Life cycle GHG assessment of fossil fuel power plants with carbon capture and storage

The evaluation of life cycle greenhouse gas emissions from power generation with carbon capture and storage (CCS) is a critical factor in energy and policy analysis. The current paper examines life cycle emissions from three types of fossil-fuel-based power plants, namely supercritical pulverized coal (super-PC), natural gas combined cycle (NGCC) and integrated gasification combined cycle (IGCC), with and without CCS. Results show that, for a 90% CO₂ capture efficiency, life cycle GHG emissions are reduced by 75–84% depending on what technology is used. With GHG emissions less than 170 g/kWh, IGCC technology is found to be favorable to NGCC with CCS. Sensitivity analysis reveals that, for coal power plants, varying the CO₂ capture efficiency and the coal transport distance has a more pronounced effect on life cycle GHG emissions than changing the length of CO₂ transport pipeline. Finally, it is concluded from the current study that while the global warming potential is reduced when MEA-based CO₂ capture is employed, the increase in other air pollutants such as NO_x and NH₃ leads to higher eutrophication and acidification potentials.     

Estimate of ecological efficiency for thermal power plants in Brazil

Global warming and the consequent climatic changes that will come as a result of the increase of CO₂ concentration in the atmosphere have increased the world’s concern regarding reduction of these emissions, mainly in developed countries that pollute the most. Electricity generation in thermal power plants, as well as other industrial activities, such as chemical and petrochemical ones, entail the emission of pollutants that are harmful to humans, animals and plants. The emissions of carbon oxides (CO and CO₂) and nitrous oxide (N₂O) are directly related to the greenhouse effect. The negative effects of sulfur oxides (SO₂ and SO₃ named SO_x) and nitrogen oxides (NO_x) are their contribution to the formation of acid rain and their impacts on human health and on the biota in general. This study intends to evaluate the environmental impacts of the atmospheric pollution resulting from the burning of fossil fuels. This study considers the emissions of CO₂, SO_x, NO_x and PM in an integral way, and they are compared to the international air quality standards that are in force using a parameter called ecological efficiency (ε).     

The outlook for improved carbon capture technology

Carbon capture and storage (CCS) is widely seen as a critical technology for reducing atmospheric emissions of carbon dioxide (CO₂) from power plants and other large industrial facilities, which are major sources of greenhouse gas emissions linked to global climate change. However, the high cost and energy requirements of current CO₂ capture processes are major barriers to their use. This paper assesses the outlook for improved, lower-cost technologies for each of the three major approaches to CO₂ capture, namely, post-combustion, pre-combustion and oxy-combustion capture. The advantages and limitations of each of method are discussed, along with the current status of projects and processes at various stages in the development cycle. We then review a variety of “roadmaps” developed by governmental and private-sector organizations to project the commercial roll-out and deployment of advanced capture technologies. For perspective, we also review recent experience with R&D programs to develop lower-cost technologies for SO₂ and NO_x capture at coal-fired power plants. For perspective on projected cost reductions for CO₂ capture we further review past experience in cost trends for SO₂ and NO_x capture systems. The key insight for improved carbon capture technology is that achieving significant cost reductions will require not only a vigorous and sustained level of research and development (R&D), but also a substantial level of commercial deployment, which, in turn, requires a significant market for CO₂ capture technologies. At present such a market does not yet exist. While various incentive programs can accelerate the development and deployment of improved CO₂ capture systems, government actions that significantly limit CO₂ emissions to the atmosphere ultimately are needed to realize substantial and sustained reductions in the future cost of CO₂ capture.     

Potential emissions reductions from grandfathered coal power plants in the United States

A two-tiered approach to environmental regulation in the United States has long allowed existing coal-fired power plants to emit air pollutants at far higher rates than new facilities. The potential for reducing the emissions of existing coal-fired facilities is quantified via two hypothetical scenarios: the installation of available retrofit control technologies, or the imposition of New Source Performance Standards (NSPS). Available control technologies could have reduced year 2005 emissions by 56% for NO_x and 72% for SO₂ for a cost of $11.3 billion/year (2004$), likely yielding far larger benefits to human health. Slightly more emission reductions would be achieved by upgrading or replacing existing facilities to achieve the NSPS emissions limits required of all new facilities. Potential CO₂ reductions are more speculative due to the emerging nature of carbon capture and efficiency retrofit technologies. Recent policies such as the Cross-State Air Pollution Rule would likely achieve most of the NO_x and SO₂ reduction potential identified by the scenario analyses for grandfathered facilities. However, escalating obstacles to new generation capacity may perpetuate the reliance on an aging fleet of power plants, resulting in higher rates of coal consumption and CO₂ emissions than could be achieved by new or retrofit units.     

Environmental impacts and benefits of regional power grid interconnections for China

This paper describes the development of China's power industry, present situation, environmental influences and potential benefits of regional power grid interconnections in China. Power plants in China are mainly thermal, burning fossil fuels especially coal which emit a great deal of pollutants and greenhouse gases such as SO₂, NO_x and CO₂. China leads all other countries in emissions of SO₂, CO₂, and the power industry is the largest contributor to these emissions. There are a number of environmental benefits through regional power grid interconnection. That is, the construction of small electricity generation capacity would be avoided; natural resources would be used to generate electricity on a regional scale; and generating sources can be separated from centers of electricity use, which will decrease emission of pollutants and greenhouse gases and help to reduce human exposure to elevated air pollutant concentrations. Therefore, gradually enlarged power grids, and power grid interconnection, should be part of the general pattern of power system development in China.     

Life cycle inventory analysis for electricity in Korea

A life cycle inventory analysis (LCI) database that encompasses the entire Korean electrical energy grid was developed. The CO₂ emission per functional unit of electricity, 1 kWh of usable electricity, was 0.49 kg/f.u. Contribution of direct emission of CO₂ to the total CO₂ emission was around 95%. In the case of emissions of SO_x, NO_x, and PM, contribution of the upstream processes including raw energy material extraction, transport, and fuel processing to the total emissions were 29%, 26%, and 43%, respectively. Emissions of air pollutants from power generation or direct emissions are much greater in quantity than those from the upstream processes. On the other hand, the opposite is true for the emissions of water pollutants. Bituminous coal was the largest source of emissions of air and water pollutants including CO₂. Natural gas was the best fuel and anthracite coal was the worst fuel with respect to the direct and upstream emissions of air and water pollutants and wastes.     

Ecological efficiency in CHP: Biodiesel case

This paper evaluates and quantifies the environmental impact resulting from the combination of biodiesel fuel (pure or blended with diesel), and diesel combustion in thermoelectric power plants that utilize combined cycle technology (CC). In regions without natural gas, the option was to utilize diesel fuel; the consequence would be a greater emission of pollutants. Biodiesel is a renewable fuel which has been considerably interesting in Brazil power matrix in recent years. The concept of ecological efficiency, largely evaluates the environmental impact caused by CO₂, SO₂, NO_x and particle matter (PM) emissions. The pollution resulting from biodiesel and diesel combustion is analyzed, separately considering CO₂, SO₂, NO_x and particulate matter gas emissions, and comparing them international standards currently used regarding air quality. It can be concluded that it is possible to calculate the qualitative environmental factor, and the ecological effect, from a thermoelectric power plant utilizing central heat power (CHP) of combined cycle. The ecological efficiency for pure biodiesel fuel (B100) is 98.16%; for biodiesel blended with conventional diesel fuel, B20 (20% biodiesel and 80% diesel) is 93.19%. Finally, ecological efficiency for conventional diesel is 92.18%, as long as a thermal efficiency of 55% for thermoelectric power plants occurs.     

Air pollution implications of Nigeria’s present strategy on improved electricity generation

One of the strategies being developed in Nigeria to increase the presently installed electricity generation of 6159 MW to the required 30,000 MW is the adoption of electric thermal plants. An emission factor approach is used in this paper to study the emission of uncontrolled air pollutants from all the existing and proposed thermal plants in the country. Calculations are performed to study the distribution of carbon monoxide (CO), oxides of nitrogen (NO_X), particulate matters (PM), sulphur dioxide (SO₂), and volatile organic compounds (VOCs). The estimated emissions ranges are 978–24,607, 1635–41,148, 37–924, 19–472, and 11–286 ton/annum for CO, NO_X, PM, SO₂, and VOCs, respectively. The present locations of these plants across the country are characterized by skewed emission distribution both per capita and across the land. Given the potential environmental and health impacts of these emissions, several measures are suggested to reduce future impacts and assist the country in achieving sustainable development.     

Spatial variation of emissions impacts due to renewable energy siting decisions in the Western U.S. under high-renewable penetration scenarios

One of the policy goals motivating programs to increase renewable energy investment is that renewable electric generation will help reduce emissions of CO₂ as well as emissions of conventional pollutants (e.g., SO₂ and NO_x). As a policy instrument, Renewable Portfolio Standards (RPS) encourage investments in wind, solar and other generation sources with the goal of reducing air emissions from electricity production. Increased electricity production from wind turbines is expected to displace electricity production from fossil-fired plants, thus reducing overall system emissions. We analyze the emissions impacts of incremental investments in utility-scale wind power, on the order of 1 GW beyond RPS goals, in the Western United States using a utility-scale generation dispatch model that incorporates the impacts of transmission constraints. We find that wind investment in some locations leads to slight increases in overall emissions of CO₂, SO₂ and NO_x. The location of wind farms influences the environmental impact by changing the utilization of transmission assets, which affects the overall utilization of power generation sources and thus system-level emissions. Our results suggest that renewable energy policy beyond RPS targets should be carefully crafted to ensure consistency with environmental goals.     

Continuous emission monitoring systems at power plants in China: Improving SO2 emission measurement

The Chinese Government recently mandated the installation of continuous emission monitoring systems (CEMS) at state-controlled key polluting facilities in order to provide direct, real-time, continuous measurements of sulfur dioxide (SO₂) emissions. By 2010, most coal-fired power plants in China have installed and are operating SO₂ CEMS. As China's Central Government strengthens the SO₂ control program and implements new nitrogen oxides (NO_X) and carbon dioxide (CO₂) control programs, the quality of and confidence in CEMS data will become more important. This study utilizes field surveys and existing literature on Chinese CEMS to analyze their operation and management. Our study found that the Chinese government has issued a set of regulations and technical guidance documents to standardize CEMS operation, management, and supervision, and to improve the quality of CEMS data. Many power plants have followed key parts of the national CEMS rules and guidance and are periodically inspected by local environmental authorities. This study suggests several options for addressing some of the gaps and problems with the CEMS operation and supervision and thus enhancing China's CEMS program.     

Performance and cost of wet and dry cooling systems for pulverized coal power plants with and without carbon capture and storage

Thermoelectric power plants require significant quantities of water, primarily for the purpose of cooling. Water also is becoming critically important for low-carbon power generation. To reduce greenhouse gas emissions from pulverized coal (PC) power plants, post-combustion carbon capture and storage (CCS) systems are receiving considerable attention. However, current CO₂ capture systems require a significant amount of cooling. This paper evaluates and quantifies the plant-level performance and cost of different cooling technologies for PC power plants with and without CO₂ capture. Included are recirculating systems with wet cooling towers and air-cooled condensers (ACCs) for dry cooling. We examine a range of key factors affecting cooling system performance, cost and plant water use, including the plant steam cycle design, coal type, carbon capture system design, and local ambient conditions. Options for reducing power plant water consumption also are presented.     

The environmental impact and risk assessment of CO2 capture, transport and storage - An evaluation of the knowledge base

In this study, we identify and characterize known and new environmental consequences associated with CO₂ capture from power plants, transport by pipeline and storage in geological formations. We have reviewed (analogous) environmental impact assessment procedures and scientific literature on carbon capture and storage (CCS) options. Analogues include the construction of new power plants, transport of natural gas by pipelines, underground natural gas storage (UGS), natural gas production and enhanced oil recovery (EOR) projects. It is investigated whether crucial knowledge on environmental impacts is lacking that may postpone the implementation of CCS projects. This review shows that the capture of CO₂ from power plants results in a change in the environmental profile of the power plant. This change encompasses both increase and reduction of key atmospheric emissions, being: NO_x, SO₂, NH₃, particulate matter, Hg, HF and HCl. The largest trade-offs are found for the emission of NO_x and NH₃ when equipping power plants with post-combustion capture. Synergy is expected for SO₂ emissions, which are low for all power plants with CO₂ capture. An increase in water consumption ranging between 32% and 93% and an increase in waste and by-product creation with tens of kilotonnes annually is expected for a large-scale power plant (1 GW_e), but exact flows and composition are uncertain. The cross-media effects of CO₂ capture are found to be uncertain and to a large extent not quantified. For the assessment of the safety of CO₂ transport by pipeline at high pressure an important knowledge gap is the absence of validated release and dispersion models for CO₂ releases. We also highlight factors that result in some (not major) uncertainties when estimating the failure rates for CO₂ pipelines. Furthermore, uniform CO₂ exposure thresholds, detailed dose-response models and specific CO₂ pipeline regulation are absent. Most gaps in environmental information regarding the CCS chain are identified and characterized for the risk assessment of the underground, non-engineered, part of the storage activity. This uncertainty is considered to be larger for aquifers than for hydrocarbon reservoirs. Failure rates are found to be heavily based on expert opinions and the dose-response models for ecosystems or target species are not yet developed. Integration and validation of various sub-models describing fate and transport of CO₂ in various compartments of the geosphere is at an infant stage. In conclusion, it is not possible to execute a quantitative risk assessment for the non-engineered part of the storage activity with high confidence.     

Estimating co-pollutant benefits from climate change policies in the electricity sector: A regression approach

We use data from US power plants and a regression based approach to empirically estimate the marginal rate of co-pollutant emission reductions resulting from a mass-based carbon reduction policy for electricity producers. The standard approach to estimating co-pollutant reductions uses Linear Programming Models. These models require millions of input variables and constraints, resulting in long computational times and an opaque simulation process, while yielding only point estimates for key variables of interest. Our regression-based approach has far fewer data requirements, needs less computational resources, and produces estimates with confidence intervals that capture estimation uncertainty. Moreover, it is straightforward and transparent to implement and provides a larger range of potential outcomes for policy makers to consider. Our results indicate that a 1% decrease in electricity output from coal (gas) power plants would reduce SO₂ by 0.6% and NO_x by 0.8% (0.7%). These are not statistically significant different than estimates reported by the Environmental Protection Agency (EPA). We estimate that reducing electricity output enough to reduce CO₂ emissions by one ton yields health benefits of $15.33 from NO_x reductions and $59.64 from SO₂ reductions.     

Internalisation of external cost in the power generation sector: Analysis with Global Multi-regional MARKAL model

The Global MARKAL-Model (GMM), a multi-regional “bottom-up” partial equilibrium model of the global energy system with endogenous technological learning, is used to address impacts of internalisation of external costs from power production. This modelling approach imposes additional charges on electricity generation, which reflect the costs of environmental and health damages from local pollutants (SO₂, NO_x) and climate change, wastes, occupational health, risk of accidents, noise and other burdens. Technologies allowing abatement of pollutants emitted from power plants are rapidly introduced into the energy system, for example, desulphurisation, NO_x removal, and CO₂ scrubbers. The modelling results indicate substantial changes in the electricity production system in favour of natural gas combined cycle, nuclear power and renewables induced by internalisation of external costs and also efficiency loss due to the use of scrubbers. Structural changes and fuel switching in the electricity sector result in significant reduction of emissions of both local pollution and CO₂ over the modelled time period. Strong decarbonisation impact of internalising local externalities suggests that ancillary benefits can be expected from policies directly addressing other issues then CO₂ mitigation. Finally, the detailed analysis of the total generation cost of different technologies points out that inclusion of external cost in the price of electricity increases competitiveness of non-fossil generation sources and fossil power plants with emission control.     

Techno-economic appraisal of fossil-fuelled power generation systems with carbon dioxide capture and storage

Carbon capture and storage (CCS) facilities coupled to power plants provide a climate change mitigation strategy that potentially permits the continued use of fossil fuels whilst reducing the carbon dioxide (CO₂) emissions. This process involves three basic stages: capture and compression of CO₂ from power stations, transport of CO₂, and storage away from the atmosphere for hundreds to thousands of years. Potential routes for the capture, transport and storage of CO₂ from United Kingdom (UK) power plants are examined. Six indicative options are evaluated, based on ‘Pulverised Coal’, ‘Natural Gas Combined Cycle’, and ‘Integrated (coal) Gasification Combined Cycle’ power stations. Chemical and physical CO₂ absorption capture techniques are employed with realistic transport possibilities to ‘Enhanced Oil Recovery’ sites or depleted gas fields in the North Sea. The selected options are quantitatively assessed against well-established economic and energy-related criteria. Results show that CO₂ capture can reduce emissions by over 90%. However, this will reduce the efficiency of the power plants concerned, incurring energy penalties between 14 and 30% compared to reference plants without capture. Costs of capture, transport and storage are concatenated to show that the whole CCS chain ‘cost of electricity’ (COE) rises by 27-142% depending on the option adopted. This is a significant cost increase, although calculations show that the average ‘cost of CO₂ captured’ is £15/tCO₂ in 2005 prices [the current base year for official UK producer price indices]. If potential governmental carbon penalties were introduced at this level, then the COE would equate to the same as the reference plant, and make CCS a viable option to help mitigate large-scale climate change.     

Effectiveness of local air pollution and GHG taxes: The case of Chilean industrial sources

In 2017, environmental taxes began to be applied to CO₂, PM, NOx and SO₂ emissions in Chile to reduce the negative environmental effects of fossil fuels burned in industrial and thermoelectric sources with a thermal power greater than or equal to 50 MW. In this context, the present study generates an economic optimization model to simulate how different tax scenarios would modify the behavior of regulated industrial sources considering the alternatives they have to minimize their costs (tax payment, fuel change and/or installation of abatement technologies). The main results show that, under the current tax scenario, CO₂, PM and SO₂ emissions would decrease by 11%, 48% and 49% respectively, while NO_X emissions would increase by 5%. By extending the tax to all industrial sources regardless of their thermal power, CO₂, PM and SO₂ emissions would decrease respectively by 14%, 98% and 66%, while NO_X emissions would increase by 7.1%. Finally, it is determined that modifying the tax rate of a single pollutant while maintaining the rest of the constant rates generates a low impact on the other pollutants emissions.     

Integration of gas switching combustion in a humid air turbine cycle for flexible power production from solid fuels with near-zero emissions of CO2 and other pollutants

This work presents a novel plant configuration for power production from solid fuels with integrated CO₂ capture. Specifically, the Gas Switching Combustion (GSC) system is integrated with a Humid Air Turbine (HAT) power cycle and a slurry fed entrained flow (GE-Texaco) gasifier or a dry fed (Shell) gasifier with a partial water quench. The primary novelty of the proposed GSC-HAT plant is that the reduction and oxidation reactor stages of the GSC operation can be decoupled allowing for flexible operation, with the oxygen carrier serving as a chemical and thermal energy storage medium. This can allow the air separation unit, gasifier, gas clean-up, CO₂ compressors and downstream CO₂ transport and storage network to be downsized for operation under steady state conditions, while the reactors and the power cycle operate flexibly to follow load. Such cost-effective flexibility will be highly valued in future energy systems with high shares of variable renewable energy. The GSC-HAT plant achieves 42.5% electrical efficiency with 95.0% CO₂ capture rate with the Shell gasifier, and 41.6% efficiency and 99.2% CO₂ capture with the GE gasifier. An exergy analysis performed for the GE gasifier case revealed that this plant reached 38.9% exergy efficiency, only 1.6%-points below an inflexible GSC-IGCC benchmark configuration, while reaching around 5%-points higher CO₂ capture rate. Near-zero SO_x and NO_x emissions are achieved through pre-combustion gas clean-up and flameless fuel combustion. Overall, this flexible and efficient near-zero emission power plant appears to be a promising alternative in a future carbon constrained world with increasing shares of variable renewables and more stringent pollutant (NO_x, SO_x) regulations.     

A system performance and economics analysis of IGCC with supercritical steam bottom cycle supplied with varying blends of coal and biomass feedstock

In recent years, Integrated Gasification Combined Cycle Technology (IGCC) has been gaining popularity for use in clean coal power operations with carbon capture and sequestration. Great efforts have been continuously spent on investigating ways to improve the efficiency and further reduce the greenhouse gas emissions of such plants. This study focuses on investigating two approaches to achieve these goals. First, replace the traditional subcritical Rankine cycle portion of the overall plant with a supercritical steam cycle. Second, add biomass as co‐feedstock to reduce carbon footprint as well as SO_x and NO_x emissions. In fact, plants that use biomass alone can be carbon neutral and even become carbon negative if CO₂ is captured. Due to a limited supply of feedstock, biomass plants are usually small, which results in higher capital and production costs. In addition, biomass can only be obtained at specific times in the year, resulting in fairly low capacity factors. Considering these challenges, it is more economically attractive and less technically challenging to co‐gasify biomass wastes with coal. The results show that for supercritical IGCC, the net efficiency increases with increased biomass in all cases. For both subcritical and supercritical cases, the efficiency increases from 0% to 10% (wt.) biomass and decreases thereafter. However, the efficiency of the blended cases always remains higher than that of the pure‐coal baseline cases. The emissions (NO_x, SO_x, and effective CO₂) and the capital costs decrease as biomass ratio (BMR) increases, but the cost of electricity (CoE) increases with BMR due to the high cost of the biomass used. Finally, implementing a supercritical steam cycle is shown to increase the net plant output power by 13% and the thermal efficiency by about 1.6 percentage points (or 4.56%) with a 6.7% reduction in capital cost, and a 3.5% decrease in CoE. Copyright © 2013 John Wiley & Sons, Ltd.     

Clean coal technology development in China

Coal is found in huge amounts throughout the world and is expected to play a crucial role as an abundant energy source. However, one critical issue in promoting coal utilization is controlling environmental pollution. Clean coal technologies are needed to utilize coal in an environmentally acceptable way and to improve coal utilization efficiency. This paper describes coal's role in China's energy system and the environmental issues related to coal use. Coal is responsible for 90% of the SO₂ emissions, 70% of the dust emissions, 67% of the NO_x emissions, and 70% of the CO₂ emissions. But as the most abundant energy resource, it will continue to be the dominant energy supply for a long time. Therefore, the development and deployment of clean coal technologies are crucial to promote sustainable development in China. Clean coal technologies currently being developed in China are described including high efficiency combustion and advanced power generation technologies, coal transformation technologies, IGCC (integrated gasification combined cycle) and carbon capture and storage (CCS). Although China only recently began developing clean coal technologies, there have been many successes. Most recent orders of coal-fired power plants are units larger than 600 MW and new orders for supercritical and ultra supercritical systems are increasing rapidly. Many national research programs, industrial research programs and international collaboration projects have been launched to develop on IGCC and CCS systems in China. Finally, suggestions are given on how to further promote clean coal technologies in China.     

Quantification of provincial-level carbon emissions from energy consumption in China

Greenhouse gas emission inventories are useful tools for monitoring air quality and assisting local policy development. This article estimates CO₂ emission inventories from energy consumption and carbon intensities of provinces and municipalities in Mainland China in 1990, 1995, 2000, and 2005–2008 using the IPCC mass balance approach. Results show that China's coal-based energy structure and unique economic development have heavily impacted CO₂ emissions. Fortunately, although coal consumption has increased to over 70% of all fuel use, the share of CO₂ emissions from coal has gradually decreased due to energy consumption restructuring. The switch from coal-dominance to cleaner, renewable energies (wind, solar, natural gas, nuclear power, geothermal, biomass energy) will undoubtedly reduce CO₂ emissions in China. Results also indicate that carbon intensity has improved steadily, as China's economic development introduces new technologies intended to minimize environmental pollution and destruction. Our results suggest that China's CO₂ emissions may not be as high as expected in future, and will gradually lessen.