Waste-to-energy and waste-to-hydrogen with CCS: Methodological assessment of pathways to carbon-negative waste treatment from an LCA perspective

A growing global population and rising living standards are producing ever greater quantities of waste, while at the same time driving ever-larger demand for energy, especially electricity, or new emerging markets, such as hydrogen in more industrialised countries. A key solution to these challenges of waste disposal, rising energy and hydrogen demand is BECCS (Bioenergy with Carbon Capture and Storage); the generation of bioenergy - in the form of electricity (WtE) or hydrogen (WtH2), as well as heat - from the thermochemical processing of waste. The addition of carbon capture and storage (CCS) to WtE or WtH2 has the potential to make waste a zero or even negative emissions energy source, thus contributing to the removal of greenhouse gases from the atmosphere. This work undertakes a pre-screening of different BECCS configurations based on state of the art technologies and then performed an assessment of representative cases in UK for WtE and WtH2, necessary to understand if novel waste thermal treatment processes may become potential alternatives or improvements to current WtE plants when retrofitted with CCS. A systematic and comprehensive examination of different key Life Cycle Assessment methodological aspects reveals the importance of the functional unit and allocation approach in determining the preferred pathway in a specific context.

Geothermal Energy Impact Estimator: A software application for estimating the life-cycle environmental impacts of geothermal energy

Geothermal energy is a renewable source of base-load power that is expected to play an important role in the transition to a low-carbon economy. In this article, we introduce a novel software application - named Geothermal Energy Impact Estimator - which computes the environmental impacts, including carbon emissions, of existing or future geothermal plants, using the Life Cycle Assessment (LCA) methodology. The software application is user-friendly and was designed to be used by geothermal companies and policy makers. We provide two specific use cases of the software application that represent existing plants in Iceland and in the UK.

The environmental impacts of different mask options for healthcare settings in the UK

During the COVID-19 pandemic, different strategies emerged to combat shortages of certified face masks used in the healthcare sector. These strategies included increasing production from the original manufacturing sites, commissioning new production facilities locally, exploring and allowing the reuse of single-use face masks via various decontamination methods, and developing reusable mask alternatives that meet the health and safety requirements set out in European Standards. In this article, we quantify and evaluate the life-cycle environmental impacts of selected mask options available for use by healthcare workers in the UK, with the objective of supporting decision- and policy-making. We investigate alternatives to traditional single-use face masks like surgical masks and respirators (or FFP3 masks), including cloth masks decontaminated in washing machines; FFP3 masks decontaminated via vapour hydrogen peroxide, and rigid half masks cleaned with antibacterial wipes. Our analysis demonstrates that: (1) the reuse options analysed are environmentally preferential to the traditional "use then dispose" of masks; (2) the environmental benefits increase with the number of reuses; and (3) the manufacturing location and the material composition of the masks have great influence over the life-cycle environmental impacts of each mask use option, in particular for single-use options.

The environmental performance of protecting seedlings with plastic tree shelters for afforestation in temperate oceanic regions: A UK case study

Restoration of forested land represents an effective strategy to achieve net-zero target emissions by enhancing the removal of greenhouse gases from the atmosphere. The most common afforestation strategy envisages planting seedlings, which are germinated and grown to the desired age at tree nurseries, with plastic shelters to increase growth and survival of trees. This article presents a comprehensive Life Cycle Assessment (LCA) study that compares the environmental performance of current and prospective scenarios for shelter-aided seedling planting compared with a base case where shelters are not employed. The study focuses on the UK, but results and conclusions are valid for other temperate oceanic regions. The scenarios investigated are a combination of different shelters materials and end-of-life (EoL) strategies. Our analysis demonstrates that (i) planting seedling without shelters is the most preferable option across most environmental impact categories (including Climate Change), and in terms of weighted results, (ii) polypropylene shelters are preferable to bio-based alternatives, including polylactic acid-starch blends and bio-polypropylene, (iii) recycling is the most environmentally advantageous EoL treatment. Our study also showed that that the carbon emissions of the scenarios investigated are negligible when compared to the amount of carbon sequestered by a tree in 25 years.

Radiological impacts in Life Cycle Assessment - Part II: Comparison of methodologies

In a complementary article, an overarching framework was proposed to include radiological impacts in Life Cycle Impact Assessment (LCIA). Two methodologies were derived embodying the framework: the Critical Group Methodology (CGM), adapted from the approach commonly used in Human and Environmental Risk Assessment (HERA), and UCrad, based on the compartment modelling approach commonly used in LCIA. In this paper, characterisation factors obtained by the two methodologies are compared in detail to investigate the consequences of the different approaches to fate modelling and the sensitivity of the characterisation factors to the radionuclides' half-life. Characterisation factors from the CGM methodology are strongly affected by radioactive decay at low half-life and by dilution at large distances. Conversely, UCrad factors are not affected by dilution and are affected less than CGM by radioactive decay. It is concluded that UCrad is more appropriate than CGM for LCA because it is consistent with the general approach used in LCIA. However, CGM can be used alongside UCrad to make recommendations on the location and scale of specific processes emitting radionuclides.

Radiological impacts in Life Cycle Assessment. Part I: General framework and two practical methodologies

To date, impacts of ionising radiations have been largely disregarded in Life Cycle Assessment (LCA). This omission can be linked to the lack of a standard and comprehensive framework for including the effects of radionuclides alongside other emissions from industrial processes. Drawing on a recent review of Radiological Impact Assessment methodologies for LCA studies, this article proposes an overarching framework for integrating impacts of radionuclides in the Impact Assessment phase of LCA. From this framework, two alternative methodologies have been derived. They differ mainly in the way transport and dispersion of radionuclides in the environment are modelled: UCrad represents the first-of-its-kind compartment-type methodology for radionuclides, whereas the alternative Critical Group Methodology (CGM) has been adapted from standard Risk Assessment practices. Characterisation factors for a range of emitted species have been calculated using both methodologies and compared with those obtained from the Human Health Damages methodology, which is the only approach to radiological impacts yet implemented in LCA. For both UCrad and CGM the results are in general agreement with the Human Health Damages methodology, but UCrad gives factors closer to those obtained by the CGM approach. UCrad represents a major step towards incorporating ionising radiation impacts in LCIA. A subsequent paper will explore quantitatively the main differences between the UCrad and CGM methodologies.

The environmental impacts and the carbon intensity of geothermal energy: A case study on the Hellisheiði plant

Geothermal energy, alongside other low-carbon and renewable energies, is set to play a key role in decarbonising the power generation industry to meet the Paris Agreement goal. Thus far the majority of Life Cycle Assessment (LCA) studies focused on enhanced geothermal plants. However, conventional geothermal plants that harness hydrothermal reservoirs dominate the production of electricity from geothermal energy worldwide. This article focuses on Hellisheiði, a combined heat and power double flash geothermal plant located in Iceland, with an installed capacity of 303.3 MW of electricity and 133 MW of hot water. The study has a twofold goal: (i) identify hot spots in the life cycle and, where possible, suggest improvements, and (ii) understand the potential of geothermal energy to decarbonise the power generation industry. First, a detailed LCA study has been performed on Hellisheiði, with cradle-to-grave system boundaries and detailed site-specific data obtained from the literature. The analysis identifies consumption of diesel for drilling and use of steel for wells casing and construction of the power plant as the main hot spots. Second, carbon intensities of electricity production for various possible configurations of the Hellisheiði power plant (including single flash, and power-only production) have been compared with those of other geothermal plants and other energy sources. Different allocation procedures have been used to allocate impacts between electricity and hot water where necessary, and Monte Carlo simulations have been used to estimate uncertainties of Hellisheiði's carbon intensities. The comparison shows that the carbon intensity of Hellisheiði is in the range of 15-24 g CO₂-eq./kWh, which is similar to those of binary cycle geothermal plants, solar (photovoltaic) and hydropower, lower than other geothermal technologies and fossil-based technologies, and higher than nuclear and onshore wind.

[Stapedial reflex under auditory masking of bone canal: 1- The effect of white noise on threshold values]

The authors have studied the behaviour of the A.R. threshold under bone way masking sent to the vertex. The masking caused changings of the recorded track; a change of the compliance was observed in the 60% of the subjects and a rythmic waving of the (isoelectric) line was observed in 40% of the subjects. Upon these changes the A.R. were recorded for the tone test sent at similar values (almost equal) at those recorded without any kind of masker, even if a threshold shift sometimes big, existed because of the high intensity of the masking noise. The authors are making further researches to explain the meaning of these changes.