Plant crown traits and carbon sequestration capability by Platanus hybrida Brot. in Rome

Measurements of carbon dioxide (CO₂) concentration carried out in the city of Rome in the period January–December 2005 showed a mean yearly CO₂ concentration of 414 ± 45 ppm; polluted sites (P sites) had 21% higher CO₂ concentration than control sites (C sites). The significant (p < 0.01) correlation analysis between CO₂ concentration and traffic density measured during the study period at P sites showed that traffic density explained 51% of the CO₂ variation. The CO₂ trend during the traffic limitation days (provision imposed by ordinance of the City Council) did not show significant differences as regards regular traffic days, suggesting the ineffectiveness of this provision. Leaf area index (LAI) of Platanus hybrida Brot. was on an average 11% lower at P sites than at C ones associated with a lower total photosynthetic leaf surface area (SPT, 34% lower at P sites than at C ones). P. hybrida had a total carbon sequestration of 117 ± 13 kg year⁻¹ (mean value of P and C sites) playing an important role in sequestering CO₂. Thus, the choice of plant species for urban areas may be set out taking into account their own air amelioration capability. Plant traits of each species may be used for urban tree planting programs to ameliorate urban air pollution.     

Forecasting future cooling demand in London

Cooling of buildings in the UK is responsible for around 15 TWh per year of energy demand, largely powered by electricity with highly related CO₂ emissions. The Greater London Authority wished to understand the potential impact of London's growing need for cooling on UK CO₂ emissions in the period up to 2030. This paper describes a model developed to analyse the cooling requirements for London's key building stock and assess how these would be affected by change in system mix, improvements in system efficiencies, and by varying degrees of climate change.The analysis showed that, if left unchecked, the growth in active cooling systems in London could lead to a doubling of CO₂ emissions from this source by 2030. This growth will be due to increase in building stock, increase in market share of cooling systems, and climate change. The last of these is difficult to predict, but by itself could add 260,000-360,000 tonnes of CO₂ emissions by 2030. This increase can be strongly mitigated, or even offset, by improvements in system efficiency. The difference between no efficiency improvements, and an assumed 1-3% annual efficiency improvement is around 340,000 tonnes by 2030.     

Long-term continuous monitoring of the dissolved CO2 performed by using a new device in groundwater of the Mt. Etna (southern Italy)

We present a new device for continuous monitoring of the concentration of CO₂ dissolved in water. The device consists of a tube made of a polymeric semi-permeable membrane connected to an infrared gas analyser (IRGA) and a pump. Several laboratory experiments were performed to set the best operating condition and test the accuracy of measurements. We used the device for performing 20 months of continuous monitoring of dissolved CO₂ concentration (DCC) in groundwater within a drainage gallery at Mt. Etna. The monitored groundwater intercepts the Pernicana Fault, along which degassing is observed related to volcano-tectonic activity. The acquired data were compared with continuous and discrete data obtained using existing methods. The measurements of DCC resulted in some period of the year well correlated with air temperature. We also found that long-term trends, as well as short-term variations, are probably linked to the dynamics of volcanic activity and/or perturbations in the local or regional stress fields.     

Effects of wood ash fertilization on forest floor greenhouse gas emissions and tree growth in nutrient poor drained peatland forests

Wood ash (3.1, 3.3 or 6.6 tonnes dry weight ha^− 1) was used to fertilize two drained and forested peatland sites in southern Sweden. The sites were chosen to represent the Swedish peatlands that are most suitable for ash fertilization, with respect to stand growth response. The fluxes of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) from the forest floor, measured using opaque static chambers, were monitored at both sites during 2004 and 2005 and at one of the sites during the period 1 October 2007-1 October 2008. No significant (p > 0.05) changes in forest floor greenhouse gas exchange were detected. The annual emissions of CO₂ from the sites varied between 6.4 and 15.4 tonnes ha^− 1, while the CH₄ fluxes varied between 1.9 and 12.5 kg ha^− 1. The emissions of N₂O were negligible. Ash fertilization increased soil pH at a depth of 0-0.05 m by up to 0.9 units (p < 0.01) at one site, 5 years after application, and by 0.4 units (p < 0.05) at the other site, 4 years after application. Over the first 5 years after fertilization, the mean annual tree stand basal area increment was significantly larger (p < 0.05) at the highest ash dose plots compared with control plots (0.64 m² ha^− 1 year^− 1 and 0.52 m² ha^− 1 year^− 1, respectively). The stand biomass, which was calculated using tree biomass functions, was not significantly affected by the ash treatment. The groundwater levels during the 2008 growing season were lower in the high ash dose plots than in the corresponding control plots (p < 0.05), indicating increased evapotranspiration as a result of increased tree growth. The larger basal area increment and the lowered groundwater levels in the high ash dose plots suggest that fertilization promoted tree growth, while not affecting greenhouse gas emissions.     

Energy efficiency in Spanish wastewater treatment plants: a non-radial DEA approach

Wastewater treatment plants (WWTPs) are energy-intensive facilities. Thus, reducing their carbon footprint is particularly important, both economically and environmentally. Knowing the real operating energy efficiency of WWTPs is the starting point for any energy-saving initiative. In this article, we applied a non-radial Data Envelopment Analysis (DEA) methodology to calculate energy efficiency indices for sampling of WWTPs located in Spain. In a second stage analysis, we examined the operating variables contributing to differences in energy efficiency among plants. It is verified that energy efficiencies of the analyzed WWTPs were quite low, with only 10% of them being efficient. We found that plant size, quantity of organic matter removed, and type of bioreactor aeration were significant variables in explaining energy efficiency differences. In contrast, age of the plant was not a determining factor in energy consumption. Lastly, we quantified the potential savings, both in economic terms and in terms of CO₂ emissions, that could be expected from an improvement in energy efficiency of WWTPs.     

Efficiency and energy requirements for the transformation of organic micropollutants by ozone, O3/H2O2 and UV/H2O2

The energy consumptions of conventional ozonation and the AOPs O₃/H₂O₂ and UV/H₂O₂ for transformation of organic micropollutants, namely atrazine (ATR), sulfamethoxazole (SMX) and N-nitrosodimethylamine (NDMA) were compared. Three lake waters and a wastewater were assessed. With p-chlorobenzoic acid (pCBA) as a hydroxyl radical (^•OH) probe compound, we experimentally determined the rate constants of organic matter of the selected waters for their reaction with ^•OH (k_OH,DOM), which varied from 2.0 × 10⁴ to 3.5 × 10⁴ L mgC⁻¹ s⁻¹. Based on these data we calculated ^•OH scavenging rates of the various water matrices, which were in the range 6.1-20 × 10⁴ s⁻¹. The varying scavenging rates influenced the required oxidant dose for the same degree of micropollutant transformation. In ozonation, for 90% pCBA transformation in the water with the lowest scavenging rate (lake Zürich water) the required O₃ dose was roughly 2.3 mg/L, and in the water with the highest scavenging rate (Dübendorf wastewater) it was 13.2 mg/L, corresponding to an energy consumption of 0.035 and 0.2 kWh/m³, respectively. The use of O₃/H₂O₂ increased the rate of micropollutant transformation and reduced bromate formation by 70%, but the H₂O₂ production increased the energy requirements by 20-25%. UV/H₂O₂ efficiently oxidized all examined micropollutants but energy requirements were substantially higher (For 90% pCBA conversion in lake Zürich water, 0.17-0.75 kWh/m³ were required, depending on the optical path length). Energy requirements between ozonation and UV/H₂O₂ were similar only in the case of NDMA, a compound that reacts slowly with ozone and ^•OH but is transformed efficiently by direct photolysis.     

Optimised design of energy efficient building façades via Evolutionary Neural Networks

Buildings are required to be more and more energy efficient, in order to comply with restrictive requirements of building regulations and energy certifications. Optimisation algorithms have shown to be effective in identifying good solutions for the design of efficient building services. In this article Evolutionary Neural Network Design (ENN-Design) has been adopted to drive the design of a typical façade module for an office building. This application is significant, since façades play a major role in the definition of the energy performance of buildings. Both single-objective and multi-objective optimisations have been carried out. The aim of the article is to introduce an innovative approach for improving the performance of building envelopes by means of a reasonable amount of calculation time.     

Energy efficient design and occupant well-being: Case studies in the UK and India

The purpose of this paper is to demonstrate the relationships between sustainable building design and occupant well-being. It starts with a definition of sustainable design and well-being, and focuses on the relationships between energy performance and occupant feedback. Methodologically it draws on detailed monitoring and surveys of 12 case study office buildings in the UK and India, and the paper uses the data to explore whether energy use and associated CO₂ emissions are correlated to occupant satisfaction and comfort. The results demonstrate that increased energy use in the case study buildings is associated with increased mechanisation (e.g. centralised air conditioning) and reduced occupant control. This reduced control in turn is shown to relate to reduced occupant comfort and satisfaction. Finally, the paper reveals that the reported health conditions of occupants correlates strongly with their levels of satisfaction. The overall conclusion is that energy use in typical office buildings is inversely correlated with the well-being of the occupants: more energy use does not improve well-being.     

European residential buildings and empirical assessment of the Hellenic building stock,energy consumption,emissions and potential energy savings

The existing building stock in European countries accounts for over 40% of final energy consumption in the European Union (EU) member states, of which residential use represents 63% of total energy consumption in the buildings sector. Consequently, an increase of building energy performance can constitute an important instrument in the efforts to alleviate the EU energy import dependency (currently at about 48%) and comply with the Kyoto Protocol to reduce carbon dioxide emissions. This is also in accordance to the European Directive (EPBD 2002/91/EC) on the energy performance of buildings, which is currently under consideration in all EU member states. This paper presents an overview of the EU residential building stock and focuses on the Hellenic buildings. It elaborates the methodology used to determine the priorities for energy conservation measures (ECMs) in Hellenic residential buildings to reduce the environmental impact from CO₂ emissions, through the implementation of a realistic and effective national action plan. A major obstacle that had to overcome was the need to make suitable assumptions for missing detailed primary data. Accordingly, a qualitative and quantitative assessment of scattered national data resulted to a realistic assessment of the existing residential building stock and energy consumption. This is the first time that this kind of aggregate data is presented on a national level. Different energy conservation scenarios and their impact on the reduction of CO₂ emissions were evaluated. Accordingly, the most effective ECMs are the insulation of external walls (33–60% energy savings), weather proofing of openings (16–21%), the installation of double-glazed windows (14–20%), the regular maintenance of central heating boilers (10–12%), and the installation of solar collectors for sanitary hot water production (50–80%).     

The effect of engine emission on canola biodiesel blends with TiO2

The role of nanoparticles and nanofluid additives for biodiesel has gained consistent position in the current trend as they contribute to increase the performance of the engine with lower emission. In addition, additives also help to increase the engine reliability and lifespan. In this work, the effects of canola biodiesel blends of 20% proportions with diesel were investigated at 100% of engine load. The fuel is tested in a multi-cylinder water-cooled direct ignition (DI) engine. There are numerous notable works on nanofluid; however, the addition of TiO₂ nanoparticle as additive to produce canola biodiesel fuel is very limited. With the addition of the TiO₂ nanoparticle on Canola biodiesel blend in the DI engine, the exhaust property of gases such as CO, HC and NO_X is reduced. Furthermore, the combustion characteristics of the engine are improved. The canola biodiesel blends also resulted in lower NO_x emission as well as low smoke.     

Heterotrophic microorganism Rhodotorula mucilaginosa R30 improves tannery sludge bioleaching through elevating dissolved CO2 and extracellular polymeric substances levels in bioleach solution as well as scavenging toxic DOM to Acidithiobacillus species

The introduction of acid-tolerant heterotrophic microorganisms into sludge bioleaching systems has been proven effective in improving sludge bioleaching processes, and such positive effect is mainly attributed to the biodegradation of low molecular weight organic acids or sludge dissolved organic matter (DOM) toxic to Acidithiobacillus species by the heterotrophic microorganisms introduced. Here we report that elevated dissolved CO₂ concentration and resulting extracellular polymeric substances (EPS) in bioleach solution due to the incorporation of heterotrophic microorganisms also play important roles in improving sludge bioleaching. It was found that in tannery sludge bioleaching system coinoculated with Rhodotorula mucilaginosa R30 and Acidithiobacillus species, dissolved CO₂ concentration in bioleach solution can be elevated from 0.23-0.54 mg/L to 0.76-1.01 mg/L compared to the control inoculated only with Acidithiobacillus species. Correspondingly, the distinct degradation of sludge DOM was also observed in this experiment. It was experimentally demonstrated that the accumulation of CO₂ did greatly enhance the growth of Acidithiobacillus thiooxidans and the decrease rate of pH in the medium. In addition, EPS derived from R. mucilaginosa R30 could bind readily Fe³⁺ in bioleach solution with maximum binding capacity (MBC) of 0.82 mg Fe³⁺ by per mg DOC of EPS secreted and the oxidization activity of EPS-bound Fe³⁺ was decreased but not totally inhibited, indicating that the formation of soluble EPS-Fe(III) complexes enhances, to a certain extent, bioleaching efficiency due to maintaining Fe³⁺ level in solution by inhibiting Fe precipitation occurrence.     

CO2流通法养护透水混凝土的性能与作用机理

为了更好地利用透水混凝土的多孔特性,提出并设计了一种新型的流通法养护装置,旨在探索更适合透水混凝土的CO₂养护方法 .通过试验探讨了养护时间这一关键参数,并且在固碳率、抗压强度和微观结构等方面与传统的静态养护方法（包括加压和常压养护）进行了对比.结果表明：流通法能够通过气流带走透水混凝土内部多余的水分,从而实现水分的均匀分布,同时还能减少预处理步骤并促进混凝土的碳酸化;流通法有效消除了试件内外的碳化不均匀,显著提升了混凝土的抗压强度.     

Thermal upgrades of existing homes in Germany: The building code, subsidies, and economic efficiency

One of the cheapest ways to reduce CO₂ emissions is thermal renovation of existing homes. Germany is a world leader in this project, with a strict building code, generous state subsidies, and an advanced renovation infrastructure. The effects of its policies are here explored in the light of progressive tightening of the building code, and the strict criteria for subsidies. Data on costs and outcomes of residential building renovations are presented from published reports on renovation projects, and cross-checked with projects investigated directly. Comparisons are made in terms of euros invested for every kilowatt hour of heating energy saved over the lifetime of the renovations, for standards ranging from 150 kWh (the lowest standard) to 15 kWh (the highest) of primary energy use per square metre of floor area per year. It is found that the lowest standard is an order of magnitude more cost-effective than the highest, in terms of both energy saved per euro invested, and return on investment over the lifetime of the renovations, regardless of fuel prices. It is argued that this throws into question Germany's policy of progressively regulating for higher renovation standards, and offering subsidies only for projects that go beyond the minimum standard.     

Optimizing CO2 emissions from heating and cooling and from the materials used in residential buildings,depending on their geometric characteristics

The objective of this research was to obtain the environmentally optimal design of a building with the following starting conditions: constant constructed surface, constant volume, square floor layout, and a variable number of floors. For this purpose, the study evaluated the impact of CO₂ emissions stemming from the energy needed to maintain the building at a constant temperature of 19 °C in winter and 25 °C in the summer. Furthermore, one of the results was the CO₂ emissions curve from the manufacturing of the materials used in the construction of the building and the building envelope.     

Chemically-speciated on-road PM2.5 motor vehicle emission factors in Hong Kong

PM_2.5 (particle with an aerodynamic diameter less than 2.5 µm) was measured in different microenvironments of Hong Kong (including one urban tunnel, one Hong Kong/Mainland boundary roadside site, two urban roadside sites, and one urban ambient site) in 2003. The concentrations of organic carbon (OC), elemental carbon (EC), water-soluble ions, and up to 40 elements (Na to U) were determined. The average PM_2.5 mass concentrations were 229 ± 90, 129 ± 95, 69 ± 12, 49 ± 18 µg m^− 3 in the urban tunnel, cross boundary roadside, urban roadside, and urban ambient environments, respectively. Carbonaceous particles (sum of organic material [OM] and EC) were the dominant constituents, on average, accounting for ∼ 82% of PM_2.5 emissions in the tunnel, ∼ 70% at the three roadside sites, and ∼ 48% at the ambient site, respectively. The OC/EC ratios were 0.6 ± 0.2 and 0.8 ± 0.1 at the tunnel and roadside sites, respectively, suggesting carbonaceous aerosols were mainly from vehicle exhausts. Higher OC/EC ratio (1.9 ± 0.7) occurred at the ambient site, indicating contributions from secondary organic aerosols. The PM_2.5 emission factor for on-road diesel-fueled vehicles in the urban area of Hong Kong was 257 ± 31 mg veh^− 1 km^− 1, with a composition of ∼ 51% EC, ∼ 26% OC, and ∼ 9% SO₄⁼. The other inorganic ions and elements made up ∼ 11% of the total PM_2.5 emissions. OC composed the largest fraction (∼ 51%) in gasoline and liquid petroleum gas (LPG) emissions, followed by EC (∼ 19%). Diesel engines showed higher emission rates than did gasoline and LPG engines for most pollutants, except for V, Br, Sb, and Ba.     

Emission of N2O and CH4 from a constructed wetland in southeastern Norway

The Skjønhaug constructed wetland (CW) is a free surface water (FSW) wetland polishing chemically treated municipal wastewater in southeastern Norway and consists of three ponds as well as trickling, unsaturated filters with light weight aggregates (LWA). Fluxes of nitrous oxide (N₂O) and methane (CH₄) have been measured during the autumn, winter and summer from all three ponds as well as from the unsaturated filters. Physicochemical parameters of the water have been measured at the same localities. The large temporal and spatial variation of N₂O fluxes was found to cover a range of − 0.49 to 110 mg N₂O–N m^− 2 day⁻¹, while the fluxes of CH₄ was found to cover a range of − 1.2 to 1900 mg m^− 2 day^− 1. Thus, both emission and consumption occurred. Regarding fluxes of N₂O there was a significant difference between the summer, winter and autumn, with the highest emissions occurring during the autumn. The fluxes of CH₄ were, on the other hand, not significantly different with regard to seasons. Both the emissions of N₂O and CH₄ were positively influenced by the amount of total organic carbon (TOC). The measured fluxes of N₂O and CH₄ are in the same range as those reported from other CWs treating wastewater. There was an approximately equal contribution to the global warming potential from N₂O and CH₄.     

A comparative study in the straight and a spiral adiabatic capillary tube

Numerical studies on straight and spiral capillary tubes are addressed for the CO₂ and R22 refrigerant. A homogenous, one-dimensional steady-state adiabatic flow model is developed using fundamental principles of fluid dynamics and thermodynamics. Churchill and Ju et al. friction factor correlations are employed. Numerical results are validated with the experimental results of Agrawal and Battacharya, Jabaraj et al. and Mittal et al. For similar operating conditions, the mass flow rate and length of the tube are significantly larger in the case of CO₂ refrigerant. A reduction in mass flow rate in the spiral capillary tube is about 22% and 15% compared to the straight capillary tube with CO₂ and R22 refrigerants, respectively.