| 1. |
- Kirsten, Franz, 1983, et al.
(författare)
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A repeating fast radio burst source in a globular cluster
- 2022
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 602:7898, s. 585-589
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Tidskriftsartikel (refereegranskat)abstract
- Fast radio bursts (FRBs) are flashes of unknown physical origin1. The majority of FRBs have been seen only once, although some are known to generate multiple flashes2,3. Many models invoke magnetically powered neutron stars (magnetars) as the source of the emission4,5. Recently, the discovery6 of another repeater (FRB 20200120E) was announced, in the direction of the nearby galaxy M81, with four potential counterparts at other wavelengths6. Here we report observations that localized the FRB to a globular cluster associated with M81, where it is 2 parsecs away from the optical centre of the cluster. Globular clusters host old stellar populations, challenging FRB models that invoke young magnetars formed in a core-collapse supernova. We propose instead that FRB 20200120E originates from a highly magnetized neutron star formed either through the accretion-induced collapse of a white dwarf, or the merger of compact stars in a binary system7. Compact binaries are efficiently formed inside globular clusters, so a model invoking them could also be responsible for the observed bursts.
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| 2. |
- Bjorn, A., et al.
(författare)
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Review of life-cycle based methods for absolute environmental sustainability assessment and their applications
- 2020
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Ingår i: Environmental Research Letters. - : IOP Publishing Ltd. - 1748-9326 .- 1748-9318. ; 15:8
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Tidskriftsartikel (refereegranskat)abstract
- In many regions and at the planetary scale, human pressures on the environment exceed levels that natural systems can sustain. These pressures are caused by networks of human activities, which often extend across countries and continents due to global trade. This has led to an increasing requirement for methods that enable absolute environmental sustainability assessment (AESA) of anthropogenic systems and which have a basis in life cycle assessment (LCA). Such methods enable the comparison of environmental impacts of products, companies, nations, etc, with an assigned share of environmental carrying capacity for various impact categories. This study is the first systematic review of LCA-based AESA methods and their applications. After developing a framework for LCA-based AESA methods, we identified 45 relevant studies through an initial survey, database searches and citation analysis. We characterized these studies according to their intended application, impact categories, basis of carrying capacity estimates, spatial differentiation of environmental model and principles for assigning carrying capacity. We then characterized all method applications and synthesized their results. Based on this assessment, we present recommendations to practitioners on the selection and use of existing LCA-based AESA methods, as well as ways to perform assessments and communicate results to decision-makers. Furthermore, we identify future research priorities intended to extend coverage of all components of the proposed method framework, improve modeling and increase the applicability of methods. © 2020 The Author(s).
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| 3. |
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| 4. |
- Byrne, D. M., et al.
(författare)
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Life cycle assessment (LCA) of urban water infrastructure: emerging approaches to balance objectives and inform comprehensive decision-making
- 2017
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Ingår i: Environmental Science: Water Research and Technology. - : Royal Society of Chemistry (RSC). - 2053-1419 .- 2053-1400. ; 3:6, s. 1002-1014
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Tidskriftsartikel (refereegranskat)abstract
- Life cycle assessment (LCA) has been widely used to quantify environmental impacts associated with urban water infrastructure, including wastewater, drinking water, stormwater, and integrated urban water systems. While LCA is applicable for the estimation of global environmental impacts, decision-makers must balance these impacts with local, often regulated, environmental and public health objectives. To characterize the state of the art for the use of LCA for urban water infrastructure, a thorough literature review was conducted of papers that applied LCA to wastewater (173 papers), drinking water (44 papers), stormwater (17 papers), and integrated urban water (22 papers) systems. Analyses revealed current preferences for functional unit basis (e.g., volume for wastewater), system boundaries (e.g., focus on operation), and impact assessment methodology (CML, ReCiPe, and Eco-Indicator). Based on these findings, LCA methodological recommendations for urban water infrastructure are made, and emerging opportunities to balance objectives and inform comprehensive decision-making are discussed. Critical opportunities include the integration of spatial considerations (e.g., spatialized characterization factors), water quantity (e.g., water quantity indicators), public health (e.g., integration with risk assessment), economic and social assessments (e.g., life cycle costing and social LCA), along with prioritization of continuous stakeholder engagement. Finally, research and development needs specific to the use of LCA for urban water infrastructure (e.g., development of new indicators coupled with case studies) are prioritized.
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| 5. |
- Kounina, Anna, et al.
(författare)
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Review of methods addressing freshwater use in life cycle inventory and impact assessment
- 2013
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Ingår i: International Journal of Life Cycle Assessment. - : Springer Science and Business Media LLC. - 1614-7502 .- 0948-3349. ; 18:3, s. 707-721
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Tidskriftsartikel (refereegranskat)abstract
- The project “review of methods addressing water” aims at reviewing and performing a systematic qualitative review ofexisting methods (environmental models, characterization methods, and life cycle impact assessment methods) linked to the assessment of water use. This work looks at similarities and differences between the characterization methods, identifies the key elements to be considered when modeling the cause effect chains in water assessment and provides indications for deriving operational characterization methods and factors to assess water use in LCA.Scientific recommendations as well as industrial interim recommendations on inventory modeling, midpoint and impactassessment methods are formulated to support practitioners in their short term application.
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| 6. |
- Ten Hoeve, Marieke, et al.
(författare)
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A life cycle perspective of slurry acidification strategies under different nitrogen regulations
- 2016
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Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 127, s. 591-599
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Tidskriftsartikel (refereegranskat)abstract
- Livestock manure is a major contributor to ammonia and greenhouse gas emissions and treatment technologies such as slurry acidification can be used to reduce both. In this study, life cycle assessment was used to compare impact potentials of slurry acidification at either the pig housing or the field application stage with conventional slurry management. Furthermore, the effects of differences in environmental regulations concerning nitrogen application limits were analysed. The impact categories analysed were terrestrial eutrophication potential, climate change potential, marine eutrophication potential and toxicity potential. Slurry acidification reduced the terrestrial eutrophication potential by 71% for in-house acidification and by 30% for field acidification. Changes in regulatory plant-available nitrogen application limits resulted in changes in climate change potential and marine eutrophication potential, with lower limits favouring in-house acidification. Acidification can substantially reduce the environmental impacts of animal slurry, but the effect depends on the context of the regulatory regime.
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| 7. |
- Ten Hoeve, Marieke, et al.
(författare)
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Life cycle assessment of pig slurry treatment technologies for nutrient redistribution in Denmark
- 2014
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Ingår i: Journal of Environmental Management. - : Elsevier BV. - 0301-4797 .- 1095-8630. ; 132, s. 60-70
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Tidskriftsartikel (refereegranskat)abstract
- Animal slurry management is associated with a range of impacts on fossil resource use and the environment. The impacts are greatest when large amounts of nutrient-rich slurry from livestock production cannot be adequately utilised on adjacent land. To facilitate nutrient redistribution, a range of different technologies are available. This study comprised a life cycle assessment of the environmental impacts from handling 1000 kg of pig slurry ex-animal. Application of untreated pig slurry onto adjacent land was compared with using four different treatment technologies to enable nutrient redistribution before land application: (a) separation by mechanical screw press, (b) screw press separation with composting of the solid fraction, (c) separation by decanter centrifuge, and (d) decanter centrifuge separation with ammonia stripping of the liquid fraction. Emissions were determined based on a combination of values derived from the literature and simulations with the Farm-N model for Danish agricultural and climatic conditions. The environmental impact categories assessed were climate change, freshwater eutrophication, marine eutrophication, terrestrial acidification, natural resource use, and soil carbon, nitrogen and phosphorus storage. In all separation scenarios, the liquid fraction was applied to land on the pig-producing (donor) farm and the solid fraction transported to a recipient farm and utilised for crop production. Separation, especially by centrifuge, was found to result in a lower environmental impact potential than application of untreated slurry to adjacent land. Composting and ammonia stripping either slightly increased or slightly decreased the environmental impact potential, depending on the impact category considered. The relative ranking of scenarios did not change after a sensitivity analysis in which coefficients for field emissions of nitrous oxide, ammonia and phosphorus were varied within the range cited in the literature. Therefore, the best technology to implement in a given situation depends on the environmental problem in question, local policy, cost and practicality.
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| 8. |
- Alvarez-Gaitan, JP, et al.
(författare)
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Consequential cradle-to-gate carbon footprint of water treatment chemicals using simple and complex marginal technologies for electricity supply
- 2014
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Ingår i: International Journal of Life Cycle Assessment. - : Springer Science and Business Media LLC. - 1614-7502 .- 0948-3349. ; 19:12, s. 1974-1984
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Tidskriftsartikel (refereegranskat)abstract
- Purpose Chemicals produced via chlor-alkali electrolysis arewidely used throughout the water industry worldwide, withtreatment chemicals often the second largest source of environmental impacts from potable water production after electricity use. Population-driven increases in the future demand for potable water will require concomitant increases in the production of water treatment chemicals, with the associated environmental impacts of chemicals production primarily arising from the additional demand for electricity. Due to the dominance of electricity in the environmental performance of chlor-alkali chemicals, assessment of the future environmental impacts of potable water production is largely dependent on proper identification of the marginal source of electricity. Inthis paper, we present a consequential cradle-to-gate carbonfootprint (cCF) for the most widely used chlor-alkali produced disinfectant (sodium hypochlorite (13 % w/w)) andcoagulant (ferric chloride (42 % w/w)) in Australia, withspecial emphasis placed upon the identification of futuremarginal electricity supply and the substitution of hydrogengas and sodium hydroxide during production. While thisanalysis is presented in an Australian context, commonalities in potable water and chlor-alkali chemical production processes internationally give the findings a broader relevance.Methods Consequential models for sodium hypochlorite (13 % w/w) and ferric chloride (42 % w/w) production were developed, and the identification of the marginal source ofelectricity was modelled using a “simple marginal technology” approach via operationalisation of the Weidema framework and a “complex marginal technology” using a partial equilibrium model. For the simple marginal technology, the levelised cost of electricity was used to select the most competitive energy generation technologies and those most relevant for the Australian market. For the complex marginal technology, the energy sector model was used to simulate the most likely electricity supply mix. Details of the different paths taken in the substitution of hydrogen gas and sodium hydroxide are also presented. To allow for proper incorporation of uncertainties arising from these key factors in the cCF, several scenarios were developed covering fuel and carbon prices for identifying the marginal supplymix of electricity, as well as the likely production routes for sodium carbonate in the context of sodium hydroxide substitution.Results and discussion cCF results of sodium hypochlorite(13%w/w) and ferric chloride (42%w/w) are presented usingsimple and complex marginal technologies, and the implications of choosing one marginal technology over the other in the context of water treatment chemicals are presented. For the simple marginal technology approach, the global warming potential (GWP) per megagram of chemical varied from 68 to 429 kg CO2-eq for sodium hypochlorite (13 % w/w) and 59–1,020 kg CO2-eq for ferric chloride (42 % w/w). For the complex marginal technology approach, the GWP per megagram of chemical varied from 266 to 332 kg CO2-eqfor sodium hypochlorite (13 % w/w) and 214–629 kg CO2-eqfor ferric chloride (42 % w/w). Insights are given in relation to the impact of the price of fossil fuels, the carbon price, and the different substitution routes.Conclusions The use of a partial equilibrium model (PEM) hasenabled a better understanding of the variability of the results in this study. For example, the use of PEM for the identification of the complex marginal source of electricity shows that, for the case of Australia, any benefit from a carbon price is lost with high prices of natural gas due to the incentive to use cheaper fuels such as black and brown coal. Likewise, the use of explorative scenarios was decisive to manage the inherent uncertainty of the parameters included in the model. In relation to substitution, the case of ferric chloride (42 % w/w) indicated that using only one substitution route was not enough to fully understand the potential continuum of cCF results. The simple marginal approach, where an exclusive marginal source of electricity or substitution route is considered, presents significant risks for the modelling accuracy of the cCF as shown here for sodium hypochlorite (13 % w/w) and ferric chloride (42 % w/w), therefore, it is not recommended.
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| 9. |
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| 10. |
- Barnes, Ashley T., et al.
(författare)
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Young massive star cluster formation in the Galactic Centre is driven by global gravitational collapse of high-mass molecular clouds
- 2019
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 486:1, s. 283-303
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Tidskriftsartikel (refereegranskat)abstract
- Young massive clusters (YMCs) are the most compact, high-mass stellar systems still forming at the present day. The precursor clouds to such systems are, however, rare due to their large initial gas mass reservoirs and rapid dispersal time-scales due to stellar feedback. None the less, unlike their high-z counterparts, these precursors are resolvable down to the sites of individually forming stars, and hence represent the ideal environments in which to test the current theories of star and cluster formation. Using high angular resolution (1 arcsec / 0.05 pc) and sensitivity ALMA observations of two YMC progenitor clouds in the Galactic Centre, we have identified a suite of molecular line transitions - e.g. c-C3H2 (7 - 6) - that are believed to be optically thin, and reliably trace the gas structure in the highest density gas on star-forming core scales. We conduct a virial analysis of the identified core and proto-cluster regions, and show that half of the cores (5/10) and both proto-clusters are unstable to gravitational collapse. This is the first kinematic evidence of global gravitational collapse in YMC precursor clouds at such an early evolutionary stage. The implications are that if these clouds are to form YMCs, then they likely do so via the 'conveyor-belt' mode, whereby stars continually form within dispersed dense gas cores as the cloud undergoes global gravitational collapse. The concurrent contraction of both the cluster-scale gas and embedded (proto-)stars ultimately leads to the high (proto-)stellar density in YMCs.
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