建筑全寿命期碳排放评估方法研究：斯里兰卡实践

瑞 亚

摘 要

当今很多全球环境问题都是由人类活动造成的。在工程建造领域，特别是房屋建筑，对环境有较大的影响。在全生命周期内，房屋建筑消耗能源，并排放温室气体，这其中二氧化碳占相当大的比例。因此，房屋建筑被认为是减缓全球碳排放方面的一个主要关注领域。要减排，就要评估当前的排放情况，所以房屋建筑的碳排放评估就成为了一个研究重点。很多国家开发了他们各自的建筑生命周期碳排放评估系统、工具及数据库，然而斯里兰卡目前还做的不够。

本研究旨在开发一个基于斯里兰卡环境下的建筑生命周期碳排放工具。本文讨论了系统要求和系统边界，建立了针对项目全生命周期每一个阶段的碳排放计算方法，进而开发了生命周期碳排放数据库和系统程序。通过多种方法在材料制造厂现场测量采集数据。通过编制生命周期所有阶段的碳排放数据，我们用 MySQL 数据库管理系统开发了一个适应斯里兰卡建筑环境的生命周期碳排放数据库。软件程序与用户界面采用.NET 框架环境下的 Visual Studio C#编程语言，与生命周期碳排放数据库集成。这个工具被应用于若干案例研究，包括了住宅和商业建筑。研究成果能够用于识别当前斯里兰卡建筑的碳排放水平。

论文研究发现商业建筑的生命周期碳排放比住宅高 2 至 3 倍。在所有案例研究的建筑中，运营阶段的生命周期碳排放都贡献了最高的占比（44-63%），然后是材料生产阶段（28-35%）。运营、材料生产和维护合起来的份额超过了整个生命周期碳排放的 90%。研究强调了建筑所呈现阶段对碳减排的重要性，如住宅建筑，在斯里兰卡其运营能源要求是很低的。论文研究分析了主要建筑材料对总材料量和碳排放的贡献度。预拌商品混凝土、碎石、黏土砖和混凝土块，在所有研究的建筑中，贡献了超过 90%的总建材质量。钢筋混凝土作为主要结构材料，在住宅和商业建筑中，分别贡献了 60%和 77%材料生产阶段碳排放。对于次要材料，如铝材、瓷砖和油漆，虽然使用的质量可忽略不计，却在碳排放中拥有较大占比。根据案例建筑的分析，大量使用的以及高碳排放强度的材料被重新认识，因而需要对这些材料特别注意以便于采用合适的减排策略。

论文提出了降低建筑生命周期碳排放的策略方法。它们包括用于优化材料用量的选择设计、通过引入水泥替代品的混凝土性质改良、低碳替代材料的选用、加速回收利用建筑拆除废物及可再生能源的使用等。研究发现这些方法对减低碳排放有显著效应。同时，开发材料环境信息以及推广环境标签将有利于材料利用决策。运营期的碳排放减低可由无成本的能源节约措施实现，比如：控制空调温度设置点，负荷卸载以及改善建筑用户的节能行为。在建筑运营中使用可再生能源将大大降低碳排放；特别是太阳能和风能，推荐作为像斯里兰卡这样热带岛屿的可再生能源。为了推动斯里兰卡的建筑生命周期碳排放评估，研究强调了形成合适政策与规范的重要性。论文研究也指出建立生命周期碳排放评估基准同样重要。

开发生命周期数据库的主要挑战是在斯里兰卡缺乏国家层面的建筑生命周期具体碳排放数据。因此，发展一套国家生命周期数据详细目录是第一要务。由于碳排放随着若干时变因素而变化，比如生产技术、能源和发电混合，建议数据库定期更新。研究建议了能源模拟和算量软件的集成，以提高工具的自动化水平。研究指出，为了促进建筑生命周期碳排放评估，提高公众和工业界人士的意识是必须的。作为一项里程碑式的研究，本文工作将会把建筑的生命周期碳排放评估引入实践，这是为实现斯里兰卡的可持续发展目标的一个适时的要求。

关键词：建筑生命周期 碳排放评估工具 碳排放数据库 内含碳 可持续建造 斯里兰卡

Abstract

Many of the global environmental challenges today are created by human activities. The construction sector, especially buildings, has a major impact on environment. Throughout their life cycle, buildings use energy, and emit greenhouse gasses, among which carbon dioxide has a predominant share. Hence, buildings were identified as a focus area for the mitigation of global carbon emission. As mitigation requires evaluation of the current performance, building carbon emission assessment has become a key area of interest. Many countries have developed their own building life cycle carbon emission assessment methods, systems, tools and databases which Sri Lanka lacks at present.

This study was aimed at establishing a building lifecycle carbon emission assessment method in the context of Sri Lanka. The system requirements and system boundary were identified and the carbon emission calculation method for each cradle-to-grave life cycle stage was established, which was followed by the development of the life cycle carbon emission database and the program. Data were collected through several methods, on-site surveys at material manufacturing facilities among them. By compiling carbon emission data of all life cycle stages, a life cycle carbon emission database for Sri Lankan buildings was developed using MySQL database management system. The software program and user interface were developed using Visual Studio C# programming language in.NET framework environment, which was integrated with the life cycle carbon emission database. The developed tool was applied to a number of case studies, both residential and commercial buildings. The findings were used to identify the current carbon emission profile of Sri Lankan buildings.

The life cycle carbon emission of commercial buildings was found to be 2-3 times higher than that of residential buildings. The operation stage contributed to the highest share of life cycle carbon emission for all case study buildings (44%-63%), which was followed by material production stage (28%-35%). The combined share of carbon emission for operation, material production and maintenance exceeded 90% of the total life cycle carbon emission. The importance of the embodied phase was emphasized, especially for residential buildings, where operational energy requirement is less. The contributions of major building materials to total material mass and carbon emission were analyzed. Ready-mixed concrete, random rubble, clay bricks and concrete blocks contributed to more than 90% of the total mass for all buildings studied. Reinforced concrete as the main structural material, contributed to 60% and 77% of carbon emission at material production stage in residential and commercial buildings respectively. Despite the negligible mass used, secondary materials such as aluminums, ceramic tiles and paint contributed to carbon emission significantly. From the analysis of case study buildings, materials which are used in high mass quantities as well as those which have high carbon emission intensity were recognized as needing special attention in identifying appropriate mitigation strategies.

Several strategies for reducing life cycle carbon emission were identified. Selecting designs that optimize quantities of mass materials, modification of concrete properties by introducing substitutes for cement, use of low-carbon alternative materials, promoting recycling and reuse of demolition waste and use of renewable energy sources for material production were found to have significant effects on reducing embodied carbon emission. The development of the environmental profiles for materials and promoting eco-labelling will increase the availability of material information for decision making. The operational carbon emission can be reduced by no-cost energy saving measures such as controlling of set point temperature of air conditioning, load shedding as well as improving the energy saving behavior of building users. The use of renewable energy sources for building operation will considerably reduce carbon emission; especially solar and wind power were recommended for a tropical island such as Sri Lanka. In order to promote building life cycle carbon emission assessment in Sri Lanka, the importance of formulating appropriate policies and regulations were highlighted. Establishing benchmarks for life cycle carbon emission assessment was also found to be important.

A number of possible improvements for the tool were identified in order to enhance its performance. The major challenge found in developing the life cycle database was the current unavailability of country-specific life cycle carbon emission data for Sri Lanka. Hence, development of national life cycle data inventories was identified as a high priority.As carbon emission varies with a number of time-dependent factors such as production technologies, energy sources and electricity generation mix, the periodic updating of the databases was recommended. The integration of energy simulation and quantity take-off software was proposed in order to increase the level of automation of the tool. Improving the awareness among general public and industry personnel was identified as essential in promoting building life cycle carbon emission assessment. As a milestone study, this research will introduce the practice of life cycle carbon emission assessment of buildings in Sri Lanka, which is a timely requirement towards achieving sustainable goals of the country.

Key words: Building life cycle  Carbon emission assessment tool  Carbon emission database  Embodied carbon Sustainable construction  Sri Lanka