric CO₂ concentrations which can affect the physiology of plants in complex ways. Our theorized understanding of plant physiological response to changing environmental conditions have been based on latitudinal and altitudinal studies or greenhouse experiments that measure plant physiological traits on one or a handful of plant species – and as scientists work to reduce the large variability that exists behind climate projections and plant community predictions, the need to collect locational and species-specific data becomes increasingly evident. This dissertation aims to address this issue by examining the physiological responses to temperature for 23 different tree species that have historically different geographic range distributions categorized into three groups: northern, central, and southern. The ranges of all species overlap and coexist at Black Rock Forest (BRF), an eastern deciduous forest located in the Hudson Highlands of New York. Chapter 1 examines the physiology of 16 coniferous and broadleaved tree species to determine if geographic provenance has a significant effect on foliar respiration rates, response to elevated temperature, and the respiratory substrate used to fuel the respiratory process. Chapter 2 compares the photosynthetic capacities and temperature responses of 17 broadleaved tree species to determine which range group may be more tolerant of a warming climate. Appended to this dissertation is preliminary data of a growth chamber experiment, examining the plasticity of physiological traits expressed under elevated temperatures to assess whether northern red oak seedlings show potential to acclimate to projected climate conditions and regenerate with minimal physiological constraints. Collectively, the results of these studies find significant differences in photosynthetic capacities and photosynthetic and respiration responses to temperature among species and among range groups. Northern, central, and southern ranged trees show an acclimated response to carbon assimilation under current climate conditions. However, central ranged trees, which includes the northern red oak, a dominant tree species in this region of New York, may be at a physiological disadvantage, showing lower rates of photosynthetic capacities and a trending decline of carbon assimilation under elevated temperatures. Furthermore, preliminary data from a greenhouse experiment suggests that leaf morphology and physiology traits are not plastic for northern red oak seedlings, which further weakens its physiological competitiveness and regeneration potential under warming temperatures. The results presented in this study on the physiological traits and temperature responses not only allows for a more thorough understanding of the physiological tolerances of migrant and resident tree species in the New York region but provides new data that could be incorporated into carbon and species distribution models for better predictions on carbon sequestration of forests and geographic ranges of tree species.

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Farmers have been disrupting the carbon cycle ever since humans started converting forests to agricultural lands. But are there farming practices that can be applied to increase the carbon storage in the soil and subsequently counteract increasing carbon dioxide levels in the atmosphere? In this study I investigate if soil organic matter (SOM) and soil organic carbon (SOC) change with longer interruption between tillage events. The study was conducted by studying SOM concentrations and SOC pools in eight fields with different time since tillage (1 to 14 years). I found that SOM concentrations increased in the O horizon of the studied soil in response to increased time since tillage. Here, SOM concentrations were on average around 13 % one year after tillage, while fourteen-year-old farmland had a concentration around 15 %. In similar, SOC pool increased from around 0.1 kg C m-2 in the O horizon of 1 year old soil to 0.33 kg C m-2 14 years after tillage. While both SOM concentrations and SOC pools increased in the O horizon over time since tillage, the SOM concentration and SOC pools decreased in the subsoil. I found no net sequestering of SOC in response to less frequent tillage in comparison to more frequency tillage. My conclusion is that limiting tillage to 14-year cycles is not enough to increase carbon sequestration.

In order to keep global average temperature below 2°C it is necessary to accelerate climate change mitigation actions and reduce global greenhouse gas emissions. This can be achieved by carbon capture and storage methods such as the production of biochar. Especially its production from municipal sewage sludge could decrease emissions and disposal costs as well as act as a valuable material for different fields of application afterwards. In this quantitative study, the potential for a biochar production system was investigated for the case of the Swedish island, Gotland. Documents and grey literature were reviewed to collect the necessary information and data and experts were asked to fill in information gaps to evaluate the following: Calculate the energy and mass balance of a biochar production system from municipal sewage sludge in 2018, to find possible applications for the produced biochar by investigating the heavy metal content as well as to assess the direct carbon sequestration potential of the produced biochar. The results indicate that in 2018, 540 t of biochar could have been produced with a net heat demand of around 543 MWhth and electricity consumption of 231 MWhel. Heavy metal contents were found to be very high especially for copper and zinc, which means that the produced biochar would only qualify for the EBC-BasicMaterial certification class of the European Biochar Certificate. The annual carbon sequestration potential resulted in 97.2 t of carbon stored in the material or 356.4 t of CO2 emissions saved. Further research needs to be conducted on economic factors of a biochar production system from municipal sewage sludge.

Compost is commonly used as an organic amendment in cropping systems such as vineyards, and has been shown to be beneficial to carbon (C) sequestration and soil health. As perennial crops, grapevines have a larger potential for C sequestration than most crops. Yet, there is a lack of understanding regarding the relationship between compost application rate, the magnitude of C sequestration, and its environmental tradeoff in the form of greenhouse gas (GHG) emissions. In the study, we investigated the effects of compost application rate on soil C sequestration, GHG emissions, crop growth, and overall soil health after two annual compost treatments at J. Lohr Vineyards and Wines, Paso Robles, CA. Compost was broadcasted to the entire plot area between harvest and the first precipitation in fall at the rate of 0 (control), 2, 4, and 6 tons/acre/year. Soil C sequestration, cumulative carbon dioxide (CO2) and nitrous oxide (N2O) emissions and soil physical properties were assessed at two functional locations (tractor row and vine row) and three depth increments (0-15, 15-30, and 30-60 cm). Cover crop biomass was determined in spring before mowing, while clusters per vine, cluster weight and yield were determined each year at harvest. Although compost application did not significantly affect total soil C stocks, significant increases in early indicators of C sequestration such as permanganate oxidizable carbon (POXC), aggregate distribution, and aggregate C content in large macroaggregates without increasing C mineralization suggests that C input from compost increased C stabilization in soil. Cumulative GHG emissions were not significantly affected by compost application. Both CO2 and N2O emissions were higher in the vine row than the tractor row in the dry season, but the trend for CO2 emissions was the opposite in the wet seasons. Seasonal patterns of GHG emissions were likely due to differences in plant activity and irrigation between functional locations. The lower bulk density in topsoil than subsoil, and the higher water holding capacity and aggregate stability in tractor row topsoil than in the vine row demonstrates how high C content improves soil physical properties. Cover crop growth and grape yield components were unaffected by compost application. Based on our results, early signs of C sequestration and improvements on overall soil health can be achieved in a coarse-texture vineyard in the Central Coast region after annually applying compost at a rate between 2 and 6 tons/acre for two years, without increasing GHG emissions or affecting grape yield. Further investigation is recommended to study the potential synergistic effects between compost application and cover cropping in vineyards if both practices are implemented at the same time.

Agricultural production in Sweden account for a large contribution of the territorial GHG emissions. System optimization, fossil fuel removal and increased circularity is therefore of great importance in order to reach the national net zero emission target by 2045. Biochar production from biomass side flows is a cost-efficient method for carbon dioxide removal which could help to reduce the climate impact of agricultural systems. This study aimed to investigate the potential for climate change mitigation by implementing biochar production from wheat straw at farm level in Sweden. A life cycle perspective was used to assess the climate change impact for production of 1 Mg wheat, with three scenarios for straw management 1) biochar production and application on fields 2) straw incorporation into soil and 3) district heat production. A time distributed LCI was used to include the time dynamics of soil processes. Climate impact was assessed using two metrics: Total GWP100 impact(static) and global surface temperature change (time dynamic). Excess thermal energy from the pyrolysis process was assumed to be used for drying of grains and heating buildings at the farm. The results showed a total GWP100 impact of 214 kg CO2-eq/Mg wheat in the scenario with biochar production, which compare to the impact of 425-429 kg CO2-eq/Mg wheat for the scenarios with conventional straw management practices. The temperature response was ca 50 % lower all throughout the analysed time period, compared to the scenarios with straw incorporation or district heat production. The largest contribution to the impact reduction was achieved from carbon sequestration from biochar application to soil amounting to 223 kg CO2-eq/Mg. A sensitivity analysis of the biochar yield (kg biochar produced per kg of dry mass feedstock) for pyrolysis of straw confirmed that biochar production was preferable over other straw management practices for lower biochar yields as well. In conclusion, utilizing straw for biochar production could have a large potential for reducing the climate impact from wheat production in Sweden. However, a combination of measures for climate change mitigation is needed to reach net zero emissions of wheat production. / Jordbruksproduktionen står idag för en betydande del av Sveriges territoriella växthusgasutsläpp. För att minska jordbrukssektorns klimatpåverkan krävs åtgärder såsom material och energiåtervinning, utfasning av fossila bränslen och elektrifiering. För att nå det nationella klimatmålet om nollutsläpp år 2045 krävs även åtgärder för infångning och lagring av koldioxid. Biokolsproduktion av restprodukter och avfall i form av biomassa är en kostnadseffektiv och lättillgänglig metod för kolinlagring. Pyrolys är en termokemisk process som sker när biomassa upphettas till höga temperaturer utan tillgång till syre. Produkterna från processen är syngas, pyrolysolja och biokol. Processen optimeras utifrån vilka produkter som är önskade och syngas förbränns ofta för att tillföra energi och upprätthålla reaktionen. Biokol används därefter främst som jordförbättringsmedel i planteringar men kan även användas för vattenfiltrering, som fyllnadsmaterial i betong, applicering på åkermark och som tillsatts i djurfoder. Efterfrågan och produktionen av biokol är än så länge relativt liten i Sverige. Då det finns en stor tillgång på biomassa från restprodukter inom jordbruket så finns även en stor möjlighet att minska sektorns klimatpåverkan genom pyrolys och biokolsproduktion. Syftet med denna studie är att undersöka hur implementering av biokolsproduktion från vetehalm skulle kunna bidra till minskad klimatpåverkan från veteproduktion. Studien utförs med ett gårdsperspektiv och har målen att: Identifiera och kvantifiera växthusgasutsläpp för relevanta materialflöden och processer inom veteproduktion. Beräkna klimatpåverkan utifrån ett livscykelperspektiv för produktion av 1 Mg vete under tre scenarion för halmhantering 1) biokolsproduktion och applicering på fält 2) halminblanding i jord 3) energiåtervinning genom produktion av fjärrvärme.  Klimatpåverkan, GWP100, beräknades med mätenheten (kg CO2-eq/Mg vete) och beskriver den totala påverkan från de ackumulerade utsläppen över en 100 års tidshorisont som förutsätter att alla utsläpp sker under det första året. För att kunna inkludera ett tidsperspektiv och ta hänsyn till icke-fossila utsläpp av CO2, markprocesser och koncentrationen av växthusgaser i atmosfären över tid, så beräknades även temperaturförändringen av den globala yttemperaturen (K/Mg vete och år), ΔT. Dessa beräkningar utfördes genom att använda tidsdistribuerade utsläpp för en 100 års period och klimatpåverkan, ΔT, beräknades för 150 år. Startåret för beräkningarna och veteproduktionen var satt till år 2019. Gården antogs producera höstvete årligen, utan växelbruk, under en tidsperiod på 20 år. Biokolsproduktion antogs ske på gården och värmeöverskottet antogs användas till torkning av vete och värme till byggnader på gården. En systemexpansion gjordes för att modellera utsläppsminskningen från ett lokalt fjärrvärmeverk där halmen antogs ersätta träpellets producerade av skogsrester.  Resultatet visade en klimatpåverkan av 214 kg CO2-eq/Mg vete. för scenariot med biokolsproduktion, 425 kg CO2-eq/Mg vete för scenariot med fjärrvärmeproduktion och 429 kg CO2-eq/Mg vete för scenariot med hamninblandning i jord. För den tidsdynamiska klimatpåverkan hade scenariot med biokolsproduktion en genomgående ca 50 % lägre temperaturpåverkan under hela tidsperioden. Resultatet visade även att kolinlagringen från biokol var den största bidragande faktorn till den minskade klimatpåverkan. Användning av överskottsvärme från pyrolysprocessen hade även ett betydande påverkan till minskade klimatutsläpp.  Biokolsproduktion av restprodukten vetehalm har därigenom en stor potential till att minska klimatpåverkan från veteproduktion. Effekten av biomassaomvandlingskvoten för pyrolys av halm (mängd producerad biokol per tillförd mängd biomassa) analyserades genom en känslighetsanalys som fann att biokolsproduktion från halm är fördelaktigt även vid lägre omvandlingskvoter, 20 %. En ökning av biomassaomvandlingskvoten med 5 % kan ge ytterligare en minskning på 16-20 % av de totala utsläppen. Även effekten av jordförbättrande egenskaper som skördeökning och minskade markutsläpp av N2O analyserades. Då biokolsmängden per hektar är relativt låg och antas ge effekt endast ett år, så var dessa effekter på den totala klimatpåverkan försumbara. De ackumulerade effekterna av biokol som jordförbättring undersöktes dock inte, men skulle eventuellt kunna ge en mer betydande effekt.  För att bättre kunna analysera klimateffekterna av jordförbättring krävs dock mer forskning om effekter av biokol under svenska odlingsförhållanden över en längre tid. För att dessutom få en mer övergripande bild av potentialen för implementering av biokolsproduktion inom jordbrukssektorn så rekommenderas framtida studier för analys av olika sorters grödor, växtföljder, restprodukter och regioner.  Utifrån resultatet dras slutsatsen att gårdsproduktion av biokol från vetehalm har en möjlighet att minska klimatpåverkan från vete med ca 50 % jämfört med annan halmhantering. Biokolsproduktion är även fördelaktigt när tidsdynamiska effekter av utsläppen inkluderas. För att nå en klimatneutral veteproduktion krävs dock även andra åtgärder.

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