| 1. |
- Bajracharya, Suman, et al.
(författare)
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Prime Techniques for Pre- and Post-Treatments of Anaerobic Effluents and Solids
- 2020
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Ingår i: Environmental Microbiology and Biotechnology. - Singapore : Springer Nature. ; , s. 255-289
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Several pre-treatment approaches have been explored to enhance the anaerobic fermentation kinetics and efficiency, which include thermal-alkaline treatment, free ammonia, sequential ultrasound techniques as well as grinding, and sieving. Additionally, valorization of mineralized compounds and production of reusable water can also be achieved via post-treatments. The post-treatment concept allows preserving or recovery of value-added byproducts in the form of manures, soil conditioners, and renewable energy. In this chapter, we explain the recent advancement in the pre-treatment and post-treatment of anaerobic digestate to enhance the anaerobic process and for the removal of undesirable compounds, recovery of energy, nutrients, and waste stabilization before disposal.
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| 2. |
- Bauer, Torben, et al.
(författare)
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Co-digestion of sewage sludge and wood fly ash
- 2022
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Ingår i: Environmental technology. - : Taylor & Francis. - 0959-3330 .- 1479-487X. ; 43:12, s. 1853-1859
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Tidskriftsartikel (refereegranskat)abstract
- This study uses a new approach for the recycling of plant nutrients by co-digesting sewage sludgewith fly ash from a wood combustion. Sewage sludge and fly ash both are enriched with nutrientsof the wastewater resp. wood, which makes these products an enhanced source for recycledfertilizers. The effects of the ash addition to the anaerobic digestion are studied in several labscale experiments including effects on the gas production and microbial activity. Following that,the fertilizing qualities of the digestate are evaluated by plant growth experiments. The resultsshow that the fertilizing qualities of the digested sludge were improved by the ash addition.Next to this, gas production results show that the methane production was not affected by theash addition, while the total gas release was reduced. The sulphur addition by the ashstimulated sulphate reducing bacteria. The sulphate reducing bacteria did not markedly inhibitthe methanogens.
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| 3. |
- Das, Oisik, et al.
(författare)
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Naturally-occurring bromophenol to develop fire retardant gluten biopolymers
- 2020
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Ingår i: Journal of Cleaner Production. - : Elsevier. - 0959-6526 .- 1879-1786. ; 243
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to impart fire retardancy in wheat gluten polymer through naturally-occurring additives such as lanosol. The fire properties of lanosol were compared with two other conventional brominated fire retardants (Tetrabromobisphenol A and Hexabromocyclododecane). Samples containing fire retardants and gluten were prepared through compression moulding process and then characterised for their fire and mechanical properties. All fire retardants enhanced the reaction-to-fire and thermal properties of gluten while generating V-0 (i.e. vertical position and self-extinguished) ratings in the UL-94 test. The presence of all the fire retardants increased the modulus of the gluten polymer but the fire retardant particles were detrimental for the tensile strength. Nevertheless, lanosol addition delayed ignition and lowered peak heat release rate of gluten by the maximum amount, thereby leading to relatively higher fire performance index (compared to the other fire retardants). Lanosol also allowed the gluten to create a dense char barrier layer during burning that impeded the transfer of heat and flammable volatiles. The fact that only 4 wt% lanosol was able to cause self-extinguishment under direct flame and reduce peak heat release rate by a significant 50% coupled with its inherent occurrence in nature, raises the question if lanosol can be a potential fire retardant in polymeric systems, although it is a bromophenol.
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| 4. |
- Krige, Adolf, 1990-
(författare)
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Microbial Fuel cells, applications and biofilm characterization
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Since the 1900’s it has been known that microorganisms are capable of generating electrical power through extracellular electron transfer by converting the energy found organic compounds (Potter, 1911). Microbial fuel cells (MFCs) has garnered more attention recently, and have shown promise in several applications, including wastewater treatment (Yakar et al., 2018), bioremediation (Rosenbaum & Franks, 2014), biosensors (ElMekawy et al., 2018) desalination (Zhang et al., 2018) and as an alternative renewable energy source in remote areas (Castro et al., 2014). In MFCs catalytic reactions of microorganisms oxidize an electron donor through extracellular electron transfer to the anode, under anaerobic conditions, with the cathode exposed to an electron acceptor, facilitating an electrical current (Zhuwei, Haoran & Tingyue, 2007; Lovley, 2006). For energy production in remote areas a low cost and easily accessible feed stock is required for the MFCs. Sweet sorghum is a drought tolerant feedstock with high biomass and sugar yields, good water-use efficiency, established production systems and the potential for genetic improvements. Because of these advantages sweet sorghum stalks were proposed as an attractive feedstock (Rooney et al., 2010; Matsakas & Christakopoulos, 2013). Dried sweet sorghum stalks were, therefore, tested as a raw material for power generation in a MFC, with anaerobic sludge from a biogas plant as inoculum (Sjöblom et al., 2017a).Using sorghum stalks the maximum voltage obtained was 546±10 mV, the maximum power and current density of 131±8 mW/m2 and 543±29 mA/m2 respectively and the coulombic efficiency was 2.2±0.5%. The Ohmic resistances were dominant, at an internal resistance of 182±17 Ω, calculated from polarization data. Furthermore, hydrolysis of the dried sorghum stalks did not improve the performance of the MFC but slightly increased the total energy per gram of substrate. During the MFC operation, the sugars were quickly fermented to formate, acetate, butyrate, lactate and propionate with acetate and butyrate being the key acids during electricity generation.Efficient electron transfer between the microorganisms and the electrodes is an essential aspect of bio-electrochemical systems such as microbial fuel cells. In order to design more efficient reactors and to modify microorganisms, for enhanced electricity production, understanding the mechanisms and dynamics of the electron transport chain is important. It has been found that outer membrane C-type cytochromes (OMCs) (including omcS and omcZ discussed in this study) play a key role in the electron transport chain of Geobacter sulfurreducens, a well-known, biofilm forming, electro-active microorganism (Millo et al., 2011; Lovley, 2008). It was found that Raman microscopy is capable of providing biochemical information, i.e., the redox state of c-type cytochromes (cyt-C) without damaging the microbial biofilm, allowing for in-situ observation.Raman microscopy was used to observe the oxidation state of OMCs in a suspended culture, as well as in a biofilm of an MFC. First, the oxidation state of the OMCs of suspended cultures from three G. sulfurreducens strains (PCA, KN400 and ΔpilA) was analyzed. It was found that the oxidation state can also be used as an indicator of the metabolic state of the cells, and it was confirmed that PilA, a structural pilin protein essential for long range electron transfer, is not required for external electron transfer. Furthermore, we designed a continuous, anaerobic MFC enabling in-situ Raman measurements of G. sulfurreducens biofilms during electricity generation, while poised using a potentiostat, in order to monitor and characterize the biofilm. Two strains were used, a wild strain, PCA, and a mutant, ΔOmcS. The cytochrome redox state, observed through the Raman spectra, could be altered by applying different poise voltages to the electrodes. This change was indirectly proportional to the modulation of current transferred from the cytochromes to the electrode. This change in Raman peak area was reproducible and reversible, indicating that the system could be used, in-situ, to analyze the oxidation state of proteins responsible for the electron transfer process and the kinetics thereof.
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| 5. |
- Ahmed, Tahmeed, et al.
(författare)
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Evaluation of the impacts of seawater integration to electrocoagulation for the removal of pollutants from textile wastewater
- 2024
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Ingår i: Environmental Sciences Europe. - : Springer Nature. - 2190-4707 .- 2190-4715. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- Recent textile industry expansion has a major environmental impact if not addressed. Being a water intensive industry, textile manufacturing is usually associated with wastewater management challenges. Electrocoagulation (EC) is recognized as one of the effective solutions to address these challenges. This study aims to investigate the potential of integrating seawater into the EC process for textile wastewater treatment, targeting optimal pollutant removal efficiencies. A simple electrolytic reactor was designed to investigate the removal efficiency of these treatments for chemical oxygen demand (COD), total suspended solids (TSS), turbidity, and color from textile wastewater at different seawater percentages and retention times. Notably, the addition of seawater not only improves the EC process efficiency but also significantly dilutes pollutants, reducing their concentrations. This dual effect enhances removal efficiency and dilution optimizes the treatment outcome. The highest removal efficiencies were achieved for COD (47.26%), TSS (99.52%), turbidity (99.30%), and color (98.19%). However, pH, dissolved oxygen (DO), and electrical conductivity increased with increasing retention times and seawater percentages in the EC process. Moreover, Seawater − EC integration reduces power usage to 15.769 Am−2 and costs approximately 0.20 USD/m3. To assess the effects of the retention times and seawater percentages on pollutant removal from textile wastewater, an analysis of variance (ANOVA) was conducted utilizing the Design-Expert 11 software. The best model obtained using Central Composite Design (CCD) was quadratic for COD (R2 = 0.9121), color (R2 = 0.9535), turbidity (R2 = 0.9525), and TSS (R2 = 0.9433). This study suggests that higher seawater percentages and longer retention times effectively eliminate contaminants but increase ion concentrations.
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| 6. |
- Börjesson, Martin, 1980, et al.
(författare)
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Bioenergy futures in Sweden - system effects of CO2 reduction and fossil fuel phase-out policies
- 2015
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Ingår i: GCB Bioenergy. - : Wiley. - 1757-1707 .- 1757-1693. ; 7:5, s. 1118-1135
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Tidskriftsartikel (refereegranskat)abstract
- Bioenergy could contribute both to the reduction of greenhouse gases and to increased energy security, but the extent of this contribution strongly depends on the cost and potential of biomass resources. For Sweden, this study investigates how the implementation of policies for CO2 reduction and for phase out of fossil fuels in road transport affect the future utilization of biomass, in the stationary energy system and in the transport sector, and its price. The analysis is based on the bottom-up, optimization MARKAL_Sweden model, which includes a comprehensive representation of the national energy system. For the analysis, the biomass supply representation of MARKAL_Sweden is updated and improved by the use of, e.g., forestry forecasting modeling and through construction of detailed biomass supply curves. A time horizon up to 2050 is applied. The results indicate a potential for significantly higher use of bioenergy. In the main analysis scenario, in which CO2 reduction of 80% by 2050 is imposed on the Swedish energy system, the total bioenergy utilization increases by 63% by 2050 compared to 2010. The largest increase occurs in the transport sector, which by 2050 accounts for 43% of the total primary bioenergy use. The high demand and strong competition significantly increase biomass prices and lead to the utilization of higher cost biomass sources such as stumps and cultivated energy forest, as well as use of pulpwood resources for energy purposes.
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| 7. |
- Hellsmark, Hans, 1974, et al.
(författare)
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Innovation policies for advanced biorefinery development: key considerations and lessons from Sweden
- 2017
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Ingår i: Biofuels, Bioproducts and Biorefining. - : Wiley. - 1932-1031 .- 1932-104X. ; 11:1, s. 28-40
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Tidskriftsartikel (refereegranskat)abstract
- This paper provides an innovation systems perspective on the combination of policy instruments that will be required to stimulate technological development in the advanced biorefinery field. We first consult the established innovation policy literature, and provide a general framework that can be used to identify the type of policy instruments needed to develop new sustainable technology. In a second step, we illustrate how these general principles can be applied in the context of future biorefineries based on either the thermochemical or biochemical conversion of lignocellulosic biomass feedstocks. We draw heavily on the experiences of biorefinery development in Sweden. A central conclusion is that in Sweden, and elsewhere, there are few niche markets for advanced biorefineries and a lack of long-term policy instruments for the more established renewable fuels. For this reason, there is a need for innovation policy instruments that create markets for renewable fuels and green chemicals, thus supporting technology development during a niche market phase and allowing for the first commercial-scale plants to be built. The aim of such a policy would be to stimulate learning, form value chains, and experiment with various design options on a larger scale; this complements the use of technology-neutral policy instruments such as carbon pricing, which primarily promotes the diffusion of mature technologies. The policy instruments that are candidates for the niche market phase include, for example, public procurement and various types of price guarantees.
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| 8. |
- Niero, Luisa, et al.
(författare)
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Short hydraulic retention time in methane production from sewage sludge hydrolysate using anaerobic moving-bed biofilm reactors (AnMBBR) under thermophilic and mesophilic conditions
- 2024
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier. - 2213-3437. ; 12:5
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Tidskriftsartikel (refereegranskat)abstract
- The use of anaerobic moving-bed biofilm reactors was investigated for biogas production from the liquid fraction of sewage sludge hydrolysate. Anaerobic digestion requires traditionally long retention times due to the slow growth of methanogens. This work investigated biogas production with 2–3 days retention time under mesophilic (37°C) and thermophilic (50°C) conditions. Two continuous reactors were operated to treat the liquid fraction of hydrolysate sewage sludge for 196 days. The mesophilic reactor showed a more stable performance compared to the thermophilic one. The mesophilic reactor kept the soluble COD removal above 80 % at a volumetric loading rate (VLR) above 7 g COD L−1 d−1, and specific surface loading rate (SARL) above 20 g SCOD m−2 d−1. In contrast, the thermophilic reactor displayed a soluble COD removal above 80 % at an average VLR of 4.2 g COD L-1 d-1, and average SARL of 14 g SCOD m−2 d−1. The biogas from both systems contained 73 % methane. The microbial analysis of the biofilm showed that 36 % of the viable cells were anaerobic microorganisms.
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| 9. |
- Rhén, Christofer, et al.
(författare)
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Effect of raw material composition in woody biomass pellets on combustion characteristics
- 2007
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Ingår i: Biomass and Bioenergy. - Oxford : Pergamon Press. - 0961-9534 .- 1873-2909. ; 31:1, s. 66-72
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Tidskriftsartikel (refereegranskat)abstract
- Char yield, char combustion time and char combustion rate of pellets made from different tree parts of Norway spruce and industrially made stem wood pellets of Norway spruce and Scots pine were studied. The pellets were incinerated in a laboratory scale oven at various temperatures, gas flows and oxygen concentrations. It was found that the combustion time for a single pellet mostly depended on the raw material composition and to a minor extent on the density. Pellets made of bark had up to a 50% longer char combustion time compared to that of stem wood pellets, due to differences in char yield. Industrially made stem wood pellets of pine and spruce sawdust were found to have small differences in combustion characteristics. The variations in combustion characteristics of pellets are discussed in relation to composition of raw material.
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| 10. |
- Öhman, Marcus, et al.
(författare)
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Reasons for slagging during stemwood pellet combustion and some measures for prevention
- 2004
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Ingår i: Biomass and Bioenergy. - Oxford : Pergamon Press. - 0961-9534 .- 1873-2909. ; 27:6, s. 597-605
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Tidskriftsartikel (refereegranskat)abstract
- Ash related problems have more than occasionally been observed in pellet burners during the last years. These problems lead to reduced accessibility of the appliances and also bad publicity for the pellet market. The objectives of the present work were therefore to: (i) determine the critical levels of the problematic ash components in stemwood pellets regarding slagging, (ii) document the variations of these problematic elements in the outgoing pellets from two pellet-mills during one operational season, (iii) determine how frequently these elements exceed the critical levels, (iv) determine how different sub-processes in the pelletising process (especially the dryer) effect the slagging properties of the pellet, and if possible (v) suggest some measures for prevention. A significant number of wood pellets reported to be problematic and problem-free, regarding slagging in ordinary residential pellet burners, were collected from the Swedish market. The ash compositions of these fuels were analysed and the results compiled in a database. Partial Least-Squares Discriminant Analysis (PLS-DA) and F-tests were used to statistically identify both the critical ash components and the critical levels of these components that separated the two reported classes. In addition, chemical equilibrium model calculations were used to interpret the findings. The variations of these elements in the in-going raw material and in the produced pellets were determined during one season in two pellet mills equipped with exhaust gas dryers. The results showed that the problematic wood-pellets had a significantly higher amount of Si, but also Al and Fe, in the fuel ash. The critical level of Si (given as SiO2) was about 20-25 wt% of the fuel ash, i.e. pellets with levels in or over this range resulted in slagging problems in residential burners. This critical Si content was exceeded once and twice for the analysed samples in the two studied pellet mills. In one of the studied mills, this was because of contamination by sand of the raw material during storage and handling, and in the other mill the reason was found to be contamination of the raw material by elutriated particles from the dryer fuel. The major conclusion of the work is that both raw materials and drying fuels/processes should be carefully treated to avoid mineral contamination, and an additional cyclone separator could potentially also be used to improve the pellet quality.
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