CO2 Intensity Research Articles

Design of a Hydrogen Production System Considering Energy Consumption, Water Consumption, CO2 Emissions and Cost

CO2 emissions associated with hydrogen production can be reduced replacing steam methane reforming with electrolysis using renewable electricity with a trade-off of increasing energy consumption, water consumption and cost. In this research, a linear programming optimization model of a hydrogen production system that considers simultaneously energy consumption, water consumption, CO2 emissions and cost on a cradle-to-gate basis was developed. The model was used to evaluate the impact of CO2 intensity on the optimum design of a hydrogen production system for Japan considering different stakeholders’ priorities. Hydrogen is produced using steam methane reforming and electrolysis. Electricity sources include grid, wind, solar photovoltaic, geothermal and hydro. Independent of the stakeholders’ priorities, steam methane reforming dominates hydrogen production for cradle-to-gate CO2 intensities larger than 9 kg CO2/kg H2, while electrolysis using renewable electricity dominates for lower cradle-to-gate CO2 intensities. Reducing the cradle-to-gate CO2 intensity increases energy consumption, water consumption and specific cost of hydrogen production. For a cradle-to-gate CO2 intensity of 0 kg CO2/kg H2, the specific cost of hydrogen production varies between 8.81 and 13.6 USD/kg H2; higher than the specific cost of hydrogen production targeted by the Japanese government in 2030 of 30 JPY/Nm3, 3.19 USD/kg H2.

A process integration-based multiperiod energy planning model for CO2-intensive industries

Multiperiod carbon-constrained energy planning considers long-term demand variations as well as progressively stringent CO2 emission limits towards net-zero carbon goals. Previous work on multiperiod energy planning has predominantly focused on the power generation sector. Nevertheless, emissions originating from industries must be mitigated to achieve decarbonisation at different (e.g., corporate, national, or regional) scales. This work develops a multiperiod energy planning model to determine the optimum deployment of energy sources for CO2-intensive industries other than the power generation sector. A hybrid approach is employed in this work, making use of the combined automated targeting model (ATM) and superstructure models. The hybrid approach in this work overcomes the non-linearity in the CO2 intensity calculations. Solving the ATM and superstructure model simultaneously ensures that both demand and CO2 emission limits for all industries are satisfied in each period. The multiperiod energy planning model is demonstrated with a case study with and without CO2 load transfer scenarios. The case study is performed for 21 industries across three 5-year periods. For the CO2 load transfer scenarios, the CO2 emission limits may be violated in earlier periods, triggering CO2 debts. The latter are compensated by CO2 credits in later periods where the total CO2 load is below the emissions limit due to aggressive mitigation strategies. Alternatively, in the absence of CO2 load transfer, the CO2 emission limits for all periods must be satisfied. Results show that the deployment of low-carbon energy sources (e.g., biomass and biogas) is necessary for the satisfaction of the CO2 emission limits within each period. Once CO2capture and storage (CCS) is available, its deployment would complement existing mitigation strategies in later periods. The deployment of CCS on power plants fueled by biomass and biogas make them as negative emissions technologies (NETs) which are useful for CO2 removal (CDR). The development of the multiperiod energy planning model in this work allows decarbonisation strategies to be simultaneously employed across all industries for a cumulative CO2 emissions reduction.

Central composite design-based development of eco-efficient high-volume fly ash mortar

High-volume fly ash (HVFA) mixtures that contain a large amount of fly ash have been widely investigated as sustainable materials with desirable mechanical properties and durability performances at mature ages. However, the low strength at early ages is the main obstacle that limits their wider applications in the practice. This work presents the development of the HVFA mortar with high early-age strength as well as low environmental impact with the help of central composite design-based statistical model. Besides, the effects of fly ash, limestone powder, asphalt emulsion content and water-to-cementitious material ratio (w/cm) as four main variables of HVFA mortar on the compressive strength and splitting tensile strength at curing ages ranging from 7 days to 28 days as the responses of this environmentally friendly material were investigated. Moreover, the multi-objective optimization was conducted to achieve the eco-efficiency of HVFA mortar. In this study, HVFA mortar with fly ash content of 67%, limestone powder content of 5%, no asphalt emulsion and w/cm of 0.25 exhibited 28-d compressive strength of 39.2 MPa and 28-d splitting tensile strength of 3.3 MPa. The optimized mix design of HVFA mortar can ensure the equivalent strength while noticeably reducing the CO2 intensity (CO2 emission per compressive strength) by 17.57%.

Effects of circular-agriculture economic measures on environmental conservation and socioeconomic development

Analyzing the effect of circular-agriculture (CA) measures could be helpful to promote its scientific development. Previous research has focused on technological measures and their effects on the agricultural sector. However, economic measures can also promote the development of CA, and due to their correlation with socio-economic sectors, CA measures can impose effects on non-agricultural sectors and on the whole socioeconomic system. In this research, a computable general equilibrium (CGE) model was established to comprehensively reveal the effects of CA measures. In this model, measure simulation and environmental blocks were extended. The production tax was adopted as the economic measure for adjusting the development of CA. Both environmental and socioeconomic effects have been explored. Hebei Province in China was adopted as the study case. Three kinds of production tax adjustment scenarios were considered: a promotion-measure scenario (decreasing the production tax for CA sectors), an inhibition-measure scenario (increasing the production tax for traditional-agriculture sectors), and a hybrid-measure scenario (implementing the promotion- and inhibition-measures simultaneously). The results showed that all three scenarios could promote the development of CA. The inhibition and hybrid measures had positive effects on GDP, and all the scenarios could decrease the intensities of CO2, COD and NH3–N emissions and water resource consumption. In addition, higher measure intensity could bring more significant effects.

The Impact of Transportation Restructuring on the Intensity of Greenhouse Gas Emissions: Empirical Data from China.

Adjusting transportation structure to reduce the intensity of greenhouse gas emissions is an effective way to address climate change issues. This paper selects six transport sectors and constructs a hybrid input-output model to study the impact of transportation restructuring on the intensity of CO2 and non-CO2 greenhouse gas emissions in each sector during different periods. The results show that the effect of transportation restructuring on greenhouse gas emissions is manifested differently in different time periods. After 2008, transportation restructuring had a significant effect on reducing the intensity of greenhouse gas emissions in all sectors. However, the impact of transportation restructuring on the intensity of non-CO2 greenhouse gas emissions is limited. It is also found that the railway transport sector has been a low-impact transport sector in terms of greenhouse gas emissions since 2004, which provides insights for the optimization of China’s transportation structure.

Fully utilizing carbonated recycled aggregates in concrete: Strength, drying shrinkage and carbon emissions analysis

In this study, natural aggregates, recycled aggregates (RAs), and carbonated RAs were combined to prepare concrete. Strength, drying shrinkage, microstructures, and the carbon emissions of concrete prepared with different aggregate combinations were explored and compared. The results show that the compressive strengths of carbonated fully recycled aggregate concrete (CFRAC) increased by 20.9% and the drying shrinkage at 180 days decreased by 23.3% compared with that of concrete with RAs due to the reduction of water absorption of RAs and the additional water. The pore structure of CFRAC was densified and improved by carbonation treatment on RAs. Furthermore, the carbon emission analysis showed that CFRAC had 7.1%∼13.3% lower carbon emission and 13.4%∼18.4% lower CO2 intensity than natural/recycled aggregate concrete due to the shorter transportation distance and the carbon absorption. Generally, CFRAC had improved properties and environmental benefits, which shows carbonation treatment is a valuable way to promote waste concrete recycling.

Intelligent Data Analytics Framework for Precision Farming Using IoT and Regressor Machine Learning Algorithms

Smart farming with precise greenhouse monitoring in various scenarios is vital for improved agricultural growth management. The Internet of Things (IoT) leads to a modern age in computer networking that is gaining traction. This paper used a regression-based supervised machine learning approach to demonstrate a precise control of sensing parameters, CO2, soil moisture, temperature, humidity, and light intensity, in a smart greenhouse agricultural system. The proposed scheme comprised four main components: cloud, fog, edge, and sensor. It was found that the greenhouse could be remotely operated for the control of CO2, soil moisture, temperature, humidity, and light, resulting in improved management. Overall implementation was remotely monitored via the IoT using Message Query Telemetry Transport (MQTT), and sensor data were analysed for their standard and anomalous behaviours. Then, for practical computation over the cloud layer, an analytics and decision-making system was developed in the fog layer and constructed using supervised machine learning algorithms for precise management using regression modelling methods. The proposed framework improved its presentation and allowed us to properly accomplish the goal of the entire framework.

Limited impact of COVID-19 recovery packages on near-term CO2 emissions pathways

Part of the economic recovery plans implemented by governments following COVID-19 is directed towards the energy transition. To understand the potential effects of these post-COVID green recovery packages on reductions of global greenhouse gas emissions until 2030, we investigated three different approaches. First, we analyzed simulation results of Integrated Assessment Models (IAMs) to infer the change in CO2 intensity of GDP that could result from post-COVID low-carbon investment plans. Second, we investigated the scenarios the International Energy Agency (IEA) provided based on a bottom-up energy system model. Combining the two approaches, we found that green recovery packages implemented and planned globally can lead to an emissions reduction of merely 1%–6% from the 2030 baseline levels at most. Third, we looked into the results of the Adaptative Regional Input-Output model, which simulates the dynamic effects of economic crisis and fiscal stimuli through supply chains following labor shortage. The third approach shows that the increase of activity driven by fiscal stimuli leads to a rebound of CO2 emissions even if they do not target carbon-intensive sectors. We conclude that green recovery packages targeting low-carbon technologies have a limited impact on near-term CO2 emissions and that demand-side incentives, as well as other policy efforts to disincentivize the use of fossil fuels, are also crucial for scaling up climate mitigation.

Implications on EROI and climate change of introducing Li-ion batteries to residential PV systems

In this study, we investigate the sustainability aspect of residential PV installations combined with batteries — with a focus on EROI (Energy Return On Invested Energy) and CO2 reduction potential. We pay special attention to situations where an excess of photovoltaic power generation is not allowed to be fully fed into the distribution grid and has to be (partly) curtailed. To this extent, we estimate the impact of residential solar batteries in three different European countries: Switzerland, Norway, and Spain. The combined EROI (PV coupled with battery) was shown to be greater for all battery sizes up to 30 kWh compared to a scenario where excess PV production would be curtailed, with Spain’s EROI almost doubling from around 8 for the case of no battery to 15 for an 18 kWh battery. For Switzerland and Norway, the EROI is improving by about 50% to 11 and 9, respectively, with the ideal size being smaller at 12 kWh. Optimal battery sizes were also calculated for different curtailment thresholds, which are set to increase in the coming years due to higher PV penetration in national power grids. Residential solar batteries were demonstrated to be a viable addition in all geographical settings from a Net Energy Analysis point of view. When considering CO2-equivalent emission reduction potential of a PV plus battery system, the local grid’s CO2 intensity is decisive, increasing the benefit in countries such as Spain and Switzerland, but worsening overall impacts in Norway for oversized batteries.

Design optimization of a district heating and cooling system with a borehole seasonal thermal energy storage

The optimal design of borehole thermal energy storage systems can ensure their techno-economical goals are met. Current design optimization methods either employ detailed modelling unsuitable for numerical optimization or use simplified models that do not consider operational conditions. This paper proposes an optimization-oriented model and a non-convex optimization formulation that, differently from other studies in the literature, can consider the influence of the seasonal storage size and temperature on its capacity, losses, heat transfer rate, and efficiency of connected heat pumps or chillers. This methodology was applied to a case study, considering two scenarios: storing only the rejected heat from cooling and integrating solar thermal generation. Results show that, with varying boundary conditions such as the electricity CO2 intensity profile, cooling demand, and price of carbon emissions, not only the optimal seasonal storage size changes but also its optimal operating conditions. The potential reduction of CO2 emissions was found, under standard boundary conditions, to be limited (up to 6.7%), but an increase in cooling demand and an enhancement of the CO2 intensity seasonal variation led to a reduction of 27.1%. Integration of solar generation further improved it to 43.7%, with a comparably small increase in annual cost, up to 6.1%.

Delayed use of bioenergy crops might threaten climate and food security.

The potential of mitigation actions to limit global warming within 2 °C (ref. 1) might rely on the abundant supply of biomass for large-scale bioenergy with carbon capture and storage (BECCS) that is assumed to scale up markedly in the future2-5. However, the detrimental effects of climate change on crop yields may reduce the capacity of BECCS and threaten food security6-8, thus creating an unrecognized positive feedback loop on global warming. We quantified the strength of this feedback by implementing the responses of crop yields to increases in growing-season temperature, atmospheric CO2 concentration and intensity of nitrogen (N) fertilization in a compact Earth system model9. Exceeding a threshold of climate change would cause transformative changes in social-ecological systems by jeopardizing climate stability and threatening food security. If global mitigation alongside large-scale BECCS is delayed to 2060 when global warming exceeds about 2.5 °C, then the yields of agricultural residues for BECCS would be too low to meet the Paris goal of 2 °C by 2200. This risk of failure is amplified by the sustained demand for food, leading to an expansion of cropland or intensification of N fertilization to compensate for climate-induced yield losses. Our findings thereby reinforce the urgency of early mitigation, preferably by 2040, to avoid irreversible climate change and serious food crises unless other negative-emission technologies become available in the near future to compensate for the reduced capacity of BECCS.

Auswirkungen eines CO2-Grenzausgleichs auf nachgelagerte Industrien

AbstractThis article analyses the cost implications of an EU Carbon Border Adjustment Mechanism (CBAM) for downstream industries in Germany. The restriction to a few basic industries as envisaged in the EU Commission’s proposal is expected to lead to only a slight increase in input costs for downstream manufacturers. This also holds if the CO2 intensities occurring in the countries of origin are used to determine the level of the border adjustment. One reason for this, apart from the restriction to a few basic materials and to direct emissions, is the small share of imports from third countries. To strengthen the steering effect of a CBAM, the inclusion of emissions at upstream production levels therefore seems manageable, to the extent that they apply to intermediate inputs that are also subject to the EU-ETS. In the long term, a CBAM should not be thought of as an end in itself, but as one of several steps towards an international climate club.

The Nexus between Pollution and Obesity and the Magnifying Role of Media Consumption: International Evidence from GMM Systems Estimates.

The aim of this paper is to uncover the associations between air pollution, media consumption, and the prevalence of obesity. Based on data availability, this study draws on an unbalanced panel of 28 countries and develops and extracts relationships through robust System-General Method of Moments (Sys-GMM) estimators that account for the dynamic nature and high persistence of the variables of interest. In light of previous findings, economic development, trade openness, and government consumption are included as controls in the dynamic panel models. The estimation results consistently indicate that pollution is a strong determinant of obesity, a link that remains robust through the alternative proxies for pollution (i.e., total greenhouse gas emissions (GHG) and carbon (CO2) intensity of energy generation). However, CO2 intensity shows the strongest association with obesity. Furthermore, the findings indicate that media consumption is an independent and significant driver of obesity, whilst its inclusion among regressors further magnifies the impact and significance of the pollution factor. Moreover, the combined effect of media consumption and pollution significantly contributes to spurring obesity in all model specifications. Thus, a vicious cycle emerges between air pollution, media consumption, and obesity, with synergistic detrimental health effects. The current findings highlight the importance of continuing and consistent efforts to mitigate pollution and reach related low-carbon policy targets. Moreover, for the sustainable reduction and prevention of obesity, these efforts should be complemented by policy interventions and public campaigns aimed at “healthy” media consumption, such as encouraging regular physical exercise and healthy nutrition.

Influence of input costs and levelised cost of energy on wind power growth

Offshore wind energy costs have fallen significantly since the initial installations of the early 1990's. While installation costs for offshore wind are higher than many other sources of low carbon energy, the relative increase in capacity factor from onshore leads to higher energy yields, meaning that the unit cost or the levelised cost of energy for offshore wind is becoming increasingly competitive. In this study, a methodology is defined for modelling ranges of levelised cost for offshore wind, analysis shows the mean values of levelised cost of offshore wind in Ireland could be as low as 122 €/MWh. However, when variables such as capital expenditure, cost of finance, variable capacity factors and commodity price shifts are considered, simulations show a large range in potential outcomes, with approximately 60% of the scenarios falling between 108 €/MWh to 137 €/MWh. The methodology and results assist decision making for investment purposes, and in determining the level of support required for offshore wind energy in Ireland. Understanding the financial components of these large-scale projects and ensuring returns on investment will ultimately lead to a reduction in CO2 intensity for electricity production in Ireland from the current levels of 316 kg CO2-eq/MWh.

Improved oil recovery techniques and their role in energy efficiency and reducing CO2 footprint of oil production

Production of mature oil fields emits significant amount of CO2 related to circulation and handling of large volumes of gas and water. This can be reduced either by (1) using a low-carbon energy source and/or (2) reducing the volumes of the non-hydrocarbon produced/injected fluids. This paper describes how improved oil recovery techniques can be designed to reduce CO2 intensity (kgCO2/bbl oil) of oil production by efficient use of the injectants. It is shown that CO2 emissions associated with injection of chemicals is strongly influenced by water cut at the start of the project, extent of the water cut reduction, and chemical utilization factor defined as the volume of produced oil per mass or volume of the injectant. As an example, for the oil field considered in this study, 3–8% reduction in water cut can result in 50–80% reduction in its CO2 intensity. In addition to the incremental oil production with lower CO2 intensity, the earlier implementation of enhanced oil recovery methods can extend the lifetime of the mature fields if carbon emission cut-offs are applied. In case of CO2 enhanced oil recovery (EOR), the large storage potential for CO2 can significantly reduce the overall CO2 emissions of oil, albeit at a large energetic cost. For CO2 EOR using CO2 captured from gas power plants, improving the utilization factor from 2 bbl/tCO2 to 4 bbl/tCO2 can reduce the CO2 intensity of the produced oil from 120 kgCO2/bbl to 80 kgCO2/bbl (33% reduction).

Multi-objective optimization of energy conservation and emission reduction in China's iron and steel industry based on dimensionality reduction

With increasingly stringent environmental restrictions, the iron and steel industry is faced with multiple targets such as energy conservation, emission reduction, and cost control, hence, making industrial-environmental management a multi-objective optimization (MOO) problem. Existing studies adopt MOO models to address this issue, however, their methods result in high-dimension problems that increase computational cost and the difficulty to formulate optimal management schemes. This study builds a constrained MOO model in China's iron and steel industry, and introduces a dimensionality reduction technique to identify redundant objectives which can be omitted without altering the Pareto dominance structure of the original high-dimension problem. NSGA-II is then applied on the resulting lower-dimension problem to optimize the application of five types of Energy Conservation and Emission Reduction (ECER) measures, consisting of 23-process equipment and 55-ECER technologies. Results show that: (1) The high-dimension problem can be reduced to a four objective optimization problem. The four key-objectives are cost, energy, CO2, and PM intensity control. Hence, ECER policies should focus on these four key-objectives since optimizing them will synergistically minimize redundant objectives like NOx and SO2 emissions; (2) For the resulting lower-dimension problem, solution quality increases as reflected by algorithm verification metrics (spacing metric and hypervolume indicator), while computational cost is reduced by 73% and the decision making process is simplified significantly; (3) By-production reutilization and cleaner production technologies are the most attractive measures, contributing about 60% of ECER potential and only 30% of total cost. Equipment upgrading also has good ECER effects, but requires strong economic incentives, while end-of-pipe and renewable energy technologies have the lowest ECER potential. In sum, this study proposed a methodology to reduce the complexity of ECER optimization under multiple objectives, and provided suggestions to enhance industrial-environmental management under increasing environmental restrictions.

Reusing waste red brick powder as partial mineral precursor in eco-friendly binders: Reaction kinetics, microstructure and life-cycle assessment

A large number of solid wastes are produced in the process of demolishing old buildings, and waste red brick is one of such wastes. To discuss the reutilization of waste red brick powder (WRBP) in alkali-activated material, a novel ternary eco-friendly binder was prepared by using slag, fly ash and WRBP as precursor. The impact of WRBP on the reaction kinetics, microstructure and life-cycle assessment of alkali-activated cement paste were evaluated. The Johnson-Mehl-Avrami-Kolmogrov model was established based on the heat release results. With the incorporation of WRBP, the degree of reaction was deepened, supporting the enhancement of matrix strength. X-ray diffraction and thermogravimetric analysis results show the consistent mineralogical composition of reaction products and increase of gel quantity. Pore characteristics determined by mercury intrusion porosimetry method exhibit that large capillary pores were refined by enrichment of gels and filling effect of WRBP. From the economic and environmental aspects, the reuse of WRBP significantly saved the energy consumption and reduced the carbon dioxide (CO2) emission. On the basis of the optimal compressive strength, the energy consumption efficiency index and CO2 intensity index were 27.3 MJ/MPa and 1.7 kg/MPa, which can provide 38.55% energy consumption and 44.90% carbon footprint savings. Such work may shed valuable insights to the recycling of various types of solid waste and low-carbonation of building field.

Carbon dioxide intensity of GDP and environmental degradation in an emerging country.

This paper investigates whether the carbon dioxide (CO2) intensity of GDP matters for environmental degradation in an emerging country, namely, Turkey, over the period of 1990-2018 while controlling economic growth, foreign direct investment, and renewable energy consumption. The present study uses both linear and nonlinear time series estimators, namely, the Gregory and Hansen cointegration test, bounds test, nonlinear autoregressive distributed lag (NARDL) model, fully modified ordinary least squares (FMOLS), dynamic ordinary least squares (DOLS), and canonical cointegrating regressions (CCR), to encapsulate the possible effect of CO2 intensity of GDP, economic growth, foreign direct investment, and renewable energy consumption on environmentaldegradation in Turkey. The empirical finding of the present study reveals that the CO2 intensity of GDP is an important factor to determine environmental degradation in Turkey and the declining CO2 intensity of GDP reduces environmentaldegradation.Moreover, economic growth is the primary environmental sustainability factor in Turkey. The result is vital for policymaking and can perhaps be applied to take decisive policy actions to mitigate environmental issues.

Combined evaluation of quality and eco-burdens of the hydrocarbon refrigerant GF-08 in tomato greenhouse air conditioning

This study focuses on a combined evaluation of GF-08, a non-CFC hydrocarbon refrigerant, to maintain the quality and reduce the environmental impact of tomatoes during air conditioning (cultivation stage) and during cold storage (storage stage). Past studies have shown that power consumption can be reduced by replacing the conventional refrigerant R410A with GF-08 for air-conditioning in a tomato farm. In addition, the CO2 intensity of GF-08 was extremely low compared to that of R410A. Regarding the air conditioner for the cultivation technology, the relationship between the energy-saving performance and the nutritional and freshness preservation of agricultural products has not been discussed. This study examined the effects of temperature and CO2 gas controls on nutritional value and freshness preservation of a tomato facility based in Kesennuma City, Miyagi Prefecture, Japan. The energy consumption and the characteristics were analyzed for the use of GF-08 and compared to the conventional refrigerant R410A. The effect of storage temperatures on the tomato quality was estimated and the energy consumption and eco-burdens were analyzed based on the LCA methodology. This combined data was further used to determine the relationship between the eco-burdens and quality of the tomato produce.

Take a ride on the (not so) green side: How do CDM projects affect Indian manufacturing firms’ environmental performance?

This study examines the causal impacts of the Clean Development Mechanism (CDM) on the environmental performance of Indian manufacturing firms, as measured by their energy use, carbon dioxide (CO2) emissions, and intensities of CO2 emissions per sales and per energy use. The impacts of CDM projects are estimated using either two-way fixed-effect regressions or an estimator built for an event study with staggered treatment (Sun and Abraham, 2021) combined with a sample of ever-treated firms only or a sample comparing treated to never-treated control firms using semi-parametric matching. We found that CDM projects significantly increased firms’ CO2 emissions and energy use after treatment, but had no effect on CO2 emission intensity per sales and only a small negative effect on the CO2 content of energy use (only for the matched sample). These results reveal that CDM projects led to a positive scale effect (increased sales) after investments were made, and that these investments triggered a limited emission-reducing technique effect (decreased CO2 intensity).