AN LCA FRAMEWORK FOR BUILDINGS IN CHINA

Transcription

1 4-41 The 25 World Sustainable Building Conference, AN LCA FRAMEWORK FOR BUILDINGS IN CHINA Daojin Gu, Ph.D Candidate 1 Yingxin Zhu, Prof. Dr. 1 Borong Lin, Dr. 1 1 Department of Building Science, School of Architecture, Tsinghua University, Beijing, China, 184, golding@tsinghua.org.cn Keywords: sustainable building, LCA, life cycle assessment, life cycle analysis, environment impact, energy saving, resource quality Summary The LCA (Life Cycle Assessment) is always used to evaluate the environment impact of products, also including building materials. But it should be different when used for whole building s process assessment since building is an interactive integration of those building matters and products instead of a simple collection. Some LCA studies considering evaluation of the whole building process appeared actively in Europe, North America, Australia, and Japan in the last few years. However, the related researches for buildings in developing country were not reported yet. Time and region limitation, lack of original data and proper environment evaluation system become points of this research. Considering the particularities of China, a general framework named EI-China for LCA of the whole building process is proposed in this paper. Different from the other LCA researches, the framework is planned not only for existing buildings, but also for general analysis of new buildings - from design stage to operation stage. It consists of some special databases and some environmental indicators considering some critical conditions in China, such as CO 2 emission, depletion of forests resource, water resource and cultivable land. Further more, an LCA case study on residential building fabrics design and construction effecting on the environment energy and resource consumption in Beijing is introduced. 1. Background As China has become one of the largest construction markets in the world, building s sustainability grows to be significant not only to the development of China, but also to the global environment. Life cycle assessment is a cradle-to-grave system approach for measuring the environmental performance of objects or processes. For public concern, the environmental performance consists of resource consumption, energy consumption, human health impacts and ecological impacts. LCA for buildings should consider the energy consumption of operation stage as the customary perspective. Moreover, the extraction of raw building materials, manufacturing of building components or building services system, packaging, distribution, construction stage, re-use, recycle, and waste disposal are supposed to be built-in. Thus different conclusions may be obtained contrasting to the traditional vision, which mainly looks from only the using period of buildings. Building LCA research in China is still in the starting period. The difficulties in this study lie in two aspects. The first one is lack of LCA database, although some researchers in the field of structural engineering have approached to do some analysis on the manufacturing of main building materials (Zhihui Zhang 24). The second difficulty is that the environmental impact of a building varies with regions where the building located, so LCA methods may vary with building s location too. So far, there are only a small number of simple LCA researches have been done on buildings in China and these works are mainly conceptual. The work introduced in this paper emphasizes on new building design and construction rather than existing buildings, aiming at providing guidelines to the building designers. The convenience in application and the practicability of the results are also concerned as the important items as well. The energy consumption composition in China is very complicated in which coal shares 66%, oil 23%, natural gas 3%, and hydro-electricity 8%(China Statistic Institute 23). And coal shares more than 8% in

2 electricity generation and urban district heating. Building energy consumption shares 1/4 in the total national energy consumption. It is reported that 8% of dust and the 9% of SO 2 emission in China is produced by coal-combustion (HaiYan Xie 2). Furthermore, the depletions of water and the forest resource are critical in China. The per capita forest resource is only 8.622m 3 (Compilation Committee of China Forestry 1997), and the per capita water resource is 22 tons(china Statistic Institute 23), which is specified as a water-lack country by U.N. 2. Building LCA Framework 2.1 System Definition The life of a building can be divided into four main stages: materials manufacturing, building construction, operation and recycle/discarding. The energy consumption and environmental impacts mainly come from the materials manufacturing and operation stages. Thus, these two stages are chosen as the main objects in this study, and energy, mineral, wood and water resource consumptions in these two stages are considered as well as environment pollution. In construction stage, only transportation of building materials and equipments are considered due to the lack of construction database for LCA at present. For the recycle/discard stage, only material resource recycle ratio is considered, and energy and water consumption will be studied in the further research as well as construction stage. From some reports, in the energy consumption of residential buildings in China, space heating and cooling shares 65%, lighting and electric appliances shares 15%. The environmental impacts of lighting and electric appliances can be determined quantitatively easily based on the electricity consumption. However, environmental impacts of HVAC system depend on the type of the energy conversion system and the primary energy input. Even the way of air handling will bring about different cooling/heating loads and energy consumptions. Therefore, methodologies to determine the energy consumption and environmental impact for HVAC system are the emphasis of this research. The premise for this research is that the life of buildings is 5 years, and the life of some materials and components are shown in Table Database for Inventory Analysis At the present time, there are two types of LCA database in the world: detailed input-output data, and simplified embodied energy data. The latter one is more applicable to the startup research stage because there are no available detailed input-output data but only a few embodied energy data on building materials in China have been reported (Laoson Bill 2; TOSHIHARU IKAGA 21; Japan Building Environment and Energy Institute 24). The simplified embodied energy database provides the convenience for calculating the fossil fuel consumption and the waste discard quantities by the basic embodied energy data. Consequently, a database with built-in simplified embodied energy data model and the additive resource consumption and waste discard model was developed in this study. Table 2 also gives the data of embodied energy of some building materials. Some of the data comes from the sections about China in Laoson s report, and the data of air conditioner and lamp are from the data of Japan and some European countries with nearly condition (Laoson Bill 2; TOSHIHARU IKAGA 21; Japan Building Environment and Energy Institute 24). Table 2 Embodied energy of main building materials Material Embodied energy(mj/kg) Lifespan (year) Material Embodied energy(mj/kg) Lifespan (year) Cement Clay Masonry Units 2 5 Steel 29 5 Concrete block Aluminum 18 5 Ceramic Glass 16 2 Common lamp Wood Unitary air conditioner (per machine)

3 2.3 Methods for Environmental Impacts Assessment The main environment impacts in building industry lies in two aspects: resource consumption and environment pollution. Resources can be divided into renewable and non-renewable. Non-renewable resource has its exploitable lifespan. Some exploitable lifespan of non-renewable resources related with building are shown in Table 3 (China Energy Report Committee 22). In China, the non-renewable resources consumed in construction sector mainly include fossil fuel resources and mineral resources. The term of mineral resource here indicates the mineral used for building material production which can be partially recycled, e.g. iron, aluminum, copper and so on. These two types of resources are considered in different way in this study. In order to emphasize the value difference between various resources, an index of resource quality is proposed. Resource quality represents the level of the resource shortage. Therefore, the resource quality value is defined as an inverse ratio to the exploitable lifespan on the basis of that the resource quality of coal is defined as 1.. Hence, the resource quality of oil will be 12 and natural gas will be 4(Table 3). Only the resource quality of fossil fuel were defined while the resource qualities of the mineral resources mentioned above are not taken into account in this framework, because some of the current reserves data of mineral resources are not reliable, and some of them are still not available. The resource quality is used to calculate the fossil fuel resource consumption of energy consumption by the consumed quantities of fuels weighted by resource quantity. For example, electricity is generated by 8% coal and 2% oil, the resource consumption of electricity equals to the sum of the coal and oil consumptions weighted with their resource qualities respectively. Different from resources consumption of energy calculation, when the mineral resources consumption of some building material is determined, all raw materials masses are simply accumulated. It should be noticed that for some materials that can be recycled--- e. g., 9% of profile steel, 5% of steel, and 95% of aluminum can be recycled--- the recycled proportion should be deducted, and the energy consumption of the recycling process should be considered as well. It should be point out that different types of energy have different qualities and environmental impacts even if the energy quantities are the same. The 1MJ energy consumed in transportation and 1MJ energy consumed in lighting cannot be compared because we don t know how these energies come out. Therefore, the comparison can be done only in case of that the environmental impact of the energy consumption is represented by resource consumptions and pollution emissions. Although environment pollution consists of air pollution (CO 2, SO 2, NOx and dust), liquid waste, solid waste, the ozone depletion and so on, in order to simplify the focal problems related to buildings, only the main air pollution is considered in this research stage. For both material manufacturing and operation stages of building, not only fossil fuel consumption but also other natural resources consumption should be considered, such as mineral consumption, forest consumption, and water consumption. Forest and water resources are both renewable in principle, but at present, the consumption of wood is much more than its regenerative quantity and there big gap between water resource and demand in China. Thus the forest and water resources are treated as un-renewable resource in current study. The treatment for forest consumption and water consumption calculation are the same as mineral resources. Table 3 Exploitable lifespan of fossil fuel resources in China Resources Exploitable Lifespan (year) Resource Quality Coal 24 1 Oil 2 12 Natural gas 6 4 The environmental impacts are characterized as resource consumption (fossil fuel, mineral, forest, and water) and air pollution (CO 2, SO 2, NO x and dust) as mentioned above. Their absolute value results are normalized by the total quantities per capita of the basic year (

4 Table 4) to obtain the relative values from which the importance comparison of environmental impact can be shown. Consequently, LCA software named EI-China was developed based on above analysis. Table 4 The per capita quantity for normalization LCA environmental impacts Resource Reserves Environmental emission Per capita quantity (kg/p) Fossil fuel Mineral 498 Forest 23 Water 2,2, CO2 238 SO NO x 7.9 Dust Case study The object studied is a typical residential building in Beijing which is still under construction. The study was conducted to the design stage. Detailed information of this building is shown in Table 5. From the analysis results given in Figure 2, it can be found that the energy consumption during operation stage is about 5 times as that during manufacturing stage, and the energy consumed by HVAC system shares 7% during total lifetime. Table 5 Information about the studied case Basic data 7 m 2,new residence, Beijing, shape coefficient.35 Steel (kg/m²) 74.9 Cement (kg/m²) 24 Material used Wood (kg/m²) 2.6 Aluminum (kg/m²) 1.2 Glass(kg/m 2 ).96 Transportation for construction HVAC system type Truck with diesel engine, 61km average transportation distance(china Statistic Institute 23) Summer: room air conditioner, Winter: district heating system Simulated heating/cooling load Heating: 189.2MJ/m 2, Cooling: 35.5MJ/m 2 Simulation tool: DeST(Developed by Tsinghua Univ.) Energy consumption for lighting 39.42MJ/m 2 Water consumption m 3 /m 2 a None middle water treatment Examining the wall insulation design through LCA study, it is found that the conclusion of the life cycle energy saving is quite different from the traditional opinion which attention was paid only to the operating stage. The result shows that the energy saving effect decreases with thickness of wall insulation if the thickness of wall insulation exceeds 9mm (supposed 1 years life cycle for insulation), see Figure 1.

5 12.2% 1.9% Materials 15.8% Manufacturing Components 1.6.4% Manufacturing 1.4 Operational 11.% 1.2 Cooling 1. Operational.8 Heating.6 Operational.4 Lighting 58.7% Equipments.2 Maintenance. energy saving(tj) energy saving in operational stage energy saving in lifetime insulation thickness(mm) Figure 2 Energy consumption in the lifetime Figure 3 Energy saving analysis between operation stage based and LCA Some studies were conducted to the total environmental impact of this building by EI-China, and results are shown in Figure 4 and Figure 5. Figure 4 shows that the operating stage consumes 4 times mineral and produces 9 times air pollution as the manufacturing stage. From the normalized results shown in Figure 5, it is found that the water consumption in buildings is the most important impact to the environment, and the dust pollution during operation stage is the most serious because the primary energy of electricity and heating is mainly coal. 1% 8% 6% 4% 2% % manufacture Mineral operation Forest Water manufacture operation 1% 8% 6% 4% 2% % CO2 SO2 NOx Dust Figure 4 Total environment impacts.4 manufacture operation 1.5 manufacture operation Mineral Forest Water CO2 SO2 NOx Dust Figure 5 Normalized total environment impacts It was reported that the energy consumption of district heating system in Beijing shares 2% of the total city energy consumption (Fei Guo 22). Different types of fuels for heating system bring on different levels of environmental impacts. Some more studies were carried on the three typical kinds of fossil fuels for heating system in this building--coal, oil and natural gas. The result (Figure 6) shows that the oil consumes more

6 resource for its high resource quality and the coal produces the most environment pollution, the natural gas should be considered as the best primary energy for heating system for its lowest emissions and lower resource consumption coal oil gas CO2 SO2 NOx Dust coal oil gas Figure 6 LCA environment impact comparison of buildings with different heating energy source 4. Conclusion EI-China is a newly developed simplified framework to predict the environmental impacts of buildings in China. It has been used to analyze a typical new residential building project in Beijing as a studied case. The result shows that the energy consumption during operation stage is about 5 times as that during manufacturing stage. The results comparison shows that from the point of view of LCA, energy consumption may not always decrease with the thickness of the insulation. Such a result is different from the conventional opinion. For a typical residential building, nearly 6% of total energy consumption is used for heating. Therefore, the primary energy of heating system becomes an important factor for building sustainability and the results shows that natural gas is proved to be the best choice for heating system. However, the work is still in the startup period, there are still much more works, such as environment impact comparison between different types of primary energies, different types of energy conversion systems and different construction design, will be done in the future. References China Energy Report Committee (22). China Energy Report 21. China Statistic Institute (23). Annual China Statistic, China Statistic Publishing House. Compilation Committee of China Forestry (1997). Forest in China, CHINA FORESTRY PUBLISHING HOUSE. Fei Guo, Y. J. (22). "The Analysis on Building Heat-supply Energy." Beijing Real Estate 12. HaiYan Xie (2). "atomosphere environmental protection by develping the clean coal-burning technology." XingJiang Environmental Protection 22(3). Japan Building Environment and Energy Institute (24). Comprehensive Assessment System for Building Environmental Efficiency Manual 1, China Building Industry Publishing House. Laoson Bill (2). "Sustainable Building Material, Energy and Environment." TOSHIHARU IKAGA (21). "Environmental Load Reduce of Air-conditioning System and Building Services." Zhihui Zhang, X. W., Houzhong Xiao (24). "Research on environmental impacts of residence in Beijing." Environmental Evaluate 9.