| 1. |
- Mukesh Kumar, Awasthi, et al.
(författare)
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Bacterial dynamics during the anaerobic digestion of toxic citrus fruit waste and semi-continues volatile fatty acids production in membrane bioreactors
- 2022
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Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 319
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Tidskriftsartikel (refereegranskat)abstract
- Citrus wastes (CW) are normally toxic to anaerobic digestion (AD) because of flavors such as D-limonene. In this study, bacterial community was evaluated during volatile fatty acids (VFAs) production from CW inoculated by sludge in a membrane bioreactor (MBR) using semi-continuous AD with different organic loading rates (OLR). Four treatments including untreated CW filled with 4 and 8 g center dot VS center dot L(-1)d(-1) OLR (UOLR4 and UOLR8), pretreated Dlimonene-free CW filled with 4 and 8 g center dot VS center dot L(-1)d(-1) OLR (POLR4 and POLR8). The initial inoculum and the CW mixture (DAY0) was used as control for comparison. There was an obviously higher bacterial diversity in raw material (66848 sequences in DAY0), while decreased after AD and higher in POLR4 and POLR8 (65239 and 63916) than UOLR4 and UOLR8 (49158 and 51936). The key bacterial associated with VFAs production mainly affiliated to Firmicutes (37.35-84.73%), Bacteroidetes (0.48-36.87%), and Actinobacteria (0.35-29.38%), and the key genus composed of Lactobacillus, Prevotella, Bacillus, Bacteroides and Olsenella which contributed in VFA generation by degradable complex organic compounds. Noticeably, methanogen completely suppressed after MBR-AD and UOLR4 has greater acid utilizing bacteria (70.09%).
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| 2. |
- 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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| 3. |
- 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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| 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. |
- Gustafsson, Marcus, 1987-, et al.
(författare)
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Climate performance of liquefied biomethane with carbon dioxide utilization or storage
- 2024
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Ingår i: Renewable and sustainable energy reviews. - : Elsevier. - 1364-0321 .- 1879-0690. ; 192
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Tidskriftsartikel (refereegranskat)abstract
- In the process of upgrading biogas to biomethane for gas grid injection or use as a vehicle fuel, biogenic carbon dioxide (CO₂) is separated and normally emitted to the atmosphere. Meanwhile, there are a number of ways of utilizing CO₂ to reduce the dependency on fossil carbon sources. This article assesses the climate performance of liquefied biomethane for road transport with different options for utilization or storage of CO₂. The analysis is done from a life cycle perspective, covering the required and avoided processes from biogas production to the end use of biomethane and CO₂. The results show that all of the studied options for CO₂ utilization can improve the climate performance of biomethane, in some cases contributing to negative CO₂ emissions. One of the best options, from a climate impact perspective, is to use the CO₂ internally to produce more methane, although continuous supply of hydrogen from renewable sources can be a challenge. Another option that stands out is concrete curing, where CO₂ can both replace conventional steam curing and be stored for a long time in mineral form. Storing CO₂ in geological formations can also lead to negative CO₂ emissions. However, with such long-term storage solutions, opportunities to recycle biogenic CO₂ are lost, together with the possibility of de-fossilizing processes that require carbon, such as chemical production and horticulture.
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| 6. |
- Persson, Michael
(författare)
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Integrated starch and lignocellulose based biorefineries : Synergies and opportunities
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The transition from a reliance on fossil resources to the use of renewables for the production of energy, fuels and chemicals is essential for ensuring the sustainability of continued human development. Plant-based biomass is a renewable resource which can be transformed into all of these products. However, biomass is a heterogeneous material composed of several fractions with different chemical properties. Furthermore, the composition varies between species. In order to maximize the environmental and economic sustainability of biomass-based production, production systems that utilize all fractions of biomass to their fullest potential have to be developed. This is the goal of a biorefinery.The work presented in this thesis mainly revolves around biorefineries that utilize feedstocks rich in starch and lignocellulose together to produce ethanol in an integrated process. The work is focused on comparing the performance of stand-alone and integrated biorefineries by investigating the impact that feedstock blending has on parameters important for the process economy, identifying potential synergies from integration and opportunities for improved material utilization.It was found in this work, that the integration of starch- and lignocellulose-based feedstocks could result in improved ethanol productivity and yield during hydrolysis and fermentation compared to a stand-alone lignocellulose process without losing performance compared to a stand-alone starch-based process.The prospects of introducing a sequential fractionation of the lignocellulosic biomass prior to integration was investigated. It was shown that this method could be used to produce separate fractions enriched in cellulose and lignin as well as improving the hydrolyzabilty of the cellulose fraction. This kind of fractionation could facility the utilization of all biomass fractions in both feedstocks by creating new byproduct streams as well as decreasing negative impacts on existing byproduct streams.
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| 7. |
- Gustafsson, Marcus, 1987-, et al.
(författare)
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Värdeskapande av koldioxid från biogasproduktion
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Koldioxid (CO₂) har en negativ påverkan på klimatet, men har även många praktiska användningsområden. Många industriella processer släpper ut CO₂ i höga koncentrationer som skulle kunna fångas in för att begränsa emissioner och samtidigt skapa värdefulla produkter. Ett exempel på en sådan process är biogasuppgradering – en separationsprocess av förnybara gaser, där metan tas till vara för användning som fordonsbränsle eller energibärare inom industri, medan CO₂ släpps ut i atmosfären. Syftet med detta projekt har varit att kartlägga möjligheter och tekniker för att tillvarata grön CO₂ från biogasproduktion, så kallad carbon capture and utilization (CCU), samt att utreda förutsättningar för att tillämpa dessa i en svensk kontext. Arbetet har vägletts av följande frågeställningar:Hur stor är den nuvarande och framtida potentialen för CCU från biogasproduktion?Vilka möjliga användningsområden finns det för CO₂ från biogasproduktion?Vilka faktorer påverkar valet av användningsområde för CO₂ från biogasproduktion?Hur stor är den miljömässiga nyttan av CCU från biogasproduktion?För att besvara dessa frågeställningar genomfördes potentialberäkningar, multikriterieanalys och livscykelanalys, med utgångspunkt i svensk biogasproduktion. En referensgrupp bestående av representanter för stora svenska företag inom biogasproduktion och teknik för biogasuppgradering användes för att möjliggöra samproduktion och nätverkande mellan forskargruppen och branschen.Produktionen av CO₂ från biogas uppskattades till 160 000 ton/år 2020, med potential att öka till 540 000 – 840 000 ton/år på medellång sikt och 790 000 – 1 230 000 ton/år på lång sikt, som en följd av en förmodad ökning av biogasproduktionen i Sverige. En stor del av koldioxiden produceras dock vid relativt små uppgraderingsanläggningar, vilket kan begränsa möjligheten att tillämpa CCU på grund av höga investerings- och driftskostnader. Att tillföra vätgas för att omvandla all CO₂ till metan skulle potentiellt kunna öka metanproduktionen från biogas från 2 till 3 TWh/år på kort sikt och från 11 till 17 TWh/år på lång sikt, förutsatt tillräckligt stor tillgång på vätgas.Andra sätt att använda CO₂ från biogas innefattar bland annat produktion av biomassa eller kemikalier, härdning av betong, pH-reglering av processvatten och användning som köldmedium. Valet av CCU- alternativ kan påverkas av miljömässiga, tekniska, ekonomiska och policyrelaterade aspekter. Ur biogasproducenternas perspektiv är metanisering det som är mest kompatibelt med det befintliga produktionssystemet och affärsmodellen, medan andra lösningar oftast innebär att en annan aktör tar hand om koldioxiden. Vätgas behövs för såväl metanisering som produktion av kemikalier. En annan begränsande faktor är höga renhetskrav på all CO₂ som distribueras och säljs på marknaden. Den geografiska spridningen på anläggningarna kan också vara en utmaning.Många CCU-alternativ kan förbättra biogasens miljöprestanda genom att ersätta fossilbaserade produkter. Klimatpåverkan blir lägst om koldioxiden metaniseras med förnybar vätgas eller mineraliseras i betong, men även andra former av miljöpåverkan kan minskas genom att tillämpa dessa eller andra CCU-alternativ. Som jämförelse kan permanent lagring av CO₂ i geologiska formationer (carbon capture and storage, CCS) endast minska klimatpåverkan, medan det ökar övriga typer av miljöpåverkan. Samtidigt kan permanent lagring av biogen CO₂ göra det svårare att minska användningen av fossil CO₂ och ställa om till ett mer hållbart samhälle. Behovet av kol i många viktiga processer och produkter talar för att biogen CO₂ bör användas och inte lagras.
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| 8. |
- Marhendraswari, M. B.D., et al.
(författare)
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Production of edible fungal (Rhizopus delemar CBS 145940) biomass from organosolv-pretreated oil palm empty fruit bunch (OPEFB) in submerged fermentation
- 2020
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Ingår i: IOP Conference Series: Materials Science and Engineering. - : Institute of Physics (IOP). - 1757-8981 .- 1757-899X. ; 991:1
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Konferensbidrag (refereegranskat)abstract
- Accumulation of oil palm empty fruit bunches (OPEFB) from palm oil industry poses challenges for the disposal process, which leads to environmental damage. For this reason, valorization of OPEFB fractions to produce edible fungal biomass was carried out in this research. The fungus was Rhizopus delemar CBS 145940, which is an edible fungus, Indonesian indigenous, and is favorable for the production of several end products. Organosolv pretreatment was first conducted on OPEFB using ethanol (50%) as the solvent. Enzymatic hydrolysis was then performed using Cellic® Ctec3 on the pretreated-OPEFB fractions. Hydrolyzates from cellulose-rich fraction, slurry (a mixture of cellulose-rich fraction and hemicellulose-rich fraction), and hemicellulose-rich fraction were used as the cultivation media for fungal growth. The corresponding yield of fungal biomass from each medium was 0.62 ± 0.07 g/g glucose; 0.41 ± 0.02; and 0.61 ± 0.13 g/g fermentable sugars, respectively. These results showed that Rhizopus delemar CBS 145940 could be grown in all the hydrolyzates from the OPEFB fractions. Nevertheless, in order to obtain higher fungal biomass, supplementation of nutrition was needed.
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| 9. |
- Mei, Daofeng, 1986, et al.
(författare)
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Investigation of LD-slag as oxygen carrier for CLC in a 10 kW unit using high-volatile biomasses
- 2023
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier Ltd. - 1750-5836 .- 1878-0148. ; 127
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Tidskriftsartikel (refereegranskat)abstract
- A steel slag from the Linz-Donawitz process, called LD-slag, having significant calcium and iron-fractions, was investigated as an oxygen carrier in a recently developed 10 kWth chemical-looping combustor with three high-volatile biomass fuels. In order to improve operability, the LD-slag was found to require heat-treatment at high temperatures before being used in the unit. In total, operation with the biomasses was conducted for more than 26 h at temperatures of 870–980 °C. The fuel thermal power was in the range of 3.4–10 kWth. The operation involved chemical looping combustion (CLC), chemical looping gasification (CLG) and oxygen carrier aided combustion (OCAC). Around 12 h was in CLC operation, 13.3 h was conducted in CLG-conditions, while the remaining 0.7 h was OCAC. Here, the results obtained during the CLC part of the campaign is reported. Increased temperature in the fuel reactor and higher airflows to the air reactor both lead to better combustion performance. Steam concentration in the fuel reactor has little effect on the performance. The LD-slag showed higher oxygen demand (31.0%) than that with ilmenite (21.5%) and a manganese ore (19.5%) with the same fuel and normal solids circulation. However, with the LD-slag, there is possibility to achieve a lower oxygen demand (15.2%) with high solids circulation. © 2023 The Author(s)
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| 10. |
- 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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