Alternative marine fuels: Prospects based on multi-criteria decision analysis involving Swedish stakeholders

There is a need for alternative marine fuels in order to reduce the environmental and climate impacts of shipping, in the short and long term. This study assesses the prospects for seven alternative fuels for the shipping sector in 2030, including biofuels, by applying a multi-criteria decision analysis approach that is based on the estimated fuel performance and on input from a panel of maritime stakeholders and by considering, explicitly, the influence of stakeholder preferences. Seven alternative marine fuels—liquefied natural gas (LNG), liquefied biogas (LBG), methanol from natural gas, renewable methanol, hydrogen for fuel cells produced from (i) natural gas or (ii) electrolysis based on renewable electricity, and hydrotreated vegetable oil (HVO)—and heavy fuel oil (HFO) as benchmark are included and ranked by ten performance criteria and their relative importance. The criteria cover economic, environmental, technical, and social aspects. Stakeholder group preferences (i.e., the relative importance groups assign to the criteria) influence the ranking of these options. For ship-owners, fuel producers, and engine manufacturers, economic criteria, in particular the fuel price, are the most important. These groups rank LNG and HFO the highest, followed by fossil methanol, and then various biofuels (LBG, renewable methanol, and HVO). Meanwhile, representatives from Swedish government authorities prioritize environmental criteria, specifically GHG emissions, and social criteria, specifically the potential to meet regulations, ranking renewable hydrogen the highest, followed by renewable methanol, and then HVO. Policy initiatives are needed to promote the introduction of renewable marine fuels

Perspectives on shipping emissions and their impacts on the surface ocean and lower atmosphere: An environmental-social-economic dimension

Shipping is the cornerstone of international trade and thus a critical economic sector. However, ships predominantly use fossil fuels for propulsion and electricity generation, which emit greenhouse gases such as carbon dioxide and methane, and air pollutants such as particulate matter, sulfur oxides, nitrogen oxides, and volatile organic compounds. The availability of Automatic Information System (AIS) data has helped to improve the emission inventories of air pollutants from ship stacks. Recent laboratory, shipborne, satellite and modeling studies provided convincing evidence that ship-emitted air pollutants have significant impacts on atmospheric chemistry, clouds, and ocean biogeochemistry. The need to improve air quality to protect human health and to mitigate climate change has driven a series of regulations at international, national, and local levels, leading to rapid energy and technology transitions. This resulted in major changes in air emissions from shipping with implications on their environmental impacts, but observational studies remain limited. Growth in shipping in polar areas is expected to have distinct impacts on these pristine and sensitive environments. The transition to more sustainable shipping is also expected to cause further changes in fuels and technologies, and thus in air emissions. However, major uncertainties remain on how future shipping emissions may affect atmospheric composition, clouds, climate, and ocean biogeochemistry, under the rapidly changing policy (e.g., targeting decarbonization), socioeconomic, and climate contexts

Uracil recognition by replicative DNA polymerases is limited to the archaea, not occurring with bacteria and eukarya

Family B DNA polymerases from archaea such as Pyrococcus furiosus, which live at temperatures ∼100°C, specifically recognize uracil in DNA templates and stall replication in response to this base. Here it is demonstrated that interaction with uracil is not restricted to hyperthermophilic archaea and that the polymerase from mesophilic Methanosarcina acetivorans shows identical behaviour. The family B DNA polymerases replicate the genomes of archaea, one of the three fundamental domains of life. This publication further shows that the DNA replicating polymerases from the other two domains, bacteria (polymerase III) and eukaryotes (polymerases δ and ε for nuclear DNA and polymerase γ for mitochondrial) are also unable to recognize uracil. Uracil occurs in DNA as a result of deamination of cytosine, either in G:C base-pairs or, more rapidly, in single stranded regions produced, for example, during replication. The resulting G:U mis-pairs/single stranded uracils are promutagenic and, unless repaired, give rise to G:C to A:T transitions in 50% of the progeny. The confinement of uracil recognition to polymerases of the archaeal domain is discussed in terms of the DNA repair pathways necessary for the elimination of uracil

Perspectives on shipping emissions and their impacts on the surface ocean and lower atmosphere: An environmental-social-economic dimension

Shipping is the cornerstone of international trade and thus a critical economic sector. However, ships predominantly use fossil fuels for propulsion and electricity generation, which emit greenhouse gases such as carbon dioxide and methane, and air pollutants such as particulate matter, sulfur oxides, nitrogen oxides, and volatile organic compounds. The availability of Automatic Information System (AIS) data has helped to improve the emission inventories of air pollutants from ship stacks. Recent laboratory, shipborne, satellite and modeling studies provided convincing evidence that ship-emitted air pollutants have significant impacts on atmospheric chemistry, clouds, and ocean biogeochemistry. The need to improve air quality to protect human health and to mitigate climate change has driven a series of regulations at international, national, and local levels, leading to rapid energy and technology transitions. This resulted in major changes in air emissions from shipping with implications on their environmental impacts, but observational studies remain limited. Growth in shipping in polar areas is expected to have distinct impacts on these pristine and sensitive environments. The transition to more sustainable shipping is also expected to cause further changes in fuels and technologies, and thus in air emissions. However, major uncertainties remain on how future shipping emissions may affect atmospheric composition, clouds, climate, and ocean biogeochemistry, under the rapidly changing policy (e.g., targeting decarbonization), socioeconomic, and climate contexts

Efficacy of conventional and digital radiographic imaging methods for diagnosis of simulated external root resorption Eficácia dos métodos radiográficos convencional e digital no diagnóstico de reabsorções radiculares simuladas

This in vitro study evaluated and compared the efficacy of conventional (Kodak F-speed (Insight), Kodak) and a digital (DRS Gnatus System, Gnatus) radiographic imaging for diagnosis of simulated external root resorption cavities. Human mandibles containing teeth were covered with bovine muscle slices in order to simulate the soft tissues. Nine teeth out of each group of teeth were investigated. Initially, three periapical radiographs of each tooth were taken using a tube shift technique with mesial and distal angulations in both methods. All teeth were subsequently extracted and had 0.7 and 1.0-mm deep cavities prepared on their buccal, mesial and distal surfaces at the cervical, middle and apical thirds. Steel cylinder burs (DORMER® - HSS) with 0.7 and 1.0-mm diameter were used. Each tooth was replaced on its socket and new radiographs were taken. Three examiners, an endodontist (1), a radiologist (2) and a general dentist (3), evaluated the images. Results were compared by z-test and showed a higher number of cavities detected by the digital method compared to the conventional, regardless of the deepness of the cavity. In decreasing order, examiners 2, 3 and 1 exhibited different potentials of detection of cavities with the conventional method. Examiners 1 and 3 exhibited superior potential than examiner 2 for detection of cavities of different sizes with the digital method.<br>O presente estudo visou avaliar e comparar, in vitro, a eficácia dos métodos radiográficos convencional (filmes de grupos de sensibilidade E/F Kodak Insight) e digital (Sistema Gnatus DRS), no diagnóstico de cavidades simulando reabsorções radiculares externas, em dentes contidos em mandíbulas humanas secas com músculo bovino simulando o tecido mole. As variáveis consideradas foram: tamanhos das cavidades e examinadores envolvidos. Foram utilizadas nove unidades de cada grupo dentário, incisivos (central e lateral), caninos, pré-molares e molares, sem lesões periapicais, as quais foram radiografadas inicialmente, em três tomadas radiográficas periapicais (orto, mesio e distorradial) pelos métodos radiográficos convencional e digital. Extraíram-se os dentes com o auxílio de fórceps e as cavidades de reabsorção foram confeccionadas com brocas cilíndricas DORMER® - HSS - Aço rápido, de 0,7 e 1,0 mm de diâmetro, nas profundidades 0,7 e 1,0 mm, para simular cavidades pequenas e médias, respectivamente, distribuídas nos terços radiculares cervical, médio e apical e nas faces vestibular, mesial e distal. Após a realização das cavidades os dentes eram reposicionados nos alvéolos e então, radiografados novamente pelos métodos convencional e digital, sendo esses passos comuns a ambos os diâmetros e profundidades das cavidades. As radiografias convencionais e digitais foram avaliadas por três cirurgiões-dentistas, sendo um radiologista, um endodontista e um clínico geral. Os resultados da investigação mostraram que, pelo método radiográfico digital o número de cavidades observadas foi maior do que pelo convencional, tanto para as cavidades pequenas (p<0,05), quanto para as médias (p<0,05)

Fuel choices for different transport modes when decarbonizing the scandinavian energy system

To meet future climate targets, shipping, aviation, and road transport need to reduce their carbon dioxide emissions. This partly by the introduction of alternative transportation fuels and a range of fuel options exist. This study provides an initial assessment of cost-effective future fuel choices for shipping, aviation and road transport in Scandinavia considering carbon reduction requirements and the entire energy system. The cost minimizing energy systems model TIMES Nordic covering Sweden, Norway and Denmark is used. For passenger and freight road transport a considerable electrification seems cost-effective. However, biofuels are needed too, not least in shipping and aviation. The findings indicate that biomass-based marine fuels and bio-jet fuels represent cost-effective mitigation measures in the shipping and aviation sector for 2030 and 2050 in all studied scenario cases. Electrofuels in the aviation and shipping sector is to some extent also a cost-effective option but only when carbon capture and storage is not deployed in large-scale. In general, the development of carbon capture and storage for biomass-based technologies and how these negative emissions will be considered in policy making is important for the development also in the transport sector and particularly for the role of biofuels

Prospects for renewable marine fuels

In order to reduce the environmental and climateimpact of shipping, in the short and long term, theintroduction of alternative fuels is required. However,there is a need for more knowledge on alternativemarine fuels. The aim of the study is to assess the prospect of renewable fuels in the shipping sector by conducting amulti-criteria decision analysis of selected alternativefuels with a panel of shipping sector relatedstakeholders. The Analytic Hierarchy Process is used. Stakeholder groups involved are authorities, ship owners, fuel manufacturers and engine manufacturers. Comparison of the ranking order of the selected alternative marine fuels shows that Hydrogen (from wind power) was the most preferred option, LNG the second most preferred fuels, whereas and natural gas based methanol the least preferred (except for from the ship owners group)

Emissions to the air

Seeing the black smoke coming out of the funnel of a manoeuvring ship makes it easy to understand that the ship\u27s propulsion contributes to the emission of air pollutants. However, there is more than meets the eye going up in smoke. A vast majority of ships use fossil fuels, increasing a positive net contribution of carbon dioxide to the atmosphere when they are combusted. Because the fuels that are used are often of low quality and possess a high sulphur content, a number of other air pollutants are also emitted. Emissions to the air from ships include greenhouse gases (such as carbon dioxide, methane and nitrous oxide), sulphur and nitrogen oxides, with both acidifying and eutrophication effects, and different forms of particles, with impacts on health and climate. However, not all emissions to the atmosphere from ships originate from the combustion of fuels for propulsion and energy production. The handling of crude oil as cargo and compounds used in refrigeration systems cause emissions of volatile organic compounds and ozone-depleting substances. The sources of the most important emissions and relevant regulations are described in this chapter