Life Cycle Assessment Method Research Articles

Life-cycle analysis of environmental loads from household septic systems in Japan focusing on effluent water discharge

Abstract Various types of small-scale wastewater treatment systems are widely used in rural areas, and life-cycle assessment (LCA) should be performed to evaluate their environmental performance. In this study, septic systems were first classified into five categories based on their wastewater treatment performance. Effluent samples from actual systems were collected, and their water qualities were determined. A model to evaluate the environmental load from the septic systems using LCA methods was then established. The water-quality values obtained were input to the model, and the life-cycle environmental costs of the classified septic systems were calculated. The mean environmental load of the effluent during the operation stage was 37.6%, confirming that evaluation of an effluent discharge inventory using LCA, inspection, and water-quality monitoring to improve operations is critical for reducing the environmental load. The operation stage accounts for over 99% of the involved eutrophication, biological toxicity, and toxic chemicals, which are strongly related to the quality of the effluent. Evaluation of the effluent discharge inventory using LCA is of great significance, even for small-scale wastewater treatment systems. The set of procedures developed in this study can be used to calculate comprehensive environmental impacts at wastewater treatment plants.

Life cycle carbon footprint assessment of coal-to-SNG/methanol polygeneration process

The coal-to-natural gas project alleviates the shortage of natural gas in China by using the abundant coal resources, but it has the problems of single product and poor ability to deal with risks. The coal to synthetic natural gas (SNG)/methanol polygeneration process can solve this by coproducing chemicals and have the advantages of high economic benefit and energy saving. The impact of polygeneration process design on carbon emission reduction is still the key issue to be solved urgently. Therefore, for the coal-to-SNG/methanol polygeneration process, this paper explores the interactions between the polygeneration process design and carbon emissions by using life-cycle assessment method, and evaluates the environmental impact potential of the process. The fluctuations of industrial parameters are also simulated using Monte Carlo analysis, and most of the results are concentrated at ±6.5 %, which verifies the reasonableness of the results. And the carbon emission reduction effect of the polygeneration process is examined by comparing with coal-to-gas and coal-to-methanol processes. The results show that the polygeneration process will reduce carbon emission by about 7.9 % under the same output, which helps to achieve carbon emission reduction.

Livestock greenhouse gas emission and mitigation potential in China

Livestock is an important source of greenhouse gas emissions (GHGE) in China. Understanding the greenhouse gas (GHG) emission trends and reduction strategies in livestock is crucial for promoting low-carbon transformation of the livestock sector (LS) and achieving the goal of “carbon peak and carbon neutralization”. First, based on the life cycle assessment and IPCC coefficient methods, we calculated the GHGE of the LS in 31 provinces of China from 2000 to 2020 and identified the temporal and spatial evolution of GHG emission intensity. The LMDI method was then used to analyze the influence of efficiency, structure, economy, and population size on GHGE. Finally, the STIRPAT model was used to simulate the future evolution trend of the LS emissions under the SSPs scenario. The results revealed that the GHGE in the life cycle of livestock production decreased from 535.47 Mt carbon dioxide equivalent (CO2e) in 2000 to 532.18 Mt CO2e in 2020, and the main source was CH4 emissions from enteric fermentation of livestock. Economic and efficiency factors markedly influenced the changes in GHGE from the LS in China. Further, economic factors contributed >40% to the increase in GHGE in most provinces. Under the SSP1, SSP2, and SSP4 scenarios, livestock production can achieve the carbon peak target in 2030. Under the baseline scenario (SSP2), the GHGE of China's LS in 2030 and 2060 are expected to be 491.48 Mt CO2e and 352.11 Mt CO2e, respectively. The focus of mitigation measures for livestock production in the future is to optimize the production structure of the LS, promote the low-carbon transformation of the energy structure of livestock feeding, and establish an efficient and intensive management model. In addition, we focus on emission reduction in key areas, such as Northeast and Northwest China, while optimizing diet and reducing food waste from the consumer side.

Optimization of rural domestic sewage treatment mode based on life cycle assessment method: A case study of Wuzhong District, Suzhou City, China

Optimizing the spatial layout of sewage treatment facilities and establishing a comprehensive benefit assessment system are imperative for improving the scientific decision-making process of rural sewage treatment modes (RSTMs) in developing countries. Based on the k-means clustering algorithm incorporating population and elevation factors, life cycle theory, and the weighted sum multi-objective optimization approach, this study developed an RSTM evaluation framework to provide spatial layout alternatives and comprehensive environmental-economic benefit assessments. Taking Wuzhong District in Suzhou, China, as an example, the results showed that the improved k-means clustering algorithm enabled the proper distribution of sewage treatment facilities to be established in villages with low elevation and a concentrated population, with a reasonable spatial layout. The entire environmental impact potential and economic cost trends of different RSTMs initially decreased before rising with the increase in facilities. These trends indicated that when facility layouts were too centralized or too decentralized, the environmental impact potential and economic cost increased. Additionally, when environmental impact is a priority factor, more facilities should be built. Alternatively, if economic factors are considered a priority, it is preferable to centralize the domestic treatment in neighboring villages and construct fewer facilities.

Evaluating Nitrogen Management Practices for Greenhouse Gas Emission Reduction in a Maize Farmland in the North China Plain: Adapting to Climate Change.

Quantification of the trade-offs among greenhouse gas (GHG) emissions, yield, and farmers' incomes is essential for proposing economic and environmental nitrogen (N) management strategies for optimizing agricultural production. A four-year (2017-2020) field experiment (including four treatments: basic N fertilizer treatment (BF), suitable utilization of fertilization (SU), emission reduction treatment (ER), and high fertilization (HF)) was conducted on maize (Zea mays L.) in the North China Plain. The Life Cycle Assessment (LCA) method was used in this study to quantify the GHG emissions and farmers' incomes during the whole maize production process. The total GHG emissions of BF, SU, ER, and HF treatments in the process of maize production are 10,755.2, 12,908.7, 11,950.1, and 14,274.5 kg CO2-eq ha-1, respectively, of which the direct emissions account for 84.8%, 76.8%, 74.9%, and 71.0%, respectively. Adding inhibitors significantly reduced direct GHG emissions, and the N2O and CO2 emissions from the maize fields in the ER treatment decreased by 30.0% and 7.9% compared to those in the SU treatment. Insignificant differences in yield were found between the SU and ER treatments, indicating that adding fertilizer inhibitors did not affect farmers' incomes while reducing GHG emissions. The yield for SU, ER, and HF treatments all significantly increased by 12.9-24.0%, 10.0-20.7%, and 2.1-17.4% compared to BF, respectively. In comparison with BF, both SU and ER significantly promoted agricultural net profit (ANP) by 16.6% and 12.2%, with mean ANP values of 3101.0 USD ha-1 and 2980.0 USD ha-1, respectively. Due to the high agricultural inputs, the ANP values in the HF treatment were 11.2%, 16.6%, and 12.4% lower than those in the SU treatment in 2018-2020. In conclusion, the combination of N fertilizer and inhibitors proved to be an environmentally friendly, high-profit, and low-emissions production technology while sustaining or even increasing maize yields in the North China Plain, which was conducive to achieving agricultural sustainability.

Turning dynamic LCA principles into practice

The building and construction sector quantifies the environmental impacts of buildings using the Life Cycle Assessment (LCA) method. To put LCA into practice often simplified application of the LCA method is used, without considering timely aspects. Instead, the method dynamic LCA includes timely aspects, which are more complex in the modeling and thus difficult to apply. To investigate the consequences of using the dynamic LCA method, this study develops a tool that takes data available in a simple LCA tool that follows the standardized LCA method and calculates dynamic LCA results. The tool reimplements the calculation engine from the simple LCA tool and adds the more complex aspects of dynamic LCA afterward. Doing so makes it possible to add other complex methods to the original calculation engine to help investigate more complex methodological aspects in the future.

Readjusting the climate change hyperfocus: how expanding the scope of impact categories will affect the evaluation of wood buildings

The sole focus on reducing the climate impact of dwellings by using wood is neglecting other impacts on nature. Therefore, this study clarifies the potential burden shift by considering ten more impact categories than greenhouse gas emissions. It assesses four wood buildings and one reference concrete building by using the method of life cycle assessment. What stands out is that wood dwellings perform better than the concrete building in most impact categories except for abiotic depletion potential and ozone layer depletion potential (ODP). The latter also experiences an impact increase when wood is used to decrease climate impact as global warming potential (GWP). The wood dwellings have a general inverse correlation between GWP ranking and ODP and some resource use indicators where plastics and cement-based materials influence the latter. Bio-based materials’ contribution to acidification and eutrophication is more considerable than to GWP. Upon the findings, increased inclusion of impact categories among researchers and practitioners must follow to expand the knowledge base. A foundation for future conscious decisions of using wood in dwellings and the challenging debate of reaching consent of which other impact categories should attain focus for being improved.

Investigation of the NO removal process of ultra-low temperature adsorption-rapid regeneration

NO removal facility installed at the very tail-end of the flue gas could reduce the effects of dust and SO2 poisoning, the problem is to figure out how to remove NOx at ultra-low temperature. Relying on rotary reactors, a NOx adsorption-enclosed regeneration process (NAER) was proposed, by which NOx is adsorbed onto the adsorbent at ambient temperature and then to on-site degrade in a high-temperature and enclosed environment with the high-concentration CO. Metal-doped activated carbon emerged as the optimal catalyst for shortening the cooling temperature difference. The results indicated that the maximum adsorption capacity for NO is 38.67 mg/g at 50 ℃, and NO conversion reaches exceed 90 % at 250 ℃ when 1400 ppm CO and 700 ppm NO are introduced into the reactor. The novel enclosed high-concentration of CO reduction regeneration encourages more NO to participate in the reaction, promoting the deep decomposition of nitrate and avoiding the overflow of NOx at the outlet. The difference between the breakthrough time and regeneration time spans 12–21 min. The carbon consumption is 0.0087 %/min, ensuring the long-term and continuous operation of the material. The current study explains the reaction mechanism of NO adsorption via in-situ FTIR. Life cycle assessment method is applied to analyze NAER’s emission standards, while life cycle inventory method calculates the economic cost, which stands at 287.06 RMB. The reduced cost is primarily reflected in the energy and raw materials inputs. The proposed process holds significant potential for optimizing the ultra-low emission of flue gas.

Development of an assessment-based planting structure optimization model for mitigating agricultural greenhouse gas emissions

Optimization of crop structure is an efficient way to reduce greenhouse gas (GHGs) from agriculture production. However, carbon footprint have rarely been incorporated into previous planting structure optimization models due to the challenges of assessing the spatial and temporal distribution of agricultural carbon footprint for multiple crops in irrigated districts. In addition, previous planting structure models suffered from strong subjectivity in objective function determination, and the obtained non-dominated solution set offered difficulties to decision-makers in selecting specific implementation options. To fill such gaps, an integrated accounting-assessment-optimization-decision making (AAODM) approach was proposed, which remedies the shortcomings of previous crop planting structure optimization models in carbon footprint mitigation, and overcomes the subjectivity of objective function determination and the difficulty in selecting specific implementation options. Firstly, life cycle assessment (LCA) method was used to account for the multi-year agricultural carbon footprints of multiple crops in the irrigation district. The optimization objective functions of planting structure optimization models can then be determined based on the assessment method of carbon footprint influencing factors. Next, the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) was used to generate a non-dominated solution set of the optimization model. The optimal planting structure can be finally obtained based on decision making methods by determining the maximum harmonic mean (HM) and knee points (KPs) of the non-dominated solution set. The developed AAODM approach was then applied to a case study of agricultural crop management in Bayan Nur City, China. The results showed that the level of economic development was a key factor influencing the increase in carbon footprint in Bayan Nur City over the past 20 years. The regulation of the level of economic development would significantly influence the agricultural carbon footprint in Bayan Nur City. Moreover, two optimal crop cultivation patterns were provided for decision-makers by selecting solutions from the Pareto front with decision making methods. The comparison results with other methods showed that the solutions obtained by NSGA-II were superior to MOPSO in terms of carbon reduction. The developed AAODM approach for agricultural GHG mitigation could help agricultural production systems in achieving low carbon emissions and high efficiency.

Framework for Increasing Eco-efficiency in the Tofu Production Process: Circular Economy Approach

Abstract This research aims to design recommendations for improving the tofu production process in Sugihmanik Village. Over 30 tofu small medium enterprises (SMEs) generate solid and liquid waste, which pollutes the river. An eco-efficiency strategy was implemented and began by identifying the tofu production process. The life cycle assessment (LCA) method and the SimaPro software were used to calculate eco-cost and eco-efficiency levels. Based on the calculations, the eco-cost value per batch is USD 10.76. If 30 batches are produced daily, the eco-cost value in one of the tofu SMEs is USD 9.10. Tofu production has an eco-efficiency index (EEI) value of 0.12. This value shows that tofu products are only affordable but have yet to be sustainable. The researchers then recommend using biogas from wastewater treatment to replace rice husks and corncobs. This study also develops a circular economy framework in the tofu production system. The output is expected to suppress the discharge of water and solid waste to increase the EEI value of the tofu production process in the future.

Multifactor configurations of coal power technology in China substantially differ in life-cycle environmental impacts

The expansion of coal power in China has led to a coexistence of multiple technologies, whereas differences in environmental impacts of each other remain hitherto unclear. This gap is largely a result of the difficulty of fully covering the factors that significantly affect environmental performances and the lack of fine data inventory. The limitation welcomes an approach that can go well beyond characterizing coal power technology with a single factor. To this end, we surveyed the information data for all coal power units in China to couple four factors (viz. operating parameter, boiler type, cooling approach, and turbine mode) into 22 types of multifactor technology configurations, as well as the first-hand operating data of nearly half of all coal power units in China to compile an elaborate data inventory that each configuration includes 88 input and output data. These fine data were modeled by the life cycle assessment method of CML 2016 to quantify twelve environmental impact categories. The results show substantial differences in environmental impacts exist for different technology configurations. High operating parameters gain environmental friendliness but the diversification of boiler type and cooling approach to improve the applicability of coal quality and water resources increases environmental impacts. The insignificant impact of the turbine mode is owning to the exergy allocation that eliminates the quality gap in electrical and thermal energy. The technology-level differences are aggregated into the provincial level by various configuration structures, which show markedly spatial heterogeneity varying by impact categories. This implies a great potential for structural adjustment and an overall improvement requires cleaner production beyond that, focused on the coal power generation process and its upstream coal supply process. Our modeling shows a majority of results with an uncertainty of lower than 10 %, which is robust for the proposal of policy suggestions.

Determination of Environmental Impacts Using Life Cycle Assessment of Plants Grown for Bioenergy: Example of Sorghum x Sudan Grass Hybrid

Renewable energy sources are the most effective and cheapest method in combating climate change. Biomass, which is one of the renewable energy sources, is also one of the raw materials of biofuels. Sorghum x sudan grass hybrid, which is drought tolerant and has a short vegetation period, is one of the biomass sources. This study was carried out to determine the ethanol yield of sorghum x sudan grass hybrid plant grown in an area with a semi-humid climate and to determine the environmental impacts of biomass. Environmental impacts were assessed using the life cycle assessment method. Environmental impact categories are divided into 11 categories according to the CML-IA Baseline model. As a result, the biomass yield was 49888 kg ha-1 and the ethanol yield was 1674.1 l ha-1. According to the life cycle impact category of sorghum x sudan grass hybrid biomass production, it was determined that the highest environmental impact was 79.21%, causing the marine aquatic ecotoxicity. According to the life cycle interpretation, it was determined that it caused a global effect with a rate of 83.87%. In addition, the global warming value was calculated as 0.195 kg CO2-eq kgbiomass-1 (9728.16 kg CO2-eq ha-1). It has been determined that the agricultural phases that have the most negative impact on the environment are irrigation and fertilization.

Potential Integration of Bridge Information Modeling and Life Cycle Assessment/Life Cycle Costing Tools for Infrastructure Projects within Construction 4.0: A Review

Construction 4.0 is a platform that combines digital and physical technologies to enhance the design and construction of the built environment. Bridge Information Modeling (BrIM), a component of Construction 4.0′s digital technologies, streamlines construction processes and promotes collaboration among project stakeholders. In this study, a comprehensive literature review and bibliometric and content analysis are conducted on building information modeling (BIM), life cycle assessment (LCA), life cycle cost (LCC), BrIM, and Bridge LCA. This study investigates the potential integration of BrIM, LCA, and LCC as inputs for bridges’ LCA to enhance decision making by providing designers with detailed and interactive cost and environmental information throughout an asset’s lifecycle and explores the functionalities of Construction 4.0 and its potential influence on the economy and sustainability of bridge projects. The reviewed literature showed that the tools currently used to apply LCA and LCC methods for infrastructure assets lack the ability to identify possible integration with BrIM and hold limitations in their key functions for identifying the utmost features that need to be adopted in the creation of any tool to increase the general resilience of bridges and infrastructure.

Research on reuse of shield soil dregs on synchronous grouting materials and its application

Shield tunnel construction will produce a large amount of soil dregs. Transporting soil dregs directly to landfills raises costs and CO2 emissions. In this paper, the shield tunnel of Intercity from Shenzhen to Huizhou is taken as an example, based on the special treating agent of shield soil dregs, the soil dregs were prepared as synchronous grouting material. The working performance and mechanical properties of soil dregs grouting material were studied. The optimal dosage of the treating agent was proposed, and the curing mechanism of the soil dregs synchronous grouting material was analyzed. The soil dregs grouting material was applied to practical engineering, and the application effect was verified by surface subsidence monitoring. The results showed that the setting time, bleeding rate, stone rate and compressive strength of the soil dregs grouting material were better than cement mortar grouting material. The treating agent realized the cementation of soil particles through the synergistic effect of epoxy resin and nano-SiO2, and the optimum dosage is 0.02 % of the solid component. The maximum surface settlement of the soil dregs grouting construction section was 10 mm, which is smaller than the maximum surface settlement of the cement mortar grouting section. Through the life cycle assessment (LCA) method, the CO2 emission reduction capacity of the soil dregs synchronous grouting material was analyzed. The soil dregs grouting material reduced the production and transportation of fly ash and bentonite, and reduces the outward transportation of soil dregs. The use of 1 t soil dregs synchronous grouting material can reduce 59.05 kg CO2 emission.

Comparative Life Cycle Assessment of Alternative Marine Fuels

With the stricter rules introduced by the policymakers in maritime transportation, harmful emissions are aimed to be mitigated. Consequently, studies on alternative fuels have emerged, and different methods had adopted to evaluate fuel choices. Within this context, a well-to-wake life cycle assessment method is used to determine the environmental impacts of the fuel options. Included fuels in the study are ammonia, biodiesel, Dimethyl ether, electro Fischer Tropsch diesel fuel, electro methanol, Fischer Tropsch diesel fuel, hydrogen, liquefied natural gas, liquefied petroleum gas, marine diesel oil, marine gas oil, marine bio-oil, methanol, pyrolysis oil, renewable diesel, straight vegetable oil, and ultra-low sulfur heavy fuel oil. The paper aims to evaluate the fuels according to the 2050 strategy of the International Maritime Organization. Hence, black carbon, carbon monoxide, carbon dioxide, nitrous oxide, nitrogen oxide, sulfur oxide, particulate matter, methane, and volatile organic compounds are considered emissions. During the study, an ocean tanker model available in the GREET Model 2022 was used for life cycle inventory analysis, and life cycle assessment was conducted by Environmental Footprint Method 3.0, which is included in the OpenLCA. The assessment was carried out according to climate change, acidification, freshwater ecotoxicity, marine eutrophication, terrestrial eutrophication, non-cancer human toxicity, particulate matter, and photochemical ozone formation criteria. The results show that out of eight criteria, marine bio-oil became the most dominant choice due to the consumption of CO2 and methane while producing and low emission generation during combustion.

Embodied carbon quantification of luminaires using life cycle assessment and CIBSE TM65 methodologies: A comparison case study

AbstractThe European legislative landscape on sustainability is steadily growing to meet objectives to reach net zero targets by mid‐century. In this context, companies and manufacturers may soon be legally required to provide quantification of the environmental impact of their products and services. A key challenge is applying a consistent and robust methodology that ensures comparability between assessments made by different companies, as there is still fragmentation among environmental impact reporting methodologies. The objective of this study is to analyze and compare the results of two different methodologies for the calculation of the embodied carbon in lighting products using the cradle‐to‐grave approach. One is the globally known life cycle assessment (LCA) method, and the other is Chartered Institution of Building Services Engineers Technical Memorandum 65's (TM65) mid‐level calculation methodology, which has been specifically tailored to building services. The two were applied to six different luminaires to evaluate their differences. Results show that the values of the embodied carbon calculated with TM65 are higher than those calculated with LCA and that the weight of the products plays a crucial role in creating discrepancies between the two methodologies.

Techno-Economic Analysis of State-of-the-Art Carbon Capture Technologies and Their Applications: Scient Metric Review

Carbon dioxide (CO2) emissions are a serious hazard to human life and the ecosystem. This is the reason that many measures have been put in place by the International Energy Agency (IEA) to reduce the anthropogenic-derived CO2 concentration in the atmosphere. Today, the potential of renewable energy sources has led to an increased interest in investment in carbon capture and storage technologies worldwide. The aim of this paper is to investigate state-of-the-art carbon capture and storage (CCS) technologies and their derivations for the identification of effective methods during the implementation of evidence-based energy policies. To this extent, this study reviews the current methods in three concepts: post-combustion; pre-combustion; and oxy-fuel combustion processes. The objective of this study is to explore the knowledge gap in recent carbon capture methods and provide a comparison between the most influential methods with high potential to aid in carbon capture. The study presents the importance of using all available technologies during the post-combustion process. To accomplish this, an ontological approach was adopted to analyze the feasibility of the CCS technologies available on the market. The study findings demonstrate that priority should be given to the applicability of certain methods for both industrial and domestic applications. On the contrary, the study also suggests that using the post-combustion method has the greatest potential, whereas other studies recommend the efficiency of the oxy-fuel process. Furthermore, the study findings also highlight the importance of using life cycle assessment (LCA) methods for the implementation of carbon capture technologies in buildings. This study contributes to the energy policy design related to carbon capture technologies in buildings.

Comparison of Methods for Calculating Indirect Upstream Carbon Emissions from Information and Communication Technology Manufacturing

The use of Information Communication technology (ICT) is rapidly increasing in an age of digitalization. Measurement of carbon dioxide equivalent (CO2e) emissions from ICT is crucial for reducing them. Most ICT organizations focus on Scope 1 and 2 emissions as they have greater control over them, commonly ignoring Scope 3 emissions. Scope 3 Category 1 (S3C1) emissions occur throughout the raw material acquisition and manufacturing stages of an ICT product's life cycle accounting for a large portion of the sector's overall CO2e emissions and energy consumption. By not reporting Scope 3 emissions, companies lose the ability to reduce their overall CO2e corporate emissions. Although Category 1 and 11 under Scope 3 account for 85% of ICT's worldwide CO2e emissions, the methodologies for calculating S3C1 emissions in ICT are understudied. This study focuses on these emissions in the framework of Sustainable Development Goals 9, 12, and 13. Product life cycle assessment (PLCA) and Spend-based methods have been used to analyze S3C1 emissions in the ICT sector with two case examples of laptop computers and smartphones. The Excel Management Life Cycle Assessment (EMLCA) tool has been used for the S3C1 emissions estimation. PLCA and Spend-based methods are compared on their ability to calculate CO2e emissions. It is concluded that the Spend-based is faster than PLCA for predicting ICT emissions with modest uncertainty for smartphone and laptop components. Furthermore, this work explores the advantages and downsides of both methods.

Effects of Straw Biochar on Carbon Footprint of Maize Farmland Ecosystem Under Mulched Drip Irrigation in Hetao Irrigation District

To explore the effect of biochar on greenhouse gas emissions and the carbon footprint of a corn farmland ecosystem under drip irrigation with film in an arid region, biochar treatments with different application rates[0 (CK), 15 (C15), 30 (C30), and 45 t·hm-2 (C45)] were established. The seasonal changes in soil greenhouse gases (CO2, N2O, and CH4) and their comprehensive warming potential in the maize farmland ecosystem were monitored for two consecutive years after a one-time application of biochar. The carbon emissions caused by agricultural production activities and their carbon footprint were estimated using the life cycle assessment method. Compared with that in CK, the cumulative CO2 emissions in the crop growing season decreased by 17.6%-24.7%, the cumulative N2O emissions decreased by 71.1%-110.4%, and the global warming potential decreased by 19.5%-25.9%. In the second year of the crop growing season after biochar application, the cumulative CO2 emissions were reduced by 19.2%-40.6%, the cumulative N2O emissions were reduced by 38.7-46.7%, and the comprehensive warming potential was reduced by 19.7%-40.5%. For two consecutive years, the treatment of C15 and C30 increased the cumulative absorption of CH4 to different degrees, whereas the treatment of C45 significantly decreased the cumulative absorption of CH4. C15 and C45 were the treatments with the least carbon footprint per unit yield in the current and the succeeding year of biochar application, and their carbon footprint per unit yield was 10.1% and 26.2% lower than that of CK, respectively. Soil greenhouse gas emissions showed the most contribution to the carbon footprint of the maize farmland ecosystem (38.1%-59.2%), followed by nitrogen fertilizer production (19.8%-33.4%), electric energy production (6.7%-8.8%), and plastic film mulching (4.4%-7.4%). Biochar contributed 5.7%-13.8% to the ecosystem's carbon footprint. The application of 30 t·hm-2 biochar had a better effect on carbon reduction, carbon fixation, and yield increase in the farmland ecosystem. Improving the biochar production process and transportation route, increasing nitrogen use efficiency, and developing water-saving and energy-saving irrigation technology are important ways to reduce the carbon footprint of farmland ecosystems in arid regions.

The influence of air pollution control devices on gas organic pollutants emission from coal-fired power plants based on LCA

Air pollutants (e.g., NOx, SO2) emitted from coal-fired power plants in China have been effectively controlled by Air Pollution Control Devices (APCDs) since 1996. However, the gas organic pollutants (typically Volatile Organic Compounds (VOCs) and Polycyclic Aromatic Hydrocarbons (PAHs)) have been overlooked for a long time. In this study, based on the life cycle assessment method, the effect of APCDs (mainly Selective Catalytic Removal (SCR), Electrostatic Precipitator (ESP), Wet Flue Gas Desulfurization (WFGD), and Wet Electrostatic Precipitator (WESP)) on gas organic pollutants (without methane) from three typical coal-fired power plants in China has been evaluated in terms of direct emission removal and indirect emissions. Detecting the gas organic pollutants concentrations at the inlet and outlet of APCDs in these three cases, it is found that the total direct emission removal efficiency is up to more than 71.97%, with SCR’s contribution being the highest. However, the manufacture and equipping of APCDs will lead to indirect emission of gas organic pollutants. The result shows that the SCR system is also the main process that induces indirect emissions of gas organic pollutants, associated with the utilization of liquid ammonia and catalyst. Compared to the direct emission of gas organic pollutants, indirect gas organic pollutants emissions can not be ignored. The calculation of net emission removal and the degree of co-effects shows that APCDs can reduce gas organic pollutants, which results in reducing the photochemical ozone creation potential of 1.81E-06~5.93E-06kg(Ethene eq.)/MW·h and human toxicity potential of 2.51E-03~8.06E-03kg (DCB eq.)/MW·h.