| 1. |
- Thomas, HS, et al.
(författare)
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- 2019
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swepub:Mat__t
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| 2. |
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| 3. |
- Drake, TM, et al.
(författare)
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Surgical site infection after gastrointestinal surgery in children: an international, multicentre, prospective cohort study
- 2020
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Ingår i: BMJ global health. - : BMJ. - 2059-7908. ; 5:12
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Tidskriftsartikel (refereegranskat)abstract
- Surgical site infection (SSI) is one of the most common healthcare-associated infections (HAIs). However, there is a lack of data available about SSI in children worldwide, especially from low-income and middle-income countries. This study aimed to estimate the incidence of SSI in children and associations between SSI and morbidity across human development settings.MethodsA multicentre, international, prospective, validated cohort study of children aged under 16 years undergoing clean-contaminated, contaminated or dirty gastrointestinal surgery. Any hospital in the world providing paediatric surgery was eligible to contribute data between January and July 2016. The primary outcome was the incidence of SSI by 30 days. Relationships between explanatory variables and SSI were examined using multilevel logistic regression. Countries were stratified into high development, middle development and low development groups using the United Nations Human Development Index (HDI).ResultsOf 1159 children across 181 hospitals in 51 countries, 523 (45·1%) children were from high HDI, 397 (34·2%) from middle HDI and 239 (20·6%) from low HDI countries. The 30-day SSI rate was 6.3% (33/523) in high HDI, 12·8% (51/397) in middle HDI and 24·7% (59/239) in low HDI countries. SSI was associated with higher incidence of 30-day mortality, intervention, organ-space infection and other HAIs, with the highest rates seen in low HDI countries. Median length of stay in patients who had an SSI was longer (7.0 days), compared with 3.0 days in patients who did not have an SSI. Use of laparoscopy was associated with significantly lower SSI rates, even after accounting for HDI.ConclusionThe odds of SSI in children is nearly four times greater in low HDI compared with high HDI countries. Policies to reduce SSI should be prioritised as part of the wider global agenda.
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| 4. |
- Bayomie, Omar S., et al.
(författare)
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Exceeding Pinch limits by process configuration of an existing modern crude oil distillation unit – A case study from refining industry
- 2019
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Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 231, s. 1050-1058
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Tidskriftsartikel (refereegranskat)abstract
- Crude Distillation Unit (CDU) represents significant challenge for retrofitting and energy optimisation as the most energy intensive consumer in a conventional crude oil refinery. Pinch Technology and its based-methodologies are found primary keys for decades to energy savings in refining industries for a range of common economic-based and environmental objectives or applications. Typical benefits in energy savings are reported within 20–40% of original designs. However, such savings are limited and questioned when modern refiners are dealt with. The current paper addresses the revamping of a modern refinery exhibiting an existing high energy efficiency (≈93%). This implies the maximum potential energy savings would only be 7% at current process conditions. The present research proposes an algorithm that tackles energy recovery of modern refiners, enabling additional savings beyond the energy targets set by the existing process. The algorithm starts by process simulation and validation against real plant data, followed by a network optimisation, e.g. stream splitting, to reach the energy targets set by Pinch Analysis. The energy targets are then moved to another lower level by performing potential process modifications to reduce the energy consumption further. Results showed that the current modern refinery unit could reach its energy targets by stream splitting modifications with hot energy savings of 2.69 MW. Process modifications resulted in additional energy savings of 31.3% beyond the current level of the existing plant alongside less than a year of payback period for estimated capital investment. An environmental assessment is performed, and comparable reductions were obtained with respect to greenhouse gas, with reduction in CO2 emissions by 45.1%. The proposed retrofit methodology is applicable to minimising energy consumptions of refiners including modern units to achieve energy levels beyond energy targets by new process modifications.
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| 5. |
- Umar, Yusuf, et al.
(författare)
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A renewable lignin-derived bio-oil for boosting the oxidation stability of biodiesel
- 2022
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481. ; 182, s. 867-878
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Tidskriftsartikel (refereegranskat)abstract
- The valorisation of lignin is being increasingly recognised to improve the economics of pulp and paper making mills. In the present study, an integrated lignin–glycerol valorisation strategy is introduced with an overarching aim for enhancing the process value chains. LignoBoost kraft lignin was subjected to base-catalysed depolymerisation using glycerol as a co-solvent. The generated bio-oil was used as a renewable additive to biodiesel for enhancing its oxygen stability. The influence of three independent parameters including temperature, time and glycerol amount on lignin depolymerisation was investigated. Response surface methodology was applied to design the experiments and to optimise the process for maximising the yield and antioxidant impact of bio-oil. The results showed that glycerol has a positive qualitative and quantitative impact on the produced bio-oil, where an enhancement in the yield (up to 23.8%) and antioxidant activity (up to 99 min induction period) were achieved using the PetroOxy method (EN16091). The addition of 1 wt% bio-oil to biodiesel has led to an improvement in the oxidation stability over a neat sample of up to ∼340%, making it compliant with European standard (EN14214). The proposed process presents a biorefinery paradigm for the integrated utilisation of waste cooking oil, lignin and glycerol.
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| 6. |
- Abdelaziz, Omar Y., et al.
(författare)
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Biological valorization of low molecular weight lignin
- 2016
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Ingår i: Biotechnology Advances. - : Elsevier BV. - 0734-9750. ; 34:8, s. 1318-1346
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Forskningsöversikt (refereegranskat)abstract
- Lignin is a major component of lignocellulosic biomass and as such, it is processed in enormous amounts in the pulp and paper industry worldwide. In such industry it mainly serves the purpose of a fuel to provide process steam and electricity, and to a minor extent to provide low grade heat for external purposes. Also from other biorefinery concepts, including 2nd generation ethanol, increasing amounts of lignin will be generated. Other uses for lignin – apart from fuel production – are of increasing interest not least in these new biorefinery concepts. These new uses can broadly be divided into application of the polymer as such, native or modified, or the use of lignin as a feedstock for the production of chemicals. The present review focuses on the latter and in particular the advances in the biological routes for chemicals production from lignin. Such a biological route will likely involve an initial depolymerization, which is followed by biological conversion of the obtained smaller lignin fragments. The conversion can be either a short catalytic conversion into desired chemicals, or a longer metabolic conversion. In this review, we give a brief summary of sources of lignin, methods of depolymerization, biological pathways for conversion of the lignin monomers and the analytical tools necessary for characterizing and evaluating key lignin attributes.
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| 7. |
- Abdelaziz, Omar Y., et al.
(författare)
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Conceptual Design of a Kraft Lignin Biorefinery for the Production of Valuable Chemicals via Oxidative Depolymerization
- 2020
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Ingår i: ACS Sustainable Chemistry & Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 8:23, s. 8823-8829
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Tidskriftsartikel (refereegranskat)abstract
- Lignin is the most abundant aromatic biopolymer on Earth, and its aromatic structure makes it a promising platform for the production of biobased chemicals and other valuable building blocks. The valorization of lignin into chemicals currently presents a challenge, and its facilitation is key in the development of viable lignocellulosic biorefinery processes. This study presents a conceptual design for a recently demonstrated process for lignin oxidative depolymerization. Modeling, simulation, and analysis were performed based on experimental data to assess the viability of the process. Mass and energy balances and main design data were determined for a 700 t/y kraft lignin biorefinery. The production capacity of aromatic chemicals, including vanillin, vanillic acid, guaiacol, and acetovanillone, was 0.3 kg aromatics/kg net lignin use. A heat-integrated process design is suggested, and the energy demands and the CO2 emissions are evaluated and compared. Assuming an interest rate of 10% and a plant lifetime of 10 years, the return on investment was calculated to be 14%, indicating that such a biorefinery is viable. A sensitivity analysis was carried out to assess the impact of the vanillin selling price and the cost of lignin on the profitability of the process. A quantitative investigation of process sustainability resulted in an E-factor of ∼1.6 for the entire synthetic route, that is, 38% material efficiency. The findings of this study underline the need for further research to develop efficient lignin conversion technologies with attractive yields in order to increase profitability on an industrial scale.
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| 8. |
- Abdelaziz, Omar Y.
(författare)
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Lignin Conversion to Value-Added Small-Molecule Chemicals : Towards Integrated Forest Biorefineries
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lignin is the most abundant aromatic biopolymer on Earth and has significant potential as a feedstock for industrial use. Due to its intrinsic heterogeneity and recalcitrance, lignin has been regarded as a low-value side-product in the pulp and paper industry and in second-generation biorefineries. However, novel technologies are currently being explored to utilize lignin as a renewable resource for bio-based chemicals, fuels, and materials. The efficient valorization of lignin would also improve the economics and sustainability of forest-based industries. Deriving value from lignin, beyond low-value heat and power, is thus essential for the success of a global circular bioeconomy employing lignocellulosic biomass as a raw material.This thesis discusses the possibility of producing high-value chemicals from technical lignin streams via thermochemical–biological methods. The work deals with four major research themes: (1) providing insights into the physicochemical properties of technical lignins that could be valuable in designing routes for their valorization, (2) developing technologies for the thermochemical depolymerization of lignin under batch and continuous-flow conditions, (3) developing strategies for the biological valorization of lignin by combining thermochemical depolymerization with microbial conversion, and (4) assessing the techno-economic viability of lignin as a feedstock for sustainable chemical production in a biorefinery.Comprehensive physicochemical characterization of technical lignins is crucial in the development of molecularly tailored lignin-based applications. Elucidating the structural and compositional features can facilitate the matching of technical lignin streams with suitable valorization strategies, including thermochemical depolymerization. Two thermochemical depolymerization approaches were investigated for the production of low-molecular-weight aromatics from technical lignin: base-catalyzed depolymerization and oxidative depolymerization. Both approaches were also found to be effective means of pretreatment enabling the microbial conversion of kraft lignin.Continuous processing allowed hydrothermal lignin treatment at exceptionally short residence times, and this is anticipated to be an important stepping-stone toward technical lignin valorization. Membrane filtration appeared to be a practical method of separating complex depolymerized lignin mixtures for product fractionation and upgrading. Bimetallic catalyst systems based on Cu, Mn, and V improved the oxidative conversion of lignosulfonate and kraft lignins into value-added aromatic compounds. Techno-economic analysis underlined the viability of large-scale chemical production from kraft lignin by oxidative depolymerization, offering opportunities for process integration with traditional pulp mills.
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| 9. |
- Abdelaziz, Omar Y, et al.
(författare)
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Lignin Depolymerisation under Continuous-Flow Conditions : Highlights of Recent Developments
- 2020
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Ingår i: ChemSusChem. - : Wiley. - 1864-564X .- 1864-5631. ; 13:17, s. 4382-4384
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Tidskriftsartikel (refereegranskat)abstract
- Lignin is a poly-aromatic polymer contained in the plant cell wall, and it is considered the most abundant non-carbohydrate polymer on Earth. The aromaticity and richness of its functional groups render lignin an attractive starting biomacromolecule for conversion into a variety of value-added products. The development of successful strategies for lignin valorisation infers the design of effective depolymerisation protocols. Most research on lignin depolymerisation have focused on batch-mode processing, whereas only a few studies have tackled such lignin transformation in continuous reactor systems. In the present paper, we highlight the emerging developments within the concept of continuous lignin processing and the challenges remaining in realising the efficient valorisation of lignin using this technology concept. A special focus is set on the hydrothermal conversion of technical lignin under continuous-flow conditions, together with suggestions for future research.
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| 10. |
- Abdelaziz, Omar Y., et al.
(författare)
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Membrane filtration of alkali-depolymerised kraft lignin for biological conversion
- 2019
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Ingår i: Bioresource Technology Reports. - : Elsevier BV. - 2589-014X. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we have investigated the possibility of membrane filtration as a means for obtaining a fraction containing mainly low-molecular-weight (LMW) compounds from depolymerised lignin (DL) for subsequent microbial conversion. A DL stream from continuous-mode alkali depolymerisation of a softwood kraft lignin produced at a temperature of 220 °C and a residence time of 2 min, using a NaOH/lignin weight ratio of 1 with 5 wt% lignin loading was fractionated using a polymeric membrane with a molecular weight cut-off of 500–700 Da. The permeate (DLP) volume recovery of LMW phenolics (250–450 Da) was 70% after filtration for 3.7 h. The DLP was used as a carbon source for growth of three bacterial strains; Pseudomonas fluorescens, P. putida EM42 and Rhodococcus opacus, and good growth was obtained by the first two microorganisms. This proof-of-concept study demonstrates a novel strategy for technical lignin valorisation by combining depolymerisation, nanofiltration and bioconversion.
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