Analysis of internally recurring unit processes in life cycle assessment

In a life cycle assessment (LCA) study, the identification and quantification of the inputs and outputs of unit processes or gate-to-gate modules are essential. In general, however, many chemical industries are composed of very complex systems with internally recurring unit processes where the upstream input to a unit process may include the downstream output from a latter unit process. Therefore, it is rather difficult to identify and quantify the inputs/outputs for those internally recurring unit processes, respectively, for life cycle inventory analysis purposes.In this study, several calculation methods which are applicable to complex systems with internally recurring unit processes are proposed as follows: (1) Determination of the inputs/outputs associated with each unit process by using simultaneous equations. In this proposal, any parameter linked to an upstream process is treated as a ‘variable’ and the set of other parameters is considered to be a ‘constant’. (2) Determination of the inputs/outputs by using appropriate cut-off criteria based on the cumulative total mass contribution. (3) Determination of the inputs/outputs by using appropriate cut-off criteria based on the number of occurrences of an individual recurring set of unit processes.The results from these methodologies are analyzed using a hypothetical example and an actual case from the petrochemical industry. These methods enhance the reliability and consideration of on-site information in recurring unit processes. In particular, the determination of the inputs/outputs associated with each unit process by using simultaneous equations does not add assumptions regarding cut-off criteria selection and provides the advantages of time conservation, consistency and affinity to on-site consideration.     

中国产品生命周期影响评价方法研究

讨论了确定中国产品生命周期影响评价所需的标准化基准和权重的确定方法和程序，包括产品系统环境影响潜值计算，数据标准化，加权评估 以及计算环境影响负荷和资源耗竭系数4个步骤。标准化基准采用1990年中国人均环境影响总潜值来表达，而权重采用1990年的基准与2000年中国政府的削减目标所估算的基准之间的比值计算。     

Utilisation options of renewable resources: a life cycle assessment of selected products

Renewable resources have increasingly drawn the attention of agriculture, industry and politics. Their utilisation is considered to lead to ecological advantages compared to fossil resources and products. They, however, also come with ecological disadvantages, particularly due to intensive land use.In this paper, the environmental impacts of some utilisation options of Miscanthus and corn to produce energy and products are determined by life cycle assessment. The following life cycle comparisons were performed: (1) insulation material from Miscanthus vs. mineral wool; (2) Miscanthus as solid fuel vs. conventional energy carriers; (3) PLA drinking cups from corn vs. polystyrene drinking cups and (4) ethanol from corn vs. gasoline. The results of the comparisons between these products from renewable resources and their conventional counterparts do not support a clear-cut decision making in favour of or against products from renewable resources.     

Assessment of the environmental impact of carnivorous finfish production systems using life cycle assessment

When evaluating the environmental impacts of finfish production systems, both regional impacts (e.g., eutrophication) and global impacts (e.g., climate change) should be taken into account. The life cycle assessment (LCA) method is well suited for this purpose. Three fish farms that represent contrasting intensive production systems were investigated using LCA: rainbow trout (Oncorhynchus mykiss) in freshwater raceways in France, sea-bass (Dicentrarchus labrax) in sea cages in Greece, and turbot (Scophtalmus maximus) in an inland re-circulating system close to the seashore in France. Two main characteristics differentiated the three farm systems: feed use and energy use. Emission of nitrogen and phosphorus accounted for more than 90% of each farm's potential eutrophication impact. In the trout and sea-bass systems, feed production was the major contributor to potential climate change and acidification impacts and net primary production use (NPPU). In these systems, the main source of variation for environmental impacts was the feed conversion ratio. Results from this study indicate that the sea-bass cage system was less efficient than the trout raceway system, with a higher level of potential eutrophication (65% greater) and NPPU (15% greater). The turbot re-circulating system was a high energy-consumer compared to the trout raceway system (four times higher) and the sea-bass cage system (five times higher). Potential climate change and acidification impacts were largely influenced by energy consumption in the turbot re-circulating system. In the turbot re-circulating system 86% of energy use was due to on-site consumption, while in the sea-bass cage farming system 72% of energy use was due to feed production. These results are discussed in relation to regional contexts of production and focus attention on the sensitivity of each aquatic environment and the use of energy carriers.     

Attributional life cycle assessment of woodchips for bioethanol production

Besides the apparent need to reduce greenhouse gas emissions, other important factors contributing to the renewed interest in biofuels are energy security concerns and the need of sustainable transportation fuel. Nearly 30% of the annual CO₂ emissions in the U.S. come from the transportation sector and more than half of the fuel is imported. Biofuels appear to be a promising option to reduce carbon dioxide emissions, and the reliance on imported oil concomitantly. The interest on (ligno) cellulosic ethanol is gaining momentum as corn-based ethanol is criticized for using agricultural outputs for fuel production. Among many lignocellulosic feedstocks, woodchips is viewed as one of the most promising feedstocks for producing liquid transportation fuels. The renewable and carbon neutral nature of the feedstocks, similar chemical and physical properties to gasoline, and the low infrastructure cost due to the availability of fuel flex vehicles and transportation networks make (ligno) cellulosic bioethanol an attractive option. An in-depth LCA of woodchips shows that harvesting and woodchips processing stage and transportation to the facility stage emit large amount of environmental pollutants compared to other life cycle stages of ethanol production. Our analysis also found that fossil fuel consumption and respiratory inorganic effects are the two most critical environmental impact categories in woodchips production. We have used Eco-indicator 99 based cradle-to-gate LCA method with a functional unit of 4 m³ of dry hardwood chips production.     

生命周期评价在玉米种植及深加工产品中的应用

对LCA在玉米种植环境影响研究中的目标与范围定义、清单分析、环境影响指标与计算方法、结果解释等方面的研究进行了梳理分析,其中大部分文献均对碳足迹进行了计算,CML（Institute of Environmental Sciences of the University of Leiden）、ReCiPe（许多LCA领域研究人员共同开发）和IPCC（Intergovernmental Panel on Climate Change）方法是应用最多的3种方法,经分析计算得到国外玉米种植单位产量碳足迹均值为0.50kg CO₂-eq/kg,我国的均值为0.58kg CO₂-eq/kg.同时本文也对LCA在玉米深加工产品中的研究进展进行了分析整理,对今后LCA应用于玉米种植及深加工产品中的发展方向进行了展望.     

典型复合包装的全生命周期环境影响评价研究

采用生命周期评价法研究了牛奶纸塑铝复合包装的全生命周期环境影响,并与塑料包装的环境影响进行比较评价.通过现场和资料调研的方式获得整个生命周期的能量物质的输入输出和环境外排的数据.结果表明,纸塑铝复合包装和塑料包装的环境影响值分别为5.225, 4.670Pt,在整个生命周期中,环境影响比重最大的是原材料获取阶段,两者均在80%左右.塑料包装在化石资源消耗方面是纸塑铝复合包装的2倍多,由于化石资源消耗是不可再生的,因此其对环境的影响无法通过相关途径降低.纸塑铝复合包装的环境影响较大的原因是其尚未得到很好的回收再生利用,通过发展铝塑分离再生技术和提高纸塑铝复合包装回收率可以降低其环境影响.     

Environmental impacts of cocoa production and processing in Ghana: life cycle assessment approach

Ghana is the world's second largest producer of cocoa beans. In addition to exporting raw cocoa beans, the country also processes some of its beans into finished and semi-finished cocoa products for both the local and international markets. This paper is aimed at providing a comprehensive picture of the environmental impacts associated with cocoa production and processing in Ghana by applying the life cycle assessment (LCA) methodology. The analysis considered the entire system required to produce and process 1 kg of cocoa bean. It included the extraction of raw materials (e.g. fossil fuels, minerals), the production of farming inputs (e.g. fertilizers and pesticides) and all agricultural operations in the field (e.g. tillage, fertilizer and pesticides application, harvest, etc.). Transportation of beans to processing factory and industrial processing of the beans into cocoa butter, liquor, cake and powder were also included. The study was conducted in accordance with the international ISO procedural framework for performing LCA in the ISO 14040–14043 series.The overall environmental impacts resulting from cocoa production and processing activities and improvement options towards the sustainability of the system studied are presented and discussed.     

设施番茄生产系统的环境影响生命周期评价

应用生命周期评价方法,以陕西省西安市郊区为例,对设施番茄生产系统进行了环境影响评价.结果表明,日光温室和塑料大棚生产1000kg番茄消耗的能源和水资源分别是1740.58 MJ、50.767 m3和1502.346 MJ、53.734 m3;全球变暖潜值(以CO2当量计)、环境酸化潜值(以SO2当量计)、富营养化潜值(以PO3-4当量计)、光化学烟雾潜值(以C2H2当量计)、土壤毒性(以1,4-DCB当量计)、水体毒性(以1,4-DCB当量计)和人类毒性潜值(以1,4-DCB计)分别为271.943 kg、2.151 kg、0.247 kg、0.157 kg、24.217 kg、19.545 kg、0.124 kg和239.163 kg、1.88 kg、0.305 kg、0.109 kg、31.686 kg、19.7 kg、0.304 kg.设施构筑物自身建设和维护带来的主要潜在环境影响是能源耗竭、全球变暖和环境酸化;番茄种植环节引起的主要潜在环境影响是水资源耗竭、富营养化、全球变暖、土壤毒性和水体毒性;农资生产环节的主要潜在环境影响是能源耗竭.设施番茄生产系统中对环境影响大的建材和农资是钢材、聚乙烯材料、氮肥、农药和含过量重金属的有机肥.设施番茄生产系统对环境的影响不容忽视,应展开以降低其环境影响为目标的设施结构与建材、温室内气候条件调控、合理施肥和施药的研究,并对采取的技术方法进行生命周期评价,以确保设施蔬菜的可持续发展.研究结果可为促进设施蔬菜生产系统的可持续发展提供科学依据.     

Software as a bridge between theory and practice in life cycle assessment

Three mutually dependent elements are required for the application of life cycle assessment: methodology, data and software. Obviously, the design of software is determined by the methodology and the type of data available. Conversely, the development of software dictates the way in which data should be collected and recorded, and improves the theoretical framework, as it forces one to state the principles clearly and unambiguously. The influence of the development of software on both data and methodology is addressed and illustrated by examples, with reference to two key terms: transparency and explicitness. Three types of influence are distinguished: the design of a protocol, the formulation in terms of recipes, and the presentation of data.     

Simulation based life cycle assessment of airborne emissions of biomass-based ethanol products from different feedstock planting areas in China

Oil shortage and environmental deterioration urge people to pay more and more attention to Biomass-based Fuel Ethanol (BFE), because it is renewable and apparently environmentally friendly. This paper aims to assess and compare the air emissions of three BEF products from different feedstock planting areas in China. For the purpose of a “cradle to grave” study of biomass-based ethanol fuel as a substitute transportation fuel, the authors chose “vehicle fueled by biomass-based E10 (a blend of 10% ethanol and 90% gasoline, v/v)” as the subject. Then, life cycle emission models of Wheat-based E10 from central China, Corn-based E10 from northeast China, and Cassava-based E10 from southwest China were set up based on surveys; life cycle emission functions of CO₂, CO, N₂O, NO_x, SO₂, CH₄, VOC, and PM₁₀ were constructed and value of each emission category was calculated based on Monte Carlo simulation of the life cycle emission models. The calculation results showed that compared with gasoline-fueled vehicles, biomass-based E10-fueled vehicles release less CO₂ and VOC in their lifecycles, but wheat-based E10-fueled and cassava-based E10-fueled ones have more emissions of CO, CH₄, N₂O, NO_x, SO₂, PM₁₀ and corn-based E10-fueled ones have more emissions of CH₄, N₂O, NO_x, SO₂, PM₁₀. Suggestions on reducing the emissions have been proposed for future actions.     

生命周期评价在我国乙烯行业环境评估中的应用

采用IMPACT 2002+方法对我国的乙烯行业进行了生命周期评价(LCA)研究,分析了包括原油生产、原煤生产、原料生产、乙烯生产和电力生产5个环节在内的13种污染物排放对乙烯行业的环境影响.结果表明,乙烯工业对不可再生能源原油的消耗,对温室效应、呼吸效应和水体酸化等的环境影响潜值最为严重.减少乙烯生产环节和原料生产环节(炼油过程)的SO2、NOx、CO2等气体的排放,以及原油开采过程的CH4逸放,是改善环境影响的关键因素.同时,以石脑油为原料裂解乙烯工艺比以轻烃为原料制乙烯工艺对环境的影响要小.而煤制烯烃工艺对环境影响较大,仍具有一定改进空间.总体来看,经过近十年发展,我国乙烯行业对资源利用效率和缓解尾气排放两方面都有显著的提升.     

Simulation and life cycle assessment of process design alternatives for biodiesel production from waste vegetable oils

This study uses the process simulator ASPEN Plus^® and Life Cycle Assessment (LCA) to compare three process design alternatives for biodiesel production from waste vegetable oils that are: the conventional alkali-catalyzed process including a free fatty acids (FFAs) pre-treatment, the acid-catalyzed process, and the supercritical methanol process using propane as co-solvent. Results show that the supercritical methanol process using propane as co-solvent is the most environmentally favorable alternative. Its smaller steam consumption in comparison with the other process design alternatives leads to a lower contribution to the potential environmental impacts (PEI’s). The acid-catalyzed process generally shows the highest PEI’s, in particular due to the high energy requirements associated with methanol recovery operations.     

风电场生命周期CO2排放核算与不确定性分析

提出了风力发电技术生命周期能耗和CO2排放核算的详细方法.应用上海某风电场数据进行核算,结果认为,风机生产阶段能耗和CO2排放占风电场生命周期能耗和CO2排放的比例均为最大,分别为68.23%和67.18%.不确定性分析认为,在所有强度参数中,钢生产综合能耗最为灵敏.风电场能耗强度和CO2强度分别为3.24gce/(kW?h)和9.47g/(kW?h),明显低于300MW火力发电机组的相同指标,分别为330gce/(kW?h)和915g/(kW?h). 20a服役期的50MW风电场满期后,同比300MW火电机组少排放CO2约234万t.     

Screening life cycle assessment (LCA) of tomato ketchup: a case study

A screening life cycle assessment (LCA) of tomato ketchup has been carried out. The purpose was to identify ‘hot-spots', that is parts of the life-cycle that are important to the total environmental impact. The system investigated includes agricultural production, industrial refining, packaging, transportation, consumption and waste management. Energy use and emissions were quantified and some of the potential environmental effects assessed. Packaging and food processing were found to be hot-spots for many, but not all, of the impact categories investigated. For primary energy use, the storage time in a refrigerator (household phase) was found to be a critical parameter.     

A comparative study on milk packaging using life cycle assessment: from PA-PE-Al laminate and polyethylene in China

A Life Cycle Assessment (LCA) approach was used to compare the environmental impacts in the life cycle of two milk packaging systems, PA-PE-Al laminate—a laminated foil made from paper, polyethylene and aluminum foil—and polyethylene. The data for the mass, energy fluxes and environmental emissions were obtained from published literature and from site investigations, for the two systems being analyzed for environmental impacts. The application of LCA using Eco-Indicator 99 has made the comparison of the environmental impacts of the two milk packages possible. The results of this LCA study are discussed and the results reveal that the composite packaging has a slightly higher environmental impact than the plastic one. In addition, the environmental impact of raw material extraction is the highest in all of the life cycle stages except for disposal. The environmental impact of composite packaging mainly comes from the fossil fuels, land use and respiratory inorganics categories, while the plastic packaging mainly comes from the fossil fuels category. However, the composite packaging has a greater environmental impact because it has not been well recycled and reused. This environmental impact could be decreased by developing the technology to separate out polyethylene and aluminum from the packaging.     

Uncertainty assessment by a Monte Carlo simulation in a life cycle inventory of electricity produced by a waste incinerator

The existence of uncertainties is often mentioned as a crucial limitation for a clear interpretation of LCA results. Due to this problem, slowly the uncertainty analysis is gaining importance in the realisation of LCAs, but its use is not common practise. As an example of application for a typical process chain of many LCAs, the uncertainties in the Life Cycle Inventory (LCI) of a life cycle study on waste incineration in Tarragona/Spain has been analysed. The procedure applied consists of selection of essential parameters, determination of probability distributions, Monte Carlo simulation, significance analysis and interpretation of the results. By the use of the obtained probability distributions for the essential factors in a Monte Carlo Simulation, the inventory results were transformed from a concrete value into a probability distribution around a mean value. The probability distributions obtained correspond to a better understanding of the magnitude of the uncertainties in LCA results.     

Life cycle assessment of different variants of sodium chromate production in Poland

Chromium chemicals are made from sodium chromate, a basic intermediate product for the production of all other chromium compounds. This article presents application of the Life Cycle Assessment (LCA) methodology to choose the best method of production of sodium chromate. Three variants of sodium chromate production were considered: the classic method with the use of dolomite (DM), the implemented method with chromic mud recycling (W1) and the target waste-free method (W2). The method for evaluating the impact of sodium chromate production on the environment proposes the subcategories that should be taken into consideration in order to establish the final impact of the production process on the environment. The LCA showed further possibilities for reducing the impact of sodium chromate process on the natural environment through the implementation of new technological solutions, especially those concerning the decrease of energy consumption.     

Development of a life cycle assessment tool for construction and maintenance of asphalt pavements

The increasing use of recycled materials in asphalt pavements calls for environmental assessment of such impacts as the energy input and CO₂ footprint. Life cycle assessment (LCA) is being accepted by the road industry for such purpose. It aims to quantify and collate all the environmental impacts from the life time of the product or process. This paper reviews relevant LCA resources worldwide, identifies the knowledge gap for the road industry, and describes the development of an LCA model for pavement construction and maintenance that accommodates recycling and up-to-date research findings. Details are provided of both the methodology and data acquisition. This is followed by a discussion of the challenges of applying LCA to the pavement construction practice, and recommendations for further work. In the case study, the model is applied to an asphalt paving project at London Heathrow Terminal-5 (LHR), in which natural aggregates were replaced with waste glass, incinerator bottom ash (IBA) and recycled asphalt pavements (RAP). Production of hot mix asphalt and bitumen was found to represent the energy intensive processes. This is followed by data analysis and sensitivity check. Further development of the model includes expanding the database to accommodate the recycling and maintenance practice in the UK, and taking into account the effect that roadwork has on traffic emissions. The LCA model can be further tested and calibrated as a decision support tool for sustainable construction in the road industry.     

Simplified life cycle sustainability assessment of mangrove management: a case of plantation on wastelands in Thailand

Sustainable mangrove management needs to consider trade-offs between multiple benefits provided by mangrove ecosystems and to balance the conflicting objectives of various stakeholders. The aim of the present study is to assess the sustainability of mangrove management based on the life cycle approach. We examine two mangrove management systems in Thailand, namely, the strict preservation and charcoal production systems. The results show that the strict preservation system has an advantage over the charcoal production system from the environmental perspective (the net amount of CO₂ absorbed by mangroves) while the charcoal production is a more favorable system than strict preservation from the social perspective (the amount of employment created in local communities). On the other hand, it is difficult to say that both systems are sustainable from an economic aspect. The charcoal production system needs to develop improved management regimes for commercial charcoal production and requires financial assistance in the period when its net cash flows are negative. As solutions for these problems, the introduction of community forest management and the utilization of a fund for REDD (Reducing Emissions from Deforestation and Degradation in Developing Countries) can be proposed.