Microplastics in the Antarctic marine system: An emerging area of research

It was thought that the Southern Ocean was relatively free of microplastic contamination; however, recent studies and citizen science projects in the Southern Ocean have reported microplastics in deep-sea sediments and surface waters. Here we reviewed available information on microplastics (including macroplastics as a source of microplastics) in the Southern Ocean. We estimated primary microplastic concentrations from personal care products and laundry, and identified potential sources and routes of transmission into the region. Estimates showed the levels of microplastic pollution released into the region from ships and scientific research stations were likely to be negligible at the scale of the Southern Ocean, but may be significant on a local scale. This was demonstrated by the detection of the first microplastics in shallow benthic sediments close to a number of research stations on King George Island. Furthermore, our predictions of primary microplastic concentrations from local sources were five orders of magnitude lower than levels reported in published sampling surveys (assuming an even dispersal at the ocean surface). Sea surface transfer from lower latitudes may contribute, at an as yet unknown level, to Southern Ocean plastic concentrations. Acknowledging the lack of data describing microplastic origins, concentrations, distribution and impacts in the Southern Ocean, we highlight the urgent need for research, and call for routine, standardised monitoring in the Antarctic marine system

Techno-economic and environmental assessment of BECCS in fuel generation for FT-fuel, bioSNG and OMEx

This study focuses on bioenergy with carbon capture and storage (BECCS) in fuel generation and assesses the potential of biofuel generation to decarbonise the fuel economy by reducing CO2emissions to the atmosphere. The research investigates the technical, economic, and environmental performances of three biofuel production routes, namely Fischer-Tropsch synthesis (FTS), bio-synthetic natural gas (bioSNG) and oxymethylene ethers (OMEx) synthesis using flowsheets developed in Aspen Plus. It constitutes the first attempt to holistically evaluate both the techno-economic performance and the environmental benefits of employing BECCS in fuel generation. For an input of 1020 dry tonnes per day of woody biomass, the FTS route yields 275 t d−1, the bioSNG route yields 238 t d−1and the OMExroute yields 635 t d−1of fuel and the energy efficiency is in the range of 44.9% to59.7% without CCS and 44.0% to 58.2% with CCS. In addition, negative emissions can be achieved for all routes with CCS in the range of 301 000 to 519 000 tCO2per year. For economic viability, the minimum selling price for FT-fuels, bioSNG, and OMExproduction with CCS have been calculated as £23.4 per GJ, £14.5 per GJ and £26.5 per GJ, respectively. However, competition with conventional fossil-derived fuels is not possible without the combination of existing financial incentives and a proposed carbon pricing. With carbon credit as the only financial incentive, carbon pricing in the range of £48 to £86 per tCO2needs to be applied to achieve feasibility. Also, more negative emissions need to be generated to decrease the value of this range and reasonably phase out dependence on fossil-derived fuels. Parametric studies identified as crucial parameters to be improved the fuel output, CAPEX, operating hours and feedstock cost

Comprehensive process simulation of a biomass-based hydrogen production system through gasification within the BECCS concept in a commercial two-stage fixed bed gasifier

Hydrogen production through biomass gasification coupled with carbon capture has the potential to be a net negative emission process. Among the different designs of biomass gasifiers, the two-stage fixed bed gasifier has proved its ability to produce high quality syngas with minimum tar content at an industrial scale. However, it has not been investigated for hydrogen production. Hence, the current study is the first attempt to assess, through process modelling, the technical feasibility of hydrogen production in a 10 MWth two-stage gasification system using wood chips as feedstock. Mass and energy balances have been established in the Aspen Plus and MATLAB software. In contrast to most models in the literature, which were based on the equilibrium approach, the proposed system utilizes reliable kinetic models for the gasifier operation and the main downstream processes. An extensive validation of the gasifier kinetic model has been carried out and then a sensitivity analysis, which has revealed that the optimum steam-to-biomass ration (SBR) is 0.8 and 1.2 for the air-steam and the oxy-steam gasification systems, respectively. Further, the optimum steam-to-CO ratio (S/CO) for the water gas shift reactors (WGSRs) is 4, under which an overall 82.9% conversion of CO has been achieved. The results show that the 10 MWth two-stage gasifier can attain a specific hydrogen yield of 81.47 gH2/kg dry biomass. Based on the carbon footprint assessment, the process is net negative with an emission factor of −1.38 kgCO2-eq/kg biomass. Further, heat integration has also been conducted and it was found that the energy conversion efficiency of the whole system is 49.6%. This study is important since it provides a reliable data source for biomass-based hydrogen production through gasification in a commercial two-stage gasifier that can dictate operational strategies of pilot and demo plants

Effect of Microporous Layer Ink Homogenisation on the Through-Plane Gas Permeability of PEFC Porous Media

The through-plane gas permeability and morphology of PEFC gas diffusion media (GDM) is investigated for different microporous layer (MPL) ink homogenisation techniques (bath sonication and magnetic stirring) for low- (Vulcan XC-72R) and high (Ketjenblack EC-300J)-surface-area carbon powders. The MPL composition is held constant at 80 wt.% carbon powder and 20 wt.% PTFE for a carbon loading of 1.0 mg cm−2. The MPL ink homogenisation time is held constant at two hours for both techniques and increased by one hour for bath sonication to compare with previous investigations. The results show that the through-plane gas permeability of the GDM is approximately doubled using magnetic stirring when compared with bath sonication for MPLs composed of Vulcan XC-72R, with a negligible change in surface morphology between the structures produced from either homogenisation technique. The variation in through-plane gas permeability is almost negligible for MPLs composed of Ketjenblack EC-300J compared with Vulcan XC-72R; however, MPL surface morphology changes considerably with bath sonication, producing smoother, less cracked surfaces compared to the large cracks produced via magnetic stirring for a large-surface-area carbon powder. An MPL ink sonication time of three hours results in a percentage reduction in through-plane gas permeability from the GDL substrate permeability by ~72% for Ketjenblack EC-300J compared to ~47% for two hours

Orbital simulations on the deflection of Near Earth Objects by directed energy

Laser ablation of a Near Earth Object (NEO) on a collision course with Earth produces a cloud of ejecta which exerts a thrust on the asteroid, deflecting it from its original trajectory. The DE-STAR system provides such a thrust by illuminating an Earth-targeting asteroid or comet from afar with a stand-off system consisting of a large phased-array laser in Earth orbit. A much smaller version of the same system called DE-STARLITE travels alongside the target, operating in a stand-on mode, slowly deflecting it over a long period. Such a stand-on system would also permit directing the thrust in any desired direction through careful positioning of the laser relative to the asteroid. We present orbital simulations comparing the effectiveness of both systems across a range of laser and asteroid parameters. Simulated parameters include magnitude, duration and, for the stand-on system, direction of the thrust, as well as the size and orbital characteristics of the target asteroid. These simulations indicate that deflection distance is, in general, proportional to the magnitude of thrust, proportional to the square of the laser on time, and inversely proportional to the mass. Furthermore, deflection distance shows strong dependence on thrust direction with optimal direction varying with the asteroid\u27s orbital eccentricity. As one example, we consider a 325 m asteroid in an orbit of eccentricity e=0.2; given 15 years of warning, a force of just 2 N from a stand-on DE-STARLITE system is sufficient to deflect the asteroid by 2 Earth radii. We discuss numerous scenarios and discuss a practical implementation of such a system consistent with current launch vehicle capabilities

The GLINT10 field trial results

Autonomous underwater vehicles (AUVs) have gained more interest in recent years for military as well as civilian applications. One potential application of AUVs is for the purpose of undersea surveillance. As research into undersea surveillance using AUVs progresses, issues arise as to how an AUV acquires, acts on, and shares information about the undersea battle space. These issues naturally touch on aspects of vehicle autonomy and underwater communications, and need to be resolved through a spiral development process that includes at sea experimentation. This paper presents a recent AUV implementation for active anti-submarine warfare tested at sea in the summer of 2010. On-board signal processing capabilities and an adaptive behavior are discussed in both a simulation and experimental context. The implications for underwater surveillance using AUVs are discussed