| 1. |
- Steinhagen, Sophie, et al.
(författare)
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Harvest time can affect the optimal yield and quality of sea lettuce (Ulva fenestrata) in a sustainable sea-based cultivation : Seasonal Cultivation of Ulva fenestrata
- 2022
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Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Seaweed biomass is a renewable resource with multiple applications. Sea-based cultivation of seaweeds can provide high biomass yields, low construction, operation, and maintenance costs and could offer an environmentally and economically sustainable alternative to land-based cultivations. The biochemical profile of sea-grown biomass depends on seasonal variation in environmental factors, and the optimization of harvest time is important for the quality of the produced biomass. To identify optimal harvest times of Swedish sea-based cultivated sea lettuce (Ulva fenestrata), this study monitored biomass yield, morphology, chemical composition, fertility, and biofouling at five different harvesting times in April - June 2020. The highest biomass yields (approx. 1.2 kg fw [m rope]-1) were observed in late spring (May). The number and size of holes in the thalli and the amount of fertile and fouled tissue increased with prolonged growth season, which together led to a significant decline in both biomass yield and quality during summer (June). Early spring (April) conditions were optimal for obtaining high fatty acid, protein, biochar, phenolic, and pigment contents in the biomass, whereas carbohydrate and ash content, as well as essential and non-essential elements, increased later in the growth season. Our study results show that the optimal harvest time of sea-based cultivated U. fenestrata depends on the downstream application of the biomass and must be carefully selected to balance yield, quality, and desired biochemical contents to maximize the output of future sea-based algal cultivations in the European Northern Hemisphere.
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| 2. |
- Amiandamhen, Stephen, 1983-, et al.
(författare)
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Bioenergy production and utilization in different sectors in Sweden: A state of the art review
- 2020
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Ingår i: BioResources. - : University of North Carolina Press. - 1930-2126. ; 15:4, s. 9834-9857
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Forskningsöversikt (refereegranskat)abstract
- In the continual desire to reduce the environmental footprints of human activities, research efforts to provide cleaner energy is increasingly becoming vital. The effect of climate change on present and future existence, sustainable processes, and utilizations of renewable resources have been active topics within international discourse. In order to reduce the greenhouse gases emissions from traditional materials and processes, there has been a shift to more environmental friendly alternatives. The conversion of biomass to bioenergy, including biofuels has been considered to contribute to the future of climate change mitigation, although there are concerns about carbon balance from forest utilization. Bioenergy accounts for more than one-third of all energy used in Sweden and biomass has provided about 60% of the fuel for district heating. Apart from heat and electricity supply, the transport sector, with about 30% of global energy use, has a significant role in a sustainable bioenergy system. This review presents the state of the art in the Swedish bioenergy sector based on literature and Swedish Energy Agency’s current statistics. The review also discusses the overall bioenergy production and utilization in different sectors in Sweden. The current potential, challenges, and environmental considerations of bioenergy production are also discussed.
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| 3. |
- Cowie, A. L., et al.
(författare)
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Applying a science-based systems perspective to dispel misconceptions about climate effects of forest bioenergy
- 2021
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Ingår i: Global Change Biology Bioenergy. - : John Wiley and Sons Inc. - 1757-1693 .- 1757-1707. ; 13:8, s. 1210-1231
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Tidskriftsartikel (refereegranskat)abstract
- The scientific literature contains contrasting findings about the climate effects of forest bioenergy, partly due to the wide diversity of bioenergy systems and associated contexts, but also due to differences in assessment methods. The climate effects of bioenergy must be accurately assessed to inform policy-making, but the complexity of bioenergy systems and associated land, industry and energy systems raises challenges for assessment. We examine misconceptions about climate effects of forest bioenergy and discuss important considerations in assessing these effects and devising measures to incentivize sustainable bioenergy as a component of climate policy. The temporal and spatial system boundary and the reference (counterfactual) scenarios are key methodology choices that strongly influence results. Focussing on carbon balances of individual forest stands and comparing emissions at the point of combustion neglect system-level interactions that influence the climate effects of forest bioenergy. We highlight the need for a systems approach, in assessing options and developing policy for forest bioenergy that: (1) considers the whole life cycle of bioenergy systems, including effects of the associated forest management and harvesting on landscape carbon balances; (2) identifies how forest bioenergy can best be deployed to support energy system transformation required to achieve climate goals; and (3) incentivizes those forest bioenergy systems that augment the mitigation value of the forest sector as a whole. Emphasis on short-term emissions reduction targets can lead to decisions that make medium- to long-term climate goals more difficult to achieve. The most important climate change mitigation measure is the transformation of energy, industry and transport systems so that fossil carbon remains underground. Narrow perspectives obscure the significant role that bioenergy can play by displacing fossil fuels now, and supporting energy system transition. Greater transparency and consistency is needed in greenhouse gas reporting and accounting related to bioenergy.
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| 4. |
- Nickel, David, 1990
(författare)
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Process development for platform chemical production from agricultural and forestry residues
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As part of a bio-based economy, biorefineries are envisaged to sustainably produce platform chemicals via biochemical conversion of agricultural and forestry residues. However, supply risks, the recalcitrance of lignocellulosic biomass, and inhibitor formation during pretreatment impair the economic feasibility of such biorefineries. In this thesis, process design and assessment were developed with the aim of addressing these hurdles and improving the cost-effectiveness of lignocellulose-derived platform chemicals. To expand the feedstock base and reduce operational costs, logging residues served as underutilised and inexpensive raw material. The major impediment in converting logging residues was their high recalcitrance and low cellulose content, which resulted in low attainable ethanol titres during simultaneous saccharification and co-fermentation (SSCF). Pretreatment optimisation reduced inhibitor formation and recalcitrance, and led to enzymatic hydrolysis yields at par with those obtained for stem wood, despite the less favourable chemical composition. Upgrading logging residues with carbohydrate-rich oat hulls increased ethanol titres to >50 g/L using batch SSCF at 20% WIS loadings, demonstrating the potential to further decrease downstream processing costs. To alleviate the toxicity of inhibitors generated during pretreatment, preadaptation was applied to Saccharomyces cerevisiae . Exposure to the inhibitors in the pretreated liquid fraction improved ethanol production during subsequent fermentation. Transferring the concept of preadaptation to lactic acid production by Bacillus coagulans cut the process times by half and more than doubled the average specific lactic acid productivity, showcasing how preadaptation could decrease operational costs. To assess the performance and robustness of process designs against process input variations, a multi-scale variability analysis framework was developed. The framework included models for bioprocess, flowsheet, techno-economic, and life cycle assessment. In a case study, multi-feed processes, in which solids and cells are fed to the process using model-based predictions, were more robust against variable cellulolytic activities than batch SSCFs in a wheat straw-based ethanol biorefinery. The developed framework can be used to identify robust biorefinery process designs, which simultaneously meet technological, economic, and environmental goals.
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| 5. |
- Spetea, Cornelia, 1968
(författare)
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Energy-efficient cultivation of marine microalgae for biomass production : Final rapport: Energimyndigheten P45907-1
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This project has demonstrated the principle of rotational cultivation of marine microalgae and that species adapted to cold climates can provide higher productivity during cold periods. By using marine species, and thus seawater instead of freshwater in cultivation, the environmental impact is reduced. Society faces major challenges to produce sufficient amounts of biomass for energy and material, and microalgae have a great potential to complement sources from forestry and agriculture. At Nordic latitudes year-round microalgae cultivation is debatable due to seasonal variations in productivity. Shall the same species be used throughout the year or shall seasonal-adapted species be used? The aims of the project were to identify suitable algal strains for a potential annual rotation model, where different strains are rotated during three cultivation seasons, and to further develop and optimize an energy-efficient cultivation process for the marine environment. To achieve these aims, a laboratory study was performed where two marine microalgal strains out of 167 were selected for intended cultivation at the west coast of Sweden. One strain belongs to the species Nannochloropsis granulata and the other to Skeletonema marinoi. The strains were cultivated in three simulated growth seasons: summer, winter and spring, and thereafter compared. We show that Nannochloropsis produced more biomass with more incorporated energy in lipids during summer and spring (25 MJ kg-1 compared to about 45 MJ kg-1 for diesel), whereas Skeletonema produced more biomass rich in carbohydrates and proteins during winter. Skeletonema was in general more efficient in taking up phosphate. Based on our results, biomass production as energy feedstock would be energy efficient only during the summer on the Swedish west coast. Nevertheless, species could be rotated for different purposes during the year. Biomass production could be combined with nutrient recycling of wastewater, for example, from fish industry. Our project faces a challenge in boosting the biomass produced in winter, but this could be solved, for example, by optimization of the cultivation medium and temperature increase with heat wastewater or other heat waste. The summer species Nannochloropsis proved to withstand winter by activating different lipid metabolic pathways than the cold-adapted species Skeletonema uses. Enhanced synthesis of proteins, such as enzymes, in Skeletonema during winter may compensate for their reduced activities, promoting growth and biomass production even at low temperatures. More species need to be studied to find those with higher productivity under winter conditions. In practice, the work-related consequences of a rotational cultivation should be weighed against its benefits, relative to a shorter cultivation season in each application. Potential applications mainly include cleaning of air and seawater, production of energy, biomass and biomaterials for the industry.
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| 6. |
- Andersson, Viktor, 1983, et al.
(författare)
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Alkali interactions with a calcium manganite oxygen carrier used in chemical looping combustion
- 2022
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 227
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Tidskriftsartikel (refereegranskat)abstract
- Chemical-Looping Combustion (CLC) of biofuels is a promising technology for cost-efficient CO2 separation and can lead to negative CO2 emissions when combined with carbon capture and storage. A potential challenge in developing CLC technology is the effects of alkali metal-containing compounds released during fuel conversion. This study investigates the interactions between alkali and an oxygen carrier (OC), CaMn0.775Ti0.125Mg0.1O3-δ, to better understand the fate of alkali in CLC. A laboratory-scale fluidized bed reactor is operated at 800–900 °C in oxidizing, reducing and inert atmospheres to mimic CLC conditions. Alkali is fed to the reactor as aerosol KCl particles, and alkali in the exhaust is measured online with a surface ionization detector. The alkali concentration changes with gas environment, temperature, and alkali loading, and the concentration profile has excellent reproducibility over repeated redox cycles. Alkali-OC interactions are dominated by alkali uptake under most conditions, except for a release during OC reduction. Uptake is significant during stable reducing conditions, and is limited under oxidizing conditions. The total uptake during a redox cycle is favored by a high alkali loading, while the influence of temperature is weak. The implications for the understanding of alkali behavior in CLC and further development are discussed.
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| 7. |
- Cao, Wenhan, et al.
(författare)
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Release of potassium in association with structural evolution during biomass combustion
- 2021
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Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 287, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- A mechanistic understanding of potassium release is essential to mitigate the potassium-induced ash problems during biomass combustion. This work studies the effects of operational condition on the potassium release and transition during the combustion of wheat straw, and elucidate the release potential of potassium associated with the structural change of biomass particles. The combustion tests were carried out in a laboratory-scale reactor, working in a wide range of temperatures and heating rates. It was found that the combustion of biomass sample at a temperature up to 1000 °C results in a release of over 60% of its initial potassium content. Raising the heating rate from 8 °C/min to 25 °C/min could lead to an additional release of up to 20% of the initial amount of potassium. A three-stage potassium release mechanism has been concluded from this work: the initial-step release stage (below 400 °C), the holding stage (400–700 °C) and the second-step release stage (above 700 °C). Comprehensive morphology analysis with elemental (i.e. K, S, O, Si) distribution was carried out; the results further confirmed that potassium is likely to exist inside the stem-like tunnel of biomass particles, mainly in forms of inorganic salts. During the heating-up process, the breakdown and collapse of biomass particle structure could expose the internally located potassium and thus accelerate the release of potassium and the transform of its existing forms. Lastly, a detailed temperature-dependent release mechanism of potassium was proposed, which could be used as the guidance to mitigate the release of detrimental potassium compounds by optimising the combustion process.
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| 8. |
- Cintas Sanchez, Olivia, 1982, et al.
(författare)
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Geospatial supply-demand modeling of lignocellulosic biomass for electricity and biofuels in the European Union
- 2021
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 144
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Tidskriftsartikel (refereegranskat)abstract
- Bioenergy can contribute to achieving European Union (EU) climate targets while mitigating impacts from current agricultural land use. A GIS-based modeling framework (1000 m resolution) is employed to match biomass supply (forest and agricultural residues, complemented by lignocellulosic energy crops where needed) with biomass demand for either electricity or bio-oil production on sites currently used for coal power in the EU-28, Norway, and Switzerland. The framework matches supply and demand based on minimizing the field-to-gate costs and is used to provide geographically explicit information on (i) plant-gate supply cost; (ii) CO2 savings; and (iii) potential mitigation opportunities for soil erosion, flooding, and eutrophication resulting from the introduction of energy crops on cropland. Converting all suitable coal power plants to biomass and assuming that biomass is sourced within a transport distance of 300 km, would produce an estimated 150 TW h biomass-derived electricity, using 1365 PJ biomass, including biomass from energy crops grown on 6 Mha. Using all existing coal power sites for bio-oil production in 100-MW pyrolysis units could produce 820 PJ of bio-oil, using 1260 PJ biomass, including biomass from energy crops grown on 1.8 Mha. Using biomass to generate electricity would correspond to an emissions reduction of 135 MtCO2, while using biomass to produce bio-oil to substitute for crude oil would correspond to a reduction of 59 MtCO2. In addition, energy crops can have a positive effect on soil organic carbon in most of the analyzed countries. The mitigation opportunities investigated range from marginal to high depending on location.
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| 9. |
- Englund, Oskar, et al.
(författare)
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Multifunctional perennial production systems for bioenergy: performance and progress
- 2020
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Ingår i: Wiley Interdisciplinary Reviews. - : Wiley. - 2041-8396 .- 2041-840X.
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Tidskriftsartikel (refereegranskat)abstract
- As the global population increases and becomes more affluent, biomass demands for food and biomaterials will increase. Demand growth is further accelerated by the implementation of climate policies and strategies to replace fossil resources with biomass. There are, however, concerns about the size of the prospective biomass demand and the environmental and social consequences of the corresponding resource mobilization, especially concerning impacts from the associated land-use change. Strategically integrating perennials into landscapes dominated by intensive agriculture can, for example, improve biodiversity, reduce soil erosion and nutrient emissions to water, increase soil carbon, enhance pollination, and avoid or mitigate flooding events. Such ?multifunctional perennial production systems? can thus contribute to improving overall land-use sustainability, while maintaining or increasing overall biomass productivity in the landscape. Seven different cases in different world regions are here reviewed to exemplify and evaluate (a) multifunctional production systems that have been established to meet emerging bioenergy demands, and (b) efforts to identify locations where the establishment of perennial crops will be particularly beneficial. An important barrier towards wider implementation of multifunctional systems is the lack of markets, or policies, compensating producers for enhanced ecosystem services and other environmental benefits. This deficiency is particularly important since prices for fossil-based fuels are low relative to bioenergy production costs. Without such compensation, multifunctional perennial production systems will be unlikely to contribute to the development of a sustainable bioeconomy.
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| 10. |
- Perruca Foncillas, Raquel
(författare)
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Evaluation of biosensors and flow cytometry as monitoring tools in lignocellulosic bioethanol production
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The significant environmental impact of the current fossil fuel-based industry is a major concern for society. Consequently, various initiatives are being undertaken to establish a more sustainable industrial model. One example is via the transition from conventional fossil fuel refineries to biorefineries, where renewable raw materials are utilised. Amongst these raw materials, the use of lignocellulosic biomass from agricultural residues or wood has been favoured, as it does not compete with food or land resources. In particular, extensive research has been conducted to produce biofuels such as bioethanol from lignocellulosic biomass, referred to as second-generation (2G) bioethanol.In this thesis work, the goal was to develop and apply new tools to address challenges encountered in 2G bioethanol production. Specifically, the work focused on monitoring the impact of inhibitory compounds and mixed sugars on the fermentation performance of the yeast Saccharomyces cerevisiae.Inhibitory compounds are released during the pretreatment of the lignocellulosic biomass, a crucial step necessary to break down its complex structure and to enhance sugar accessibility This thesis work specifically focused on the redox imbalance induced in cells exposed to furaldehydes such as furfural or HMF. To study this effect, a biosensor for redox imbalance, TRX2p-yEGFP, was introduced into the cells and its fluorescence signal was monitored in real-time using flow cytometry. One potential strategy for enhancing the cells' tolerance to these inhibitors is to prepare them by introducing lignocellulosic hydrolysate in the feed during cell propagation. During this pre-exposure phase, a transient induction of the TRX2p-yEGFP biosensor signal for redox imbalance was observed, which gradually diminished. This indicated that, by the time of cell collection, the cells had adapted to the inhibitor concentration within the culture. To examine whether an increased induction level of the biosensor at the time of cell collection influenced the fermentation performance, an automated control system was devised. This system utilised data from the flow cytometry analysis to control the level of inhibitors in the cultivation feed. Consequently, when the biosensor signal began to decline, higher amounts of inhibitors were added, as long as the addition did not lead to an increase in the number of damaged cells.A second biosensor was used in this thesis work to investigate the sugar signalling response of S. cerevisiae to the presence of xylose. Xylose is the second most abundant sugar in lignocellulosic biomass; however, naturally, S. cerevisiae cannot metabolise it. Genetically modified S. cerevisiae strains have been generated by introducing heterologous pathways such as the XR/XDH or XI pathways to enable xylose consumption. Nevertheless, xylose consumption rates remain lower compared to glucose. Sugar signalling emerged as a potential bottleneck in the efficient utilisation of xylose. In the present work, the response of the SUC2p-yEGFP biosensor for sugar signalling was found to vary significantly depending on the pathway employed. A higher induction for the strains carrying the XI pathway was associated with poorer growth on xylose. Lastly, the effect of introducing a xylose epimerase capable of catalysing the conversion between the two anomers, α-D-xylopyranose and β-D-xylopyranose, as a strategy to improve xylose consumption was studied. The effect was enzyme-specific and proved to be particularly beneficial in strains utilising the xylose isomerase from Lachnoclostridium phytofermentans.In conclusion, the results presented in this thesis demonstrate how biosensors can facilitate the understanding and monitoring of intracellular processes that occur within the cell under stress conditions and be a key tool for improving production processes.
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