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Aerial view of Vauban neighbourhood in Freiburg, Germany. Copyright permission by Erich Meyer, Hasel|Stadt Freiburg (2012)

Aerial view of Vauban neighbourhood in Freiburg, Germany. Copyright permission by Erich Meyer, Hasel|Stadt Freiburg (2012)

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Climate change represents an existential, global threat to humanity, yet its delocalized nature complicates climate action. Here, the authors propose retrofitting air conditioning units as integrated, scalable, and renewable-powered devices capable of decentralized CO2 conversion and energy democratization.

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... which technically need ventilation to fulfil hygienestandards (humidity and odours), because their highly insulated walls and windows don't allow sufficient air exchange. Especially interesting is the implementation in neighbourhoods with a high share of low-energy houses like for instance the Vauban neighbourhood in Freiburg, Germany (see Fig. 5). For a 70 m 2 flat (average for one flat in Vauban 41 ) with one bathroom, one extra WC, one kitchen and a cellar room a minimum rated airflow of 140 m 3 h −1 can be estimated following the national standard of DIN1946-6 42 . With 5−6 flats per house (average in Vauban 41 ) and 400 ppm CO 2 in ambient air 33 , one building could ...

Citations

... Furthermore, DACCS could also be used in remote areas where the construction of BECCS plants is not possible. Some researchers have envisioned that the technology could be utilized in urban areas by retrofitting existing air conditioning units in larger office buildings [92]. In that regard, the only limiting spatial factor relevant to DACCS is the continuous supply of renewable energy [93]. ...
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Negative emissions technologies (NETs) approaches are an essential part of virtually any scenario in which global warming is limited to 1.5 °C in accordance with the Paris Agreement. Discussions often focus on two technologies due to their substantial carbon dioxide (CO2) sequestration potential: bioenergy with carbon capture and storage (BECCS) and direct air carbon capture and storage (DACCS). However, the large-scale deployment of both technologies—especially BECCS—may lead to significant human rights infringements. This paper aims to analyze the impact of both technologies on human rights from the methodological perspective of a legal interpretation of international law. It shows that a large-scale BECCS strategy, which inevitably requires enormous land-use changes, will most likely infringe upon the right to food, the right to water, and the right to a healthy environment. In contrast, large-scale DACCS approaches will likely have a smaller human rights impact, but the energy-intensive process could also infringe upon the right to energy. Balancing these human rights with other freedom rights, e.g., of consumers and enterprises, the paper will further demonstrate that from the perspective of human rights, rapid emission reductions and the minimization of livestock farming—and also less risky nature-based options such as peatland and forest management—should prevail before any large-scale industrial NET strategies.
... In scenario C, this unit is centralized and powered by waste heat from the vacuum system and the Rankine cycle. Oppositely, in scenario D, the carbon capture is decentralized and the CO2 is extracted from the heating, ventilation and air conditioning systems (HVAC) of skyscrapers located near the plant [43]. ...
... In scenario C, this unit is centralized and powered by waste heat from the vacuum system and the Rankine cycle. Oppositely, in scenario D, the carbon capture is decentralized and the CO 2 is extracted from the heating, ventilation and air conditioning systems (HVAC) of skyscrapers located near the plant [43]. ...
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Non-abatable emissions are one of the decarbonization challenges that could be addressed with carbon-neutral fuels. One promising production pathway is the direct air capture (DAC) of carbon dioxide, followed by a solar thermochemical cycle and liquid fuel synthesis. In this study, we explore different combinations of these technologies to produce methanol from an economic perspective in order to determine the most efficient one. For this purpose, a model is built and simulated in Aspen Plus®, and a solar field is designed and sized with HFLCAL®. The inherent dynamics of solar irradiation were considered with the meteorological data from Meteonorm® at the chosen location (Riyadh, Saudi Arabia). Four different integration strategies are assessed by determining the minimum selling price of methanol for each technology combination. These values were compared against a baseline with no synergies between the DAC and the solar fuels production. The results show that the most economical methanol is produced with a central low-temperature DAC unit that consumes the low-quality waste heat of the downstream process. Additionally, it is determined with a sensitivity analysis that the optimal annual production of methanol is 11.8 kt/y for a solar field with a design thermal output of 280 MW.
... However, all these processes are energy intensive and put an additional strain on the energy system, thus they are effective if supplied by renewable energy [101]. In the case of direct air carbon capture and use (DACCU), the captured CO2 is converted into hydrocarbon fuels and materials with the help of H2 and renewable energy [e.g., 100]. These fuels and materials can be used as substitutes for fossil carbon materials and fuels in industrial processes and even the aviation sector, thereby reducing emissions in sectors for which emissions are otherwise hard to abate [e.g., 51,97,100]. ...
... In the case of direct air carbon capture and use (DACCU), the captured CO2 is converted into hydrocarbon fuels and materials with the help of H2 and renewable energy [e.g., 100]. These fuels and materials can be used as substitutes for fossil carbon materials and fuels in industrial processes and even the aviation sector, thereby reducing emissions in sectors for which emissions are otherwise hard to abate [e.g., 51,97,100]. Looking back from the year 2050, the most cost-effective strategy of reaching net-zero CO2 was avoiding emissions from major emitters by transforming towards a more sustainable energy supply. ...
... These plants provide the option to produce concentrated CO2 taken directly from the atmosphere. However, since this process is rather energy-intensive (mostly heat but also power), and therefore inefficient in low insolation areas like Germany, another solution was found: Today, almost every big office or retail building has an air carbon capture unit integrated in the Heating, Ventilation and Air-Conditioning (HVAC) system capturing a total of 17 Mt CO2 [100,101]. The hotter summers caused an expansion in air conditioning needs for buildings, and this demand was used to retrofit existing HVAC-systems as well as install new HVAC-systems which are now included in the CO2 transportation and storage system. ...
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Plain Language Summary Here a net‐zero‐2050 Germany is envisioned by combining analysis from an energy‐system model with insights into approaches that allow for a higher carbon circularity in the German system, and first results from assessments of national carbon dioxide removal potentials. A back‐casting perspective is applied on how net‐zero Germany could look like in 2050. We are looking back from 2050, and analyzing how Germany for the first time reached a balance between its sources of CO2 to the atmosphere and the anthropogenic sinks created. This would consider full decarbonization in the entire energy sector and being entirely emission‐free by 2050 within three priorities identified as being the most useful strategies for achieving net‐zero: (a) Avoiding‐ (b) Reducing‐ (c) Removing emissions. This work is a collaboration of interdisciplinary scientists with the Net‐Zero‐2050 cluster of the Helmholtz Climate Initiative HI‐CAM.
... Considering that the average CO 2 concentration in the office during the daytime is about 600 ppm and that the air conditioning system ventilates several times in an hour (about 5 times), the weight of CO 2 in this ventilation air is about 17,000 tons/year. 180 If, for example, 25% of this CO 2 is to be recovered, 4,200 tons of CO 2 can be collected from just one building. Considering a large number of office buildings, this could be a significant amount of CO 2 capture. ...
... However, the permeability and selectivity of CO 2 vary even with the same thickness reported. (see the supporting information of Ref. 180). The fabrication of thin membranes with stable CO 2 permeation has been a central issue in membrane fabrication. ...
... In this context, water electrolysis or photocatalytic splitting appears to be the most promising when sustainability is concerned. 129 ...
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Circular chemistry (CC) is an approach for establishing chemical processes to become truly circular and sustainable. It adopts the principles of circular economy (CE), employing life cycle approaches and systems thinking, which help to understand and address the sustainability issues of chemical processes and products. Within this whole context, it is possible to identify some problems of the current lifestyle, such as plastic waste disposal, CO2 emission, e-waste, among others, which need to be addressed accordingly. The reuse provided, well-structured within the context of circular chemistry, can bring benefits in all spheres: social, environmental and economic. Thus, the purpose of this revision is to present CE and CC as the pillars for a sustainable development, bringing discussions about: CE and CC systems; sustainable chemistry; and chemistry 4.0, which embeds digitization, sustainability, and circular economy in industrial chemical processes. Through the knowledge of chemistry, both CC and CE can contribute with innovative methods and processes which maximize benefits, eliminating, or, at least, reducing adverse impacts, thus contributing to construct a mutually beneficial relationship between science and society, its surroundings, and the environment. Therefore, implementing this new model is an opportunity that challenges the human imagination in building a better world.
... However, all these processes are energy intensive and put an additional strain on the energy system, thus they are effective if supplied by RE (HI-CAM, 2020). In the case of direct air carbon capture and use, the captured CO 2 is converted into hydrocarbon fuels and materials with the help of H 2 and RE (e.g., Dittmeyer, et al., 2019). These fuels and materials can be used as substitutes for fossil carbon materials and fuels in industrial processes and even the aviation sector, thereby reducing emissions in sectors for which emissions are otherwise hard to abate (e.g., Airbus, 2020;Billig et al., 2019;Dittmeyer, et al., 2019). ...
... In the case of direct air carbon capture and use, the captured CO 2 is converted into hydrocarbon fuels and materials with the help of H 2 and RE (e.g., Dittmeyer, et al., 2019). These fuels and materials can be used as substitutes for fossil carbon materials and fuels in industrial processes and even the aviation sector, thereby reducing emissions in sectors for which emissions are otherwise hard to abate (e.g., Airbus, 2020;Billig et al., 2019;Dittmeyer, et al., 2019). Bioenergy and Carbon Capture and Storage (BECCS) is the process which combines generation of energy (e.g., electricity, heat, biofuels) from biomass with capturing and storing of the otherwise emitted CO 2 in geological storage sites (e.g., Furre et al., 2019;Gluyas & Bagudu, 2020;Knopf & May, 2017;Porthos, 2019;Swennenhuis, et al., 2020). ...
... These plants provide the option to produce concentrated CO 2 taken directly from the atmosphere. However, since this process is rather energy-intensive (mostly heat but also power), and therefore inefficient in low insolation areas like Germany, another solution was found: Today, almost every big office or retail building has an air carbon capture unit integrated in the heating, ventilation and air-conditioning (HVAC) system capturing a total of 17 Mt CO 2 (Dittmeyer et al., 2019;HI-CAM, 2020). The hotter summers caused an expansion in air conditioning needs for buildings, and this demand was used to retrofit existing HVAC-systems as well as install new HVAC-systems which are now included in the CO 2 transportation and storage system. ...
Full-text available
Article
ere a net-zero-2050 Germany is envisioned by combining analysis from an energy-system model with insights into approaches that allow for a higher carbon circularity in the German system, and first results from assessments of national carbon dioxide removal potentials. A back-casting perspective is applied on how net-zero Germany could look like in 2050. We are looking back from 2050, and analyzing how Germany for the first time reached a balance between its sources of CO2 to the atmosphere and the anthropogenic sinks created. This would consider full decarbonization in the entire energy sector and being entirely emission-free by 2050 within three priorities identified as being the most useful strategies for achieving net-zero: (a) Avoiding- (b) Reducing- (c) Removing emissions. This work is a collaboration of interdisciplinary scientists with the Net-Zero-2050 cluster of the Helmholtz Climate Initiative HI-CAM
... However, all these processes are energy intensive and put an additional strain on the energy system, thus they are effective if supplied by RE (HI-CAM, 2020). In the case of direct air carbon capture and use, the captured CO 2 is converted into hydrocarbon fuels and materials with the help of H 2 and RE (e.g., Dittmeyer, et al., 2019). These fuels and materials can be used as substitutes for fossil carbon materials and fuels in industrial processes and even the aviation sector, thereby reducing emissions in sectors for which emissions are otherwise hard to abate (e.g., Airbus, 2020;Billig et al., 2019;Dittmeyer, et al., 2019). ...
... In the case of direct air carbon capture and use, the captured CO 2 is converted into hydrocarbon fuels and materials with the help of H 2 and RE (e.g., Dittmeyer, et al., 2019). These fuels and materials can be used as substitutes for fossil carbon materials and fuels in industrial processes and even the aviation sector, thereby reducing emissions in sectors for which emissions are otherwise hard to abate (e.g., Airbus, 2020;Billig et al., 2019;Dittmeyer, et al., 2019). Bioenergy and Carbon Capture and Storage (BECCS) is the process which combines generation of energy (e.g., electricity, heat, biofuels) from biomass with capturing and storing of the otherwise emitted CO 2 in geological storage sites (e.g., Furre et al., 2019;Gluyas & Bagudu, 2020;Knopf & May, 2017;Porthos, 2019;Swennenhuis, et al., 2020). ...
... These plants provide the option to produce concentrated CO 2 taken directly from the atmosphere. However, since this process is rather energy-intensive (mostly heat but also power), and therefore inefficient in low insolation areas like Germany, another solution was found: Today, almost every big office or retail building has an air carbon capture unit integrated in the heating, ventilation and air-conditioning (HVAC) system capturing a total of 17 Mt CO 2 (Dittmeyer et al., 2019;HI-CAM, 2020). The hotter summers caused an expansion in air conditioning needs for buildings, and this demand was used to retrofit existing HVAC-systems as well as install new HVAC-systems which are now included in the CO 2 transportation and storage system. ...
Article
Germany 2050: For the first time Germany reached a balance between its sources of anthropogenic CO2 to the atmosphere and newly created anthropogenic sinks. This backcasting study presents a fictional future in which this goal was achieved by avoiding (around 645 Mt CO2), reducing (around 50 Mt CO2) and removing (around 60 Mt CO2) carbon emissions. This meant substantial transformation of the energy system, increasing energy efficiency, sector coupling, and electrification, energy storage solutions including synthetic energy carriers, sector-specific solutions for industry, transport, and agriculture, as well as natural-sink enhancement and technological carbon dioxide options. All of the above was necessary to achieve a net-zero CO2 system for Germany by 2050.
... Fossil fuel has been a primary energy source since the Industrial Revolution, creating a strong economic foundation for modern human society (Smil, 2016). However, fossil fuel is non-renewable and will soon be depleted, leading to a risk of global energy crisis (Dittmeyer et al., 2019). In addition, the combustion of fossil fuel emits greenhouse gases resulting in severe environmental issues such as higher global temperature, higher sea levels, ocean acidification and extreme weather (Day and Day, 2017). ...
Article
This study reviews the recent advances and innovations in the application of additives to improve biomethane and biohydrogen production. Biochar, nanostructured materials, novel biopolymers, zeolites, and clays are described in terms of chemical composition, properties and impact on anaerobic digestion, dark fermentation, and photofermentation. These additives can have both a simple physical effect of microbial adhesion and growth, and a more complex biochemical impact on the regulation of key parameters for CH4 and H2 production: in this study, these effects in different experimental conditions are reviewed and described. The considered parameters include pH, volatile fatty acids (VFA), C:N ratio, and NH3; additionally, the global impact on the total production yield of biogas and bioH2 is reviewed. A special focus is given to NH3, due to its strong inhibition effect towards methanogens, and its contribution to digestate quality, leaching, and emissions into the atmosphere.
... The DAC-technique and its potential role in future's energy and chemical industry has recently been object of scientific discussions [25][26][27][28]. Common DAC-principles are well known. ...
... The potential of buildings' exhaust air was recently pointed out by Dittmeyer et al., who mentioned the vast amount of ventilated air in the HVAC-systems of large buildings [26]. Starting from that point, where the main reason to use the exhaust air of buildings is the reduced effort to mechanically move air, the idea is extended to make use of the CO 2 -depleted air. ...
Article
This concept study presents an approach for resolving the trade-off between energy-efficient building operation and the provision of hygienically harmless indoor air quality. A novel coupling of HVAC-systems (heating, ventilation and air conditioning systems) with DAC-technology (direct air capturing technology) is proposed to separate CO2 in the exhaust air of buildings and recirculate the CO2-depleted air back into the building. In a mainly theoretical approach, the corresponding potentials and limitations of the novel HVAC/DAC-coupling in recirculation mode are evaluated. For that purpose, CO2-loads in the feed and exhaust air of four buildings located in Germany were measured using calibrated non-dispersive infrared (NDIR) sensors with pyroelectric detection principle. Subsequent numerical model simulations resort to typical meteorological data as well as building operation parameters grouped in different scenarios. The measurement and simulation results were assessed with regard to: (i) the unique possibilities of a HVAC/DAC-coupling in recirculation mode for the improvement of indoor air quality, (ii) the energy saving potentials through reduced air conditioning requirements enabled by a HVAC/DAC-coupling in recirculation mode, and (iii) the potential allocation of CO2 separated from building exhaust air for energetic and/or material reutilization in decentralized systems. In conclusion, a HVAC/DAC-coupling in recirculation mode can not only reduce the energy demand of buildings but also facilitates access to unutilized CO2-resources transported in the built environment and additionally offers the potential to improve indoor air quality. However, a suitable DAC module for operation in indoor air is not yet commercially available.
... Carbon capture and utilization (CCU) is critical to reducing CO 2 emissions and mitigating global warming. 1 Through the production of carbon-rich hydrocarbons via CO 2 valorization, 2,3 CCU is expected to pave the route for the transition to renewable, non-fossil-fuel-based energy sources. 4 One of the most promising approaches toward CO 2 valorization consists of the combination of conventional metallic catalysts with acidic zeolites. 5 This combination can directly transform CO 2 to a great variety of chemicals with a selectivity above the limitation of the Anderson−Schulz−Flory distribution (ASF). ...
... Zn(CH 3 COO) 2 (99.99%), Zr(OH) 4 , PVP (Mwt 10000), DMF (99.8%), and ethylene glycol (99.8%) were purchased from Sigma-Aldrich and used as received. ZSM-5 (SiO 2 / Al 2 O 3 = 23) was purchased from Zeolyst. ...
... The colloidal mixture was cooled, centrifuged, and washed with acetone and then dispersed in ethanol. The dispersed colloidal mixture in ethanol was added to 6 g of Zr(OH) 4 powder and stirred for 20 h at room temperature. The resulting mixture was oven-dried and calcined at 500°C for 3 h. ...
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Article
The production of carbon-rich hydrocarbons via CO2 valorization is essential for the transition to renewable, non-fossil-fuel-based energy sources. However, most of the recent works in the state of the art are devoted to the formation of olefins and aromatics, ignoring the rest of the hydrocarbon commodities that, like propane, are essential to our economy. Hence, in this work, we have developed a highly active and selective PdZn/ZrO2+SAPO-34 multifunctional catalyst for the direct conversion of CO2 to propane. Our multifunctional system displays a total selectivity to propane higher than 50% (with 20% CO, 6% C1, 13% C2, 10% C4, and 1% C5) and a CO2 conversion close to 40% at 350 °C, 50 bar, and 1500 mL g–1 h–1. We attribute these results to the synergy between the intimately mixed PdZn/ZrO2 and SAPO-34 components that shifts the overall reaction equilibrium, boosting CO2 conversion and minimizing CO selectivity. Comparison to a PdZn/ZrO2+ZSM-5 system showed that propane selectivity is further boosted by the topology of SAPO-34. The presence of Pd in the catalyst drives paraffin production via hydrogenation, with more than 99.9% of the products being saturated hydrocarbons, offering very important advantages for the purification of the products.