Open Access

Aim: European cities are facing heighten hydrological risks as a result of climate change at the same time as ecological degradation has reduced the environmental capacity to absorb and regulate such fluctuations. Climate forecasts predict more intense convective rainfall and winter flood events in the Wupper Basin in Germany, against a background trend of reduced mean rainfall during the summer months. On 14 July 2021 intense convective rainfall fell at points across Western Germany and led to flash floods in the Wupper Basin, many sites were inundated and the Wupper and Dhünn rivers rose to new record highs. Green-blue infrastructure offers strategies to reduce the impacts of hazards at the same time as providing a range of co-benefits. A study was undertaken to find which green-blue interventions will be most effective at reducing the impacts of hydrometeorological hazards for a study area in the west of the Wupper basin. Furthermore, as landscape features are highly influential in hydrology, the study sought to establish which sites within the landscape can provide maximum results from green-blue interventions, with a minimum of change to current land uses. Region: Europe, peri-urban and rural, undulating, low mountainous landscapes Methods: Literature findings on observed and projected climate data are summarised and long-term rainfall data from the study area is analysed to confirm rainfall trends. A state-of-the-art review is conducted and summarised to form a toolbox of potential interventions. The most recent hazardous hydrometeorological event is analysed to inform the locational priorities of potential interventions. Landscape features that have the most influence on basin hydrology are identified from the literature. These sites are paired with green-blue interventions that are shown to have the highest potential impact on interception, infiltration, runoff and flooding. A series of spatial analyses are carried out to produce maps detailing location and intervention with high potential to reduce the impact of hydrometeorological hazards in the study area. All of the evidence gathered from the literature analysis is combined in an implementation guide for green-blue interventions in the Wupper Basin. Results: The hazards caused by the hydrometeorological extremes of flooding and drought are addressed or minimised through the green-blue interventions that increase interception and infiltration and reduce runoff and flooding. Priority locations are identified as the riparian zone with slope ≤15%, hilltop, lower slope and toe slope, all locations with a slope ≥30% and areas with a high topographic wetness index (TWI). A series of spatial analyses were carried out and suggestions made including potential locations for retention or detention areas and ponds, sites for revegetation and potential locations for implementation of shelterbelts/hedgerows, buffer strips, conservation tillage or strip tillage, reduced mowing intensity or frequency and biochar additions. An implementation guide is created that provides a summary of the highest potential green-blue interventions and landscape locations, and a description of the mechanisms involved in addressing the hydrometeorological hazards. Keywords: Green-blue interventions, hydrometeorological hazard reduction, Wupper Basin hydrology

Austria is committed to the net-zero climate goal along with the European Union. This requires all sectors to be decarbonized. Hereby, hydrogen plays a vital role as stated in the national hydrogen strategy. A report commissioned by the Austrian government predicts a minimum hydrogen demand of 16 TWh per year in Austria in 2040. Besides hydrogen imports, domestic production can ensure supply. Hence, this study analyses the levelized cost of hydrogen for an off-grid production plant including a proton exchange membrane electrolyzer, wind power and solar photovoltaics in Austria. In the first step, the capacity factors of the renewable electricity sources are determined by conducting a geographic information system analysis. Secondly, the levelized cost of electricity for wind power and solarphotovoltaics plants in Austria is calculated. Thirdly, the most cost-efficient portfolio of wind power and solar photovoltaics plants is determined using electricity generation profiles with a 10-min granularity. The modelled system variants differ among location, capacity factors of the renewable electricity sources and the full load hours of the electrolyzer. Finally, selected variables are tested for their sensitivities. With the applied model, the hydrogen production cost for decentralized production plants can be calculated for any specific location. The levelized cost of hydrogen estimates range from 3.08 EUR/kg to 13.12 EUR/kg of hydrogen, whereas it was found that the costs are most sensitive to the capacity factors of the renewable electricity sources and the full load hours of the electrolyzer. The novelty of the paper stems from the model applied that calculates the levelized cost of renewable hydrogen in an off-grid hydrogen production system. The model finds a cost-efficient portfolio of directly coupled wind power and solar photovoltaics systems for 80 different variants in an Austria-specific context.

The European heating sector is currently heavily dominated by fossil fuels. Composting is a naturally occurring process in which heat is liberated from the composting substrate at a higher rate than the process needs to support itself. This difference could be harnessed for low-heat applications such as residential consumption, alleviating some of the impacts fossil fuel emissions represent. In this study, the composting heat recovery reported in the literature was compared to the energy demand for space and water heating in four European countries. A review of potential heat production from the waste representative of the residential sector was performed. We found that the theoretically recoverable composting heat does not significantly reduce the need for district heating. However, it can significantly reduce the energy demand for water heating, being able to supply countries such as Greece with between 36% and 100% of the yearly hot water demand, or 12% to 53% of the yearly hot water of countries such as Switzerland, depending on the efficiency of heat recovery.

Due to its location at the south-west coast of Ireland County (Co.) Cork is frequently affected by post tropical cyclones (PTCs). There have been several records of these post hurricanes in the past with the last severe PTC being Hurricane Ophelia in 2017. It caused severe disruption in the whole country, especially in Co. Cork with several thousand people without water, power and mobile service for up to 10 days and thousands of uprooted trees which blocked roads. PTCs, like Ophelia, will become more frequent under climate change conditions due to warmer sea surface temperatures and decreased vertical wind shear. Hence, hurricanes can reach northern latitudes more easily and have a higher chance of making landfall in Co. Cork. This thesis assesses the risk perception towards natural hazards (NHs) and the perception of the risk communication of hurricane Ophelia by the citizens of Co. Cork and suggests improvements in communication based on the people’s perception. This was achieved by conducting a standardised survey to analyse the perception. The risk communication chain, its content and media involved were evaluated with interviews with professionals involved in risk management in Ireland. Improvement suggestions were extracted of the survey and the expert interviews as well and have been ranked by the participating experts according to their importance. The people of Co. Cork are not overly concerned about being affected by NHs. The three hazards they feel threatened by most, after Ophelia hit the country, are storms, river floodings and hurricanes. Before Ophelia made landfall, they only ranked hurricanes in the 8th place (out of 8). Ergo, after experiencing Ophelia people are much more aware of hurricane risk in Ireland. People were very satisfied with the information they received during Ophelia. The improvements they wished for are: 1) information on how to deal with and how to prepare for impacts of the storm, 2) the impacts that can be expected locally and 3) information where to go to in case of severe impact to property. These are mostly in line with the improvements the experts ranked as most important for Cork. Experts voted the suggestion to include information on behavioural advice into risk communication before the NH hits and advice on how to organise for impacts afterwards as their number one priority. Their second rank is to have education and training for the citizens in Cork. On third place they voted for a change to impact forecasting. Even there are no central buildings or shelters available in Co. Cork, this improvement suggestion was only voted on rank 13 by the experts (out of 14). Having a participatory approach in risk communication can overcome the discrepancies between the wishes of the population and the ones of the experts and would lead to a better understanding of all stakeholders involved in risk communication and can reduce vulnerability of the people in Co. Cork to the impacts of NHs. The implementation of these activities would be in line with best practice examples and would support the guidelines of the Irish Framework for Major Emergency Management.

Wheat straw could be used for pellet production and therefore as solid fuel. However, it presents challenges due to its inferior combustion properties such as high ash content, low gross calorific value (GCV), and low ash melting temperature. To evaluate its combustion properties and based on recent work that improved methane production, wheat straw was subjected to thermobiological pretreatments. Nine pretreated samples based on wheat straw and nine pretreated samples based on compost-wheat straw mixture were produced. In addition, due to the ability to remove minerals and decrease the ash content, a washing process with water as a solvent was used. Ash content, net calorific value (NCV) and ash melting temperatures were evaluated. For the pretreated wheat straw (SW) samples, a 5,8% reduction in ash content was obtained due to the pretreatments when compared to untreated wheat straw. A 55% decrease in ash content was obtained when comparing the same materials before and after the washing process. No statistically significant changes in GCV were found. As for the ash melting temperatures, due to the incubation pretreatment, an average increase in the shrinkage starting temperature (SST) of 4,4% was obtained for anaerobic conditions and a decrease of 2,5% for aerobic conditions, compared to the same material without heat treatment. In addition, an increase in all ash melting temperatures was observed because of the washing process. It was possible to obtain a pellet complying with standard ISO 17225-6 that can be used in medium or large burners and significantly reduces the effort during combustion. For samples pretreated with a homogeneous compost-wheat straw (SKW) mixture, an average ash content decrease of 27% was obtained after using autoclave pretreatment at 140°C, compared to the same material without thermal pretreatment. The biggest decrease was due to the washing process, reducing the ash content on average by 43% when comparing the same materials before and after washing. GCV were 13% lower than samples pretreated with wheat straw, due to the low calorific value and high ash content of the compost. During ash melting temperature tests, an average 60% increase in SST was observed compared to pretreated SW ashes due to the high melting temperature of compost. Results are considered satisfactory since pellets based on this mixture would not cause ash sintering or slagging. However, counter effects were observed as the addition of compost increased the ash content and decreased the GCV, not complying with ISO 17225-6 for non-woody pellets. To achieve a pellet based on a compost-wheat straw mixture that complies with the standards, it is recommended for future research to control the percentage of compost added to the mixture.