Air Pollution Control Technologies Research Articles

State-of-the-Art and Recent Advances in the Abatement of Gaseous Pollutants from Waste-to-Energy

Despite their key role in integrated waste management, direct (incineration) and indirect (gasification/pyrolysis) waste combustion processes are still opposed by some of the general public due to the past emission levels of air pollutants. In fact, although the release of air pollutants (especially dioxin) to the atmosphere from waste combustion processes has gradually decreased over the years, thanks to the introduction of stricter regulations and more advanced removal technologies, there is still an unsolved problem regarding the public acceptance of waste-to-energy facilities. The aim of this paper is to provide an overview of the state-of-the-art air pollution control (APC) technologies used in waste combustion facilities. Air pollution control technologies are designed to reduce or eliminate the emissions of harmful pollutants into the atmosphere. These technologies are important for safeguarding public health, protecting ecosystems, complying with regulations, and promoting a more sustainable and resilient future for both local and global communities. This paper will highlight the complexity behind emission control and the efforts made by this sector over the years. This paper will also propose suggested configurations based on the interactions/complementarity between different APC technologies and recent findings to improve their performance.

Visible-Light-Induced photocatalytic oxidation of gaseous ammonia on Mo, c-codoped TiO2: Synthesis, performance and mechanism

Ammonia gas (NH3) is a notorious malodorous pollutant with detrimental effects on environment and human health. Removing NH3 through photocatalytic oxidation remains a challenging task due to unclear reaction mechanisms. In this study, DFT simulation results revealed that Cdoped TiO2 could extend the photo-response range to the visible region, but the introduction of deep impurity levels was found to accelerate photogenerated carrier recombination. Fortunately, the rational doping of Mo was found to mitigate this negative effect. Accordingly, Mo, C co-doped TiO2 was synthesized via a facile low-temperature calcination process, resulting in unique band structure that enhanced the photocatalytic oxidation of NH3. Notably, in-situ DRIFTS and DFT results demonstrated that the gradual reaction of NH3 adsorbed on Mo atoms with oxygen species through the N2H4 mechanism, promoting the formation of N2. These findings offer insights into the design of efficient photocatalysts for NH3 removal under visible light, and present a promising technology for indoor air pollution control.

Emission Characteristics, Speciation, and Potential Environmental Risks of Heavy Metals from Coal-Fired Boilers: A Review

Coal-fired boilers, including coal-fired power plants (CFPPs) and coal-fired industrial boilers (CFIBs), are an important area for achieving sustainability globally as they are one of the globally important sources of anthropogenic emissions of heavy metals (HMs) due to huge amount of coal consumption. To date, the investigation of atmospheric emission characteristics, speciation, and potential environmental risks of HMs from coal-fired boilers has received widespread attention and achieved significant progress. To characterise the emissions of HMs from coal-fired boilers, research is currently being carried out in the areas of (1) studying the release of HMs from coal combustion processes, (2) developing emission factors and emission inventories, and (3) revealing the cross-media partitioning of HMs between different output streams. Research on the chemical forms of HMs in waste from coal-fired boiler is currently focused on chemical valence and speciation components. The sequential chemical extraction method is currently the most widely used method for investigating the chemical fractionations of HMs in wastes from coal-fired boilers. Studies indicate that different HM elements display differentiated characteristics of speciation in waste from coal-fired boilers. Early studies on potential environmental risk and ecological risk caused by HMs are usually based on actual monitoring values of HMs in the target environmental media. The risk assessment code method and the leaching toxicity method are the most widely used method to study the potential environmental risk of HMs in waste from coal-fired boilers. With the implementation of global carbon emission reduction strategies, the scale of coal-fired boilers and air pollution control technologies are bound to change in the future. Therefore, as an important component of global efforts to achieve sustainable development, more research is needed in the future to improve the accuracy of emission inventories, reveal the mechanisms of HM chemical transformation, and establish methods for potential environmental risk assessment at regional scales.

Hydrophobic air pollutants removal at one second gas contact in a multi-channel capillary bioreactor

Biological processes are increasingly applied for gas purification as a sustainable and economical alternative to conventional physical-chemical processes (chemical absorption, incineration, adsorption). Although biological gas treatment is accepted as an economical, safe, and reliable air pollution control technology, it faces important limitations when applied for the treatment of poorly water-soluble compounds due to mass transfer limitations. A twenty-five capillary channels bioreactor was studied to characterize mass transfer coefficients and the removal of hydrophobic air pollutants under segmented gas-liquid flow pattern. The removal efficiency of hexane, toluene and α-pinene vapors reached values up to about 75%, 99% and 75%, respectively, at a gas contact time of less than 1 s, which is at least one, but closer to two orders of magnitude shorter than conventional biological gas purification systems. The bioreactor displayed stable operation for 100 days and was robust against common upsets, which opens the new opportunities for expanding the application field of biological processes for air pollution control and the mitigation of greenhouse gases in dilute air streams. SynopsisThis study breaks through existing barriers of gas treating biotechnologies which allows expansion of the application field of more sustainable processes for air pollution control.

Temporal and spatial analysis of anthropogenic mercury and CO2 emissions from municipal solid waste incineration in China: Implications for mercury and climate change mitigation

The contribution of municipal solid waste incineration (MSWI) to anthropogenic mercury and CO2 emissions have become increasingly important over the past decade. This study developed an inventory of anthropogenic mercury emissions and CO2 emissions during the period of 2014–2020, of MSWI process in China using a bottom-up inventory at the plant level. Overall, national MSWI anthropogenic mercury emissions increased from 2014 to 2020 by province. It was estimated that total 8321.09 kg of anthropogenic mercury emissions from 548 MSWI plants were scattered in 31 provinces of mainland China in 2020. The average intensity of mercury emission in China was 0.06 g·t−1 in 2020, which was much lower than the pre-2010 level. Furthermore, the increased CO2 emission generated by MSWI from 2014 to 2020 is 1.97 times. Anthropogenic mercury emissions and CO2 emissions were concentrated mainly in developed coastal provinces and cities. The general uncertainty of national mercury emissions and CO2 emissions was estimated to be −123% to 323% and −130% to 335%, respectively. Furthermore, future emissions were predicted from 2030 to 2060 based on different scenarios of the independent and collaborative effects of control proposals, the results indicate that the enhancement of advanced air pollution control technologies and effective management of MSWI represent pivotal factors in realizing future reductions in CO2 and mercury emissions. The findings will supplement those for mercury and CO2 emissions, and be useful for relevant policy-making and to improve urban air quality, as well as human health.

Enhancing NOx removal in a high-gravity rotating packed bed with gaseous ClO2 oxidation-absorption: Kinetic, mass transfer, and cost analysis

The application of ClO2(g) for NO oxidation presents a promising approach to improving air pollution control technology. In this study, an integration of ClO2(g) with absorption using a high-gravity rotating packed bed (HiGee RPB) was proposed for NOx removal. The results showed that ClO2(g) has a comparable oxidation efficiency (close to 100%) to O3 in converting NO to NO2, while the dosage of ClO2(g) required was two times smaller than that of O3. The gas-phase oxidation kinetic analysis between ClO2(g)-NOx, using an ideal plug flow model, simulated the potential amount of NOx species produced in a short reaction distance in the pipeline. Furthermore, at higher gas-liquid ratios and in high-gravity fields, the effective mass transfer interfacial area for NO2 absorption was mainly controlled by the liquid film rather than droplet behavior, resulting in decreased absorption capacity. The empirical model for predicting the gas-side mass transfer coefficient confirmed that the interaction between mass transfer performance and chemical absorption was independent. Therefore, selecting the appropriate absorbent is a key factor in achieving high-loading NO2 concentrations after oxidation by ClO2(g). Another interesting finding is that balancing system energy consumption and the target treated NOx concentration played a critical role in enhancing the NOx absorption capacity. The cost analysis showed that substituting existing scrubbers with RPB processes could facilitate NOx absorption capacity (g-NOx/kWh) with cost-effectiveness. Overall, this study provides valuable insights into the development of effective and efficient NOx removal technologies, and future research in this area can build on these findings.

Identifying influential countries in air pollution control technologies: A social network analysis approach

Clarifying the spatial correlation network of country–level air pollution control technology (APCT) is essential for transregional collaborative emission reduction in global warming. Previous research mainly focused on identifying the network structures of green technology linkages in a single country or region. In reality, cross–border technological cooperation has become a strategy for countries to achieve technological breakthroughs, and non–adjacent countries can be interconnected. Based on 217,392 patents, this study uses the Social Network Analysis method and Quadratic Assignment Procedure to discuss the spatio-temporal evolution and influence mechanisms of 57 countries’ APCT spatial correlation network from 1990 to 2020. The results indicate the following: (1) The network density in APCT decreased from 0.428 to 0.355 between 1990 and 2020, and the overall network presents prominent core–periphery structural features. The developing countries accounted for 44.44% of the core area countries. (2) The United States and Canada, the United Kingdom, Germany, China, and Japan are at the center of the Americas, Europe, and Asia. (3) Narrowing the gap in greenhouse gas emissions in manufacturing industries and construction contributes to forming potential routes of multinational cooperation; however, the role of geographical distance becomes insignificant (0.282). Lastly, a multicenter knowledge flow network should facilitate global knowledge transfer, absorption, and sharing.

A Study on the Particle Removal Efficiency and Durability According to the Material of the Ionizer of the Fiber Brush Type Electric Precipitator

In this study, we investigated the particulate matter (PM) removal efficiency and durability of the two-stage electrostatic precipitator (ESP) different materials of brush-typed ionizers (non-metal: carbon fiber/metal: stainless steel (SUS) fiber). The PM removal efficiency was reduced when the average diameter and number of fibers of the brush-typed ionizer increased due to thin and multi-edge in a large number of fibers, which decreased the average electric field, resulting in lower PM removal efficiencies. In contrast with the carbon fiber ionizer, when the SUS fiber ionizer was used, the PM removal efficiency was maintained for a long time, due to its lower electrical resistivity (∼6.9 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−7</sup> Ω * m) of the SUS fiber compared with the carbon fiber (∼5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> Ω * m), which prevents the positive ions to be stacked on the fiber. Therefore, the present research showed the potential use to apply SUS fiber ionizers as two-stage ESPs for a future air pollution control technology with high PM removal efficiency and durability without ozone emission and additional maintenance.

Advances in air pollution control for key industries in China during the 13th five-year plan

Industrial development is an essential foundation of the national economy, but the industry is also the largest source of air pollution, of which power plants, iron and steel, building materials, and other industries emit large amounts of pollutants. Therefore, the Chinese government has promulgated a series of stringent emission regulations, and it is against this backdrop that research into air pollution control technologies for key industrial sectors is in full swing. In particular, during the 13th Five-Year Plan, breakthroughs have been made in pollution control technology for key industrial sectors. A multi-pollutant treatment technology system of desulfurization, denitrification, and dust collection, which applies to key industries such as power plants, steel, and building materials, has been developed. High-performance materials for the treatment of different pollutants, such as denitrification catalysts and desulfurization absorbers, were developed. At the same time, multi-pollutant synergistic removal technologies for flue gas in various industries have also become a hot research topic, with important breakthroughs in the synergistic removal of NOx, SOx, and Hg. Due to the increasingly stringent emission standards and regulations in China, there is still a need to work on the development of multi-pollutant synergistic technologies and further research and development of synergistic abatement technologies for CO2 to meet the requirements of ultra-low emissions in industrial sectors.

Compilation of reaction kinetics parameters determined in the Key Development Project for Air Pollution Formation Mechanism and Control Technologies in China

A compilation of new advances made in the research field of laboratory reaction kinetics in China's Key Development Project for Air Pollution Formation Mechanism and Control Technologies was presented. These advances are grouped into six broad, interrelated categories, including volatile organic compound (VOC) oxidation, secondary organic aerosol (SOA) formation, new particle formation (NPF) and gas-particle partitioning, ozone chemistry, model parameters, and secondary inorganic aerosol (SIA) formation, highlighting the laboratory work done by Chinese researchers. For smog chamber applications, the current knowledge gained from laboratory studies is reviewed, with emphasis on summarizing the oxidation mechanisms of long-chain alkanes, aromatics, alkenes, aldehydes/ketones in the atmosphere, SOA formation from anthropogenic emission sources, and oxidation of aromatics, isoprene, and limonene, as well as SIA formation. For flow tube applications, atmospheric oxidation mechanisms of toluene and methacrolein, SOA formation from limonene oxidation by ozone, gas-particle partitioning of peroxides, and sulfuric acid-water (H2SO4-H2O) binary nucleation, methanesulfonic acid-water (MSA-H2O) binary nucleation, and sulfuric acid-ammonia-water (H2SO4-NH3-H2O) ternary nucleation are discussed.

A mixed agro-waste based biofilter for the removal of methyl ethyl ketone: Kinetics and modeling

Biofiltration has grown worldwide, as an inexpensive and consistent air pollution control technology for the elimination of numerous organic compounds. In this work, the biofiltration of methyl ethyl ketone (MEK) has been studied. The agro-wastes namely pressmud and cornstack are mixed and used as packing materials for the removal of MEK. The performance of the biofilter has been explored over 200 days. Experiments are carried out in four periods. In every period, the biofiltration of pollutants is performed for various inlet concentrations (IC) of MEK (0.2–1.2 g m−3) and gas flow rates (GFR) (0.03 m3 h−1 to 0.12 m3 h−1). The biofilter performances are investigated by their removal rates, elimination capacity, temperature, pressure drop, carbon dioxide production, and variation of bed height at the time of operations. For the IC of 0.2 ± 10% g m−3 and GFR of 0.03 m3 h−1, the removal efficiency (RE) of MEK is 97% using the mixture of cornstack (80%) and pressmud (20%). The MEK removal efficiency decreases, when the cornstack ratio increases. The maximum RE is obtained at the IC of 1.2 g m−3 and GFR of 0.12 m3 h−1 for all the tested conditions. The pressure drop (PD) is also measured for all the operating conditions. It is found that the PD rises with an increase in height. The temperature is monitored throughout the biofiltration process. It is observed that an increase in RE leads to a rise in temperature in the biofilter. SEM images confirm the growth of microbes on the packing material. The kinetics of removal of MEK is investigated by using Ottengraf–van den Oever model.

Advances in air pollution control for vessels in China

Vessel emissions have contributed a great deal to air quality deterioration in China. Hence, the Chinese government has promulgated a series of stringent emission regulations. It is in this context that vessel emission control technology research is in full swing. In particular, during the 13th Five-Year Plan, the air pollution control technology of vessels has greatly improved. Vessel emission control has followed two main governance routes: source emission reduction and aftertreatment technology. Source control focuses on alternative fuels, with two main directions, the development of new fuels and the modification of existing fuels. Moreover, after-treatment technologies have also been developed, including wet desulfurization technology using seawater or alkaline liquids as wet washing liquids and selective catalytic reduction (SCR) for the control of NOx emission. Due to China's increasingly stringent emissions standards and regulations, work on the development of clean alternative fuels and further upgrading the collaborative application of after-treatment technologies to meet the near-zero-emissions requirements of vessels is still necessary.

Simultaneous catalytic removal of NO, mercury and chlorobenzene over WCeMnOx/TiO2–ZrO2: Performance study of microscopic morphology and phase composition

Nitrogen oxides, mercury and chlorobenzene are important air pollutants emitted by waste incineration and other industries. Coordinated control of multiple pollutants has become an important technology for air pollution control. Through solid-phase structure control, the catalytic performance of the WCeMnOx/TiO2–ZrO2 catalyst for simultaneous catalytic removal of NO, mercury and simultaneous removal of NO and chlorobenzene were improved. MnWO4 improved the solid acidity of the catalyst and improved the catalytic activity at high temperature. The formation of Ce0·75Zr0·25O2, Ce2WO6, Ce2Zr2O7 and Ce2Ti2O7 improved the catalytic activity at low temperature. The presence of TiOSO4 would affect the valence of metal ions and the reduction of chemisorbed oxygen, thereby reducing the catalytic activity at low temperature. Within the same size range of nanoparticles, cyclic nanoparticles exposed more active sites due to their hollow structure, and their catalytic performance was better than spherical nanoparticles. The thickness of the circular nanoparticles of WCM/TZ-14 catalyst was about 14 nm, and the diameter was about 40 nm Ce0.75Zr0.25O2 and MnWO4 were also present in the phase composition. Therefore, it exhibited the best performance for simultaneous catalytic removal of NO, mercury and simultaneous removal of NO and chlorobenzene. The coincidence temperature window was 347–516 °C. Finally, WCM/TZ-14 catalyst followed both E-R and L-H mechanisms in the NH3-SCR reaction.

A decision support system for sustainability prioritization of air pollution control technologies in energy and carbon management: Oil & gas industry of Iran

The environmental, economic, social, and technical challenges associated with implementing the air pollution control technologies (APCTs) in oil, gas, and petrochemical industries (OGPIs) necessitate a sustainability prioritization analysis. Environmental issues, economic parameters, social concerns, and technical performances all must assessed and weighted. Accomplishing such a crucial decision with rigorous potential environmental, economic, social, and technical effects needs a robust decision support system (DSS) for guiding the sustainability prioritization process of the technologies. This study purposes in developing a hybrid DSS by integrating the analytical network process (ANP), decision-making trial and evaluation laboratory (DEMATEL), and multi-objective optimization on the basis of ration analysis (MULTIMOORA) methods based on the fuzzy set theory for sustainability prioritization of implementing APCTs. Three cases of the petrochemical plant, gas refinery, and oil refinery in Iran are selected to assess and prioritize the most commonly used of APCTs including four alternatives of Electrostatic precipitators, Fabric filters, and Wet scrubbers, and Cyclones by the proposed DSS. The sustainability ranking of implementing the four technologies sequentially for three cases is obtained. The suggested DSS is feasible for group decision-making based on experts’ opinions and uncertain data. It can assist the stakeholders/decision-makers to attain the energy and carbon management (ECM) policies in three cases and apply to advance the oil & gas supply chains towards the targets of sustainability, green growth, and low-carbon economy. Finally, sensitivity analysis indicates the robustness of the proposed approach for the prioritization order.

Determination of activated carbon fiber adsorption capacity for several common organic vapors: applications for respiratory protection

ABSTRACT In the context of workplace safety, activated carbon in the fiber form (i.e., activated carbon fiber, ACF) represents an alternative adsorbent to granular activated carbon (GAC) for use in organic vapor respiratory protection devices. ACFs are high surface area carbonaceous materials that are often available in a self-supporting non-woven form. The physical form of ACF suggests the potential for a filtration medium that is capable of supporting both organic vapor adsorption and particulate filtration. To study the application of these materials in respiratory protection devices, ACFs (ACFF 1200 m2/g, ACFF 1800 m2/g, and ACFF 2000 m2/g) were challenged with representative organic vapors (toluene, hexane, and methyl ethyl ketone (MEK)) at an occupationally relevant concentration (200 ppm). Breakthrough curves were generated for at least three different bed weights of adsorbent. Pressure drop (i.e., the resistance across the filtration media) was also measured to determine maximum ACF bed depths for use in respiratory protection devices. Breakthrough experiments indicate that ACFF 2000 has the highest adsorption capacity for toluene (381 mg/g), followed by ACFF 1800 and ACFF 1200 (344 mg/g and 239 mg/g, respectively). A similar trend was observed for hexane: 221 mg/g, 196 mg/g, and 146 mg/g for ACFF 2000, ACFF 1800, and ACFF 1200, respectively. ACFF 1200 showed the highest adsorption capacity for the polar adsorbate MEK (168 mg/g), followed by ACFF 1800 and ACFF 2000 (166 mg/g and 147 mg/g, respectively). Based on the constraints of pressure drop, it seems unlikely the exclusive use of ACF in a filtering facepiece respirator can provide an adsorbent mass sufficient for full shift protection against organic vapor contaminants at or above the legally enforceable permissible exposure level (PEL). Nevertheless, the incorporation of ACF into a facepiece respirator appears promising for “nuisance odor” applications; i.e., the further reduction of organic vapor concentrations when workplace exposures are already below PEL concentrations. Implications: This research brings innovation to the field of occupational health and air pollution control technology by investigating the adsorption performance of activated carbon fiber (ACF) media in the context of worker respiratory protection. ACF properties such as high specific surface area (m2/g), high permeability to airflow, and rapid adsorption kinetics make it ideal for use in thin, N95-style respirators for organic vapors. Respiratory protection is an exciting and relevant application for ACF media. A lightweight adsorbent such as ACF, if incorporated into an N95-style respirator, could potentially provide nuisance-level VOC protection in a physical form that is accessible to workers and consistent with OSHA’s voluntary use provisions for facepiece respirators. The research presented in this manuscript represents one of several steps planned in the characterization of ACF media for this particular application.

Improving the performance of double-expansion chamber muffler using dielectric beads; optimization using factorial design.

Noise pollution is a common health hazard worldwide which is emitted along with chemical air pollutants, simultaneously from many sources. Some studies have been conducted to control these pollutants, simultaneously with promising results being achieved. Dielectric beads have been used in air pollution control technologies, successfully and probable effectiveness of them in noise reduction can be promising in dual use of them in the exhausts emitting noise and air pollution, simultaneously. In order to investigate the effectiveness of dielectric beads in noise reduction, two types of them; namely glass and ceramic beads, were placed separately inside the connecting tube of a double-expansion chamber muffler. Then the transmission loss (TL) of muffler was examined using impedance tube. A factorial design was used to evaluate and optimize the effect of noise related parameters on TL of such a system. Results show that the presence of dielectric beads has significant effect on TL of muffler. The maximum TL was obtained as 74.76dB for muffler with ceramic beads, under the optimal condition of 5250Hz and 120dB. Measurement of TL and sound absorption coefficient (SAC) of glass and ceramic beads showed that the noise reduction in muffler with ceramic and glass beads is probably due to SAC in ceramic beads and noise reflections in glass beads, respectively. These results promise the dual use of dielectric beads in the exhausts emitting noise and air pollution simultaneously.

Assessment of air pollution control technologies to reduce SOx emission from thermal oxidizer for oil and gas industry

Many countries have put in place, various legislations that govern air emission limits/pollutants from the industries. The common pollutants being monitored are Sulphur Oxides (SOx), Nitrogen Oxides (NOx), Carbon Monoxide (CO), Carbon Dioxide (CO2), Volatile Organic Compounds (VOCs), particulate matters and dioxins. In Malaysia, the regulatory requirement aims to regulate emissions of air pollutants from industrial activities including oil and gas, power plants, waste fuel plants and asphalt mixing plants. One of the emission limits under Clean Air Regulation (CAR2014) is emission level for SOx should be less than 600 mg/m3 (reference condition at 3 % of O2, 273 K, 101.3 kPa) whereby sum of SO2 and SO3 expressed as SOx. Excessive SOx emission can affect both health and the environment. Aligning with the regulation requirement, Group Technical Solution (GTS) under PETRONAS has embarked on assessment of technology solutions to meet the emission limit on SOx emission limit for thermal oxidizers which cover new and existing facilities. This paper describes on the work methodology and approach adopted during the assessment. The objective of the assessment is to determine the suitable process technology to reduce SOx emission in order to achieve the desired emission limit for flue gas at outlet stream of thermal oxidizer. Thorough evaluation was carried out based on proposal submission from various technology providers and Vendors. The selection criteria was developed and established. For existing thermal oxidizers, the assessment is more complex taking into consideration the nature of brownfield project and to ensure the proposed modification has minor impact to operability and maintainability of existing facilities. This study has successfully enabled identification of feasible process technologies such as Caustic Scrubber, Seawater Flue Gas Desulfurization and Ammonia based Desulfurization to meet the desired emission limit at thermal oxidizer outlet for Oil and Gas Industry and supporting environmental protection. The selected technology is varies based on plant/project specific requirement. Among main considerations are the by-product management, consumable and utility consumption as well as compatibility of the technology with existing plant on shutdown requirement.

Environmental assessment of carbon capture and storage (CCS) as a post-treatment technology in waste incineration.

The effects of amending municipal solid waste incineration (MSWI) with carbon capture and storage (CCS) via MEA (Monoethanolamine) technology differ according to the air pollution control technologies and energy recovery systems. Electricity output reduces by one-third for power-only plants and halves for combined heat-and-power plants, while variations in heat recovery depend on the presence of flue gas condensation. MSWI with CCS can capture roughly 800kg of compressed CO2 per tonne of waste treated. Life cycle assessment (LCA) modelling of MSWI, with and without CCS, illustrates that despite energy penalties, CCS lowers its climate change impact. The difference in climate change impacts as a result of CCS amendment depends on the energy system in which MSWI operates. In a near-future energy system, MSWI with CCS reduces climate change impacts by 700kg CO2-eq/tonne wet waste compared to MSWI without CCS. The climate change saving of CCS became increasingly larger as the energy system became "greener"; the climate change saving ultimately approached the capture efficiency (85% of CO2 in the flue gas) multiplied by the carbon content of the waste converted to CO2. Sensitivity analysis showed that capture efficiency was the main factor affecting the overall results, with increasing importance in non-fossil fuel-based energy systems. Likely changes in residual waste composition, as source segregation and collection systems improve, had only minor effects on the environmental benefits of CCS. The effects of CCS amendments on 13 other impact categories were marginal compared to the effects of different MSWI configurations.

Air emissions in waste to energy (W2E) plants

Along with waste minimization techniques and recycling measures, waste to energy (W2E) plants play a considerable role in reaching the goals of waste management. Recovery of energy and valuable products from wastes through W2E process essentially depends on efficient management and control of air pollutants emitted in various steps of the W2E process. In this manuscript, major air pollutants emitted from W2E plants with associated health effects, classical and innovative air pollution control (APC) technologies used in W2E plants along with the advantages and disadvantages are reviewed. The scope of this contribution is limited to discuss the efficient management and control of air emissions in W2E plants rather than the overall W2E process.

Evaluation of Tomato-Based Packing Material for Retention of Ammonia, Nitrous Oxide, Carbon Dioxide and Methane in Gas Phase Biofilters: A Laboratory Study

Biofilters are an effective air pollution control technology to break down gaseous contaminants and produce innocuous end products. This laboratory study aimed to evaluate a biofilter media, mainly composed by tomato waste, as packing material to reduce NH3, N2O, CO2 and CH4 losses from stored pig slurry. Three mixtures of packing materials, with and without oxalic acid, were arranged in treatments, namely: mixture of tomato waste, pine bark and agricultural compost; mixture of tomato waste and rice husk; tomato waste only. A control treatment (no biofilter) was also included. The experiments were conducted using a system of laboratory scale biofilters connected to jars filled with pig slurry and under a constant airflow rate. The gas concentrations were measured for 14 days and the physicochemical of the packing materials were assessed. Results showed that biofilter media mixtures had a potential for NH3 retention ranging from 51 to 77% and the addition of oxalic acid to these biofilters increased NH3 retention to 72–79%. Additionally, the biofilter media mixtures with and without oxalic acid showed a potential retention for CH4 (29–69%) but not for N2O, yet with no impact on the global warming potential. It can be concluded that tomato based biofilters had the potential to reduce gaseous emissions from slurry.