Decision-Support Tool for Assessing the Environmental Effects of Constructing Commercial Buildings

Construction of commercial buildings consumes significant amounts of energy and produces lots of emissions and waste. Where should environmental improvement efforts be focused during design and construction? The Construction Environmental Decision-Support Tool allows designers and industry practitioners to quantify energy use, emissions, and waste generation rates due to the construction phase of commercial buildings. A case study of the Bren School at the University of California, Santa Barbara, and several relevant construction scenarios are analyzed. When considering the complete building over its entire life cycle, the construction phase comprised 2% of energy consumption, 1% of CO2 emissions, 7% of CO emissions, 8% of NOx emissions, 8% of PM10 emissions, and 1% of SO2 emissions. This is due to the dominance of the long-term use phase (50?years) compared to a relatively short construction phase (2?years). Scaling up to the national level, however, construction impacts of projects are significant. In each of the categories studied (temporary materials, equipment and materials transportation, equipment use, waste generation), there are actions that can be taken by designers and builders to improve construction phase environmental effects. In structural frame construction, particular areas of concern include material and equipment selection and temporary material use. Energy use and air emissions are primarily due to equipment use, which accounts for at least 50% of most types of emissions. The major contributors are concrete mixer trucks, concrete pumps, cranes, and air compressors. A single feasible decision, such as using a concrete mixer truck with a 335?hp engine instead of one with a 565?hp engine (but having the same capacity) would reduce total construction energy demand by 12%, and the emissions of CO, NO2, PM10, SO2, CO2, and HC by 3, 12, 8, 10, 12, and 10%, respectively. The use of significantly older equipment can have a formidable effect on construction phase emissions. In general, equipment larger that 175?hp made prior to 1996 tends to have significantly greater emissions of HC, CO, and NO2 than more recent models. The majority of waste generated during construction of the structural frame consists of concrete and wood.     

Life-Cycle Analysis of Energy and Greenhouse Gas Emissions from Anaerobic Biodegradation of Municipal Solid Waste

Energy requirements and greenhouse gas (GHG) emissions for current landfilling of municipal solid waste (MSW) was compared to potential biodegradation of MSW in anaerobic digesters (AD) throughout the United States. A hybrid life-cycle analysis was completed to assess the potential for anaerobic biodegradation of MSW to methane, a valuable energy source. Conversion of MSW to methane in AD would generate a form of renewable energy, reduce GHG emissions, and save landfill space for nonbiodegradable materials. Based on laboratory- and pilot-scale studies conducted in the United States, full-scale data from facilities in Europe, and economic input-output life-cycle analysis, the annual 127 million t of MSW landfilled in the United States could be biologically converted to 5.9?billion?m3 of methane. Net methane production would have an estimated value of $1.5 billion/year when converted to an equivalent amount of electricity at an assumed value of $0.1/kWh. The 15 billion kWh/year of renewable energy released through the biodegradation process is estimated to satisfy the annual consumption of 1.3 million United States households. The analysis also suggests that diversion of MSW from landfills to AD systems would result in GHG emissions reductions of 146 million t CO2e per year, due to decreased landfill activity and use of biogenic methane instead of fossil fuel for electricity production. This represents a reduction in total emissions of 1.9% compared to U.S. GHG emissions in 2006. Nationwide AD systems are projected to reduce cumulative energy consumption by nearly 15 million TJ and reduce GHG emissions by 7.2 billion t CO2e, over a 50-year period. Logistics and capital costs of developing a nationwide reactor-based system for MSW management are considerable. Development of appropriate national policy and incentives would be needed to stimulate such a transition from the current landfill-based system that currently exists. It is estimated that a carbon emissions credit on the order of $30 to $60/t CO2e would facilitate break-even economics for nationwide implementation of AD systems. Alternatively, renewable energy credits would enhance the value of electricity produced from AD biogas. Carbon emissions taxes on landfills would further improve the economics of AD systems.     

Embodied Energy and Gas Emissions of Retaining Wall Structures

The embodied energy (EE) and gas emissions of four design alternatives for an embankment retaining wall system are analyzed for a hypothetical highway construction project. The airborne emissions considered are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulphur oxides (SOX), and nitrogen oxides (NOX). The process stages considered in this study are the initial materials production, transportation of construction machineries and materials, machinery operation during installation, and machinery depreciations. The objectives are (1)?to determine whether there are statistically significant differences among the structural alternatives; (2)?to understand the relative proportions of impacts for the process stages within each design; (3)?to contextualize the impacts to other aspects in life by comparing the computed EE values to household energy consumption and car emission values; and (4)?to examine the validity of the adopted EE as an environmental impact indicator through comparison with the amount of gas emissions. For the project considered in this study, the calculated results indicate that propped steel sheet pile wall and minipile wall systems have less embodied energy and gas emissions than cantilever steel tubular wall and secant concrete pile wall systems. The difference in CO2 emission for the retaining wall of 100?m length between the most and least environmentally preferable wall design is equivalent to an average 2.0?L family car being driven for 6.2?million miles (or 62 cars with a mileage of 10,000??miles/year for 10?years). The impacts in construction are generally notable and careful consideration and optimization of designs will reduce such impacts. The use of recycled steel or steel pile as reinforcement bar is effective in reducing the environmental impact. The embodied energy value of a given design is correlated to the amount of gas emissions.     

Contribution of Traffic-Generated Nonexhaust PAHs, Elemental Carbon, and Organic Carbon Emission to Air and Urban Runoff Pollution

Emissions of polycyclic aromatic hydrocarbons (PAHs), elemental carbon (EC), organic carbon (OC), and size distributions of particulate matter from summer tire-concrete road interaction were studied. Based on particle size distribution, particles were categorized in three groups: (1) PM10?(0.02%); (2) PM10–100?(44.20%); and (3) PM100–2,000?(55.78%). The emission factor for total of four PAHs [fluoranthene, phenenthrene, pyrene, and benzo(ghi)perylene] was estimated as 378?ng?tire?1?km?1 for small cars (engine displacement volume ? 1,000?cm3; load ? 170?kg?tire?1). Out of eight PAHS analyzed in particles (all sizes), the main PAH compounds were pyrene (54%) and benzo(ghi)perylene (21%). Emission factors for EC and OC were 1.46 and 2.37?mg?tire?1?km?1.     

Emission Standards Development for an Inspection/Maintenance Program

This paper presents the results of vehicle exhaust measurements that were used to establish emission standards for an inspection/maintenance (I/M) program. For this purpose, a total number of 100 private autos distributed across model years ranging between 1972 and 2002 were tested under idling conditions. The monitored indicators included air to fuel ratio (%), CO (%), CO2 (%), HC (parts per million, ppm), NOx (ppm), and O2 (%). Private autos with model years greater than 1994 were found to be compliant with international standards and are relatively well maintained. Emissions from older models increased significantly with a lack of engine maintenance. The paper concludes with criteria for proposing I/M emission standards based on exhaust measurements taking country-specific socioeconomic characteristics into consideration.     

Effects of grades and other loads on on-road emissions of hydrocarbons and carbon monoxide

This project was developed to assess driving patterns that promote high emissions episodes, also known as emission excursions, particularly while driving on roads with grade. An instrumented vehicle was equipped to record driving conditions such as speed and grade, as well as measure emission rates of total hydrocarbons and carbon monoxide. Controlled runs with predetermined cruise speeds between 35 and 55 mph and accelerations less than 3.3 mph/second were conducted on flat terrain and on hills with grades ranging from 0 to 7%. The hills were located in metropolitan Los Angeles, both along freeways and arterial roads. For hydrocarbons, the increase in emissions was about 0.04 g/mile for each 1% grade increment. For carbon monoxide (CO), the increase was more dramatic: 3.0 g/mile for each 1% grade increment. For a fully occupied vehicle with four passengers on a 4.5% grade, emissions increased by 0.07 g/mile for hydrocarbons and 10.2 g/mile for CO. Air conditioning operation, at full setting, further increased emissions while driving on hills (4.5 and 6.7% grades) by 0.07 g/mile for hydrocarbons and 31.9 g/mile for CO.     

Decarbonization and chromium conservation thermodynamics of partial CO2 instead of Ar or O2 in AOD furnace

Decarbonization and chromium conservation technology is mainly achieved by blowing O2 and Ar during the traditional AOD furnace smelting process. The CO2 emissions per ton of steel production in the steel industry are about 1. 57t. If the CO2 emissions can be collected and recycled in the steel production process, it can not only save energy and reduce emissions, but also reduce the cost of smelting. The feasibility of using CO2 instead of Ar or O2 to be injected for smelting stainless steels was verified by thermodynamic calculations. The reaction limits of the different carbon content, the rising and falling temperature of elemental oxidation, the reaction rate under different ratios of CO2 injection, the depth of decarburization, and the result of chromium retention were also calculated. The thermodynamic mechanism of blowing CO2 to replace O2 decarburizing and protecting chromium was analyzed. The results show that blowing CO2- O2 mixed gas in high carbon zone is conducive to decarbonization and chromium conservation in the AOD smelting process. With the increase of CO2 ratio, the effect of chromium retention is enhanced whereas the decarburization rate is reduced. When the CO2 injection amount is increased, the decarburization reaction rate in the molten pool is too slow, causing the molten pool temperature to be low, and the CO2 injection ratio should be controlled between 20 vol.% and 40 vol.%.     

Mechanisms of Neutralization of Bauxite Residue by Carbon Dioxide

Bauxite residue (red mud), an alkaline slurry from alumina refining, is produced in large volumes and disposed of in large surface impoundments. The objectives of this study were to measure the extent of neutralization of bauxite residue by carbon dioxide as a function of CO2 partial pressure and to determine the geochemical reactions responsible for carbon sequestration. Bauxite residue was exposed to carbon dioxide (CO2) at partial pressures ranging from 10?3.5?to?1?atm and the residue pore-water pH was measured until a steady state pH was achieved. Using pure CO2 (PCO2 = 1?atm), a steady state pH of 7.7 was established in 1?day while it took 9?days to reach a pH of 9.8 at PCO2 = 10?3.5?atm. The pH rebounded to 9.9 after 1?day when bauxite residue first neutralized at PCO2 of 1, 0.1, or 0.01?atm for 10?days was subsequently exposed to PCO2 = 10?3.5?atm, indicating that the pH change during short-term carbonation (t ? 10?days) was due to reactions of carbonic acid and OH? in the pore water. A longer reaction time (30?days) at PCO2 = 1?atm indicated carbonation of tricalcium aluminate (C3A solid) and conversion to calcite. This was confirmed in aged field samples that had been carbonated in air (PCO2 = 10?3.5?atm) for 30?years. The maximum solid-phase CO2 sequestration (as calcite) potential of red mud can be realized at PCO2 = 10?3.5?atm; however, the sequestration rate is limited by slow dissolution of C3A. The CO2 sequestration potential is small (0.029–0.057 MMT CO2/year) compared to annual CO2 emissions (110?MMT/year) for bauxite refining and red mud production of 30?MMT/year.     

石灰石替代石灰作炼钢造渣原料节能减排估算

对比分析了石灰石造渣炼钢工艺相较于现行石灰造渣炼钢工艺的节能减排环节,采用IPCC提供的排放因子法计算了每个环节的节能减排量,结果表明,石灰石造渣炼钢工艺较现行工艺节省能耗18.32kg(标煤)/t(钢),相当于减排45.80kgCO2/t(钢);减排粉尘量约5.34g/t(钢),SO2约14.15g/t(钢)、NOx约70.77g/t(钢),减排可致灰霾颗粒物127.39g/t(钢)。     

Destruction of 1,1,1-Trichloroethane Using Dielectric Barrier Discharge Nonthermal Plasma

This study investigates the feasibility of using nonthermal plasma produced in a dielectric barrier discharge reactor to destroy 1,1,1-trichloroethane (TCA) in a stream of air. The effects of various operating parameters on the destruction and removal efficiency (DRE) of TCA were examined. The experiments indicated that the water vapor concentration greatly influenced the destruction of TCA and the relative amount of oxidation by-products. DRE as high as 99.9% could be achieved at very low relative humidity (RH) conditions. Analysis of the CO/CO2 concentrations in the reactor effluent indicated a decrease in the amount of CO generated as the RH was increased. The lowest CO/CO2 ratio, 1:3, was observed at 88% RH. The estimated cost and energy requirement for operation were also determined. The calculated energy density values (β) varied with respect to the RH, and ranged from 1,478 to 3,010 J/L over a RH range of 0–88%.     

Life-Cycle Inventory of Municipal Solid Waste and Yard Waste Windrow Composting in the United States

This paper presents a life-cycle inventory (LCI) for solid waste composting. Three LCIs were developed for two typical municipal solid waste (MSW) composting facilities (MSWCFs) and one typical yard waste (YW) composting facility (YWCF). Municipal solid waste was assumed to comprise three organic components, food wastes, yard wastes, and mixed paper, as well as various inorganic components. Total costs, combined precombustion, and combustion energy requirements and 29 selected material flows—also referred to as LCI coefficients—were calculated by accounting for both the processes involved in originally producing, refining and transporting a material used in the facility as well as consumption during normal facility operation. Total costs ranged from $15/t to $50/t and energy requirements from 29?kw?h/t to 167?kw?h/t for a YWCF and a high quality MSW composting facility, respectively. More than 90% of the overall CO2 emissions in all facilities were due to the biological decomposition of the organic substrate, while the rest was due to fossil fuel combustion.     

Considering Carbon Capture and Storage for Energy Generation from Municipal Solid Waste

Modern waste management practices encourage the recovery of energy from municipal solid waste after efforts to reduce, reuse, and recycle appropriate materials. Energy can be recovered through direct mass burn in a waste-to-energy (WTE) facility or through the collection and combustion of biogas generated in sanitary landfills. Many comparisons have been made although rarely using best practice assumptions for both technologies; WTE proponents tend to assume low collection efficiency while landfill proponents tend to assume low electrical conversion efficiency. In general, WTE plants can be considered to have a better environmental performance (reduced emissions) with landfill having lower total costs (social and environmental). Both strategies have similar costs when considering 77% collection efficiency and a high efficiency (30% electrical conversion) WTE plant that displaces electricity from coal. The introduction of carbon capture and storage (CCS) technologies to waste management changes the landscape by increasing the capital costs and improving the environmental performance. The air emissions are significantly reduced, practically eliminated with oxygen combustion, as the capture of CO2 requires significant flue gas scrubbing. The introduction of CCS results in a net environmental benefit for WTE plants with a turnaround electricity price of $7/MWh, as compared to landfill gas with capture. The largest environmental cost for WTE plants is the classification of fly ash as chemical waste, which is reduced with oxygen combustion. The net cost of capturing CO2 from WTE facilities is estimated at $39/t CO2, one-third of the cost of CO2 capture from landfills.     

烧结温度对锂离子电池负极材料Li4Ti5O12性能的影响

采用钛酸四丁酯为钛源、一水合氢氧化锂为锂源,利用水热法制备锂离子电池负极材料Li₄Ti₅O₁₂（LTO）,研究了水热后不同烧结温度对LTO相组成、微观形貌及电化学性能的影响。结果表明:当煅烧温度分别为500、550、600、650、700℃时,烧结LTO均为尖晶石型;500、550、600℃烧结LTO的微观形貌为纳米片状结构,当温度升高到650℃时,LTO出现纳米棒状结构,随着温度继续升高,LTO在700℃时生成较厚的纳米片状结构;当烧结温度为650℃时,LTO的比表面积为94.5907 m2·g-1,气孔体积为0.9663 mL·g-1,此时Li₄Ti₅O₁₂的放电比容量达到最大值240 mAh·g-1;电流密度100 mA·g-1、循环260次条件下,LTO容量保持率达96.45%,电流密度为1和2 A·g-1、循环1000次条件下,LTO容量保持率达92.97%和77.21%。     

静电纺丝法制备空心钛酸锂材料

为进一步提升钛酸锂材料的性能, 本文在传统静电纺丝技术的基础上, 将纺丝喷头改进成内外嵌套的同轴喷头, 以两种溶液的形式进行同轴共纺, 得到了具有空心结构的钛酸锂纤维丝.将其与传统静电纺丝法制备的实心结构钛酸锂纤维丝进行对比, 结果表明: 空心钛酸锂材料粒度均一、无团聚现象, 材料具有明显的空心结构, 结晶性能良好, 比表面积是实心结构的1.3倍.形貌结构的改善极大地提高了空心钛酸锂材料的电化学性能, 表现为小倍率下二者的放电比容量接近理论比容量, 但在20C倍率下空心结构的钛酸锂材料优于实心钛酸锂, 仍可达到130 mA·h·g-1, 循环200周后容量保持率仍达98%, 具有良好的稳定性; 循环伏安和交流阻抗曲线也表明: 空心结构使得钛酸锂材料的极化程度减少, 电化学反应阻抗降低, 更有利于电化学反应的进行.      

联合钢厂采用无碳排放的ENERGIRON直接还原方案减少温室气体的排放

在基于高炉冶炼的联合企业中,始终有一些过剩的焦炉煤气、转炉煤气和高炉炉顶煤气,通常这些煤气用于电厂发电。另一种替代方法是使用这些现有的能源气体生产直接还原铁(DRI),将其作为金属化炉料加入高炉,提高粗钢产量,以减少化石燃料单耗。优化利用主要的化石燃料可以显著降低吨钢CO2排放量。采用传统的BF-BOF流程,即使在优化工艺流程的基础上,吨钢CO2排放量也有1.7～1.8t左右。而用产自天然气、焦炉煤气和高炉炉顶煤气的DRI作为金属化炉料加入高炉或电炉,却可显著降低CO2排放量。     

飞机机翼缘条紧固孔细节原始疲劳质量评估方法

为了对飞机机翼缘条紧固孔细节原始疲劳质量进行评估,本文首先对飞机机翼缘条结构中常用的BXXX铝合金紧固孔试件分别开展了高、中、低3种应力水平下的疲劳试验,通过断口判读和反推得到3组关于裂纹长度a和疲劳寿命t的（a?t）数据,在此基础上应用当量初始缺陷尺寸（EIFS）控制方程对每个试件的EIFS值进行计算并初步评估,验证了在不同应力水平下紧固孔结构细节的EIFS无显著性差异;得到了紧固孔结构细节的裂纹萌生时间（TTCI）分布,在指定应力水平下对紧固孔结构细节95%置信水平下的经济寿命进行预测,并与设计寿命进行对比,提出了一种不同超越概率P下的结构细节当量初始缺陷尺寸模型,基于给定5%的裂纹超越概率,对结构细节的通用EIFS分布进行评估。通过以上对飞机机翼缘条紧固孔细节原始疲劳质量的三重评估,得到综合评估结果:飞机机翼缘条紧固孔细节原始疲劳质量满足要求。      

Electrochemical Desulfurization of Waste Gases in a Batch Reactor

To meet the increasing need for reduction of exhaust emissions from stationary sources, many technologies have been developed to remove SO2 from flue gas. In this study the anodic oxidation of sulfur dioxide in aqueous solutions of sulfuric acid with a unique reactor design and electrode configuration has been investigated. An electrochemical absorption column larger than laboratory scale was employed. A titanium rod cathode and platinum expanded mesh anode separated by a cation exchange membrane were used as electrodes in the cylindrical electrochemical reactor. The effects of current densities of 10, 1, and 0.1?Am?2, initial SO2 concentrations of 500, 2,500, and 5,000?ppm, gas flow rates of 0.75, 1.5, and 5?L min?1, sulfuric acid concentrations of 1, 5, and 10%(w), gas composition, and electrolysis time on removal efficiency, current efficiency, energy consumption, and mass transfer coefficient were reported. Removal efficiency of 94% was obtained with a high current efficiency of 94%, energy consumption of 2.22×10?2?kW?hm?3, and mass transfer coefficient of 5.9×10?5?ms?1 without additives or pretreatment. At the current densities of 0.1, 1, and 10?Am?2, the removal efficiencies were 10, 94, and 98%, respectively. Removal efficiency was observed to decrease as inlet SO2 concentration, gas flow rate, and electrolyte concentration increased. The presence of CO2 in the gas mixture led to a decrease in the SO2 removal efficiency. During electrochemical absorption of SO2 into the H2SO4 solution, the concentration of acid is increased from 5 to 10%. At the end of the studies, electrochemical desulfurization succeeded in meeting the regulation requirement, and the absorbing liquid remained in a reusable form.     

Microalgal Biomass for Greenhouse Gas Reductions: Potential for Replacement of Fossil Fuels and Animal Feeds

Microalgal biomass production offers a number of advantages over conventional biomass production, including higher productivities, use of otherwise nonproductive land, reuse and recovery of waste nutrients, use of saline or brackish waters, and reuse of CO2 from power-plant flue gas or similar sources. Microalgal biomass production and utilization offers potential for greenhouse gas (GHG) avoidance by providing biofuel replacement of fossil fuels and carbon-neutral animal feeds. This paper presents an initial analysis of the potential for GHG avoidance using a proposed algal biomass production system coupled to recovery of flue-gas CO2 combined with waste sludge and/or animal manure utilization. A model is constructed around a 50-MW natural gas-fired electrical generation plant operating at 50% capacity as a semibase-load facility. This facility is projected to produce 216 million k?Wh/240-day season while releasing 30.3 million kg-C/season of GHG-CO2. An algal system designed to capture 70% of flue-gas CO2 would produce 42,400 t (dry wt) of algal biomass/season and requires 880 ha of high-rate algal ponds operating at a productivity of 20?g-dry-wt/m2-day. This algal biomass is assumed to be fractionated into 20% extractable algal oil, useful for biodiesel, with the 50% protein content providing animal feed replacement and 30% residual algal biomass digested to produce methane gas, providing gross GHG avoidances of 20, 8.5, and 7.8%, respectively. The total gross GHG avoidance potential of 36.3% results in a net GHG avoidance of 26.3% after accounting for 10% parasitic energy costs. Parasitic energy is required to deliver CO2 to the algal culture and to harvest and process algal biomass and algal products. At CO2 utilization efficiencies predicted to range from 60–80%, net GHG avoidances are estimated to range from 22–30%. To provide nutrients for algal growth and to ensure optimal algae digestion, importation of 53 t/day of waste paper, municipal sludge, or animal manure would be required. This analysis does not address the economics of the processes considered. Rather, the focus is directed at determination of the technical feasibility of applying integrated algal processes for fossil-fuel replacement and power-plant GHG avoidance. The technology discussed remains in early stages of development, with many important technical issues yet to be addressed. Although theoretically promising, successful integration of waste treatment processes with algal recovery of flue-gas CO2 will require pilot-scale trials and field demonstrations to more precisely define the many detailed design requirements.     

Durability of three-way and close-coupled catalysts for Euro Ⅳ regulation

The durability of three-way catalyst (TWC) and corresponding close-coupled catalyst (CCC) for Euro Ⅳ stage regulation was in-vestigated through Vehicle Road Running Mode tests, whereas emissions of regulated pollutants of three car fleet were investigated at every 100,000 km miles. The results showed that HC, NOx, and CO emission values could meet Euro Ⅳ regulation limits at every point. The redox properties of TWC and CCC were measured by CO reduction during each isothermal. It was obvious that both aged TWC and aged CCC behaved a good redox property at 673 and 773 K. Based on XRD and BET measurement results, TWC and CCC washcoat were character-ized with good thermal stability.     

Electron Beam Irradiation for Mercury Oxidation and Mercury Emissions Control

A variety of air pollution control strategies have been investigated to reduce mercury emissions from coal-fired sources. The most developed and deployed technologies are based on adsorption of mercury onto powdered activated carbon followed by carbon collection. Mercury oxidation over selective catalytic reduction catalysts followed by wet scrubbing is another potential technique, and tests suggest that emissions reductions of 20–80% are possible, but test results are variable and ultrahigh removal (95%+) is unusual. The objective of this study was to investigate the effectiveness of electron beam irradiation to oxidize mercury vapor, to improve mercury removal with wet scrubbers or wet electrostatic precipitators (ESPs). Metallic mercury vapor samples in air and other atmospheres were prepared at concentrations of approximately 16?μg/m3. Samples were electron irradiated at energy levels of 2.5–10 kGy, equivalent to 3.1–12.4?kJ/m3 stack gas. Results show that mercury oxidation rate was dependent on both the gaseous atmosphere composition and the irradiation energy level. At medium energy levels, approximately 98% of gaseous mercury vapor was readily oxidized. Electron beam irradiation demonstrated high levels of mercury oxidation at the bench scale, and the technology might help improve mercury removal in wet scrubbers or wet ESPs when employed as a primary or secondary mercury oxidation technique.