Fossil CO2 Research Articles

Durability of carbon dioxide removal is critical for Paris climate goals

Abstract Carbon Dioxide Removal is essential for achieving net zero emissions, as it is required to neutralize any residual CO2 emissions. The scientifically recognized definition of Carbon Dioxide Removal requires removed atmospheric CO2 to be stored “durably”; however, it remains unclear what is meant by durably, and interpretations have varied from decades to millennia. Using a reduced-complexity climate model, here we examined the effect of Carbon Dioxide Removal with varying CO2 storage durations. We found that storage duration substantially affects whether net zero emissions achieve the desired temperature outcomes. With a typical 100-year storage duration, net zero CO2 emissions with 6 GtCO2 per year residual emissions result in an additional warming of 1.1 °C by 2500 compared to permanent storage, thus putting the internationally agreed temperature limits at risk. Our findings suggest that a CO2 storage period of less than 1000 years is insufficient for neutralizing remaining fossil CO2 emissions under net zero emissions. These results reinforce the principle that credible neutralization claims using Carbon Dioxide Removal in a net zero framework require balancing emissions with removals of similar atmospheric residence time and storage reservoir, e.g., geological or biogenic.

Estimating countries’ additional carbon accountability for closing the mitigation gap based on past and future emissions

Quantifying fair national shares of the remaining global carbon budget has proven challenging. Here, we propose an indicator—additional carbon accountability—that quantifies countries’ responsibility for mitigation and CO2 removal in addition to achieving their own targets. Considering carbon debts since 1990 and future claims based on countries’ emission pathways, the indicator uses an equal cumulative per capita emissions approach to allocate accountability for closing the mitigation gap among countries with a positive total excessive carbon claim. The carbon budget is exceeded by 576 Gigatonnes of fossil CO2 when limiting warming below 1.5 °C (50% probability). Additional carbon accountability is highest for the United States and China, and highest per capita for the United Arab Emirates and Russia. Assumptions on carbon debts strongly impact the results for most countries. The ability to pay for this accountability is challenging for Iran, Kazakhstan and several BRICS+ members, in contrast to the G7 members.

Improving the method for calculating carbon emissions from waste incineration: confirmed with carbon-14 testing of flue gas

An improved method was developed to calculate direct emissions from seven municipal solid waste incineration plants by adjusting the physical compositions of waste by invoking the proportion of co-incinerated waste and the bottom ash yield. The fossil carbon fractions of the waste components were determined by carbon-14 (14C) testing. Based on the improved method, direct emissions were in the range of 222–610 kg CO2-eq/t waste, corresponding to reductions of 3.4–221 kg CO2-eq/t waste compared with the method without waste composition adjustment. The 14C contents of the flue gas before and after gas cleaning were tested to validate the improved method, and indicated fossil CO2 emissions of 249–446 and 233–405 kg CO2-eq/t waste, respectively. The direct emissions obtained by the improved method were closer to the results of 14C testing, due to more accurate estimations of the actual waste composition. The method was further combined with a life cycle analysis of the waste incineration process, obtaining total carbon emissions in the range from –33.2 to 483 kg CO2-eq/t waste. The findings provide a new means of accurately calculating carbon emissions from waste incineration.Graphical

Opportunities for carbon sequestration from removing or intensifying pasture-based beef production

Pastures, on which ruminant livestock graze, occupy one third of the earth's surface. Removing livestock from pastures can support climate change mitigation through carbon sequestration in regrowing vegetation and recovering soils, particularly in potentially forested areas. However, this would also decrease food and fiber production, generating a tradeoff with pasture productivity and the ruminant meat production pastures support. We evaluate the magnitude and distribution of this tradeoff globally, called the "carbon opportunity intensity" of pastures, at a 5-arcminute resolution. We find that removing beef-producing cattle from high-carbon intensity pastures could sequester 34 (22 to 43) GtC i.e. 125 (80 to 158) GtCO2 into ecosystems, which is an amount greater than global fossil CO2 emissions from 2021-2023. This would lead to only a minor loss of 13 (9 to 18)% of the global total beef production on pastures, predominantly within high- and upper-middle-income countries. If areas with low-carbon intensity pastures and less efficient beef production simultaneously intensified their beef production to 47% of OECD levels, this could fully counterbalance the global loss of beef production. The carbon opportunity intensity can inform policy approaches to restore ecosystems while minimizing food losses. Future work should aim to provide higher-resolution estimates for use at local and farm scales, and to incorporate a wider set of environmental indicators of outcomes beyond carbon.

Synthetic natural gas (SNG) production by biomass gasification with CO2 capture: Techno-economic and life cycle analysis (LCA)

The integration of renewables with CCUS technologies has the promising potential to deliver energy applications with overall negative CO2 emissions which would significantly contribute to the climate neutrality. Moreover, the renewable-based synthetic fuels are predicted to replace the conventional fossil fuels. The current work evaluates key techno-economic and environmental indicators for the SNG production from various renewable fuels (e.g., sawdust, residual wood, organic wastes, agricultural and urban wastes etc.) through gasification process fitted with decarbonization capability. The investigated plant capacity was set to 500 MWth SNG with 60 % CO2 capture rate of primary fuel (biomass). The overall concept was evaluated using various process engineering approaches e.g., reactor & process modelling and simulation, model validation, heat and power analysis, techno-economic assessment combined with detailed environmental impact by Life Cycle Analysis (LCA). The investigated design shows promising performance indicators such as high cumulative energy efficiency (69 %) and carbon conversion to SNG, almost zero plant specific CO2 emissions (3 kg/MWh) and overall negative carbon emissions (−457 kg/MWh) from the whole biomass chain. The SNG production cost is not yet fully competitive versus the EU natural gas prices (53 vs. 30–35 €/MWh) but it shows promising potential considering the trends of increasing fossil prices and CO2 emission tax.

The nonlinear impact of renewable energy, fossil energy and CO2 emissions on human development index for the eight developing countries

This study analyzes the impact of renewable energy, fossil energy, CO2 emissions, urbanization, international trade and industrialization on human development for the eight developing countries over the period 1990–2021 using Karavias and Tzavalis (2014) panel unit root test regarding structural breaks and cross-section dependence and feasible generalized least squares (FGLS) estimator technique. The countries of interest are Brazil, Russia, India, China, South Africa (BRICS countries) plus Egypt, Iran and Turkey while human development index is used as a measure of human development. The findings reveal that there exists a U-shaped relationship between renewable energy consumption and HDI an inverted U-shaped relationship between fossil energy/CO2 emissions and HDI is relevant. Moreover, the positive impact of urbanization, international trade and industrialization on HDI is determined. As for policy implications, the policies oriented to renewable energy and to reduce fossil energy dependence and CO2 emissions should be adopted to improve human development in the developing countries. Additionally, policies promoting urbanization, international trade, and industrialization are necessary to achieve high levels of human development, provided that the negative effects of these policies are mitigated.

Determining the Relationship Between Economic Growth, Carbon Emission and Energy Consumption: Panel Cointegration and Causality Approach in G20 Countries

As it is known, CO2 is a greenhouse gas. Greenhouse gases contained in fossil fuels mix with the atmosphere and cause global warming on earth. Global warming causes many negative situations such as irregular rainfall, drought, difficulties in accessing fresh water, and changes in living biology. Thus, life on earth is becoming increasingly threatened. In this study, the relationship between CO2 emissions and renewable and fossil-based energy use, which are among the factors affecting economic growth, was applied in G-20 countries with panel data analysis. The data of the study were collected from the World Bank. A total of 589 data were studied in 19 countries and 31 time dimensions. AMG method was used for long-term estimation of the data by performing cross-section dependence, unit root tests and homogeneity tests. Granger causality test was performed between the variables. A positive relationship was found between GDP growth and CO2, and it was found that a one-unit increase in CO2 use would cause a 0.88-unit increase in GDP growth. Additionally, the study found that there is a unidirectional causality from renewable energy, fossil energy consumption and CO2 usage to GDP growth.

Combustion Process of Coal–Açai Seed Mixtures in a Circulating Fluidized Bed Boiler

This study investigates the effects of the co-combustion of coal and açai seed in circulating fluidized bed (CFB) boilers, highlighting the increase in thermal efficiency and relevance of a less-polluting source of energy. Using the computer software 1.5D CeSFaMB™® v4.3.0, simulations of the co-combustion process of coal and biomass were carried out in a CFB boiler, obtaining results such as the temperature profile, boiler efficiency and emissions. The work acquired data regarding the equipment in real operational conditions, consisting of the fundamental geometric and operational parameters used in the simulation campaign. The thermal and chemical properties of the fuels were analyzed by carrying out proximate, ultimate, heating value, particle size and specific mass analyses. The model validation was achieved by simulating the boiler in its real operating conditions and comparing the obtained results with the real data; the obtained error was below 10%. Simulations with different fractions of açai seed for energy replacement (10% and 30%) were carried out. As a result, an increase in the average temperature of the bed was observed, highlighting the region immediately above the dense bed. An increase in boiler efficiency was verified from 56% to 85% with 10% açai and to 83% with 30% açai seed. Decreases in SO2 and CO emissions with the insertion of açai were obtained, showing that co-combustion is more complete, while CO2 emissions were increased due to the higher quantity of fuel inserted into the equipment. The fossil CO2 emissions were reduced.

A mini-review for identifying future directions in modelling heating values for sustainable waste management.

Global estimations suggest energy content within municipal solid waste (MSW) is underutilized, compromising efforts to reduce fossil CO2 emissions and missing the opportunities for pursuing circular economy in energy consumption. The energy content of the MSW, represented by heating values (HVs), is a major determinant for the suitability of incinerating the waste for energy and managing waste flows. Literature reveals limitations in traditional statistical HV modelling approaches, which assume a linear and additive relationship between physiochemical properties of MSW samples and their HVs, as well as overlook the impact of non-combustible substances in MSW mixtures on energy harvest. Artificial intelligence (AI)-based models show promise but pose challenges in interpretation based on established combustion theories. From the variable selection perspectives, using MSW physical composition categories as explanatory variables neglects intra-category variations in energy contents while applying environmental or socio-economic factors emerges to address waste composition changes as society develops. The article contributes by showing to professionals and modellers that leveraging AI technology and incorporating societal and environmental factors are meaningful directions for advancing HV prediction in waste management. These approaches promise more precise evaluations of incinerating waste for energy and enhancing sustainable waste management practices.

Realization of Bio-Coal Injection into the Blast Furnace

The steel industry accounts, according to the International Energy Agency, for ~6.7% of global CO2 emissions, and the major portion of its contribution is from steelmaking via the blast furnace (BF) route. In the short term, a significant reduction in fossil CO2 emissions can be achieved through the introduction of bio-coal into the BF as part of cold bonded briquettes, by injection, or as part of coke. The use of bio-coal-containing residue briquettes was previously demonstrated in industrial trials in Sweden, whereas bio-coal injection was only tested on a pilot scale or in one-tuyere tests. Therefore, industrial trials replacing part of the pulverized coal (PC) were conducted. It was concluded that the grinding, conveying, and injection of up to 10% of charcoal (CC) with PC can be safely achieved without negative impacts on PC injection plant or BF operational conditions and without losses of CC with the dust. From a process point of view, higher addition is possible, but it must be verified that grinding and conveying is feasible. Through an experimentally validated computational fluid flow model, it was shown that a high moisture content and the presence of oversized particles delay devolatilization and ignition, lowering the combustion efficiency. By using CC with similar heating value to PC, compositional variations in the injected blend are not critical.

Hydrogen Blending in Natural Gas Grid: Energy, Environmental, and Economic Implications in the Residential Sector

The forthcoming implementation of national policies towards hydrogen blending into the natural gas grid will affect the technical and economic parameters that must be taken into account in the design of building heating systems. This study evaluates the implications of using hydrogen-enriched natural gas (H2NG) blends in condensing boilers and Gas Adsorption Heat Pumps (GAHPs) in a residential building in Rome, Italy. The analysis considers several parameters, including non-renewable primary energy consumption, CO2 emissions, Levelized Cost of Heat (LCOH), and Carbon Abatement Cost (CAC). The results show that a 30% hydrogen blend achieves a primary energy consumption reduction of 12.05% and 11.19% in boilers and GAHPs, respectively. The presence of hydrogen in the mixture exerts a more pronounced influence on the reduction in fossil primary energy and CO2 emissions in condensing boilers, as it enhances combustion efficiency. The GAHP system turns out to be more cost-effective due to its higher efficiency. At current hydrogen costs, the LCOH of both technologies increases as the volume fraction of hydrogen increases. The forthcoming cost reduction in hydrogen will reduce the LCOH and the decarbonization cost for both technologies. At low hydrogen prices, the CAC for boilers is lower than for GAHPs; therefore, replacing boilers with other gas technologies rather than electric heat pumps increases the risk of creating stranded assets. In conclusion, blending hydrogen into the gas grid can be a useful policy to reduce emissions from the overall natural gas consumption during the process of end-use electrification, while stimulating the development of a hydrogen economy.

Production of Sustainable Methanol from Industrial Exhaust Gases

AbstractCarbon capture and utilization (CCU) is part of the European Union (EU)’s strategy to become climate‐neutral by 2050. CO2 is needed as a feedstock for the production of climate‐friendly base chemicals and sustainable fuels. Although CO2 capture from industrial point sources is technically feasible and requires less energy than direct air capture, its integration into the circular economy is challenging due to only the temporary recognition of fossil CO2 as a source for the production of climate‐friendly renewable fuels. In this article, CO2 sources such as waste incineration plants, lime production, and steel production are analyzed based on process simulation in terms of their energy demand for CCU and compliance with current EU legislation on renewable fuels over the service life of a CCU plant.

Capacity of Forests and Grasslands to Achieve Carbon Neutrality in China

Forests and grasslands play an important role in carbon cycling. They not only absorb CO2 from the air through vegetation biomass and soil carbon sinks, but also reduce and control the horizontal transport of soil carbon (i.e., reinforcing soil carbon storage via soil conservation), thus avoiding erosion-induced CO2 emissions. In this study, vegetation biomass and soil carbon sinks, soil carbon reinforcement and reduced carbon emissions via soil conservation by forests and grasslands were quantified on the scale of the whole of China. The analysis was based on the distribution of biomass and the soil carbon pool and soil erosion rates derived from national surveys, as well as carbon density values from field surveys and literature. In 2021, forests and grasslands in China generated 394.18 Mt C/year (y) of steady-state carbon sinks through vertical biomass and soil absorption. The biomass carbon sinks of grasslands, and those of leaves, twigs, flowers and fruits of the forests, were not taken into account when quantifying the stable biomass sink, because they can become net producers of CO2 due to seasonal withering and carryover, or they can form soil organic carbon as potential soil carbon sinks. The amount of horizontal soil carbon reinforcement in China’s forests and grasslands in 2021 was 20.31 Mt C/y, which was positively correlated with the reduction in the water erosion area; consequently, vertical emissions of approximately 14.89–29.78 Mt of CO2 into the atmosphere were avoided. Overall, in 2021, China’s forests and grasslands absorbed atmospheric CO2 and reduced emissions by 1.46–1.47 Gt CO2/y, equivalent to approximately 13% of China’s annual fossil CO2 emissions. This study demonstrates the fact that the adoption of forest and grassland measures sequesters carbon in soil and biota and reduces the risks of CO2 emissions by both vertical and horizontal paths, which is important for achieving carbon neutrality and mitigating climate change.

The Effects of Fossil Fuel Consumption-Related CO2 on Health Outcomes in South Africa

The consumption of fossil fuel significantly contributes to the growth of South Africa’s economy but produces carbon dioxide (CO2), which is detrimental to environmental sustainability with overall effects on health outcomes. This study sought to (i) examine the impacts of fossil energy consumption-related CO2 emissions on the under-five mortality and infant mortality rates in South Africa and (ii) analyse the causal relationship between fossil energy consumption, CO2 emissions, and mortality rates in South Africa. Linear and nonlinear ARDL bounds and the Toda–Yamamoto causality test were used to establish the equilibrium property in the long run and the causal effects of the models’ variables. Health outcome data include the under-five mortality rate (MTR1) and infant mortality rate (MTR2). Other explanatory variables include fossil energy consumption (FOC), inflation (Inf), carbon dioxide emissions (CO2), and government expenditure (GEH). It is evident from the results of linear ARDL that the first lag of the under-five mortality rate in the short run has a positive and significant impact on the under-five mortality rate in South Africa. Holding the other variables constant, the under-five mortality rate in South Africa would increase by 0.630% for every 1% increase in its lagged values. Fossil energy consumption has a positive and significant effect on the under-five mortality rate in South Africa. This significant relationship implies that a 1% increase in fossil energy consumption increases the under-five mortality rate per 1000 persons per year in South Africa by 0.418% in the short run, all things being equal. The results from the Toda–Yamamoto causality test revealed that there is no causality between the under-five mortality rate and both the consumption of fossil fuel and CO2 emissions in South Africa. The results from nonlinear ARDL presented four separate scenarios. In the short run, during increasing levels of CO2 in the initial period (lag of CO2), a 1% increase in CO2 would decrease the under-five mortality rate by 1.15%. During periods of decreasing levels of CO2 in the short run, a 1% increase in CO2 would increase the infant mortality rate by 0.66%. Again, during previous and current periods of decreasing levels of FEC, a 1% increase in FEC would increase the infant mortality rate by 0.45% and 0.32%, respectively. In the long run, during periods of increasing levels of CO2, a 1% increase in CO2 would decrease the infant mortality rate by 4.62% whereas during decreasing levels of CO2, a 1% increase in CO2 would increase the infant mortality rate by 2.3%. The risk posed by CO2 emissions and their effects on humans can then be minimised through a government expansionary policy within health programmes.

Performance of wastewater treatment plants in emission of greenhouse gases

The present work has estimated greenhouse gas emissions in aerobic and anaerobic Wastewater Treatment Plants in Southern Italy. Greenhouse gases emissions from each treatment unit were calculated based on emission factors related to Chemical Oxygen Demand removal for biogenic CO2 and CH4 assessment and on Nitrogen removal for N2O. N2O, biogenic CO2, and CH4 emissions vary for aerobic and anaerobic-based WWTPs respectively from 73 kgCO2eq/PE*y for anaerobic plants to 91 kgCO2eq/PE*y for aerobic plants. In aerobic and anaerobic digestion systems WWTPs the contributions to CO2eq total emissions from N2O, CH4, biogenic CO2, and fossil CO2 are 30 %–33 %, 20 %–29 %, 22 %–25 %, and 26 %–16 %, respectively. N2O emissions from biological processes were found the most contributing sources of greenhouse gases while in the physical processes higher contribution is indirect carbon dioxide related to energy consumption. Compensatory measures are reported to reduce greenhouse gases emissions.

Carbon Cycle Models Quantify for a Green and Low-Carbon Economy

CO2 emissions from the combustion of fossil fuels represent the largest anthropogenic disruption of the natural global carbon cycle and lead to an undesirable increase in atmospheric CO2 levels. The so-called "carbon-neutral" renewable energy source biomass appears to be a promising replacement for fossil fuels. The "Combined Energy and Biosphere Model" (CEBM), was developed as a method for calculating the atmospheric CO2 content after intensive use of biomass. It includes (i) a biosphere part computing the annual cycle of carbon in the biosphere on 2,433 grid elements covering the continents’ plant mass and soil, as well as (ii) an energy economic part for calculating the fossil CO2 emissions of 119 countries. As the history of understanding the carbon cycle (including quantification of plant growth and decay by formulae, inclusion of deforestation, fossil fuel use and the fertilizer effect) shows, such a global carbon cycle model (as the CEBM) provides the needed methodology to assess the net effects of large-scale biomass energy use on the plant’s atmosphere. Results show that biomass (in a systemic view) is “only half as carbon neutral” as previously thought, even on a principal level. The conclusions indicate that (even if biomass is a valuable mitigation strategy) its global potential is limited. When interpreting CEBM scenarios, as a very first priority, reducing the current annual increase in energy demand is most highly needed for preserving climate.

An Overview of Waste-to-Energy Incineration Integrated with Carbon Capture Utilization or Storage Retrofit Application

This paper provides an overview of the integration of Carbon Capture, Utilization, or Storage (CCUS) technologies with Waste-to-Energy (WtE) incineration plants in retrofit applications. It explains the operational principles of WtE incineration, including the generation of both biogenic and fossil CO2 emissions and the potential for CCUS technologies to mitigate these emissions. In addition, the paper covers the regulatory framework influencing the adoption of such technologies and highlights the recent Directive 2023/959 for the inclusion of WtE incinerators in the European Union Emissions Trading System (EU ETS) by 2028. This measure could provide a significant impulse for the integration of CCUS in WtE incineration plants. Moreover, it discusses the use of CO2 captured, which could be used in Carbon Capture and Storage (CCS) and Carbon Capture and Utilization (CCU), and offers a comparison of the CCUS projects that have already been implemented worldwide, with a focus on the Netherlands and Italy. It illustrates the Netherlands’ advantageous position due to its developed CO2 market and early CCUS adoption, compared to Italy’s emerging market and initial storage solutions.

On the cost of zero carbon electricity: A techno-economic analysis of combined cycle gas turbines with post-combustion CO2 capture

To achieve a sustainable electricity grid, affordable and dispatchable power capacity that supports grid stability and does not increase atmospheric CO2 levels will be required. Combined cycle gas turbines (CCGTs) with post-combustion CO2 capture (PCC) can meet these requirements by capturing and permanently storing all combustion CO2 emissions and, coupled with negative emissions technologies, any remaining life-cycle emissions. For the first time, we present a comprehensive analysis of the technical and financial challenges of producing zero-carbon electricity from CCGTs on a life-cycle basis. We conclude that when the design is optimised, fossil CO2 capture fractions can be increased from 96% to 100% with minimal process modification, commercially available technology and an additional 0.5% decrease in thermal efficiency. This represents a significant 60–70% reduction in the additional efficiency penalty required to reach zero CO2 emission operation. The Cost of CO2 Avoided of 100% fossil CO2 capture is just 128 £/tCO2, a 3 £/tCO2 increase over the 95% gross CO2 capture fraction required to permit PCC projects in the UK. Indeed, within the bounds of the UK power CCS business model, we show that 100% fossil CO2 capture maximises both variable and capacity payments to the producer, resulting in a 2% decrease in the cost of power produced. For zero-carbon electricity on a life-cycle basis, the recapture and permanent geological storage of all remaining life-cycle CO2e emissions from plant construction & decommissioning, CO2 T&S network operation and the natural gas supply chain (operational CO2e emissions and methane leakage) increases the median Cost of CO2 Avoided to 178 £/tCO2 (130–371 £/tCO2), leading to the novel conclusion that a market mechanism equating to a CO2 price of over 178£/tCO2 is likely sufficient to incentivise the development of truly CO2-neutral CCGTs.

Tracing fossil-based plastics, chemicals and fertilizers production in China

Phasing down fossil fuels is crucial for climate mitigation. Even though 80–90% of fossil fuels are used to provide energy, their use as feedstock to produce plastics, fertilizers, and chemicals, is associated with substantial CO2 emissions. However, our understanding of hard-to-abate chemical production remains limited. Here we developed a chemical process-based material flow model to investigate the non-energy use of fossil fuels and CO2 emissions in China. Results show in 2017, the chemical industry used 0.18 Gt of coal, 88.8 Mt of crude oil, and 12.9 Mt of natural gas as feedstock, constituting 5%, 15%, and 7% of China’s respective total use. Coal-fed production of methanol, ammonia, and PVCs contributes to 0.27 Gt CO2 emissions ( ~ 3% of China’s emissions). As China seeks to balance high CO2 emissions of coal-fed production with import dependence on oil and gas, improving energy efficiency and coupling green hydrogen emerges as attractive alternatives for decarbonization.

Techno-economic analysis for the sunlight-powered reverse water gas shift process: Scenarios, costs, and comparative insights

The deployment of renewable chemicals and fuels production is directly connected to technical developments, political incentives and investments. The route towards market competitiveness of such chemicals and fuels requires significant cost reduction from state-of-the-art production and operation. In this manuscript, we estimate to what extent the expected technical improvements of the sunlight-powered reverse water gas shift process catalysed by a Au/TiO2 photocatalyst can improve its economic performance. Multiple factors and different scenarios are explored to identify the main dependencies that drive price reductions for this technology. Our projections indicate that the total capital investments required to deploy this green CO production route have the potential to decline from 325 million euros down to 51 million euros for an annual CO production of 100 kton based on the technical improvements. The levelized cost of CO could decrease from around 205 €/GJ CO to 53 €/GJ CO. These results indicate that sunlight-powered chemistry can become competitive when higher carbon taxes are applied to the production of fossil CO (75-200€/ton CO2).