Residual Emissions Research Articles

Technology to the rescue? Techno-scientific practices in the United Kingdom Net Zero Strategy and their role in locking in high energy decarbonisation pathways

The development of country specific decarbonisation pathways is becoming increasingly common as more governments commit to achieving Net Zero. These pathways are critical for setting the direction and pace of decarbonisation.This article reviews the characteristics of fifteen different UK Net Zero pathways (three government pathways and 12 additional pathways) and shows how the expectation of technology innovation and low-carbon energy abundance closes down the space potential pathways can occupy. In particular, we find that while conceptually different, the three government pathways display a high degree of similarity and that the majority of pathways rely on significant amounts of new clean energy and retain large residual emissions in 2050 which requires the deployment of significant new carbon dioxide removal technologies.The dominance of high energy and high residual emission pathways is also observed in international scenarios including IPCC's Shared Socioeconomic Baseline Pathways and the IEA's Net Zero Energy Scenario. By situating these domestic plans within an international context, the paper explores how the reliance on new technology in developed countries perpetuates an unjust model of fossil-fuelled development and blocks the development of alternative, transformative decarbonisation pathways from being considered.

Analysis of The Need for Green Open Spaces in Reducing CO2 Carbon Dioxide Emissions in the Bahteramas Hospital Area of Southeast Sulawesi Province

This study aims to determine CO2 emissions resulting from transportation sources, residents, electricity and the ability of green open spaces (RTH) to reduce CO2 gas emissions in the Bahteramas Hospital Area. This research was conducted in December 2022-January 2023 at Bahteramas Baruga Hospital, Kendari City, Southeast Sulawesi Province. The results showed that the highest CO2 emission load was generated from the use of electricity with a total of 54,119 kg/day, then population emissions were 4,933 kg/day, while the lowest emission load was generated from CO2 transportation emissions of 4,437 kg/day. The total emission generated in the Bahteramas Hospital Area is 63,489 kg /day. The ability of green open space to reduce CO2 emissions is 8,399 kg/day so that it still has residual CO2 emissions that have not been able to be absorbed by the existing green open space of 55,090 kg/ day.

The role of hydrogen in a net-zero emission economy under alternative policy scenarios

Low emission and green hydrogen as a carbon-free energy carrier has attracted worldwide attention in decarbonizing the energy system and meeting the Paris agreement target of limiting warming to 2 °C or below. This study investigates the contribution of different hydrogen pathways to the energy transition and sheds light on adopting different decarbonization scenarios for Quebec, Canada, while including biogenic emissions from forest-based biomass consumption. We assess various alternative policy scenarios using a TIMES model for North America (NATEM), a bottom-up techno-economic approach. This study examines the role of various hydrogen pathways in Quebec's energy transition by considering different net-zero policy scenarios and an additional set of “green” scenarios, which prohibit the use of fossil fuel-based hydrogen. The results show that varying the penetration of hydrogen provides a key trade-off between reliance on direct air capture, reliance on carbon storage, reliance on wind and solar buildout, the inter-sector allocation of residual emissions, and the overall cost of achieving emission targets. In particular, the use of hydrogen in the industrial sector, a sector known to be difficult to decarbonize, reduces industrial emissions and reliance on direct air capture (DAC). Clustering industrial plants to use captured CO2 as a feedstock for synthetic fuel production may not reduce industrial GHG emissions by 2050, but it offers the opportunity to use captured CO2 instead of sequestering it in deep saline aquifers. Even though increasing industrial green hydrogen penetration increases marginal GHG abatement costs in the green net-zero scenario by 2050, it further minimizes industrial GHG emissions and the need for DAC among all net-zero scenarios by 2050. Hydrogen plays a significant role in achieving ambitious net-zero emission target, especially where electrification is not feasible, or electricitystorage is required.

Forests: A passive CO2 sink or an active CO2 pump?

Forests are considered an important component on the road to climate neutrality. Together with technical and other nature-based solutions, they should help to compensate for unavoidable residual emissions. Forests are seen primarily as a carbon sink, removing CO2 from the atmosphere through biomass growth. The desire to increase the sink capacity of forests to achieve climate neutrality suggests the removal of C through timber harvesting. Without timber harvesting, wood-based products would have to be replaced by products based on other raw materials, which generally cause higher emissions during production. The goal of climate neutrality is thus jeopardized. Forests can make a much greater contribution to climate neutrality by harvesting their wood and supplying it to low-emission processing operations, and by sequestering the carbon contained in the biomass used in wood products over the long term.

Neutralizing China's transportation sector requires combined decarbonization efforts from power and hydrogen supply

Transportation is vital to meeting China's carbon neutrality target by 2060. Nevertheless, the question of how to reach it remains unclear. Here, we employ a bottom-up energy system optimization model to investigate carbon dioxide emission trends using two sets of scenarios. The first relies solely on the efforts of the transportation sector, employing the avoid-shift-improve approach. In contrast, the second set of scenarios involves collaborative collaboration from the transportation, power and hydrogen sectors. The results reveal that achieving carbon neutrality solely through the efforts of the transportation sector is a challenging task. However, integrating negative emission technologies from the power and hydrogen sectors makes it feasible for the transportation sector to achieve carbon neutrality. Our findings suggest that in order to meet the carbon neutrality target, the energy structure of the transportation sector will undergo a fundamental transformation, with a significant increase in the use of electricity and hydrogen by 2060. Meanwhile, the power and hydrogen sectors will need to rely heavily on renewable energy sources and implement carbon capture and storage technologies to achieve substantial emissions reductions and offset the residual emissions from transportation. This study puts forward a comprehensive pathway that integrates the transportation sector with the power and hydrogen supply sectors, aiming to achieve carbon neutrality by 2060.

University of Genoa best practices in managing Energy and Climate Change

Since 2011, the University of Genoa (UniGe), Italy, focused on sustainable management of its campuses. In one of them, the Savona Campus, research and projects are specifically focused on Sustainable Energy and Smart City topics. Great efforts were made to reduce the carbon footprint by the creation of two large Research Infrastructures (a Smart Microgrid and an energy self-sufficient building) integrating different renewable energy sources and system automation. These infrastructures allowed to improve the energy performance of the Campus. Several actions have been then carried out also in the Genova Campus, including the implementation of a system for the real-time monitoring of the consumption of electricity for the most energy-intensive buildings. Results permitted to reduce energy consumption and provided significative and practical guidelines for energy saving. In 2015, the UniGe Commission on Environmental Sustainability was created and since then UniGe joined several international sustainability networks, such as ISCN (International Sustainable Campus Network) and UNICA GREEN (Network of Universities from the Capitals of Europe), sharing its best practices with other universities. UniGe is also active member of the Italian Universities’ Network for Sustainable Development (RUS). In 2022 UniGe made a strong and explicit pledge against climate change, defining its Climate Neutrality Strategy 2022-2030. The strategy, starting from its latest UniGe greenhouse gases (GHG) inventory, outlines a path that the university must follow to reduce both direct and indirect emissions and defines the actions to do for the offsetting of residual emissions. This is the last step of the strong and continuous commitment towards the spreading of the sustainability culture in all the Campus activities.

Carbon accounting of negative emissions technologies integrated in the life cycle of spirulina supplements

Carbon dioxide removal (CDR) technologies are considered essential to accomplish the Paris Agreement targets. Given the important contribution of the food sector to climate change, this study aims to investigate the role of two carbon capture and utilization (CCU) technologies in decarbonizing the production of spirulina, an algae product commonly consumed for its nutritional characteristics. The proposed scenarios considered the replacement of synthetic food-grade CO2 in Arthrospira platensis cultivation (BAU scenario) with CO2 from beer fermentation (BRW) and CO2 from DACC (direct air carbon capture) (SDACC), representing two alternatives with great potential in the short and medium-long term, respectively. The methodology follows the Life Cycle Assessment guidelines, considering a cradle-to-gate scope and a functional unit equivalent to the annual production of spirulina in a Spanish artisanal plant. Results showed a better environmental performance of both CCU scenarios as compared to BAU, reaching a reduction of greenhouse gas (GHG) emissions of 52 % in BRW and of 46 % in SDACC. Although the brewery CCU offers a deeper carbon mitigation of spirulina production, the process cannot reach net zero GHG emissions due to residual burdens across the supply chain. In comparison, the DACC unit could potentially supply both the CO2 needed in spirulina production and work as a CDR to compensate residual emissions, which opens the door for further research on its technical and economic feasibility in the food sector.

On the cost of zero carbon hydrogen: A techno-economic analysis of steam methane reforming with carbon capture and storage

This article challenges the view that zero carbon hydrogen from steam methane reforming (SMR) is prohibitively expensive and that the cost of CO2 capture increases exponentially as residual emissions approach zero; a flawed narrative often eliminating SMR produced hydrogen as a route to net zero. We show that the capture and geological storage of 100% of the fossil CO2 produced in a SMR is achievable with commercially available post-combustion capture technology and an open art solvent. The Levelised Cost of Hydrogen (LCOH) of 69£/MWhth HHV (2.7£/kg) for UK production remains competitive to other forms of low carbon hydrogen, but retains a hydrogen lifecycle carbon intensity of 5 gCO2e/MJ (LHV) due to natural gas supply chain and embodied greenhouse gas (GHG) emissions. Compensating for the remaining lifecycle GHG emissions via Direct Air Capture with geological CO2 Storage (DACCS) increases the LCOH to 71–86 £/MWhth HHV (+3–25%) for a cost estimate of 100–1000 £/tCO2 for DACCS and the 2022 UK natural gas supply chain methane emission rates. Finally, we put in perspective the cost of CO2 avoidance of fuel switching from natural gas to hydrogen with long term price estimates for natural gas use and DACCS, and hydrogen produced from electrolysis.

German citizens’ preference for domestic carbon dioxide removal by afforestation is incompatible with national removal potential

Efficient and sustainable solutions for offsetting residual emissions via carbon dioxide removal are a major challenge. Proposed removal methods result in trade-offs with other Sustainable Development Goals, and the removal needs of many countries exceed their domestic potentials. Here, we examine the public acceptability of conducting afforestation and direct air capture programmes domestically in Germany or abroad. To uncover the relative importance of various programme attributes, we use a multifactorial vignette experiment. We find that afforestation receives stronger support than direct capture. Next to the costs to households, minimising environmental impacts on biodiversity in forests and the use of renewable energy for direct capture are more important for acceptability than the permanence of storage. Further, individuals strongly prefer domestic programmes to offsets in other countries. These findings suggest significant discrepancies between strong public preferences for domestic carbon removal with low environmental side-effects and the too low potential for such removals.

Reducing plastic film mulching and optimizing agronomic management can ensure food security and reduce carbon emissions in irrigated maize areas

Increasing crop yields to ensure food security while also reducing agriculture's environmental impacts to ensure green sustainable development are great challenges for global agriculture. Plastic film, widely used to improve crop yield, also creates plastic film residue pollution and greenhouse gas emissions that restricts the development of sustainable agriculture. So, one of those challenges is to reduce plastic film use while also ensuring food security, and thus promote green and sustainable development. A field experiment was conducted during 2017–2020 at 3 farmland areas, each with different altitudes and climate conditions, in northern Xinjiang, China. We investigated the effects on maize yield, economic returns, and greenhouse gas (GHG) emissions of plastic film mulching (PFM) versus no mulching (NM) methods in drip-irrigated maize production. We also chose maize hybrids with 3 different maturation times and used 2 planting densities to further investigate how those differences more specifically affect maize yield, economic returns, and greenhouse gas (GHG) emissions under each mulching method. We found that by using maize varieties with a utilization rate of accumulated temperature (URAT) <86.6 % with NM, and increasing the planting density by 3 plants m−2, yields and economic returns improved and GHG emissions reduced by 33.1 %, compared to those of PFM maize. The maize varieties with URATs between 88.2 % to 89.2 %, had the lowest GHG emissions. We discovered that by matching the required accumulated temperatures of various maize varieties to environmental accumulated temperatures, along with filmless and higher density planting, and modern irrigation and fertilization practices, yields increased and residual plastic film pollution and carbon emissions reduced. Therefore, these advances in agronomic management are important steps toward reducing pollution and achieving carbon peak and carbon neutrality goals.

Experimental evaluation of soapberry seed oil biodiesel performance in CRDI diesel engine

Due to the ongoing demand for alternative fuels for CI engines, biodiesel-based research has received support globally. In this study, soapberry seed oil produced by transesterification process to creates biodiesel. It is referred to as BDSS (Biodiesel of Soapberry Seed). According to criteria, the oil qualities are recognized, hence, three different blends and pure diesel were tested in CRDI (Common Rail Direct Injection) engines. The blends descriptions are: 10BDSS (10% BDSS + 90% diesel), 20BDSS (20% BDSS + 80% diesel), and 30BDSS (30% BDSS + 70% diesel). The outcomes of the related tests for combustion, performance, and pollution were contrasted with those achieved using 100% diesel fuel. In this case, the mixing has resulted in worse braking thermal efficiency than diesel and lower residual emissions with greater NOx emissions. The superior results were obtained by 30BDSS, which had BTE of 27.82%, NOx emissions of 1348 ppm, peak pressure of 78.93 bar, heat release rate (HRR) of 61.15 J/deg, emissions of CO (0.81%), HC (11 ppm), and smoke opacity of 15.38%.

Towards the first cohort of climate-neutral cities: Expected impact, current gaps, and next steps to take to establish evidence-based zero-emission urban futures

Cities are increasingly becoming critical climate actors. However, their preparedness and ambition in forging climate-neutral futures is hard to ascertain. In this study, we analyse the Expressions of Interest in the Mission on 100 Climate-Neutral and Smart Cities by 2030, an unprecedented dataset of city inputs to 374 different questions on the transition to (net) zero. We i) delineate emissions baselines, accounting methodologies, and inventories’ completeness (sectors/sources, carriers, gases), ii) analyse emission trends and cities’ capacity to deliver on their climate mitigation commitments, iii) examine the estimated magnitude and origin of residual emissions by 2030 together with the envisioned offsetting strategies, and iv) elucidate gaps, methodological deficiencies, and forms of assistance. Data suggest that if all 362 eligible cities were to reach climate neutrality, approximately 650 MtCO2eq would be removed. However, this would require at least a quadruple effort in half the time compared to current mitigation achievements. Beyond the challenge of emissions baselining, cities lack adequate data collection and monitoring systems and show little familiarity with non-technological and technological avenues to tackle harder-to-eradicate emissions. Capacity building will be key across multiple (e.g., technical, financial, operational) domains to turn ambitious mayoral commitments into factual contributions to climate mitigation.

Volatilization and partitioning of residual electronic cigarette emissions to particulate matter

The growing prevalence of electronic cigarettes (e-cigs) prompts investigation of their impact on indoor air quality. While the investigation of residual cigarette smoke, also known as third-hand smoke (THS), has been increasing, there is minimal literature on similar residue from e-cig emissions. Lab generated ammonium sulfate aerosol was introduced into a stainless-steel chamber which previously contained JUUL electronic cigarette vape. Aerosol composition was monitored using a high-resolution aerosol mass spectrometer. This was performed in the same chamber 3 times over 5 days. Species from electronic cigarette residue (nicotine and vegetable glycerin) were found to partition to particles with decreasing concentration over the multiple experiments while maintaining a consistent chemical signature. This signature matches closely to that of the primary electronic cigarette vape with notable exclusions of propylene glycol, benzoic acid, and cadmium. Electronic cigarette vape can deposit onto surfaces and act as a long-term source of gas phase nicotine which can concentrate on aerosols and increase human exposure. The chemical processing of vape residue observed here is less substantial than has been previously presented for residual cigarette smoke. While our experiments were performed under controlled conditions, they highlight the importance of understanding indoor electronic cigarette use and unintended routes of exposure.Copyright © 2023 American Association for Aerosol Research

Impact of binary blends of biodiesels on fuel quality, engine performance and emission characteristics

AbstractThe incessant pressure of energy requirements by the growing global populace has led to the exploration of unconventional methods to produce renewable and sustainable fuels. Among these, biodiesel is most suited to the present needs of eco-friendly standards to keep the atmosphere free from residual emissions. Various fuel-modification methods were developed over a couple of decades to make biodiesel suitable for diesel engines. In the present research, Jatropha curcas biodiesel and waste-cooking-oil (WCO) biodiesel were used to craft a unique binary blend to obtain desirable fuel properties and operational suitability for the diesel engine. The blend with 80% WCO biodiesel and 20% J. curcas biodiesel, which had the most suitable fuel properties, was tested on a four-stroke single-cylinder vertical diesel engine. The emissions and operational parameters were analysed and compared with diesel. The results of the study indicated that engine emissions for binary blend, carbon monoxide and unburnt hydrocarbon emissions were highly reduced, and carbon dioxide and nitrogen oxide (NOx) emissions increased relative to diesel. At full load, NOx emission was found to be 51.32% higher than that from diesel and 3.8% lower than that from WCO biodiesel. Engine performance showed that for the binary blend, at full load, the brake-specific fuel consumption was 396.82 g/kWh, which was 15.26% higher, and the brake thermal efficiency was 22.7%, which was 2.74% lower than regular diesel fuel. The present study suggests that the binary blend of J. curcas biodiesel and WCO biodiesel can be a promising approach towards advancements in the fuel properties of biodiesels.

Study of Vegetation's Capacity to Reduce of the CO2 Emissions from Vehicle Engine Contribution in Green Open Space Pinang Masak Campus, Jambi University Reevaluation on Period 2016–2022

The atmosphere's carbon dioxide (CO2) content raises global temperatures. OGS, or green open space, has the power to absorb carbon dioxide. The OGS of Pinang Masak Campus, Jambi University, too has this potential, although the number of vehicles keeps rising yearly. The reduction of flora at Jambi University's Pinang Masak Campus will result in higher carbon emissions. The three-month study was carried out at the Pinang Masak Campus Jambi University. This study directly measured the crown and counted the number of individual trees. There are 62 species of trees in all, totaling 1455 individuals. Motorcycles are the most common form of vehicle to enter the college area. According to calculations of carbon absorption, the rates of emissions produced by cars, 583,619 kg/hour, and 581,779.330 kg/hour, respectively, are 1,839.667 kg/hour, 583,619 kg/hour, and 581,779.330 kg/hour, respectively. According to these findings, based on positive residual emissions, the Green Open Space of Pinang Masak Campus is less able to absorb carbon emissions from automobiles.

An evidence-based approach towards sustainable anaesthesia

Health and social care currently account for between 4-5% of UK annual emissions1. Recognising this, the NHS has set a net zero goal for direct emissions by 2040, alongside an 80% reduction goal before 20322. Net zero here refers to a balance between residual emissions and carbon offsets. To this end, trusts are exploring measures to reduce their direct emissions through changes in practice, renewable electricity generation, and energy efficiency improvements. The NHS will then offset any remaining emissions after 2040. Surgery and anaesthesia together account for 8% of the carbon footprint associated with acute trusts at present, with nearly half of this due to the use of anaesthetic vapours and gases, predominantly nitrous oxide and desflurane3. The NHS net zero panel expect 2% of its total emissions reduction will be achieved through changes to the delivery of anaesthesia4. This raises the question: what changes can be made to anaesthetic practise to achieve this goal?

The role of carbon capture and storage to achieve net-zero energy systems: Trade-offs between economics and the environment

Carbon capture and storage can both reduce greenhouse gas emissions and provide negative emissions to contribute to the transition to a net-zero society. The contribution of carbon capture and storage has been investigated within cross-sectorial energy system models. However, such models commonly focus on cost and greenhouse gas emissions, while broader environmental impacts are investigated for individual technologies only. Here, we analyze economic and environmental impacts of the transition to net-zero emissions by combining energy system modeling with life-cycle assessment. We focus on the system-wide implications of carbon dioxide storage on economic or environmental impacts. In our investigation of the transition of the German energy system until 2045, net-zero emissions require a minimal amount of carbon capture and storage. However, increasing carbon dioxide storage beyond the minimum amount significantly lowers cost and environmental impacts in up to 13 out of 16 impact categories by avoiding investments into material-intensive technologies, such as power-to-methane or renewable power plants in areas with low generation potential. In scenarios without electricity imports, carbon dioxide storage ranges between 118Mt to 379Mt in 2045 with cost increasing by 105% when carbon dioxide storage is minimized. 84% of the cost increase is incurred for eliminating the final 23Mt of carbon dioxide stored.The benefits of applying carbon capture and storage are robust to variations in the amount of renewable electricity imports and residual emissions that require compensation. Hence, the results suggest that carbon capture and storage can offer economic and environmental benefits in the transition to net-zero energy systems beyond greenhouse gas emission mitigation.

Why residual emissions matter right now

Net-zero targets imply that continuing residual emissions will be balanced by carbon dioxide removal. However, residual emissions are typically not well defined, conceptually or quantitatively. We analysed governments’ long-term strategies submitted to the UNFCCC to explore projections of residual emissions, including amounts and sectors. We found substantial levels of residual emissions at net-zero greenhouse gas emissions, on average 18% of current emissions for Annex I countries. The majority of strategies were imprecise about which sectors residual emissions would originate from, and few offered specific projections of how residual emissions could be balanced by carbon removal. Our findings indicate the need for a consistent definition of residual emissions, as well as processes that standardize and compare expectations about residual emissions across countries. This is necessary for two reasons: to avoid projections of excessive residuals and correspondent unsustainable or unfeasible carbon-removal levels and to send clearer signals about the temporality of fossil fuel use.

Net zero and the unexplored politics of residual emissions

In this perspective article, we call for more engagement with the unexplored politics of residual emissions. Residual emissions are those emissions that remain at the point of net zero, despite abatement efforts. Unlike carbon dioxide removal, which has been the focus of a lively research and policy debate, the notion of residual emissions remains relatively unexplored so far. With the mainstreaming of net zero as the long-term goal of climate policy, the politics of residual emissions are set to become a key point of contestation. Claims about residual emissions tend to revolve around notions of necessity and possibility, i.e. emissions that derive from activities deemed socially necessary yet impossible to fully abate. In this perspective article, we highlight how such claims are socially constructed and ultimately contingent on values, norms and interests. We call upon researchers to help render visible the geographically and historically contingent claims to necessity and possibility that underpin projected residual emissions. We see this as an important means to repoliticize debates about the limits and possibilities of emissions abatement, and suggest entry points for such research efforts.

Countries’ long-term climate strategies fail to define residual emissions

Achieving net zero means balancing remaining emissions with carbon removal, and understanding the nature and scope of residual emissions is key to planning decarbonized energy and industrial systems. However, our analysis of long-term climate strategies shows that many governments lack clear projections for residual emissions at net zero.