Material flow analysis (MFA) of an eco-economic system: a case study of Wujin District, Changzhou, China

The economic and ecological aspects of a social system are coherently linked and can be examined by its material and energy flows. In this study, we used the material flow analysis (MFA) to model the material input and output of the Wujin District of Changzhou City, Jiangsu Province in China. It was revealed that: (1) total material input and material input per capita increased with economic development, while the total material output and material output per capita decreased consistently; (2) except for water, the total material input continued to increase. Input of solid materials grew faster than that of gaseous materials, while the total material output declined. The gas output accounted for the largest proportion of the output resulting in primary environmental pollution as burned fossil fuel; (3) water use in agriculture continued with an increasing trend while that in industrial and residential sectors decreased per capita. The total wastewater discharge and wastewater discharge per capita decreased with a faster decreasing rate of residential wastewater discharge followed by industrial wastewater discharge; (4) material input per unit GDP fluctuated and material output per unit GDP decreased. A decreasing trend in both water use and wastewater discharge per unit GDP was disclosed. These results suggest that the efficiency of resource use in the Wujin District has improved. This weakened the direct link between economic development and environmental deterioration. Additionally, we discussed the harmonic development between environment and economy. Potential limitations of MFA’s application were also discussed. It is suggested that effective measures should be taken for the enforcement of circular economic strategies and the construction of a resource-saving economy __________ Translated from Acta Ecologica Sinica, 2006, (8): 2578–2586 [译自:生态学报]     

Material flow analysis (MFA) of an eco-economic system:a case study of Wujin District,Changzhou,China

The economic and ecological aspects of a social system are coherently linked and can be examined by its material and energy flows.In this study,we used the material flow analysis (MFA) to model the material input and output of the Wujin District of Changzhou City,Jiangsu Province in China.It was revealed that:(1) total material input and material input per capita increased with economic development,while the total material out-put and material output per capita decreased consistently;(2) except for water,the total material input continued to increase.Input of solid materials grew faster than that of gaseous materials,while the total material output declined.The gas output accounted for the largest pro-portion of the output resulting in primary environmental pollution as burned fossil fuel; (3) water use in agriculture continued with an increasing trend while that in industrial and residential sectors decreased per capita.The total wastewater discharge and wastewater discharge per capita decreased with a faster decreasing rate of residential was-tewater discharge followed by industrial wastewater dis-charge; (4) material input per unit GDP fluctuated and material output per unit GDP decreased.A decreasing trend in both water use and wastewater discharge per unit GDP was disclosed.These results suggest that the effi-ciency of resource use in the Wujin District has improved.This weakened the direct link between economic develop-ment and environmental deterioration.Additionally,we discussed the harmonic development between environ-ment and economy.Potential limitations of MFA's application were also discussed.It is suggested that effec-tive measures should be taken for the enforcement of cir-cular economic strategies and the construction of a resource-saving economy     

区域生态经济系统的物质输入与输出分析——以常州市武进区为例

运用物质流分析（MFA）方法,对江苏省常州市武进区生态经济系统中物质输入与输出进行了系统的分析,结果表明：（1）随着社会经济发展和人口增长,武进区物质输入总量及人均物质输入量也在增加,但递增速率均远小于GDP增长速率,而物质输出总量及人均物质输出量则呈现递减趋势;（2）在不考虑水的因素情况下,武进区物质输入量保持较快的上升速度,其中固体物质的增长速率远远大于气体物质的增长速率;物质输出量则呈总体下降趋势,其中以气体物质输出量的贡献最大,对环境造成污染的物质以气体特别是以化石燃料燃烧排放的废气和工业废气为主;（3）排除占大部分比例农业用水的上升,工业用水、城镇生活用水和地下水总量及人均利用强度都在减少;同时,总的废水排放量及人均排放量在减少,其中又以生活废水排放量的减少最快,其次是工业废水;（4）单位GDP物质输入量的变化处于波动状态,同期的单位GDP物质输出量则呈递减趋势,单位GDP用水量和单位GDP废水排放量则有相同的递减趋势,表征了武进区资源利用效率的稳步提高,区域经济增长和环境压力也在逐步脱钩。上述结果体现了武进区近年来循环经济发展模式的优势,但还存在较多问题,说明武进区在调整物质利用强度和提高资源利用效率方面还需下更大的功夫,并采取相关措施,以期提高实施循环经济战略与建设节约型社会的地位和意义。文章最后结合研究区实际情况就区域环境一经济的协调发展进行了展望,指出了物质流分析方法在应用中的一些缺陷,为今后该领域的进一步研究提供了借鉴。     

A Methodical Approach for Systematic Life Cycle Assessment of Wood‐Based Furniture

Existing life cycle assessment (LCA) studies for furniture focus on single pieces of furniture and use a bottom‐up approach based on their bill of materials (BOM) to build up the data inventories. This approach does not ensure completeness regarding material and energy fluxes and representativeness regarding the product portfolio. Integrating material and energy fluxes collected at company level into product LCA (top‐down approach) over‐rides this drawback. This article presents a method for systematic LCA of industrially produced furniture that merges the top‐down approach and bottom‐up approach. The developed method assigns data collected at the company level to the different products while, at the same time, considering that wood‐based furniture is a complex product. Hence, several classifications to reduce the complexity to a manageable level have been developed. Simultaneously, a systematic calculation routine was established. The practical implementation of the developed method for systematic LCA is carried out in a case study within the German furniture industry. The system boundary was set in accord with the EN 15804 specification cradle‐to‐gate‐with‐options. The analysis therefore includes the manufacturing phase supplemented by an end‐of‐life scenario. The case study shows that the manufacturing of semifinished products (especially wood‐based panels and metal components) as well as the electric energy demand in furniture manufacturing account for a notable share of the environmental impacts. A sensitivity analysis indicates that up to roughly 10% of the greenhouse gas emissions are not recorded when conducting an LCA based on a BOM instead of applying the developed approach.     

Bridging the climate mitigation gap with economy‐wide material productivity

Projections of UK greenhouse gas emissions estimate a shortfall in existing and planned climate policies meeting UK climate targets: the UK's mitigation gap. Material and product demand is driving industrial greenhouse gas emissions at a rate greater than carbon intensity improvements in the economy. Evidence shows that products can be produced with fewer carbon intensive inputs and demand for new products can be reduced. The economy‐wide contribution of material productivity and lifestyle changes to bridging the UK's mitigation gap is understudied. We integrate an input‐output framework with econometric analysis and case study evidence to analyse the potential of material productivity to help the UK bridge its anticipated emissions deficits, and the additional effort required to achieve transformative change aligned with 2 and 1.5°C temperature targets. We estimate that the emissions savings from material productivity measures are comparable to those from the Government's planned climate policy package. These additional measures could reduce the UK's anticipated emissions deficit up to 73%. The results demonstrate that material productivity deserves greater consideration in climate policy.     

Spatial analysis of urban material stock with clustering algorithms: A Northern European case study

A large share of construction material stock (MS) accumulates in urban built environments. To attain a more sustainable use of resources, knowledge about the spatial distribution of urban MS is needed. In this article, an innovative spatial analysis approach to urban MS is proposed. Within this scope, MS indicators are defined at neighborhood level and clustered with k‐mean algorithms. The MS is estimated bottom‐up with (a) material‐intensity coefficients and (b) spatial data for three built environment components: buildings, road transportation, and pipes, using seven material categories. The city of Gothenburg, Sweden is used as a case study. Moreover, being the first case study in Northern Europe, the results are explored through various aspects (material composition, age distribution, material density), and, finally, contrasted on a per capita basis with other studies worldwide. The stock is estimated at circa 84 million metric tons. Buildings account for 73% of the stock, road transport 26%, and pipes 1%. Mineral‐binding materials take the largest share of the stock, followed by aggregates, brick, asphalt, steel, and wood. Per capita, the MS is estimated at 153 metric tons; 62 metric tons are residential, which, in an international context, is a medium estimate. Denser neighborhoods with a mix of nonresidential and residential buildings have a lower proportion of MS in roads and pipes than low‐density single‐family residential neighborhoods. Furthermore, single‐family residential neighborhoods cluster in mixed‐age classes and show the largest content of wood. Multifamily buildings cluster in three distinct age classes, and each represent a specific material composition of brick, mineral binding, and steel. Future work should focus on megacities and contrasting multiple urban areas and, methodologically, should concentrate on algorithms, MS indicators, and spatial divisions of urban stock.     

Materials Metabolism Analysis of China's Highway Traffic System (HTS) for Promoting Circular Economy

With the rapid growth of highway mileage and vehicles, the Chinese highway traffic system (HTS) has become one of the great resource consumers. This article attempts to evaluate the material metabolism of China's HTS during 2001–2005 using the approach of material flow analysis (MFA) and to explore possible measures to promote circular economy throughout HTS. We measured a set of indicators to illustrate the whole material metabolism of China's HTS. The results indicated that the direct material input (DMI) of China's HTS increased from 1181.26 million tonnes (Mt) in 2001 to 1,874.57 Mt in 2005, and about 80% of DMI was accumulated in the system as infrastructure and vehicles. The domestic processed output (DPO) increased by 59.0% from 2001 to 2005. Carbon dioxide and solid waste accounted for 80.5% and 10.4% of DPO, respectively. The increase of resource consumption and pollutant emissions kept pace with the growth of transportation turnover. All these suggest that China's HTS still followed an extensive linear developing pattern with large resource consumption and heavy pollution emissions during the study period, which brought great challenges to the resources and the environment. Therefore, it's high time for China to implement a circular economy throughout the HTS by instituting resource and energy savings, by reducing emissions in the field of infrastructure construction and maintenance, by reducing vehicles’ energy and materials consumption, and by recycling waste materials.     

Estimation of Life Cycle Material Costs of Cadmium Telluride– and Copper Indium Gallium Diselenide–Photovoltaic Absorber Materials based on Life Cycle Material Flows

Chalcogenide and chalcopyrite photovoltaic (PV) technologies are highly suitable for solar energy conversion because of their high efficiency, long‐term stable performance, and low‐cost production. However, the absorber materials that are used, such as indium, gallium, and tellurium, are regarded as critical, and their limited availability can hinder market expansion. Therefore, we assess how material efficiency measures along the PV module's life cycle can reduce the net material demand of the absorber materials and thus the material costs. In order to estimate the material flows, we developed a closed‐loop model for the life cycle representing the phases module production, module collection, module recycling, and refinement. In order to reflect the variety and uncertainty in each phase, we compose three different efficiency scenarios by varying material efficiency measures on process and product levels. For each scenario, we compute the life cycle material costs based on the computed material flows. The results show that, in the long term, the material demand can be reduced down to one fourth of the required feedstock for module manufacturing; that is, three fourths of the absorber material stays in the life cycle in a very efficient scenario. Thus, total material costs along the life cycle could be significantly reduced, because the costs for material recycling are lower than the costs for “new” technical‐grade material. This reduction in life cycle material costs means that cadmium telluride– and copper indium gallium diselenide–PV can still be financially viable even if the price of the absorber materials increases significantly. Hence those technologies will still be competitive against crystalline silicon PV in the mid to long term.     

Cape Town’s Metabolism: Insights from a Material Flow Analysis

This work aims to contribute to the number of urban metabolism case studies using a standardized methodology. An economy‐wide material flow analysis (EW‐MFA) was conducted on the Metropolitan Municipality of Cape Town (South Africa) for the year 2013, using the Eurostat framework. The study provides insights into the city's metabolism through various indicators including direct material input (DMI), domestic material consumption (DMC), and direct material output (DMO), among others. In order to report on the uncertainty of the data, a set of data quality indicators originating from the life cycle assessment literature was used. The results show that domestic extraction involves significant quantities of non‐metallic minerals, and that imports consist primarily of biomass and fossil fuels. The role of the city as a regional hub is also made clear from this study and illustrated by large quantities of food and other materials flowing through the city on their way to or from international markets. The results are compared with indicators from other cities and with previous metabolism work done on Cape Town. To fully grasp the impacts of the city's metabolism, more work needs to be done. It will be necessary to understand the upstream impact of local consumption, and consumption patterns should be differentiated on a more nuanced level (taking into account large differences between household income levels as well as separating the metabolism of industry and commerce from residential consumption).     

Features and influencing factors of carbon emissions indicators in the perspective of residential consumption: Evidence from Beijing,China

This research establishes a residential indirect carbon emissions model through input–output structure decomposition analysis (IO-SDA) and LMDI, analyses the influencing factors affecting urban and rural residential carbon emissions indicators in Beijing through input–output tables from 2000 to 2010, and calculates the direct carbon emissions from residential consumption. As the results suggest, the total carbon emissions from residential consumption in Beijing showed volatility. Growing rural and urban differences in direct emissions, and for indirect emissions, mean that urban greatly exceeds rural in this regard. Rising per capita GDP and population, as well as intermediate demand and sectoral emissions intensity change induce growth in indirect emissions in both urban and rural settings: of which, per capita GDP contributes the most. Declining energy intensity contributes the most to emission reductions, followed by residential consumption rates, the rural to urban consumption ratio and consumption structure effects are much smaller.     

Energy Use and Greenhouse Gas Emissions of Air‐Source Heat Pump and Innovative Ground‐Source Air Heat Pump in a Cold Climate

This article compares climate impacts of two heat‐pump systems for domestic heating, that is, energy consumption for space heating of a residential building. Using a life cycle approach, the study compared the energy use and greenhouse gas (GHG) emissions of direct electric heating, a conventional air‐source heat pump, and a novel ground‐source air heat pump innovated by a citizen user, to assess whether such user innovation holds benefit. The energy use of the heat pumps was modeled at six temperature intervals based on duration curves of outdoor temperature. Additionally, two heat pump end‐of‐life scenarios were analyzed. Probabilistic uncertainty analysis was applied using a Monte Carlo simulation. The results indicated that, in ideal conditions, that is, assuming perfect air mixing, the conventional air‐source heat pump's emissions were over 40% lower and the ground‐air heat pump's emissions over 70% lower than in the case of direct electric heating. Although proper handling of the refrigerant is important, total leakage from the retirement of the heat‐pump appliance would increase GHG emissions by just 10%. According to the sensitivity analysis, the most influential input parameters are the emission factor related to electricity and the amount of electricity used for heating.     

Ambient air levels of Aspergillus fumigatus and thermophilic actinomycetes in a residential neighborhood near a yard-waste composting facility

Composting is a biological process that has thepotential to emit large quantities ofbioaerosols and, therefore, could adverselyaffect public health. Numerous previousstudies have demonstrated bioaerosol levelselevated above background adjacent tocomposting waste materials, but effects onoffsite bioaerosol levels due tocomposting-facility bioaerosol emissions havenot been extensively investigated. Of the fewsuch studies published, most have not foundelevated compost-related bioaerosols downwindfrom the composting operation. We investigatedviable Aspergillus fumigatus andthermophilic actinomycete levels upwind anddownwind of a large yard-waste compostingfacility and sought to determine whether levelsin a residential neighborhood near the facilitywere elevated above background levels due tofacility bioaerosol emissions. Mean bioaerosollevels at the composting facility weresignificantly higher than the mean backgroundlevels, exceeding the background means byroughly 20-fold. When a neighborhood samplingsite about 500 m from the facility was in thedownwind direction mean levels weresignificantly higher than for other winddirections, and excursions well abovebackground levels were significantly morefrequent than at background sites. There was asignificant temporal correlation betweenbioaerosol levels at the composting facilityand the downwind sampling site. The resultsindicate that bioaerosol emissions from a largeyard-waste composting facility cansignificantly increase bioaerosol exposurelevels at least 500 m downwind from thefacility.     

Economy‐wide Material Flow Indicators on a Sectoral Level and Strategies for Decreasing Material Inputs of Sectors

The article presents a method for the calculation of selected economy‐wide material flow indicators (namely, direct material input [DMI] and raw material input [RMI]) for economic sectors. Whereas sectoral DMI was calculated using direct data from statistics, we applied a concept of total flows and a hybrid input‐output life cycle assessment method to calculate sectoral RMI. We calculated the indicators for the Czech Republic for 2000–2011. We argue that DMI of economic sectors can be used for policies aiming at decreasing the direct input of extracted raw materials, and imported raw materials and products, whereas sectoral RMI can be better used for justifying support for or weakening the role of individual sectors within the economy. High‐input material flows are associated in the Czech Republic with the extractive industries (agriculture and forestry, the mining of fossil fuels [FFs], other types of mining, and quarrying), with several manufacturing industries (manufacturing of beverages, basic metals, motor vehicles or electricity, and gas and steam supply) and with construction. Viable options for reducing inputs of agricultural biomass include changes in people's diet toward a lower amount of animal‐based food and a decrease in the wasting of food. For FFs, one should think of changing the structure of total primary energy supply toward cleaner gaseous and renewable energy sources, innovations in transportation systems, and improvements in overall energy efficiency. For metal ores, viable options include technological changes leading to smaller and lighter products, as well as consistent recycling and use of secondary metals.     

Assessing Socioeconomic Metabolism Through Hybrid Life Cycle Assessment

This article applies a combined input−output and life cycle inventory (LCI) method to the calculation of emissions and material requirements of the Czech economy in 2003. The main focus is on materials and emissions embodied in the international trade of the Czech Republic. Emissions and material extraction avoided due to imports are calculated according to an input−output approach that assumes the same production technology for imports as for domestic production. Because not all products are provided by the domestic economy, the LCI data are incorporated into the monetary input−output model.
The results show that incorporating the LCI data into an input−output model is reasonable. The emissions embodied in the international trade of the Czech Republic are comparable to the domestic emissions. We compare the economy-wide material flow indicators, such as direct material input, domestic material consumption, and physical trade balance, to their raw material equivalents. The results of our calculation show that the Czech Republic exerts environmental pressure on the environment in other countries through international trade.
We argue that raw material equivalents should be used to express the flows across national boundaries. Furthermore, we recommend a raw material consumption indicator for international comparisons.     

The Metabolic Transition in Japan

The notion of a (socio‐) metabolic transition has been used to describe fundamental changes in socioeconomic energy and material use during industrialization. During the last century, Japan developed from a largely agrarian economy to one of the world's leading industrial nations. It is one of the few industrial countries that has experienced prolonged dematerialization and recently has adopted a rigorous resource policy. This article investigates changes in Japan's metabolism during industrialization on the basis of a material flow account for the period from 1878 to 2005. It presents annual data for material extraction, trade, and domestic consumption by major material group and explores the relations among population growth, economic development, and material (and energy) use. During the observed period, the size of Japan's metabolism grew by a factor of 40, and the share of mineral and fossil materials in domestic material consumption (DMC) grew to more than 90%. Much of the growth in the Japanese metabolism was based on imported materials and occurred in only 20 years after World War II (WWII), when Japan rapidly built up large stocks of built infrastructure, developed heavy industry, and adopted patterns of mass production and consumption. The surge in material use came to an abrupt halt with the first oil crisis, however. Material use stabilized, and the economy eventually began to dematerialize. Although gross domestic product (GDP) grew much faster than material use, improvements in material intensity are a relatively recent phenomenon. Japan emerges as a role model for the metabolic transition but is also exceptional in many ways.     

Environmental effects from a recycling rate increase of cardboard of aseptic packaging system for milk using life cycle approach

Goal, Scope and Background  Despite the well-known advantages of recycling materials to reduce solid waste or save natural resources, the recycling stage is an additional process within the life cycle that has its own energy and input requirements, as well as specific emissions. The objective of the present paper is to analyze the life cycle inventory associated with the increase in recycling rate (from 2% up to 22% at present) of the cardboard contained in the aseptic packaging for long-life milk. The main aspects of the manufacturing of the Tetra Pak aseptic package, including the filling of the product, the distribution of the conditioned product, up to the final disposal and recycling rates, were considered. Materials and Methods  This study was conducted in accordance with the general directives of the ISO 14040 series. The packaging material system was assessed using 1000 liters of milk as a functional unit, in a packaging system containing 12 units of 1 L cartons each, placed on a corrugated paperboard tray wrapped in polyethylene shrink film and arranged onto one-way wooden pallets. Brazilian inventories for energy, carton, corrugated paperboard and aluminum, based on site-collected data were employed. The final disposal of used packages was modeled using the Average Brazilian Municipal Solid Waste Management data collected for the purpose of the census of the year 2000. Results  Comparison of the total energy consumption throughout the whole life cycle of two recycling scenarios (i.e. different recycling rates) analyzed shows that the higher recycling rate led to a 6% reduction of the total energy requirement for the long-life milk package material system. The most significant reductions in the consumption of natural resources were: 8% water, 11% wood and 10% land use savings. Greenhouse gases were the main reduced air emissions and contributed with a reduction of 9.7% in GWP. Most water emissions were reduced: 10% COD, 9% BOD and 6% TSS. A unique drawback directly caused by the increase of the recycling rate was an increase of 14.4 g in TDS emissions (57%). Discussion  The reduction in energy requirements are related and limited to the proportionality among the different materials that make up the packaging system. Most emission reductions result from the replacement of virgin materials with recycled materials in the packaging system. Although the average balance of water emissions is positive, the need to improve wastewater treatment processes in the paper recycling plants to reduce TDS is highlighted as a key issue. Conclusions  It may be concluded that the increase in the recycling rate brings about a series of benefits in terms of reduction of energy and natural resource consumption, air pollutants and most water emissions. In this case, the increase of the recycling rate improved the overall environmental performance of the aseptic Tetra Pak system for milk. Recommendations and Perspectives  The authors are currently analyzing alternative recycling scenarios that will enable one to evaluate maximum reduction in GWP. Further studies could include the agriculture stages, livestock and consumer phase to broaden the environmental evaluation. ESS-Submission Editor: Dr. Andreas A. Detzel (andreas.detzel@ifeu.de)     

Life cycle assessment and cost analysis of residential buildings in south east of Turkey: part 1—review and methodology

Purpose

Buildings are responsible for more than 40 % of global energy used, and as much as 30 % of global greenhouse gas emissions. In order to quantify the energy and material inputs and environmental releases associated with each stage of construction sector, life cycle energy, greenhouse gas emissions, and cost analysis of contemporary residential buildings have been conducted within two parts.

Methods

This paper is the first part of the study which includes the literature review and methodology used for such a comprehensive analysis. It was determined that there are three basic methods used in life cycle analysis: process analysis, input–output (I–O) analysis, and hybrid analysis. In this study, Inventory of Carbon and Energy (ICE) is used for the calculation of primary energy requirements and greenhouse gas emissions. The second part of this study is about the application of the methodology which considers two actual buildings constructed in Gaziantep, Turkey.

Results and discussion

The proposed research focused on building construction, operating, and demolition phases. Energy efficiency, emission parameters, and costs are defined for the building per square meter basis. It is seen that the primary energy use and emissions of residential buildings around the world falls in the range of about 10 to 40 GJ/m² and 1–10 t CO₂/m² respectively.

Conclusions

The literature survey demonstrates that there are limited number of studies about life cycle cost assessment (LCCA) of residential buildings in the world. It was decided to use the ICE database as it is one of the most comprehensive databases for building materials, globally. The results of the study show that minimizing energy, material, and land use by considering potential impacts to the environment on a life cycle basis are the basic steps in designing an energy-efficient and environmental-friendly building.

     

Maintenance and Expansion: Modeling Material Stocks and Flows for Residential Buildings and Transportation Networks in the EU25

Material stocks are an important part of the social metabolism. Owing to long service lifetimes of stocks, they not only shape resource flows during construction, but also during use, maintenance, and at the end of their useful lifetime. This makes them an important topic for sustainable development. In this work, a model of stocks and flows for nonmetallic minerals in residential buildings, roads, and railways in the EU25, from 2004 to 2009 is presented. The changing material composition of the stock is modeled using a typology of 72 residential buildings, four road and two railway types, throughout the EU25. This allows for estimating the amounts of materials in in‐use stocks of residential buildings and transportation networks, as well as input and output flows. We compare the magnitude of material demands for expansion versus those for maintenance of existing stock. Then, recycling potentials are quantitatively explored by comparing the magnitude of estimated input, waste, and recycling flows from 2004 to 2009 and in a business‐as‐usual scenario for 2020. Thereby, we assess the potential impacts of the European Waste Framework Directive, which strives for a significant increase in recycling. We find that in the EU25, consisting of highly industrialized countries, a large share of material inputs are directed at maintaining existing stocks. Proper management of existing transportation networks and residential buildings is therefore crucial for the future size of flows of nonmetallic minerals.     

Life-cycle assessment and cost analysis of residential buildings in South East of Turkey: part 2—a case study

Purpose

Residential buildings play an important role in consumption of energy resources. About 40 % of all primary energy is used in buildings all over the world. This paper is the second part of the study on the life-cycle energy (LCEA), emissions (LCCO₂A) and cost (LCCA) assessment of two residential buildings constructed in urban and rural areas.

Methods

In the first part, the methodology, formulations and procedure for such a comprehensive analysis are provided, while this paper provides an application of the methodology that considers two actual buildings located in Gaziantep, Turkey. The proposed model focused on building construction, operation and demolition phases to estimate energy use, carbon emissions and costs per square meter over a 50-year lifespan. The optimum thickness of insulation used to reduce energy consumption and emissions per square meter is determined.

Results and discussion

It is found that the operating phase is dominant in both urban and rural residential buildings and contributes 87–85 % of the primary energy requirements and 88–82 % of CO₂ emissions, respectively. Life-cycle greenhouse gas emissions were 5.8 and 3.9 tons CO₂ eqv. for BT1 and BT2, respectively. It is calculated that the life-cycle energy consumption and CO₂ emissions of the residential buildings can be reduced by up to 22.8 and 23.4 %, respectively, by using a proper insulation material for the external walls. The life-cycle cost, consisting of mortgage, energy, maintenance, service and demolition payments are calculated to be 7.28 and 1.72 million USD for BT1 and BT2, respectively.

Conclusions

Building envelope developments, such as better wall insulation, provide noteworthy potential energy savings and contribute to the reductions from cooling and space heating. Therefore, primary strategies and technologies needed for efficient buildings include optimal insulation of external walls. The economic insulation thickness of the residential buildings in Gaziantep is determined to be 80 mm by using a life-cycle cost analysis. The results show that because of the differences in building structures and living standards, life-cycle energy intensity and CO₂ emissions in urban residential buildings are 29 and 25 % higher than in rural conditions.

     

Life-Cycle Energy, Costs, and Strategies for Improving a Single-Family House

The life-cycle energy, greenhouse gas emissions, and costs of a contemporary 2,450 sq ft (228 m³) U.S. residential home (the standard home, or SH) were evaluated to study opportunities for conserving energy throughout pre-use (materials production and construction), use (including maintenance and improvement), and demolition phases. Home construction and maintenance materials and appliances were inventoried totaling 306 metric tons. The use phase accounted for 91% of the total life-cycle energy consumption over a 50-year home life. A functionally equivalent energy-efficient house (EEH) was modeled that incorporated 11 energy efficiency strategies. These strategies led to a dramatic reduction in the EEH total life-cycle energy; 6,400 GJ for the EEH compared to 16,000 GJ for the SH. For energy-efficient homes, embodied energy of materials is important; pre-use energy accounted for 26% of life-cycle energy. The discounted (4%) life-cycle cost, consisting of mortgage, energy, maintenance, and improvement payments varied between 426,700 and 454,300 for a SH using four energy price forecast scenarios. In the case of the EEH, energy cost savings were offset by higher mortgage costs, resulting in total life-cycle cost between 434,100 and 443,200. Life-cycle greenhouse gas emissions were 1,010 metric tons CO₂ equivalent for an SH and 370 metric tons for an EEH.