Increasing urbanization and the effects of climate change will bring new challenges for cities, such as energy saving and supply of renewable energy, preventing urban heat islands and water retention to deal with more frequent downpours. A major urban surface, the surface of roofs, is nowadays hardly exploited and could be used to make cities more ‘future proof’ or resilient. Many Dutch municipalities have become aware that the use of green roofs as opposed to bituminous roofs positively contributes to these challenges and are stimulating building-owners to retrofit their building with green roofs. This study aims at comparing costs and benefits of roof types, focused on green roofs (intensive and extensive) both on building- and city scale. Core question is the balance between costs and benefits for both scales, given varying local conditions. Which policy measures might be needed in the future in order to apply green roofs strategically in regard to local demands? To answer this question the balance of costs and benefits of green roofs is divided into a public and an individual part. Both balances use a strengths, weaknesses, opportunities and threats framework to determine the chance of success for the application of green roofs, considering that the balance for green roofs on an individual scale influences the balance on a public scale. The outcome of this combined analyses in the conclusion verifies that a responsible policy and a local approach towards green roofs is necessary to prepare the city sufficiently for future climate changes. http://dx.doi.org/10.13044/j.sdewes.d6.0225
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Lebanon’s economic crisis has disrupted the country’s energy and water sectors, highlighting their interdependence. The methodologyinvolves surveying 150 municipalities across all Lebanese governorates, ensuring a comprehensive coverage of public and private waterresources. Data on water and energy were collected before and during the crisis to explore this nexus during periods of economic turmoil.The findings reveal a decline in water provision during the crisis, with the average weekly water supply plummeting from 49 h in 2019 to 22 hin 2023. Concurrently, the use of water tankers has surged from 26 to 44%, indicating a concerning shift in water acquisition methods.Despite the crisis, conventional water sources remain predominant, while unconventional sources account for less than 1% of the totalsupply. In response to the energy shortage, renewable energy sources have gained traction in residential, commercial, and industrial sectors.The scarcity and rising cost of electricity have driven the adoption of solar photovoltaics in the water sector, reaching 4.8% for extraction fromunderground reservoirs and 2.8% for distribution. Similarly, the use of solar water heaters has increased from 7.9 to 15.4% in 2023. Thesefindings underscore the interplay between energy and water security during periods of economic instability.
Wind and solar power generation will continue to grow in the energy supply of the future, but its inherent variability (intermittency) requires appropriate energy systems for storing and using power. Storage of possibly temporary excess of power as methane from hydrogen gas and carbon dioxide is a promising option. With electrolysis hydrogen gas can be generated from (renewable) power. The combination of such hydrogen with carbon dioxide results in the energy carrier methane that can be handled well and may may serve as carbon feedstock of the future. Biogas from biomass delivers both methane and carbon dioxide. Anaerobic microorganisms can make additional methane from hydrogen and carbon dioxide in a biomethanation process that compares favourably with its chemical counterpart. Biomethanation for renewable power storage and use makes appropriate use of the existing infrastructure and knowledge base for natural gas. Addition of hydrogen to a dedicated biogas reactor after fermentation optimizes the biomethanation conditions and gives maximum flexibility. The low water solubility of hydrogen gas limits the methane production rate. The use of hollow fibers, nano-bubbles or better-tailored methane-forming microorganisms may overcome this bottleneck. Analyses of patent applications on biomethanation suggest a lot of freedom to operate. Assessment of biomethanation for economic feasibility and environmental value is extremely challenging and will require future data and experiences. Currently biomethanation is not yet economically feasible, but this may be different in the energy systems of the near future.
