CO2 mineralization is a crucial carbon capture and utlization technique because it can sequester CO2 emissions permanently. There are various CO2 mineralization technological pathways, all of which are based on the reaction of CO2 with the metal oxides present in cementitious materials and virgin minerals. However, there are techno-economic obstacles that hinder their deployment, as well as various knowledge gaps regarding the prospective supply chains. Although these pathways have several differences, such as process configuration and costs, each is usually addressed individually and comparative analysis is lacking. In this contribution, we aim to address this knowledge gap via investigating the entire supply chain of each technology and contrasting their differences by presenting a case study from the German federal state of North Rhine-Westphalia. Methodologically, several approaches and tools are used, such as cost modeling and geographic information systems. Herein, we investigate the advantages and limitations by assessing six scenarios representing the different configurations of the relevant supply chains. Most scenarios are deemed infeasible at lower carbon prices, with only three considered viable below 100 €/ton CO2. Also, while concrete curing and concrete waste processes are constrained by material availability and logistics, CO2 mineralization of virgin minerals offers a more abundant alternative, albeit at a higher levelized cost. Therefore, the study provides valuable insights for the design of optimal and efficient CO2 mineralization supply chains, highlighting the need for a balanced approach that leverages the strengths of different pathways.

The paper introduces a dynamic-locational MFA model to analyze the urban stock of bridges by integrating quantity, time, and location in one framework. The model is developed to assess existing materials in the urban stock, predict future demolition activities, quantify material flows, and analyze their spatial distribution. The derived framework depends on the structural conditions to anticipate lifetime and survival. For the empirical analysis and demonstration, a dataset of >12,000 bridges in North Rhine-Westphalia was compiled to provide the required information such as location, area, type and material. The analyses demonstrate significant variability in material flows across different times and locations. Some regions exhibited exceptional material flows, while others had very low flows, highlighting the importance of temporal and spatial aspects. The results also predict significant material flows over the next two decades in the investigated region, underscoring the urgency of circular economy and closer cooperation between stakeholders.

The effectiveness of biochar as a soil amendment is highly dependent on local physical and chemical soil properties. Although the literature has already addressed biochar in several studies, there are still knowledge gaps. One the one hand, the relevant studies have primarily focused on field trials and small-scale applications at regional levels, overlooking the global perspective and regional differences. One the other hand, geospatial assessments lack quantitative evaluations and explanation, which are crucial for the model's applicability and the optimisation of biochar supply chains. Thus, this study addresses this gap by examining the impact of biochar on agriculture at a global scale. First, correlations between climate, soil, and fertiliser data, and maize yield are derived through Random Forrest machine learning algorithm. Subsequently, the relevant soil properties are adjusted to simulate the potential changes upon implementing biochar. Finally, the model projects the estimated maize yield following the introduction of biochar. Our findings demonstrate diverse effects of biochar, with notable increase in maize yield in arid regions of Africa and Asia. A substantial increase in maize yield is particularly expected in regions with a high bulk density, as biochar effectively loosens the soil, and in areas with a low soil organic carbon content, which is enhanced by biochar. Contrariwise, in northern South America, Central and North America, South-East Asia, and parts of Europe show low potential or even maize yield decreases. The model was also validated by comparing the results with 8 field trials from different countries, demonstrating a high level of accuracy. The outcomes are crucial for optimising biomass utilisation pathways, as it predicts the impact of biochar in different regions. Consequently, policy frameworks can be tailored to encourage biochar use in agriculture, especially in regions with the highest potentials, to fully leverage its sustainability and productivity benefits.

Carbon capture and storage will be necessary for some industries to reach carbon neutrality. One of the main associated challenges is the design of the network linking the CO ₂ sources to the storage sites. Establishing a CO ₂ network can be impacted by many uncertainties such as CO ₂ amounts, pipeline routes and the locations of emitters and carbon sinks. We present a framework to investigate different scenarios of a future CO ₂ network in Germany. The analyses compare the routes and associated costs of different scenarios. The developed model uses several geospatial datasets and an optimization scheme to yield realistic and cost-efficient outcomes. Parameters such as population density and existing infrastructure are integrated to calculate potential routes, which are then used as an input for the developed heuristic model to determine the optimum network. The derived framework is flexible and can be used for investigating other scenarios, regions and settings. The results show that the different scenarios have a profound impact on the optimal layout and costs. The investment costs of the investigated scenarios range between 1.3 and 3 billion EUR. The outcomes are important for academia, industry and policymaking for the ongoing discussions regarding the development of carbon infrastructure.

Conventional substrates like peat, stone wool and coconut coir are responsible for high greenhouse gas emissions in the horticultural sector, necessitating low-emission and cost-efficient alternatives. Herein, using miscanthus and biochar as substrate components as well as in cascading substrate application can be alternative practices in a sustainable bioeconomy. However, the carbon footprint and economic impacts of these practices in relation to crop yields have not yet been investigated. Hence, we combined life cycle carbon footprint assessment and costing to analyze the Global Warming Potential and value chain costs of horticultural substrates in tomato cultivation in North-Rhine Westphalia. We conducted a comparison between conventional substrates (peat, stone wool, and coconut coir) and single use and cascading miscanthus-based substrates with and without 1–2 % biochar addition of the miscanthus mass. Also, a subsequent scenario analysis was carried out to examine alterations in inputs and costs. Our results demonstrate that miscanthus-based substrates are climate-friendly and low-cost alternatives to the conventional practices. Switching to miscanthus-based substrates results in more emission savings than other input scenarios investigated. Additionally, incorporating biochar and adopting cascading methods contribute to lower emissions. Notably, biochar has the most significant impact, as its amount correlates with higher emission reductions. Additionally, costs for cascading miscanthus-based substrates are lower compared to conventional substrates. Overall, there is only a slight variance in costs between conventional and miscanthus-based substrates. However, with the introduction of carbon emission pricing and carbon removal certificates, miscanthus-based and biochar-containing substrates may emerge as more cost-efficient alternatives. Thus, by advancing financial instruments on carbon emissions and removal, introducing cascade use within and beyond the horticulture sector, and supporting cultivation of sustainable biomasses, miscanthus and biochar can effectively contribute to the development of a sustainable bioeconomy.

Polylactic acid (PLA) is the bioplastic with the highest market share. However, it is mainly produced from first-generation feedstock and there are various inconsistencies in the literature in terms of its production and recycling processes, carbon footprint, and prices. The aim of this study is to compile and contrast these aspects and investigate second-generation PLA production from technical, economic, and ecological perspectives simultaneously. The comprehensive analyses also show the chances and challenges of originating a PLA supply chain in a specific region. Herein, the German Federal State of North Rhine-Westphalia (NRW) has been chosen as a region of interest. In addition to highlighting the industrial capabilities and synergies, the study quantifies and illustrates the locations of different suitable second-generation feedstocks in the region. However, the identified potentials can be challenged by various obstacles such as the high demand of bioresources, feedstock quality, spatial aspects, and logistics. Furthermore, the substantial price gap between PLA and fossil-based plastics can also discourage the investors to include PLA on their portfolios. Thus, the study also provides recommendations to overcome these obstacles and promote the regional value chains of bioplastics which may serve as prototype for other regions.

Energy transition as a response to climate change requires structural transformation in the industrial sector. While some industries have already gained the attention of research studies due to their high production and emissions levels, there is an obvious lack of analyses on small but energy intensive sectors such as casting industry. Herein, the aim of this paper is to fill this knowledge gap by implementing an environmental assessment of the cast iron and steel melting technologies. The carbon footprint of four main types of furnaces and their variants have been determined. Moreover, sensitivity analyses have been conducted to quantify the impact of energy sources and electricity-mix. The analyses show the major differences between the environmental performances of melting technologies. As the GHG emissions depend on the adopted technology linked with specific amounts and sources of energy, the current technologies are associated with high carbon footprints (especially cupola furnaces). Therefore, reaching carbon neutrality necessitates fundamental changes in terms of types of furnaces and related energy sources.

Reaching carbon neutrality necessitates radical changes in terms of energy sources and industrial technologies. Some industries such as cement and lime emit significant amounts of process emissions, which will continue to be generated regardless of the type of energy source employed. One way to address such ‘hard-to-abate’ emissions is by employing carbon capture, utilization and storage (CCUS) technologies. Novel technologies such as CCUS undergoes continuous innovation before reaching high technological maturity and their commercial potential. To that extent, research and pilot projects represent an effective technology-push tool to minimize relevant uncertainties, risks and costs and increase the technology’s readiness level. In recent years, different CCUS demonstration projects have been implemented and financed differently. This study investigates the role of these projects in the future deployment of CCUS technologies, with focus on the European cement sector specifically. Overall, the paper aims to evaluate the status quo of decarbonization of the cement sector via CCUS and to discuss the required future activities and measures to enhance the technology’s integration into the sector.

North-Rhine Westphalia is the center of the German and European steel production. Its steel industry is heavily based on the primary production route and emits up to 30 Mt CO ₂ annually. One possible and increasingly prominent alternative to reduce these emissions is the hydrogen-based direct reduction. While this technology allows for a near climate-neutral production of primary steel, it poses substantial impacts on regional energy and material flows. Hence, the aim of this paper is to quantify the alterations in energy and material flows over time via integrating top-down energy and material flow models with bottom-up process models. The resulting values of emissions, energy, and material flows are then used to develop prospective scenarios that depict the requirements and consequences of potential pathways toward a climate-neutral steel production by 2045. The outcomes show that decarbonizing the North Rhine-Westphalian steel industry leads to an additional demand for renewable energies of up to 52.5 TWh per year, which represents 10% of the current electricity production in Germany. As securing the green electricity demand is a large challenge, the study also analyzes the impact of a partial recourse to natural gas as a reducing agent in combination with other measures like carbon capture and utilization/storage. The results show that such a recourse would reduce the electricity demand to 36.8 TWh. Hence, the paper illustrates relevant implications of the different scenarios, which can be used by policymakers to develop more realistic and resilient strategies for reaching carbon neutrality.

Carbon capture and utilization (CCU) is an essential method to sequester unavoidable CO ₂ emissions in regions with insufficient geological storage capacities. Nonetheless, there are several uncertainties and knowledge gaps in terms of the future value chains of some CCU technologies (e.g. carbonation). This paper analyzes the potentials of coupling CCU with the supply chains of the construction industry by means of carbonating the concrete products and waste concrete in the German federal state of North Rhine–Westphalia. Based on extensive data and statistical analyses, the locations and outputs of the concrete and recycling plants have been determined in order to quantify their CO ₂ sequestration capacities. Location-allocation models have been applied to allocate the carbon sources to the potential carbon sinks and calculate the minimum transportation costs. The analysis shows that the total annual sequestration capacity is up to 1 Mt CO ₂ with an average transportation distance of 37.4 km (8.3 EUR/ton). Nonetheless, some emission sources have a clear comparative advantage in terms of their proximity to the carbon sinks as the distance ranges between 0.7 km and 99.7 km. Also, some carbon sinks have a comparative advantage in terms of capacities and technology readiness levels. Therefore, the paper also presents models for the different products in order to display the potentials of each category separately and offer more flexibility to the stakeholders.

The industrial sector is responsible for significant amounts of CO ₂ emissions. Although research activities have already given their attention to major industries such as steel, small sectors such as metal casting have been overlooked. Therefore, there are evident knowledge gaps regarding the environmental impact of the foundry industry and the possibilities of decarbonizing the sector. Herein, this study focuses on the CO ₂ emissions associated with cast iron production and introduces an interdisciplinary framework in order to study the environmental impact, technical performance and production costs. The theoretical and experimental analyses illustrate the interconnections between the environmental, technical and economic aspects of cast iron production. The results emphasize the role of the smelting process and renewable energies in decreasing the carbon footprint. In terms of the input materials, the outcomes demonstrate that increasing the steel scrap content achieves considerable reductions in the CO ₂ emissions. An alloy composition with a steel scrap content of 25% leads to a minimum carbon footprint of 650 kg CO ₂ eq./ton. However, increasing the steel scrap content further results in higher carbon footprints due to the additional materials required to maintain the alloy composition. Moreover, a higher strength and lower ductility of the alloy were recorded due to higher amounts of carbide stabilizing elements. The study highlights the importance of adopting a holistic approach in order to define the optimal material combinations. Hence, the presented interdisciplinary approach can be applied by the foundries in order to achieving the technical, economic and ecological goals of the sector.

Defossilizing the energy and industrial systems and transformation towards a circular economy have versatile impacts on the availability and demand of alternative resources. However, systematic analyses on these interrelations are very sparse. Thus, this paper investigates the interlinkages between the energy transition and the transformation towards a circular economy in Germany. The study is based on material flow analysis models of the steel and cement industries as well as the coal and lignite power plants in order to depict a comprehensive description of the material, energy and emission flows of these sectors and their interdependencies. The analyses prove the inherent interrelation between energy transition and circular economy. On the one hand, energy transition does not only bear various techno-economic challenges and have substantial effects on the production costs, but it also affects the availability of secondary materials. For instance, the coal phase-out and the introduction of green steel imply that the current supplies of blast furnace slag, fly ash and FGD gypsum cannot be maintained. On the other hand, circularity approaches can also influence the energy transition. For example, banning single-use plastics and increasing recycling rates of plastics can deprive the cement industry from significant amounts of energy resources with low-carbon footprint. Contrariwise, CO ₂ recycling can promote the energy transition by means of mitigating CO ₂ emissions via carbonation. Therefore, the study can help policymakers to understand the indirect effects of existing and future policies. Also, it can help to develop future strategies to handle associated impacts and avoid material shortages.

Construction and demolition waste (CDW) constitutes the biggest share of all waste generated. In addition to the environmental advantages, CDW recycling provides also high resource conservation benefits if used as recycled aggregates. Integrated forecasting of demolition and construction activities is crucial for quantifying and reconciling future supply and demand. While spatial characteristics are significant to minimize transportation costs, temporal aspects and material characteristic are important to regard for the development of the urban stock over time. This paper presents a Dynamic-Locational MFA as a model that integrates spatial, temporal and CDW material characteristics into material flow analysis at the demand and supply side. The relevant drivers of construction and demolition activities are defined in order to derive the required equations. Also, the empirical analysis is used to conclude the parameters and demonstrate the model on a real case study. Hence, the synergies between the recycling and construction activities are identified and the supply and demand of materials can be reconciled. The outcomes are not only important in terms of resource efficiency, but also help in anticipating and planning the restructuring of the value chain of the construction sector, such as the locations and capacities of concrete and recycling plants.