Xianzheng Gong

Bio: Xianzheng Gong is an academic researcher from Beijing University of Technology. The author has contributed to research in topics: Life-cycle assessment & Greenhouse gas. The author has an hindex of 12, co-authored 34 publications receiving 611 citations.

Life Cycle Energy Consumption and Carbon Dioxide Emission of Residential Building Designs in Beijing

Abstract: Summary This study is based on the three types of residential buildings with framework structures in Beijing: concrete framework construction (CFC), light-gauge steel framework construction (SFC), and wood framework construction (WFC). The analysis of the environmental load across the life cycle of the three types of buildings is conducted using life cycle assessment (LCA) according to the protocols of the International Organization for Standardization (ISO) 14040/44. The functional unit is the three material building designs, which possess the same function and design plan, and are built in concrete, light-gauge steel, and light frame wood, inclusive of their respective envelope materials. Throughout the investigation, the calculations of the environmental load data of materials, energy consumption, and carbon dioxide (CO2) emissions are comprehensively assessed and compared. The study shows that over the life cycle, the energy consumption of CFC is almost the same as that of SFC, and each of them is approximately 30% higher than that of WFC. Building use, steel material production, cement production, gypsum board production, and material transport are the main construction activities related to the energy consumption; the net CO2 emission of CFC is 44% higher than that of SFC and 49% higher than that of WFC. The main source of CO2 emission is the use of electricity; its contributions to the net CO2 emissions of WFC, SFC, and CFC are 67%, 64%, and 44%, respectively. The net CO2 emissions in the transport category cannot be ignored, with proportions amounting to 8%, 12%, and 11% for WFC, SFC, and CFC, respectively.

The life cycle inventory study of cement manufacture in China

Abstract: To make clear the environmental damages and potential improvements of Chinese cement industry, the detailed life cycle inventory (LCI) of cement manufacture with direct input and output in the boundary of cement plant as well as corresponded transport is conducted. The functional units are 1 t of Portland Ordinary cement and 1 t of clinker. The input data contain not only the traditional items such as raw materials (limestone, sandstone, ferrous tailings and gypsums), energy (coal and electricity), and admixtures (fly ash and furnace slag), but also fresh water which is not paid attention in other literature. The output data contain not only greenhouse gas (CO2) and primary pollution (NOx, PM, SO2), but also the hazardous air pollutants (HCl, NMVOC, PCDD/Fs, PAHs and fluoride) as well as noise and heavy metal emissions (As, Cd, Cr, Hg, Ni, Pb, Zn, Cu) which are usually neglected by others. The data were measured on-site. The applications of reducing pollutants and waste heat recovery technologies, and AFRs usage in cement industry are evaluated. The three steps of developments of LCI study for China cement industry are discussed.

Environmental impact analysis of blast furnace slag applied to ordinary Portland cement production

Abstract: This study was conducted based on the ISO 14040/14044 standards to analyze the environmental impact caused by blast furnace slag utilization for ordinary Portland cement production in typical plants in Beijing. In addition, sensitivity analysis of resource consumption, transport distance, the allocation methods and life cycle impact assessment model were discussed in detail. The results showed that global warming potential and acidification potential were the most significant environmental impacts resulted by slag-based cement production, accounting for 58.5% and 21.7% of the total environmental impact, respectively. Moreover, the cement production and energy generation phases accounted for 66.6% and 29.6% of total environmental loads of slag-based cement from cradle to gate, respectively. Sensitivity analysis showed that the comprehensive environmental impact of slag-based cement was sensitive to the consumption of limestone and energy, as well as the allocation methods and life cycle impact assessment model; but was insensitive to the consumption and transport distance of blast furnace slag. Compared with traditional Portland cement, except for the approximately 9% increase of human toxicity potential, the other impacts of slag-based cement decreased to a certain extent. In particular, abiotic depletion potential and land use potential significantly reduced by 72% and 41%, respectively. Therefore, producing cement with blast furnace slag would slightly increase electricity consumption, but significantly improve the benefits of land resource and materials conservation and significantly decrease the comprehensive environmental impact of cement.

The LCA of portland cement production in China

Abstract: Cement production is associated with a considerable environmental load, which needs to be fully understood before effective measures can be taken. The existing literature did not give detailed life cycle assessment (LCA) study of China and had limited potential for investigating how best available techniques (BATs) would provide a maximum benefit when they are applied in China. Japan was selected as a good example to achieve better environmental performance of cement production. We identified potentials for reducing emissions and saving energy and natural resources in Chinese cement industry through the comparative analysis. This paper follows the principal of Life Cycle Assessment and International Reference Life Cycle Data System (ILCD). The functional units are “1 t of portland cement” and with 42.5 MPa of strength grade. The input (limestone, sandstone, ferrous tailings, coal, and electricity) and output (CO2 from limestone decomposition and coal combustion, NOx, PM, and SO2) of cement manufacturing were calculated by use of on-site measurements, calculation by estimated coefficients, and derivation by mass and heat balance principle. The direct (cement manufacturing) and indirect (electricity production) LCI are added to be total LCI results (cement production). The impact categories of global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), photochemical oxidant formation potential (POCP), and human toxicity potential (HTP) are used to calculate environmental impact. Only in GWP of cement manufacturing China has advantage. Japanese cement industry shows remarkable superiorities in the environmental impacts of AP, POCP, HTP, and EP due to advanced technologies. SO2 emissions make the corresponding AP and HTP. PM emissions result in part of HTP. The NOx emissions are the major contributors of POCP, AP, EP, and HTP in China. China emits fewer CO2 emissions (2.09 %) in cement manufacturing than Japan but finally makes higher total GWP than Japan due to more GWP of electricity generation in power stations. The waste heat recovery technology can save electricity but bring more coal use and CO2 emissions. The alternative fuel and raw materials usage and denitration and de-dust technologies can relieve the environmental load. Using the functional unit with the strength grade, the life cycle impact assessment (LCIA) results are affected. LCA study allows a clear understanding from the view of total environmental impact rather than by the gross domestic product (GDP) unit from an economic development perspective. In an LCA study, the power generation should be considered in the life cycle of cement production.

Greenhouse gas emissions and reduction potential of primary aluminum production in China

Abstract: A cradle-to-gate life cycle assessment was conducted in this paper to calculate the greenhouse gas (GHG) emissions, such as CO2, CH4, CF4 and C2F6 emissions, based on statistic data of Chinese aluminum industry of the year 2003. The results showed that the GHG emissions for 1 t primary aluminum production was 21.6 t CO2 equivalent which is 70% higher than that of worldwide average level of the year 2000. The main contributors of emission were the alumina refining and aluminum smelting process accounting for 72% and 22% in accumulative emission, respectively. According to the development and application of new process technologies for primary aluminum production and the ‘target of energy-saving and emissions-reducing’ of Chinese government, the reduction potential of the GHG emissions for alumina and aluminum production were estimated. The results indicated that China aluminum industry would achieve the target of reducing about 25% GHG emissions by the end of 2010.

Life cycle assessment (LCA) and life cycle energy analysis (LCEA) of buildings and the building sector: A review

Abstract: This review summarizes and organizes the literature on life cycle assessment (LCA), life cycle energy analysis (LCEA) and life cycle cost analysis (LCCA) studies carried out for environmental evaluation of buildings and building related industry and sector (including construction products, construction systems, buildings, and civil engineering constructions). The review shows that most LCA and LCEA are carried out in what is shown as “exemplary buildings”, that is, buildings that have been designed and constructed as low energy buildings, but there are very few studies on “traditional buildings”, that is, buildings such as those mostly found in our cities. Similarly, most studies are carried out in urban areas, while rural areas are not well represented in the literature. Finally, studies are not equally distributed around the world.

Modeling of energy consumption and environmental life cycle assessment for incineration and landfill systems of municipal solid waste management - A case study in Tehran Metropolis of Iran

Abstract: As the economy has improved in Iran, residents have produced more municipal solid wastes in recent decades. The various scenarios for municipal solid waste management are projected with the main purpose for reduction of environmental impact and energy production. The aim of this study is to evaluate the energy consumption and environmental impacts of incineration and landfill scenarios. The data used in this study are supplied by Waste Management Organization of Tehran Municipality, Iran. Results of the energy analysis show that 406.08 GJ (8500 t MSW)−1 of energy is consumed in the process of incineration and landfill with transportation system. Most energy consumption is related to transportation. Life cycle assessment indicates that incineration leads to the reduction of detrimental factors related to toxicity as the results of electricity generation and the production of phosphate fertilizers. Besides, the rates of daily greenhouse gas emissions from incineration and landfill are estimated at 4499.07 and 92,170.30 kg CO2 eq., respectively. In this study, feed-forward back-propagation models based on Levenberg-Marquardt training algorithm are developed for predicting electricity and environmental factors against energy consumption for municipal solid waste management. An Artificial Neural Network model with 4-5-5-11 structure is selected as the best structure. Results show that, in the selected model, the amount of R2 varies in the ranges of 0.948–0.999 for training, testing and validation, demonstrating excellent performance in predicting all outputs based on the input factors. Sensitivity analysis for Artificial Neural Network model indicates that transportation has the highest sensitivity in four impact categories including eutrophication, marine aquatic ecotoxicity, human toxicity and terrestrial ecotoxicity.

Cement industry greenhouse gas emissions – management options and abatement cost

Abstract: Growing anthropogenic greenhouse gas emissions and increasing global demand for cement are general drivers for managing greenhouse gas emissions (GHG) in the cement industry. Overall CO 2 dominates cement sector GHG emissions. The aim was to study how the management of GHG emissions in the cement production chain is related to (1) clinker substitutes, (2) primary source of energy, (3) electricity emissions, (4) technology in use and (5) geographic location. Therefore regional CO 2 emissions in the cement industry were analyzed by applying a climate impact management matrix on a cradle-to-gate basis. The use of clinker substitutes in cement varied from 3% to 36.4%. The results show that the variation of process technology and thermal energy use related CO 2 emissions is more significant than that of electricity emissions. The highest near term potential to avoid emissions is replacing clinker with mineral components (MIC). Increasing the global use of MIC to a level of 34.2%in cement would save 312 Mt CO 2 with the 2013 level of annual cement production. Similarly, a 2.7% reduction in thermal energy use would save 28 Mt CO 2 annually, and a 10% decrease of emissions from electricity use would save 26 Mt CO 2 . The best long term options from 2030 onwards are different carbon capture technologies and MgO and geopolymer cements. In addition, the CO 2 abatement costs of different investment projects were compared by using a uniform capital recovery factor. The abatement cost of avoided emissions varied from US$4 to US$ 448 per ton of CO 2 depending on the technology, geographical location and initial level of CO 2 emissions.

Reducing Greenhouse Gasses Emissions by Fostering the Deployment of Alternative Raw Materials and Energy Sources in the Cleaner Cement Manufacturing Process

Abstract: The cement production industry worldwide is one of the largest CO2 emitting industrial sectors. It accounts for a considerable amount of total global greenhouse gas (GHG) emissions. Due to the increasing awareness of global warming, more energy efficient cement production is increasingly being emphasized. One of the priorities is to reduce the energy demand and innovate the production process to move towards the cleaner production as: Energy efficiency improvements; Waste heat recovery; Reduction of clinker/cement ratio and use of alternative raw materials; Substitution of fossil fuels with alternative energy sources. When the GHG emissions at source opportunities are close to being exhausted, the other mitigations options should be considered such as: CO2 capture and storage. This is however in most cases not the final solution from the point of Life cycle assessment (LCA). In recent years various mitigation measures are gaining on the importance and the cement industry is more and more shifting to cleaner production. Among the others, there are two measures, which can reduce the GHG emissions considerably: the use of alternative raw materials and alternative fuels. The challenge for the cement industry is to use alternative raw materials especially those originating from other industries where they are considered as by-products or even waste. Some of these by-products include: Bottom ash from municipal solid waste incinerators; Fly ash from coal power plants; Gypsum from the desulfurization plants used in power plants. Another important measure is the energy efficiency improvement in existing cement plants. There are various approaches for controlling and improving the energy efficiency within existing cement manufacturing units, however, mathematical modelling, simulation, optimisation and Process Integration are increasingly gaining in importance. The mathematical modelling approach uses the numerical simulations for the investigation of the thermo-chemical processes occurring inside of the manufacturing unit. The results gained are being used to enhance the efficiency of cement production. They improve the understanding of the flow characteristics and transport phenomena taking place inside the cement combustion unit. The objective of this paper is to review the current status of the cleaner cement manufacturing, the cement industry's shifting to alternative raw materials and alternative energy sources, and the modelling of the thermo-chemical processes inside the cement combustion units. Additionally, some critical issues, which up to now have not been adequately resolved, are outlined.

The circular economy in the construction and demolition waste sector – A review and an integrative model approach

Abstract: Construction and demolition waste (CDW) is a priority for many policies at global level. This is due to the high volume of CDW that is produced and its inadequate management. This situation leads to serious environmental effects, which are mainly associated with manufacturing processes for new building materials because of low product recovery rates. In this context, the concept of Circular Economy (CE) is a potential solution in many sectors, as it involves more efficient use of resources and energy, which leads to waste minimization and reduction of the environmental impacts of product cycles. Moreover, it represents potential economic opportunities. The main aim of this study was to identify factors that could influence the adoption of the Circular Economy concept in the construction and demolition sector. A systematic literature review was conducted to understand the main strategies involved in the development of integral circular strategies. The main contribution of this paper is a theoretical framework for the Circular Economy in the construction and demolition sector. The framework is comprised of 14 strategies within the five lifecycle stages of construction and demolition activities. Particularly, the framework emphasizes waste management and recirculation of recovered materials for their use as secondary building materials.