An analysis of the use of life cycle assessment for waste co-incineration in cement kilns

Life cycle assessment, LCA, has become a key methodology to evaluate the environmental performance of products, services and processes and it is considered a powerful tool for decision makers. Waste treatment options are frequently evaluated using LCA methodologies in order to determine the option with the lowest environmental impact. Due to the approximate nature of LCA, where results are highly influenced by the assumptions made in the definition of the system, this methodology has certain non-negligible limitations. Because of that, the use of LCA to assess waste co-incineration in cement kilns is reviewed in this paper, with a special attention to those key inventory results highly dependent on the initial assumptions made. Therefore, the main focus of this paper is the life cycle inventory, LCI, of carbon emissions, primary energy and air emissions. When the focus is made on cement production, a tonne of cement is usually the functional unit. In this case, waste co-incineration has a non-significant role on CO₂ emissions from the cement kiln and an important energy efficiency loss can be deduced from the industry performance data, which is rarely taken into account by LCA practitioners. If cement kilns are considered as another waste treatment option, the functional unit is usually 1 t of waste to be treated. In this case, it has been observed that contradictory results may arise depending on the initial assumptions, generating high uncertainty in the results. Air emissions, as heavy metals, are quite relevant when assessing waste co-incineration, as the amount of pollutants in the input are increased. Constant transfer factors are mainly used for heavy metals, but it may not be the correct approach for mercury emissions.     

ENVIRONMENTAL AUDITING: The Functional Unit in the Life Cycle Inventory Analysis of Degreasing Processes in the Metal-Processing Industry

1 and C₂ hydrocarbons (trichloroethane, trichloroethene, tetrachloroethene, dichloromethane). Measures aiming at the reduction of toxic emissions and ozone depletion potential (ODP) may possibly lead to a shift of environmental impacts towards higher energy consumption, emission of waste water, and volatile organic compounds (VOC) with photochemical oxidant creation potential (POCP). The present article concerns itself with a life cycle assessment of the three main degreasing processes in order to compare their integral environmental impacts with one another. This is supplemented by presenting the methodology of the life cycle inventory life cycle inventory analysis (LCI). Generally, the applicability of the established LCI method can be shown quite clearly. However, some difficulties arise, especially at the stage of the goal definition, as the use of the process and the functional unit cannot be pinned down as easily and neatly as for most other products. The definition of the use of the process and the functional unit is not as straightforward as for most products. Among the potential functional units identified are the mass of removed impurities, cleaning time, cleaning work, percentage of purity, throughput of parts, loads, mass or surface and virtual coefficients. The mass of removed impurities turned out to be the most suitable parameter for measuring the technical performance of degreasing processes. The article discusses background, purpose, scope, system boundaries, target group, process tree and representativeness of the present study.     

Validation of a hybrid life-cycle inventory analysis method

The life-cycle inventory analysis step of a life-cycle assessment (LCA) may currently suffer from several limitations, mainly concerned with the use of incomplete and unreliable data sources and methods of assessment. Many past LCA studies have used traditional inventory analysis methods, namely process analysis and input-output analysis. More recently, hybrid inventory analysis methods have been developed, combining these two traditional methods in an attempt to minimise their limitations. In light of recent improvements, these hybrid methods need to be compared and validated, as these too have been considered to have several limitations. This paper evaluates a recently developed hybrid inventory analysis method which aims to improve the limitations of previous methods. It was found that the truncation associated with process analysis can be up to 87%, reflecting the considerable shortcomings in the quantity of process data currently available. Capital inputs were found to account for up to 22% of the total inputs to a particular product. These findings suggest that current best-practice methods are sufficiently accurate for most typical applications, but this is heavily dependent upon data quality and availability. The use of input-output data assists in improving the system boundary completeness of life-cycle inventories. However, the use of input-output analysis alone does not always provide an accurate model for replacing process data. Further improvements in the quantity of process data currently available are needed to increase the reliability of life-cycle inventories.     

General mathematical models for LCI recycling

Life cycle inventory (LCI) is becoming more widely used as a tool to evaluate the resource and energy use and the environmental releases associated with various products. The methodology for handling different recycling scenarios is also becoming increasingly important. Several different methods exist for handling recycling in an LCI. The method described in this paper uses mathematical models to show that the same basic equations can be used to handle a variety of recycling options for multi-product systems.     

Indirect carbon reduction by residential vegetation and planting strategies in Chicago, USA

Concern about climate change has evoked interest in the potential for urban vegetation to help reduce the levels of atmospheric carbon. This study applied computer simulations to try to quantify the modifying effects of existing vegetation on the indirect reduction of atmospheric carbon for two residential neighborhoods in north-west Chicago. The effects of shading, evapotranspiration, and windspeed reduction were considered and were found to have decreased carbon emissions by 3.2 to 3.9% per year for building types in study block 1 where tree cover was 33%, and -0.2 to 3.8% in block 2 where tree cover was 11%. This resulted in a total annual reduction of carbon emission averaging 158.7 (+/- 12.8) kg per residence in block 1 and 18.1 (+/- 5.4) kg per residence in block 2. Windspeed reduction greatly contributed to the decrease of carbon emission. However, shading increased annual carbon emission from the combined change in heating and cooling energy use due to many trees in the wrong locations, which increase heating energy use during the winter. The increase of carbon emission from shading is somewhat specific to Chicago, due in part to the large amount of clean, nuclear-generated cooling energy and the long heating season. In Chicago, heating energy is required for about eight months from October to May and cooling energy is used for the remaining 4 months from June to September. If fossil fuels had been the primary source for cooling energy and the heating season had been shorter, the shading effects on the reduction of carbon emission would be greater. Planting of large trees close to the west wall of buildings, dense planting on the north, and avoidance of planting on the south are recommended to maximize indirect carbon reduction by residential vegetation, in Chicago and other mid and high-latitude cities with long heating seasons.     

The toxic release inventory: Fact or fiction? A case study of the primary aluminum industry

Since 1989 manufacturing facilities across the USA must report toxic chemical emissions to the EPA's toxic release inventory (TRI). Public release of this information and increased public scrutiny are believed to significantly contribute to the over 45% reduction in toxic chemical releases since inception of the program and to growing support for this type of informational regulation instead of traditional command-and-control. However, prior research indicates a tendency to under-report emissions. We find specific evidence of under-reporting of polycyclic aromatic hydrocarbons (PAH) to the TRI by primary aluminum facilities after promulgation of the industry's maximum available control technology (MACT) standard in 1997. We also find evidence of dislocation of emission overseas due to these regulatory requirements. Additionally, changes in energy prices affected aluminum production and further distort reported PAH emissions levels. This suggests the possibility of more widespread under-reporting that is modulated by various factors, including market conditions and new regulations, and which may partially explain the downward trend in TRI emissions. It also suggests that the quality of TRI data may improve once facilities are subject to monitoring of emissions of a TRI listed pollutant due to command-and-control regulation.     

Privacy-preserving aggregation in life cycle assessment

Life cycle assessment (LCA) is the standard technique used to make a quantitative evaluation about the ecological sustainability of a product or service. The life cycle inventory (LCI) data sets that provide input to LCA computations can express essential information about the operation of a process or production step. As a consequence, LCI data are often regarded as confidential and are typically concealed through aggregation with other data sets. Despite the importance of privacy protection in publishing LCA studies, the community lacks a formal framework for managing private data, and no techniques exist for performing aggregation of LCI data sets that preserve the privacy of input data. However, emerging computational techniques known as “secure multiparty computation” enable data contributors to jointly compute numerical results without enabling any party to determine another party’s private data. In the proposed approach, parties who agree on a shared computation model, but do not trust one another and also do not trust a common third party, can collaboratively compute a weighted average of an LCA metric without sharing their private data with any other party. First, we formulate the LCA aggregation problem as an inner product over a foreground inventory model. Then, we show how LCA aggregations can be computed as the ratio of two secure sums. The protocol is useful when preparing LCA studies involving mutually competitive firms.     

Photovoltaic-thermal (PV/t) panel to minimize electrical and air conditioning energy consumption of a typical office in Beirut

A combined photovoltaic–thermal (PV/t) panel is proposed to produce simultaneously electricity and heat from one integrated unit. The unit utilizes effectively the solar energy through achieving higher PV electrical efficiency and using the thermal energy for heating applications. To predict the performance of the PV/t at a given environmental conditions, a transient mathematical model was developed. The model was integrated in a heating application for a typical office space in the city of Beirut to provide the office needs for electricity, heating during winter season, and dehumidification and evaporative cooling during the summer season. To minimize the yearly office energy (electrical and heat) needs, the PV/t panel cooling air flow rate and the dehumidification regeneration temperature were determined for opimal unit operation. Thermal energy savings of up to 85% in winter and 71% in summer were achived compared to conventional systems at a payback period of 8 years for the panels.     

Environmental impact of meat meal fertilizer vs. chemical fertilizer

Animal by-products (ABP) are rich in nutrients and energy. This LCA study assessed and compared the environmental impact of using meat meal as fertilizer with that of using chemical fertilizer. In one system the nutrient content of ABP Category 2 was recovered and used as a meat meal fertilizer on arable land, replacing chemical fertilizers. In the other system a chemical fertilizer was used and the energy content of the ABP material recovered. The functional unit consisted of one kg of harvested spring wheat and treatment of 0.59 kg of ABP Category 2. The system for nutrient recovery and chemical fertilizer replacement had lower emissions of greenhouse gases and acidification than the energy recovery system, but had higher total use of energy and eutrophying emissions. Overall, the results of the study greatly depended on the fuels replaced.     

Paper and biomass for energy?: The impact of paper recycling on energy and CO2 emissions

The pulp and paper industry is placed in a unique position as biomass used as feedstock is now in increasingly high demand from the energy sector. Increased demand for biomass increases pressure on the availability of this resource, which might strengthen the need for recycling of paper. In this study, we calculate the energy use and carbon dioxide emissions for paper production from three pulp types. Increased recycling enables an increase in biomass availability and reduces life-cycle energy use and carbon dioxide emissions. Recovered paper as feedstock leads to lowest energy use (22 GJ/t) and CO₂ emissions (−1100 kg CO₂/t) when biomass not used for paper production is assumed to be converted into bio-energy. Large differences exist between paper grades in e.g. electricity and heat use during production, fibre furnish, filler content and recyclability. We found large variation in energy use over the life-cycle of different grades. However, in all paper grades, life-cycle energy use decreases with increased recycling rates and increased use of recovered fibres. The average life-cycle energy use of the paper mix produced in The Netherlands, where the recycling rate is approximately 75%, is about 14 GJ/t. This equals CO₂ savings of about 1 t CO₂/t paper if no recycled fibres would be used.     

The energy,water, and air pollution implications of tapping China's shale gas reserves

China has laid out an ambitious strategy for developing its vast shale gas reserves. This study developed an input–output based hybrid life-cycle inventory model to estimate the energy use, water consumption, and air emissions implications of shale gas infrastructure development in China over the period 2013–2020, including well drilling and operation, land rig and fracturing fleet manufacture, and pipeline construction. Multiple scenarios were analyzed based on different combinations of well development rates, well productivities, and success rates. Results suggest that 700–5100 petajoules (PJ) of primary energy will be required for shale gas infrastructure development, while the net primary energy yield of shale gas production over 2013–2020 was estimated at 1650–7150 PJ, suggesting a favorable energy balance. Associated emissions of CO₂e were estimated at 80–580 million metric tons, and were primarily attributable to coal-fired electricity generation, fugitive methane, and flaring of methane during shale gas processing and transmission. Direct water consumption was estimated at 20–720 million metric tons. The largest sources of energy use and emissions for infrastructure development were the metals, mining, non-metal mineral products, and power sectors, which should be the focus of energy efficiency initiatives to reduce the impacts of shale gas infrastructure development moving forward.     

全国碳市场启动后北京热电行业低碳运行管理方式研究

随着四大热电中心的建成投产,北京市完成了由燃机替代煤机的转变,实现了更加智能化的清洁能源发电供热。2013年北京市碳市场启动运行,给刚起步的燃气供热机组运行赋予了更广阔和更深远的意义;2017年12月19日,以发电行业为突破口,全国碳排放交易体系正式启动,北京市热电行业低碳运行管理意义重大而深远。本文以燃气热电联产机组运行数据为基础,通过计算分析,提出燃气热电联产机组清洁、高效、低碳运行方式,为全国碳市场启动后,北京乃至全国热电行业低碳运行管理提供经验借鉴。     

Alternative energy balances for Bulgaria to mitigate climate change

Alternative energy balances aimed to mitigate greenhouse gas (GHG) emissions are developed as alternatives to the baseline energy balance. The section of mitigation options is based on the results of the GHG emission inventory for the 1987–1992 period. The energy sector is the main contributor to the total CO₂ emissions of Bulgaria. Stationary combustion for heat and electricity production as well as direct end-use combustion amounts to 80% of the total emissions. The parts of the energy network that could have the biggest influence on GHG emission reduction are identified. The potential effects of the following mitigation measures are discussed: rehabilitation of the combustion facilities currently in operation; repowering to natural gas; reduction of losses in thermal and electrical transmission and distribution networks; penetration of new combustion technologies; tariff structure improvement; renewable sources for electricity and heat production; wasteheat utilization; and supply of households with natural gas to substitute for electricity in space heating and cooking. The total available and the achievable potentials are estimated and the implementation barriers are discussed.

     

深圳市南山区碳平衡测算研究

运用《省级温室气体清单编制指南》、《IPCC国家温室气体清单指南》和相关文献推荐方法,利用南山区能源消费数据、工业产品量、废弃物处理量、森林面积和海洋面积等基础数据,对南山区能源利用过程、工业生产过程和产品使用、废弃物处理等3大类碳源温室气体排放量以及区域森林(包括湿地)、城市绿地和海域等3大类碳汇储存量进行了测算,计算表明南山区年碳排放总量达到756.17万t,该测算为南山区未来区域碳减排提供基础数据依据。     

Techno-economic and environmental analysis of an integrated standalone hybrid solar hydrogen system to supply CCHP loads of a greenhouse in Iran

The techno-economic and environmental performance of hybrid solar hydrogen energy systems was investigated to provide combined cooling, heating and power (CCHP) demands of a standalone greenhouse in Iran to achieve sustainable agriculture based on an optimization procedure. From the environmental point of view, by deploying hybrid energy systems, 83%, to 100% of emissions can be avoided. Also a sensitivity analysis was performed on the hybrid energy systems in order to study the effect of major parameter variation on the systems justification. It was concluded that hybrid solar systems are economically competitive with conventional systems, for high solar intensity locations with high diesel fuel prices and decreased prices for PV and hydrogen storage technology.     

Alternative scenarios to meet the demands of sustainable waste management

This paper analyses different alternatives for solid waste management that can be implemented to enable the targets required by the European Landfill and Packaging and Packaging Waste Directives to be achieved in the Valencian Community, on the east coast of Spain. The methodology applied to evaluate the environmental performance of each alternative is Life Cycle Assessment (LCA). The analysis has been performed at two levels; first, the emissions accounted for in the inventory stage have been arranged into impact categories to obtain an indicator for each category; and secondly, the weighting of environmental data to a single unit has been applied. Despite quantitative differences between the results obtained with four alternative impact assessment methods, the same preference ranking has been established: scenarios with energy recovery (1v and 2v) achieve major improvements compared to baseline, with scenario 1v being better than 2v for all impact assessment methods except for the EPS'00 method, which obtains better results for scenario 2v. Sensitivity analysis has been used to test some of the assumptions used in the initial life cycle inventory model but none have a significant effect on the overall results. As a result, the best alternative to the existing waste management system can be identified.     

Process intensification in the textile industry: the role of membrane technology

Process intensification is a concept that was recently introduced in the chemical industry for the purpose of reducing environmental emissions, energy consumption and materials consumption. The principle of process intensification can be used in related industries as well; textile finishing is an exemplary activity where it may have a significant long-term added value. Membrane technology can be a key factor in the recycling and reuse of energy, water and chemicals. In this paper, an integral approach for treatment of aqueous process streams in the textile finishing industry is proposed. The proposed process includes microfiltration pretreatment of used finishing baths, followed by a dual nanofiltration (NF) unit. These can be operated at elevated temperatures so that no further energy is needed for preheating of recycle streams. In the proposed treatment scheme, the first of the NF units uses a loose nanofiltration membrane that retains most of the organic fraction but not the dissolved salts. The second unit uses a tight nanofiltration membrane, which produces a permeate fraction that can be directly reused, and a concentrated brine that is fed to a membrane crystallizer. In this unit, salts are recovered and recycled for use in new dye baths. The concentrate stream from the first NF unit is fed to a membrane distillation unit, where the high temperature is advantageously used for further concentration. The remaining fraction is not reusable, given the fact that most dyes are hydrolyzed after exhaustion of the bath, but has a significant energetic value, which can be utilized for compensation of energy losses and preheating of suppletion water, by using an incineration process with energy recovery. The concept was not tested experimentally, but a simulation for a 500 m3/d production unit shows that it is feasible, although modifications may be necessary depending on the nature of the finishing baths. Furthermore, the membrane choice in the first NF unit is a critical aspect.     

青岛市大气环境质量状况分析与评价

对青岛市大气主要污染物变化趋势进行了分析,并利用模糊综合评价模型对各年大气环境质量状况进行了综合评价。研究结果表明:近10年来青岛市大气环境质量处于尚清洁状况,且在不断改善;受工业扬尘和建筑扬尘影响,青岛市主要污染物是可吸入颗粒物PM10;以煤炭为主的能源结构加之落后的工艺设备等原因使得大气中二氧化硫浓度一直处于较高水平;随着青岛市机动车保有量的增长,以氮氧化物为特征的机动车尾气污染日趋明显,因此,冬季采暖燃煤利用、机动车尾气控制及城市扬尘抑制仍是青岛市未来大气污染的治理重点,强化燃煤脱硫技术和改善机动车尾气排放是青岛市大气环境质量改善的关键。     

Environmental assessment of different management options for individual waste fractions by means of life-cycle assessment modelling

Several alternatives exist for handling of individual waste fractions, including recycling, incineration and landfilling. From an environmental point of view, the latter is commonly considered as the least desirable option. Many studies based on life-cycle assessment (LCA) highlight the environmental benefits offered by incineration and especially by recycling. However, the landfilling option is often approached unjustly in these studies, maybe disregarding the remarkable technological improvements that landfills have undergone in the last decades in many parts of the world.This study, by means of LCA-modelling, aims at comparing the environmental performance of three major management options (landfilling, recycling and incineration or composting) for a number of individual waste fractions. The landfilling option is here approached comprehensively, accounting for all technical and environmental factors involved, including energy generation from landfill gas and storage of biogenic carbon. Leachate and gas emissions associated to each individual waste fraction have been estimated by means of a mathematical modelling. This approach towards landfilling emissions allows for a more precise quantification of the landfill impacts when comparing management options for selected waste fractions.Results from the life-cycle impact assessment (LCIA) show that the environmental performance estimated for landfilling with energy recovery of the fractions “organics” and “recyclable paper” is comparable with composting (for “organics”) and incineration (for “recyclable paper”). This however requires high degree of control over gas and leachate emissions, high gas collection efficiency and extensive gas utilization at the landfill. For the other waste fractions, recycling and incineration are favourable, although specific emissions of a variety of toxic compounds (VOCs, PAHs, NO_x, heavy metals, etc.) may significantly worsen their environmental performance.     

Evaluation of recycling efforts of aircraft companies in Wichita

The number of manufactured aircraft has been continuously increasing worldwide because of the high demand for airline transportation. During manufacturing, many advanced materials and devices are used to build various sizes and shapes of aircraft. However, most of these materials and devices require considerable energy and labor to produce, so reusing these at any life stage of the aircraft offers many economic and environmental benefits, and is considered lucrative and environmentally responsible. Several recyclable materials—composites, metals and alloys, wires, wood, paper, plastics, electronics, and avionics—emerge as waste streams during the manufacturing of aircraft. Many aircraft companies have been recycling these materials to remanufacture aircraft parts or other products for more sustainable production. In the present study, we evaluated the recycling efforts of local aircraft companies in Wichita, KS. These efforts were considered in terms of recycling efficiency/rate and environmental benefits. These included cradle-to-gate (CTG) life-cycle inventory analysis of the materials, carbon dioxide emissions, virgin material replacement with recycled materials, and natural resources usage. Our findings show that there exists a significant potential for contributions to sustainability as well as environmental and health benefits in the region from recycling by aircraft manufacturing plants.