Christian Moretti

Last Name

Moretti

First Name

Christian

ORCID

0000-0001-5682-287X

Organisational unit

01709 - Lehre Umweltsystemwissenschaften

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Publications1 - 10 of 23

The role of direct air capture in achieving climate-neutral aviation
Brazzola, Nicoletta; Meskaldji, Amir; Patt, Anthony; et al. (2025)
Nature Communications
Growing demand for air travel and limited scalable solutions pose significant challenges to the mitigation of aviation's climate change impact. Direct air capture (DAC) may gain prominence due to its versatile applications for either carbon removal (direct air carbon capture and storage, DACCS) or synthetic fuel production (direct air carbon capture and utilization, DACCU). Through a comprehensive and time-dynamic techno-economic assessment, we explore the conditions for synthetic fuels from DACCU to become cost-competitive with an emit-and-remove strategy based on DACCS under 2050 CO2 and climate neutrality targets. We find that synthetic fuels could achieve climate neutrality at lower cost than an emit-and-remove strategy due to their ability to cost-effectively mitigate contrails. Under demand reductions, contrail avoidance, and CO2 neutrality targets the cost advantage of synthetic fuels weakens or disappears. Low electricity cost (0.02 kWh-1) and high fossil kerosene prices (0.9 l-1) can favor synthetic fuels' cost-competitiveness even under these conditions. Strategic interventions, such as optimal siting and the elimination of fossil fuel subsidies, can thus favor a shift away from fossil-reliant aviation.
Solar Thermochemical Jet Fuel Production from Air-Captured H2O and CO2 – Reactor Modelling, Upscaling, and Techno-Economic Analysis
Schäppi, Remo; Moretti, Christian; Patil, Vikas; et al. (2024)
We report on the solar thermochemical fuel production from H2O and CO2 obtained by direct air capture [1]. We present a heat and mass transfer model of the solar reactor. We further present the results of an energy efficiency and techno-economic analysis of an industrial-scale fuel plant [2]. The core of the process is the simultaneous co-splitting of CO2 and H2O via a ceria-based thermochemical redox cycle driven by concentrated solar process heat. The characteristic redox cycle is operated under a temperature/pressure-swing mode, consisting of three phases: 1) The reduction phase, during which the solar reactor is heated with concentrated sunlight up to the desired reduction-end temperature of up to 1500°C to release O2 from CeO2, assisted through lowered O2 partial pressure by a vacuum pump and sweep gas flow. 2) A cool-down phase under atmospheric pressure during which the solar reactor, re-pressurized by injecting CO2, cools down to the oxidation start temperature. 3) The oxidation phase, during which CO2 and H2O are co-injected into the reactor’s cavity, react with the reduced ceria to form syngas – a tailored mixture of CO and H2. The syngas can then be further processed to liquid hydrocarbon fuels via established gas-to-liquid processes such as Fischer-Tropsch synthesis. We present the results of a dynamic grey-box model of the solar reactor for solving the governing energy and mass conservation equations. The analysis compares the implementation of the modelled reactors in a 2-reactor versus 3-reactor system under different solar input conditions and compares the findings to experimental results obtained with a 2-reactor pilot demonstration plant. We present an energy efficiency analysis of an industrial-scale solar fuel plant that uses the concentrated solar energy of a heliostat field as the source of high-temperature process heat and integrates a thermal energy storage system for round-the-clock continuous operation. We further report on the techno-economic assessment of such an industrial-scale plant. Two scenarios are considered for a location with high direct normal irradiation (e.g. annual DNI > 3400 kW/m2): near-term future by the year 2030 and long-term future beyond 2030 with advancements in solar receiver, redox reactor, high-temperature heat recovery and direct air capture technologies. The minimum fuel selling price is estimated at around 2.5 €/L jet fuel in the near-term future, and 0.6-1.3 €/L jet fuel in the long-term future. Greenhouse gas savings can exceed 70% already in the near-term future.
Metrics for minimising environmental impacts while maximising circularity in biobased products: The case of lignin-based asphalt
Corona, Blanca; Hoefnagels, Ric; Vural Gürsel, Iris; et al. (2022)
Journal of Cleaner Production
Achieving a circular economy (CE) is seen by society and policymakers as crucial to achieving a sustainable, resource-efficient, renewable and competitive economy. Given the current threat of climate change, we must develop new products that not only maximise the circularity of resources but also minimise climate change impacts. While these two goals are usually aligned, trade-offs exist. For instance, recycling biobased asphalt is a better end-of-life option than landfilling from a resource efficiency perspective. However, landfilling of biogenic non-biodegradable material leads to permanent carbon storage and, therefore, climate benefits. To fully understand the potential benefits and impacts of biobased circular innovations, we need metrics to capture their complexity from both a circular and climate point of view. This study explores the use of different circularity and sustainability metrics to understand the impacts and trade-offs of lignin-based versus bitumen-based asphalts. The analysis is done by calculating the Material Circularity Index (MCI) and two newly developed indicators quantifying the biogenic carbon storage (BCS) of products (BCS100 and c-BCS) while following the CE principles. In addition, the impacts regarding climate change, life cycle costs and ECI (environmental costs indicator) are also provided. Based on the MCI, it can be concluded that lignin-based asphalt roads have slightly higher material circularity than their bitumen-based counterparts. The BCS analysis indicated that the least circular lignin-based alternative sequesters the highest amount of carbon in the long term due to permanent storage in foundations. Despite these trade-offs, the results from the newly developed BCS indicators allowed to align both climate and circularity goals, guiding policymakers and industry actors to implement circular biobased strategies where the value of biobased materials is optimised. Finally, this article discusses the use of different circularity and environmental metrics for decision making in the context of a circular biobased economy.
Policy Pathways to Reduce DAC Costs
Brazzola, Nicoletta; Moretti, Christian; Sievert, Katrin; et al. (2023)
Prospective life cycle assessment of cost-effective pathways for achieving the FuelEU Maritime Regulation targets
Ingwersen, Anna; Hahn Menacho, Alvaro J.; Pfister, Stephan; et al. (2025)
Science of The Total Environment
To reduce environmental impacts from the shipping industry, the FuelEU Maritime Regulation has set a binding 80 % reduction target for well-to-wake (WTW) greenhouse gas (GHG) emissions by 2050. This article presents a prospective life cycle assessment (LCA) comparing the environmental impacts of e-ammonia, e-methanol, e-Fischer Tropsch (FT) diesel, and e-liquefied natural gas (LNG)—for maritime applications in Europe. In addition to e-fuels, traditional propulsion technologies using very low sulfur fuel oil (VLSFO) and LNG are assessed, both with and without integrating ship-based carbon capture (SBCC) systems. Key factors considered include the impact of different production locations in Europe, electrolysis technology choices, and global climate policies. Beyond analysing the environmental footprints, the study examines the economic and externality costs associated with each fuel option, contextualizing these findings within the GHG mitigation targets set by the FuelEU Maritime regulation. The results indicate that e-ammonia, e-FT diesel, and e-methanol could meet the 2050 FuelEU Maritime target, but e-LNG and SBCCS could not. Although it is the most immature technology, e-ammonia could be the cheapest option with the lowest overall environmental impacts. E-LNG shows higher life cycle climate change impacts due to ship-level methane slip but has lower impacts across other environmental categories because of low NOx emissions. E-methanol has higher toxicity risks over the life cycle and higher costs.
Global greenhouse gas emissions mitigation potential of existing and planned hydrogen projects
Terlouw, Tom Mike; Moretti, Christian; Harpprecht, Carina; et al. (2025)
Nature Energy
Hydrogen will play a critical role in decarbonizing diverse economic sectors. However, given limited sustainable resources and the energy-intensive nature of its production, prioritizing its applications will be essential. Here, we analyse approximately 2,000 (low-carbon) hydrogen projects worldwide, encompassing operational and planned initiatives until 2043, quantifying their greenhouse gas (GHG) emissions and mitigation potential from a life cycle perspective. Our results demonstrate the variability in GHG emissions of hydrogen applications, depending on the geographical location and hydrogen source used. The most climate-effective hydrogen applications include steel-making, biofuels and ammonia, while hydrogen use for road transport, power generation and domestic heating should be discouraged as more favourable alternatives exist. Planned low-carbon hydrogen projects could generate 110 MtH2 yr⁻¹, emit approximately 0.4 GtCO2e yr⁻¹, and potentially reduce net life cycle GHG emissions by 0.2–1.1 GtCO2e yr⁻¹ by 2043, depending on the substituted product or service. Addressing the current hydrogen implementation gap and prioritizing climate-effective applications are crucial for meeting decarbonization goals.
Mitigating future winter electricity deficits: A case study from Switzerland
Mellot, Adrien; Moretti, Christian; Tröndle, Tim; et al. (2024)
Energy Conversion and Management
The transition to a net-zero economy with increased electrification of transport and heating poses electricity supply challenges during the winter months, particularly in PV-dominated systems. This study explores comprehensively various strategies and their combinations to address potential winter electricity deficits in Switzerland. Our innovative modelling integrates three sectors (electricity, heat, and transport), neighbouring countries, and environmental life cycle considerations. Among potential strategies to mitigate Swiss winter electricity deficit, electricity imports from neighbouring countries are taken as the benchmark policy strategy. Our analysis reveals that only gas-fired power plants and alpine PV, if applied in isolation, are technology options that alleviate the Swiss winter deficit and reduce cost at the same time. Increasing other single power technologies individually, or importing hydrogen, alleviate the deficit, too, but they inflate energy system costs by 18%–34% compared to relying on electricity imports. Despite the strategies for mitigating the winter deficit assessed being substantially different, our study found no significant environmental concerns regarding local land requirements or critical raw material needs. However, each strategy might imply the need for certain fuel imports and can have a profound impact on determining cost-optimal heating strategies for buildings. With an additional 1.4 GW of gas-fired power plant fuelled by domestic bio-methane, 4 GW of alpine PV, 2.2 GW of wind turbines, and no cost increase compared to its current roadmap, Switzerland could have a fully renewable energy system with a reduced winter deficit and no fuel imports.
Exploratory Analysis of Direct Load Control Policies for Heat Pumps in the Future Swiss Electricity System
Mellot, Adrien; Linder, Jan; Garrison, Jared; et al. (2025)
2025 21st International Conference on the European Energy Market (EEM)
New flexible electrical loads such as heat pumps present major demand-side flexibility opportunities thanks to their load shifting potential. In this study, we analyze to what extent the direct load control (DLC) of heat pumps within realistic bounds facilitates their integration in the Swiss energy system as it decarbonizes, by coupling a bottom-up building stock model and a high-resolution electricity system model. We rely on recently offered DLC contracts by Swiss distribution system operators to set these bounds and study the impact of different DLC settings. We find that contract parameters such as allowing preheating and prolonging shifting windows significantly impact how much DLC is performed. However, even high levels of DLC lead to small impacts on the electricity system's cost and renewables' integration in Switzerland, possibly only having a significant effect on peak electricity prices.
Ensuring the environmental sustainability of emerging technologies applications using bio-based residues
Moretti, Christian (2023)
Ensuring the environmental sustainability of emerging technologies -2. Edited volume
The European Green Deal with related EU chemical and bioeconomy strategies aim to accelerate the development of innovative conversion technologies to produce bio-based alternatives in European sectors traditionally dominated by petrochemical products. As a result of this effort to reduce fossil fuel dependence and climate change impacts, the growing global trend of innovative bio-based commodities is expected to continue. The significant investments in future emerging technologies for biobased products should be guided towards those that are environmentally sustainable. This is possible only with science-based evidence on their environmental impacts at an early stage. In particular, unlocking the full potential of locally sourced bio-based residues is crucial to expanding the number of bio-based products produced sustainably in the EU. This feedstock does not generate concerns about food security and land competition. Furthermore, it is usually cheaper than dedicated crops and does not require transoceanic imports. For these reasons, products from biobased residues are expected to be the core of future bio-based innovation to move towards a circular economy via better valorization of natural resources. Moreover, avoiding dedicated cultivation with required fertilizers, fuel consumption in tractors, irrigation, etc., bio-based residues are expected to have a lower climate change impact than dedicated crops. Life cycle assessment (LCA) methodology is an internationally standardized method to assess products’ and services' life cycle environmental impacts. Various policy regulation mechanisms already rely on LCA results to incentivize bio-based products based on their environmental performance. However, these policy instruments mostly cover climate change impacts, i.e., incentives are based on greenhouse gas mitigation potentials (Edwards et al., 2017). So, other environmental tradeoffs typically existing between bio-based and petrochemical products are neglected. When the scientific literature considered additional environmental impact categories, bio-based products often showed higher eutrophication and water depletion impacts than their petrochemical counterparts due to biomass cultivation (EC, 2019). So far, there is still a lack of comprehensive understanding of environmental tradeoffs of emerging products made from biobased residue streams not requiring dedicated cultivation. This paper aims to reflect on critical considerations necessary to avoid that a greenness claim of a future technology utilizing a bio-based residue is challenged at a late investment stage for its adverse environmental impacts.
Valorization of Demolition Waste and Biomass Byproduct into Sustainable Building Materials via Carbon Mineralization and 3D Printing
Ding, Yong; Kindler, Robert Oswin; Cen, Tianyu; et al. (2026)
Chemistry—Methods
Reducing atmospheric CO2 is crucial for mitigating climate change and ensuring a sustainable future. The building sector is a major contributor, consuming 40% of global raw materials and accounting for 35% of global energy consumption. As a result, there is a growing demand for more sustainable building materials. Herein, a scalable, energy-efficient, and low-emission approach is presented to convert various waste streams into building materials via carbon mineralization and 3D printing. Calcium ions are extracted from recycled concrete using ammonium salt leaching methods and then reacted with CO2 gas to form high-purity calcium carbonate through mineralization. This calcium carbonate is formulated into a bio-based mineral binder by incorporating kraft lignin as a rheological modifier. The binder is further combined with sawdust to produce printable inks for additive manufacturing. The resulting 3D-printed structures demonstrate robust mechanical properties and modular design potential, making them suitable for non-load-bearing building applications. By integrating CO2 sequestration and renewable materials, this work demonstrates a closed-loop strategy for carbon capture, waste valorization, and digital fabrication, providing a new avenue for decarbonizing the built environment.

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