Ramboll

This paper reports on a benchmark study based on small-scale (1:50) measurements of a single, oscillating water column chamber mounted sideways in a long flume. The geometry of the OWC chamber is extracted from a barge-like, attenuator-type floating concept “KNSwing” with 40 chambers targeted for deployment in the Danish part of the North Sea. In addition to traditional two-way energy extraction we also consider one-way energy extraction with passive venting and compare chamber response, pressures and total absorbed energy between the two methods. A blind study was established for the numerical modeling, with participants applying several implementations of weakly nonlinear potential flow theory and commercial Navier–Stokes solvers (CFD). Both compressible and incompressible models were used for the air phase. Potential flow calculations predict more energy absorption near the chamber resonance for one-way absorption than for two-way absorption, but the opposite is found from the experimental measurements. This outcome is mainly attributed to energy losses in the experimental passive valve system, but this conclusion must be confirmed by better experimental measurements. Modeling the one-way valve in CFD proved to be very challenging and only one team was able to provide results which were generally closer to the experiments. The study illustrates the challenges associated with both numerical and experimental analysis of OWC chambers. Air compressibility effects were not found to be important at this scale, even with the large volume of additional air used for the one-way case.

Mangrove forest restoration can improve services and functions across associated coastal ecosystems. However, the effectiveness of mangrove restoration efforts is highly dependent on knowing the locations and habitat requirements of target species within the landscape of interest. Habitat suitability models are powerful tools that identify suitable environmental conditions and reduce the risk of poor site selection. When coupled with information on potential future climate conditions, land‐use conflicts, and co‐benefits (e.g., biodiversity), these models can be used to identify and prioritize areas that meet multiple stakeholder objectives and help implement a broader ecosystem‐based approach to restoration. In this study, we coupled habitat suitability models with machine learning to assess present and future habitat suitability of mangrove forests across the Arabian Gulf. We then incorporated land‐use and marine habitat data from Qatar to prioritize areas for mangrove restoration in a country where mangroves constitute the only type of forest. All the tested machine learning models (artificial neural networks, boosted regression trees, random forest, Maxent, and Maxnet) showed high predictive performance, but the percentage of contributions of each environmental predictor differed across the models. Important predictors of mangrove habitat suitability in Qatar included elevation, slope, distance to coastline, temperature, and precipitation. While most models predicted a future reduction in suitable habitat for mangrove forests in the country and across the region, there were suitable sites in Qatar located within currently protected areas. We identified several potential areas of high restoration impact (i.e., high present and future suitability, far from urban areas, and closest to live coral areas) across the northwest side of Qatar. These results demonstrate that habitat suitability modeling can be paired with information on land‐use restrictions, proximity to infrastructure, and other ecosystems to integrate an ecosystem‐based approach to guide restoration site selection.

Stress relaxation of quartz sands is simulated using a recently proposed physically based time-to-fracture discrete element method framework. The framework incorporates time-dependency through stress-corrosion-induced grain fracture. This feature is embedded into a pre-existing particle-splitting-based rough-contact crushable model. The model is calibrated to represent Fontainebleau sand, a quartz sand. A controlled on–off computational strategy is adopted to advance the simulation efficiently. Model predictions are shown to compare favourably with laboratory results in oedometric and triaxial conditions in terms of stress relaxation and relaxation rate. Grain size distribution evolution is also tracked and shown to compare well with available laboratory results. The influence of initial mobilized strength q/qmax on stress relaxation is recovered by the model, and explained through increased grain breakage. The simulated relaxation results are examined at the microscale and compared with those from creep experiments. The model displays the nonisochronous behaviour characteristic of sands. The relaxation tests display a state shift towards higher dilatancy conditions that may offer a possible explanation for some observations of pile set-up.

Objectives To quantify, after extending follow-up 15 years, the relationship between occupational respirable crystalline silica (RCS) exposure and risk of silicosis diagnosis and lung cancer mortality in the German Porcelain Workers Cohort Study, and to estimate possible exposure thresholds for these. Methods Porcelain workers enrolled between January 1, 1985, and December 31, 1987, in a mandatory medical surveillance program including triennial chest x-rays and alive at the end of the previous study follow-up (2005) were followed through December 2020, for lung cancer mortality and silicosis incidence. Cause of death was determined from death certificates. Silicosis cases were identified by re-reading x-rays of individuals remaining in the medical surveillance program or filing insurance claims for silicosis. RCS exposure was estimated for each cohort member using a job exposure matrix (JEM) based on about 8,000 historical industrial hygiene RCS measurements. Cause-specific standardized mortality ratios (SMRs) and Cox proportional hazards ratios (HRs) and their 95% confidence intervals (95% CIs) were estimated by cumulative and average exposure groups, controlling for age, sex, smoking status and employment duration. Exposure-response analyses were performed to identify possible exposure thresholds for lung cancer and silicosis risk. Results Total deaths increased from 1,610 (9.1%) to 4,586 (26%) over 537,129 total person-years at risk. All-cause mortality was elevated among men (SMR = 1.10, 95% CI 1.06–1.14); however, a deficit was seen among women (SMR = 0.93, 95% CI 0.89–0.98). No statistically significantly increased mortality was seen due to lung cancer, renal cancer, or non-malignant renal disease – conditions reportedly associated with RCS exposure. Lung cancer mortality was unrelated to RCS exposure level. However, for silicosis cases classified using International Labor Organization (ILO) categories ≥1/1 or 1/0, risk was strongly associated with estimated average exposure >0.10 mg/m³ and 0.15 mg/m³, and cumulative exposure >3.0 mg/m³-years and > 1.0 mg/m³-years, respectively. Conclusion Despite the large number (n = 284) of lung cancer deaths and high historical RCS exposures, no excess risk and no relationship with exposure level were seen. However, RCS exposure was strongly associated with silicosis risk, with clear exposure thresholds. This study further confirms the lack of increased lung cancer risk at RCS levels historically prevalent in the German porcelain industry and that exposures exceeding estimated thresholds clearly increased silicosis risk. Occupational exposure levels in the German porcelain industry in recent decades have remained well below these thresholds; therefore, few additional silicosis cases are expected.

This study examines how a combination of prospective life cycle assessment (pLCA) and absolute environmental sustainability assessment (AESA) can support shaping environmental strategies in the building sector. The paper highlights the benefits of pLCA as a forward-looking approach that integrates technological and socio-economic scenario projections. Through a case study of the Danish building sector, it investigates the potential of technological advancements to meet absolute sustainability targets and explores mitigation strategies to bridge the gap between current impacts and absolute targets. The study covers 16 environmental impact categories. The study identifies which building materials have the strongest potential to mitigate climate impacts and reveals risks of burden shifts towards other impact categories. By modelling future construction in Denmark (2025–2050), the study finds a significant divergence from current consumption patterns and exceedance of the planetary boundaries suggesting that technological advancements cannot alone take construction in Denmark towards sustainable practices. The study therefore suggests a shift towards biobased materials and reduced construction activity as viable mitigation strategies. The study highlights a trade-off between climate change and land use when conventional building materials (concrete, steel etc.) are replaced by biobased materials. More over, the study shows that anticipated changes in the background system rely on solutions that will increase some environmental impacts e.g. land use and resource use of metals and minerals. Overall, the findings underline the importance of adjusting current LCA methods to ensure relevant assessments that can support decision making for achieving rapid climate mitigation as expressed by the IPCC and ensure that burdens are not shifted unintentionally.

Recognizing methanol's versatile role as a chemical precursor and energy carrier, this study addresses its traditional production from fossil fuels and the associated challenges in pivoting to green alternatives due to the cost of green hydrogen. The research focuses on techno-economic analysis and optimization, employing a validated chemical process simulation tool integrated with economic analyses, reflecting CAPEX and OPEX models, and considering heat recovery to promote self-sufficiency. The study compares grey (traditional syngas) and green (biogenic CO2 and green hydrogen) methanol production pathways while also optimizing process factors, such as feed pressure, purge rate, temperature and catalyst volume, to achieve cost-effectiveness. In green methanol production specifically, the paper finds that optimal conditions are slightly milder than for grey methanol, highlighting the importance of process variables like purge rate given the high cost of green hydrogen. Still with current price level of hydrogen from electrolysis the levelised cost of methanol is several times more expensive via direct hydrogenation compared to production from fossil syngas. Results from the simulation-driven optimization underline the delicate balance between various objectives, such as minimizing costs or maximizing output, and demonstrate instances of pareto optimality. This study thus contributes with an integrated assessment of methanol production techniques, utilizing process simulation, economic evaluation, and heat integration for both grey and green methanol, aiming to pave the way for more sustainable chemical processes in the industry.

Successful management of chalk reservoirs for various subsurface applications often depends on reliable estimates of rock mechanical properties. Yet, rock stiffness and strength data collected at in situ temperature are typically limited. Accordingly, a mechanical testing program was designed to investigate how testing temperature impacts stiffness and yield properties of high porosity North Sea chalk. Tests were conducted at ambient (≈ 25 ℃) and in situ temperatures (75 or 85 ℃) and as uniaxial strain and hydrostatic compaction. Core plugs were either oil or water saturated, and the static moduli and yield strength were derived from stress–strain curves. Irrespective of saturating fluid, no clear temperature effect was observed on the static moduli or yield strength, yet a water weakening effect was seen. The impact of testing temperature on stress–strain behaviour and static moduli are thus of similar magnitude to effects from initial fractures and natural sample variations identified from CT-scans. In contrast, the dynamic moduli derived from elastic wave velocities and density indicated a minor stiffness decrease at increased testing temperature. The observed decrease in dynamic moduli for increased testing temperature aligns with the temperature-induced stiffness decrease of the constituting calcite minerals. Accordingly, the largest temperature-induced stiffness decrease is for the uniaxial compressional modulus and the lowest for the shear modulus. The observed effect of increased temperature on elastic moduli of the studied chalk may be due to two opposing effects on the solid frame; stiffening from thermal expansion that opposes the thermal softening of the constituting calcite minerals.

One way to decrease the carbon emissions from concrete structures is to make smarter and more optimal structural designs. Prefabricated concrete walls are widely used in building structures. However, buildings made of traditional precast wall elements contain very little flexibility if you need an opening like a door hole or a larger opening in the wall in the future. To enable circular use of buildings with concrete walls, a new optimized concept for precast concrete walls is suggested in this paper. It is called a modifiable concrete wall and consists of two zones: a frame zone and a flexible zone. A new opening can be cut in the flexible zone without, or with little, strengthening of the structure. This will potentially prolong the lifespan of the building and reduce carbon emissions (CO 2 e) in the long run. To also reduce carbon emissions in the short run, the carbon footprint from the materials of the wall is minimized. This is done by allowing a very low concrete strength and small amount of reinforcement in the flexible zone. Furthermore, a material optimization framework using finite element limit analysis (FELA) is developed. For one or more given load cases, the optimization framework finds the optimal concrete strength and amount of reinforcement, which minimizes the carbon footprint. A realistic example of a wall structure of a five‐floor apartment building is made. The carbon footprint of the optimized modifiable concrete element is compared to a standard wall element, and reductions in the order of 40%–60% are found.

Malminkenttä is an old airfield covering an area of around 2.4 km2. Area is on soft subsoil which consists mainly of 5 to 20 m deep clay layers. The amount of required column stabilization is estimated to be about 10 million meters in total. The clay layer is a challenging task for deep mixing. The uppermost clay layer is sulphate clay where the pH value is even at level 4 at the oxidized layer. The water content of the clay layer is up to 160 %. The City of Helsinki has decided to discontinue the use of lime cement in column stabilisation due to its high carbon dioxide emissions. The city has decided to use low-carbon binders, only some of which the city has previous experience, in column stabilisation in the future. One aspect at the construction at Malminkenttä area is the creek Longinoja, which is located next to the construction area and is an important living area for threatened trout and thus any negative effect to water quality of the creek is not allowed. All this together means that laboratory testing, test stabilization and environmental monitoring are very appropriated.

Malminkenttä, in the northern part of city of Helsinki, will be a new residential area. The surface area is about 2.4 km2. The soil conditions of the area are mainly soft sensitive clay that requires intensive ground improvement actions for the development of the residential project. Dry deep mixing (DDM) has been planned as one of the key ground improvement methods. The preliminary preconstruction plan made in 2017 showed that if lime-cement were used as binder material for DDM in Malminkenttä the CO2 emissions would be vast. Therefore, low-carbon binders have been studied widely to reduce emissions. This paper presents performance comparison of laboratory test results for different binders. The aim is to show that low-carbon binders are a real solution for DDM and that they can perform even better than traditional lime-cement. The laboratory tests include characterization, uniaxial compression and triaxial tests. Another aim is to analyze the differences of shear strength, yield stresses and deformation moduli determined by uniaxial compression and triaxial test.

City of Helsinki has a goal of carbon neutrality by 2030, and this article explores methods to mitigate carbon emissions in ground improvement projects in the residential areas of Malminkenttä. The article focuses on the feasibility and low-carbon opportunities of using low-carbon binders in place of conventional lime-cement binders in deep mixing. Through laboratory and field tests, alternative binders are validated for their efficiency in reducing emissions. Carbon accountings confirm the potential for significant emission reductions in the residential areas which are characterized by deep clay layers. The study concludes that using low-carbon binders and low-carbon ground improvement methods, as well as implementing effective carbon management procedures, can successfully lead to emission reduction targets in ground improvement projects.

Recognizing methanol's versatile role as a chemical precursor and energy carrier, the study addresses its traditional production from fossil fuels and the associated challenges in pivoting to green alternatives due to the cost of green hydrogen. The research focuses on techno-economic analysis and optimization, employing a validated chemical process simulation tool integrated with economic analyses, reflecting CAPEX and OPEX models, and considering heat recovery to promote self-sufficiency. The study compares grey (traditional syngas) and green (biogenic CO$_2$ and green hydrogen) methanol production pathways while also optimizing process factors, such as feed pressure, purge rate, temperature and catalyst volume, to achieve cost-effectiveness. In green methanol production specifically, the paper finds that optimal conditions are slightly milder than for grey methanol, highlighting the importance of process variables like purge rate given the high cost of green hydrogen. Still with current price level of hydrogen from electrolysis the levelised cost of methanol is several times more expensive via direct hydrogenation compared to production from fossil syngas. Results from the simulation-driven optimization underline the delicate balance between various objectives, such as minimizing costs or maximizing output, and demonstrate instances of pareto optimality. This study thus contributes with an integrated assessment of methanol production techniques, utilizing process simulation, economic evaluation, and heat integration for both grey and green methanol, aiming to pave the way for more sustainable chemical processes in the industry.

As the European Union (EU) is aiming to realize climate neutrality by 2050, there is a need to investigate greenhouse gas (GHG) reduction and carbon dioxide removal strategies (CRRS) from a life cycle perspective. Existing literature lacks harmonization of building-related strategies considering the whole-life cycle of buildings and the interlinkages across life cycle stages. The aim and novelty of this study was to systematically identify, classify and quantify the impacts of CRRS, as well as assess their applicability in different EU Member States. We identified a total of 35 measures grouped in 11 CRRS for the whole-life cycle of buildings. We classified these measures according to various criteria, such as the avoid–shift–improve framework or the life cycle stages influenced. We then assessed the potential diffusion of these strategies in each EU Member State up to 2050 via qualitative assessment criteria. We could achieve notable short-term reductions in GHG emissions by improving use-phase energy use, selecting low-carbon materials or reducing the per capital space demand. In the medium to long term, the applicability and reduction potential of strategies such as circularity and prioritizing renovation over new construction will increase as supply chains and skills develop across the EU. Due to their different potentials and times of implementation, the entire range of strategies is needed to support building and construction transition efforts.

Biodegradable plastics have certain challenges in a waste management perspective. The existing literature reviews fail to provide a consolidated overview of different process steps of biodegradable plastic waste management and to discuss the support provided by the existing legislation for the same. The present review provides a holistic overview of these process steps and a comprehensive relative summary of 13 existing European Union (EU) laws related to waste management and circular economy, and national legislations plus source separation guidelines of 13 countries, to ensure the optimal use of resources in the future. Following were the major findings: (i) numerous types and low volumes of biodegradable plastics pose a challenge to developing cost-effective waste management infrastructure; (ii) biodegradable plastics are promoted as food-waste collection aids, but consumers are often confused about their proper disposal and are prone to greenwashing from manufacturers; (iii) industry-level studies demonstrating mechanical recycling on a full scale are unavailable; (iv) the existing EU legislation dealt with general topics related to biodegradable plastics; however, only the new proposal on plastic packaging waste and the EU policy framework for bioplastics clearly mentioned their disposal and (v) clear disparities were observed between disposal methods suggested by national legislation and available source separation guidelines. Thus, to appropriately manage biodegradable plastic waste, it is necessary to develop waste processing and material utilization infrastructure as well as create consumer awareness. In the end, recommendations were provided for improved biodegradable plastic waste management from the perspective of systemic challenges identified from the literature review.

Plain Language Summary Halogens such as chlorine, bromine, and iodine are highly reactive gases that participate in atmospheric chemistry, including ozone destruction, particle formation, modification of greenhouse gas lifetime (i.e., methane, dimethylsulfide), and the oxidation of elemental mercury. Iodine mainly enters the atmosphere from oceans; therefore, past measurements of atmospheric iodine have focused on marine and polar regions. This study describes the first lower atmospheric measurements of iodine monoxide (IO) radicals at a remote mountaintop site in the central continental United States. These measurements indicate that the concentration of IO radicals showed a large range over the course of 1 month and reached levels up to three times higher than predicted by a global atmospheric chemistry model. These observations suggest that our understanding of the iodine sources and sinks to the free troposphere may be incomplete. Moreover, we suggest that iodine's contribution to ozone destruction and mercury chemistry may be underestimated; in particular, iodine may be competitive with bromine in the oxidation of elemental mercury in the free troposphere.

– This paper presents a framework for optimisation and techno-economic analysis of various pressurisation pathways for CO2 pipeline transportation. The pressurisation pathways include a conventional compression only case from initial to final pressure, a sub-critical compression part followed by cooling, liquefaction and pumping and also a super-critical compression part followed by cooling and dense phase pumping. The presented framework is developed based on open-source components and information available in the public domain. The framework includes a high level of flexibility to study variations in initial and final pressures, inclusion of inter-stage pressure drop, inter-stage cooling temperature, liquefaction/pumping pressure, among others. The implemented methods i.e. the thermodynamic and economic models applied, are rigorously validated and bench-marked against literature data. Contrary to former studies that focus mainly on reduction of the work required for pressurisation, the presented method includes additional capabilities to assess CAPEX, OPEX and the levelised cost of CO2 compression. The analysis shows that in some cases the minimum levelised cost does not coincide with the minimum work. It is also demonstrated that for some cases the super-critical compression/cooling/pumping case and the sub-critical compression/cooling/liquefaction/pumping pathways provide optimal levelised cost compared to a multi-stage compression only case.