Total Emergy Research Articles

Emergy-Based Evaluation of the Sustainability of Agricultural Ecosystem in Dazhou, China, from 2002 to 2022

Our aim is to analyze the emergy evaluation indicators of the agricultural ecosystem in Dazhou, northeastern Sichuan, and provide practical and effective recommendations for sustainable agricultural development. Using emergy analysis, the emergy inputs and outputs of an agricultural ecosystem from 2002 to 2022 were calculated. Five emergy indicators were selected for evaluation: emergy yield ratio (EYR), emergy self-sufficiency ratio (ESR), emergy input ratio (EIR), environmental load ratio (ELR), and emergy sustainable indices (ESI). The total emergy input of the agricultural ecosystem showed an upward trend from 2002 to 2017, thus the industrial auxiliary emergy input decreased, somewhat curbing its continued rise from 2017 to 2022. The structure of emergy inputs, in descending order, is as follows: industrial auxiliary > organic emergy > renewable environmental resources > non-renewable environmental resources. The total emergy output of the agricultural ecosystem was highest in 2007, reaching 2.31 × 1022 Sej, and lowest in 2012, at 1.83 × 1022 Sej. The structure of emergy outputs, in descending order, is as follows: livestock > planting > fishery > forestry. The emergy yield ratio fluctuated down from 3.12 to 2.51, with an average of 2.88, below the provincial average of 3.07. The emergy self-sufficiency ratio fluctuated down from 0.30 to 0.26, with an average of 0.27, above the provincial average of 0.13. The emergy input ratio fluctuated up from 2.31 to 2.91, with an average of 2.66, above the provincial average of 1.86. The environmental load ratio fluctuated from 3.8 to 4.75, with an average of 4.40, which is higher than the provincial average of 1.68. The emergy sustainable indices fluctuated down from 0.81 to 0.53, with an average of 0.67, below the provincial average of 1.17. The efficiency of resource utilization in the agricultural ecosystem of Dazhou has decreased, economic inputs have increased, and it is in a consumptive production process. The pressure on the local natural environment is increasing, and the capacity for sustainable development remains at a low level over the long term.

Emergy-Based Evaluation of Xiaolangdi Reservoir’s Impact on the Ecosystem Health and Services of the Lower Yellow River

The disturbance in river ecosystems caused by reservoirs and dams has become a critical topic, attracting increasing attention. However, the extent to which reservoir and dam construction and operation impact downstream river ecosystem health and ecosystem service functions is not fully understood. This research examines the Xiaolangdi Reservoir and the Lower Yellow River (LYR) ecosystem in China as a case study. We analyzed the complex material and energy flows in the LYR ecosystem using emergy theory and developed a set of emergy-based indicators for the quantitative assessment of river ecosystem health and services under reservoir operation interference. The results indicate that the total natural capital and environmental endowments of the LYR ecosystem have remained relatively stable after the operation of the Xiaolangdi Reservoir, with an increase in renewable emergy input. The ecosystem’s vigor decreased slightly, while the biomass emergy diversity index remained stable. However, the total emergy inputs increased significantly, with external feedback inputs becoming the most important emergy source for the LYR ecosystem. The resilience of the LYR ecosystem improved, with a significant increase in emergy density and a decrease in the emergy sustainability index. These findings suggest that although the river ecosystem continues to provide supporting services to human society, the extent of these services has diminished compared to pre-perturbation levels. In this research, a methodology for analyzing the impact of key reservoir operations on the ecosystem health and services of a large river is proposed to provide support for large river sustainable development studies.

Rethinking the China-U.S. Trade balance from 2001–2020 based on emergy perspective

In the year 2018, escalating trade imbalances between China and the United States led to a trade war over tariffs and trade policies that garnered global attention. While trade deficits are primarily reflected in currency terms, trade involves a broader exchange of different resources. Hence, this study employs Emergy Accounting approach (EMA), an environmental quality-oriented assessment method, to collect official statistical data from both countries and consider differences in statistical data weight. Utilizing the NEAD V2.0 database, this research calculates and discusses the total emergy flow, trade imbalances, and structures in China-U.S. trade from 2001 to 2020. Additionally, it computes and analyzes emergy indicators, delving into the dynamic changes in the emergy values of various categories of goods. The results indicate a gradual balance in the emergy trade deficit between China and the United States, with both countries benefiting from the trade. Specifically, China benefits from importing raw materials from the United States, while the U.S. gains from importing inexpensive embodied labor from China. Considering differences in data statistical calibers and applying the EMA contribute to a more accurate understanding of the trade situation and the correction or prevention of errors. The Emergy theory provides a new perspective for a comprehensive assessment of trade relationships. China and the United States have the potential to establish a fairer, more balanced, collaborative, and sustainable trade relationship, contributing to global sustainable development.

Optimizing Ghana’s Socioeconomic Metabolism Amid Urbanization from 2000 to 2019: An Emergy Synthesis

This study assessed Ghana’s sustainability from 2000 to 2019 using emergy synthesis. This research study also explored the relationship between changes in Ghana’s socioeconomic metabolism and the expansion of urban areas. The results showed a significant increase of 126% in total emergy use during the study period. This increase was mainly due to a rise in import emergy, which went up from 2.90% to 37.47%, while Ghana’s self-sufficiency capacity decreased from 97.10% to 62.53%. This shift in total emergy utilization indicates that Ghana’s socioeconomic system is transitioning from relying heavily on indigenous resources to increasingly depending on purchased resources to drive economic growth. The emergy sustainability index (EmSI) suggests that Ghana’s socioeconomic system is resource-consuming and has low system performance. To address this situation, this study recommends restructuring Ghana’s socioeconomic system to optimize its indigenous renewable resources while reducing import dependency and environmental stress. Expanding urban areas contributes to resource consumption, especially refined fuels and construction materials. This underscores the importance of urban policies that take into account changes in socioeconomic metabolism as a reference for effective urban land administration.

Spatial Analysis on Resource Utilization, Environmental Consequences and Sustainability of Rice–Crayfish Rotation System in Jianghan Plain, China

The rice–crayfish rotation system (RCR), originating in the Jianghan Plain, is developing rapidly in various regions of China and has been characterized by unbalanced regional development, which has also led to widespread concerns and discussion on its environmental impacts and sustainability. This study selects representative RCR production areas in the Jianghan Plain, including Jianli, Qianjiang, Shishou, Shayang, Gong’an and Honghu, to analyze resource inputs, resource utilization efficiency, environmental impacts and sustainability by employing the emergy analysis method. Our analysis of Jianli, Honghu, Qianjiang, Gong’an, Shishou and Shayang reports total emergy inputs ranging from 6.46 × 1016 to 8.25 × 1016, with renewable rates between 78.38% and 84.34%. Shishou leads in the unit emergy value (5.58 × 10−1) and the emergy yield ratio (5.30). The sustainability evaluation finds that the environmental loading ratio is from 0.19 to 0.28 and the emergy index for sustainable development varies between 1.27 and 3.00. This analysis indicates that the southern regions have higher inputs and efficiency, with southeastern areas showing lower environmental impact and higher sustainability. We also underscore the impact of non-renewable resources on environmental outcomes and sustainability, suggesting tailored development strategies for the rice–crayfish rotation system’s optimization and sustainable growth.

Study on the Structure, Efficiency, and Driving Factors of an Eco-Agricultural Park Based on Emergy: A Case Study of Jinchuan Eco-Agricultural Park

The eco-agricultural park is a new comprehensive agricultural technology system integrating agricultural production, rural economic development, ecological environment protection, and efficient resource utilization. Therefore, an in-depth analysis of the ecosystem structure of eco-agricultural parks will help achieve the goal of coordinated symbiosis between human development and environmental protection. This study takes the research area of the Eco-agricultural Park of Jinchuan Town, Huinan County, a typical town in the Changbai Mountains of Northeast China. Based on field surveys, market research, farmer consultation, and related data collection, emergy theory and methods are used to construct an emergy model for the park. The value evaluation index system integrates the unique emergy index of the agricultural ecosystem with the traditional emergy index system to conduct a targeted evaluation of the park’s functional structure and sustainable development capabilities in order to improve the efficiency of material and energy use and provide technical reference for ecological construction and comprehensive development of agricultural industry in mountainous areas in northern China. The research results show that: (1) The annual input total emergy of the eco-agricultural park is 4.04E+24 sej/a, and the emergy of labor input, electricity input, and topsoil loss is relatively high. The park is in a labor-intensive stage. The annual output total emergy is 5.09E+24 sej/a, the park is dominated by planting and forestry industries. (2) The park’s emergy utilization intensity is high—production efficiency is high, economic development is advanced, and the system’s self-control, adjustment, and feedback functions are vital—and plays a significant role in promoting the development of the regional economy. However, the park relies more on investment from external resources, and production in the park puts pressure on the environment. (3) The current sustainable development capability of the study area is weak, and the factors affecting the sustainable development capability are mainly energy loss and uneven distribution of industrial areas in the park. Effective measures to promote the transformation of the park to develop technology-intensive industries and improve the sustainable development performance of the park were proposed. These include: adjusting the proportion of industries in the park; reducing high-energy external input emergy, such as industrial auxiliary emergy; reducing the loss of non-renewable natural resources through ecological engineering measures, such as reducing the depth of slope runoff in the park; and combining modern resource-based production technology and environmentally sound management methods to reduce energy loss and rational use of natural resources.

Sustainability evaluation of a PEMFC system for coalbed methane recovery based on life cycle assessment and emergy analysis

To promote the sustainable development of clean energy, a novel integrated system coupled coalbed methane recovery and proton exchange membrane fuel cell (PEMFC) is developed. Life cycle assessment (LCA) and emergy analysis model are established to analyze sustainability of the proposed system. The parametric analysis is performed to assess the effects of the reforming temperature, steam carbon ratio and current density on the emergy performance. The LCA results indicate that the construction phase has the most significant impact on system sustainability, accounting for 51.65%. Reducing the use of stainless steel and copper in the construction phase and improving the recycling process in the recovery phase can help improve the sustainability performance. The emergy analysis results show that the total emergy consumption of the system is 8.53E+16, the use phase accounted for 55.8%, the construction phase accounted for 43.8%, and the recovery phase only accounted for 0.4%. Parametric analysis shows that the emergy savings ratio increases by 7.11% as the reforming temperature is 800 °C. The emergy sustainability index ranges from 3.04 to 4.45 with great sustainability performance, as the increase of steam carbon ratio. The system has low environmental load and high sustainability when the current density is close to 1. This research will help improve the sustainability evaluation system of the energy system and promote the sustainable development of clean energy.

Sustainability of frankincense production in Tigray, Ethiopia: an emergy synthesis

The frankincense from Boswellia papyrifera plays important roles in rural livelihoods and the national economy. On the other hand, Boswellia papyrifera is under threat of extinction. Nevertheless, little is known about the sustainability and fair-trade relationship of the current production system of the frankincense commodity. The current paper primarily analyzed sustainability of the production, processing, and exporting systems of frankincense production using the total emergy flows to the product. Data were primarily collected through key informant interviews and from secondary sources in the Tigray region, northern Ethiopia. An emergy synthesis method was used to assess the direct and indirect environmental energy requirements for the production, processing, and exporting of frankincense. The Emergy Sustainability Index (ESI), and Ratios were used as indicators of ecological sustainability. Whereas the Emergy Exchange Ratio (EER) was used to evaluate the level of fair trade of frankincense with importing countries. The average total emergy of the system was 50.14E+20sej/year, of which 3.92E+20sej are from local renewable, 45.20E+20sej from local nonrenewable and 1.02E+20sej from imported nonrenewable sources. The Percent Renewable (% Ren), Environmental Loading Ratio (ELR), Emergy Yield Ratio (EYR) and ESI were 7.82, 11.79, 49.50 and 4.19, respectively. The EER showed that the region exported 11.8 times more emergy in frankincense products than it received in the money paid for it in 2008/09, showing unfair trade between the exporting and importing countries. According to our results, it can be concluded that the current production, processing, and exporting of frankincense is not sustainable.

Integrated life cycle assessment and emergy analysis of liquid dehumidification absorption refrigeration driven by solar energy

The cascade utilization of solar energy is significant in alleviating energy and environmental problems. A novel solar-driven liquid dehumidification cascade absorption refrigeration (SLDAR) system applied to hot summer and cold winter areas of China is proposed in this paper. In order to evaluate the environmental and economic sustainability of the system, an integrating life cycle assessment and emergy analysis (LCA-EmA) method is developed. Parameter sensitivity analysis is conducted to determine the effects of solar radiation intensity, air temperature and relative humidity on the sustainability of the system. The results reveal that the total potential environmental impact of the system is 7.29E+03, of which the construction stage accounted for the most part of 65.36%. The total emergy input of the system is 1.61E+17 sej/yr, the operation stage accounted for the highest proportion of 73.29%. According to the integrated LCA-EmA, the emergy sustainability index of the system is 3.89, which reduces by 29.01% than the result of the emergy analysis. The parameter sensitivity analysis states that the system has higher resource use efficiency and emergy yield ratio in higher solar radiation intensity. And the emergy sustainability index of the system increases first and then decreases as the air temperature increases. The environmental load rate increases by 15.19% and the emergy sustainability index decreases by 44.50% as the increase of relative humidity. This study proves the feasibility and sustainability of the solar-driven cascade system.

A Sustainability Analysis Based on the LCA–Emergy–Carbon Emission Approach in the Building System

Ecologically sustainable buildings and their carbon emissions are two popular ideas for building life cycle systems. It is a challenge to comprehensively assess the sustainability of building cases using two different methods. Based on over a decade of research, this paper attempts to explore the possibility of quantitatively integrating both approaches. In this study, we adopted the emergy method and carbon emission approach to assess and analyze a building system. In particular, similarities and differences have been identified through emergy and carbon emissions at each stage of the building’s whole life cycle. The results demonstrate that the building operation phase is the critical contributor (Approximately 79.6% of the total emergy and 97.9% of the entire carbon emission), which occupies the most emergy and carbon emission amounts of the whole building system. In order to improve the ecological sustainability of the building system, renewable energy subsystems are considered and explored. While the overall sustainability of the building system is enhanced, the new systems will aggrandize the carbon emissions. Therefore, the ecological sustainability of building systems and carbon emissions should be considered comprehensively, and the relationship between the two views needs to be balanced.

Emergy-based sustainability evaluation model of hydropower megaproject incorporating the social-economic-ecological losses

The sustainable development of the hydropower megaproject (HM) is one of the critical components of sustainable water resources management. Hence, an accurate assessment of the impacts of social-economic-ecological losses (SEEL) on the sustainability of the HM system is of utmost importance. This study proposes an emergy-based sustainability evaluation model incorporating the social-economic-ecological losses (ESM-SEEL), which integrated the inputs and outputs during HM's construction and operation into an emergy calculation account. The Three Gorges Project (TGP) on the Yangtze River is selected as a case study to comprehensively evaluate the HM's sustainability from 1993 to 2020. Subsequently, the emergy-based indicators of TGP are compared with several hydropower projects in China and worldwide to analyze the multi-impacts of hydropower development. The results showed that the river chemical potential (2.35 E+24sej) and the emergy losses (L) (1.39 E+24sej) are the primary emergy inflow sections (U) of the TGP system, accounting for 51.1% and 30.4% of the U, respectively. The flood control function of the TGP produced tremendous socio-economic benefits (1.24 E+24sej), accounting for 37.8% of the total emergy yield. The resettlement and compensation, water pollution during operation, fish biodiversity loss, and sediment deposition are the main L of the TGP, accounting for 77.8%, 8.4%, 5.6%, and 2.6%, respectively. Based on the enhanced emergy-based indicators, the assessment reveals that the sustainability level of the TGP falls in the middle range compared to other hydropower projects. Thus, along with maximizing the benefits of the HM system, it is necessary to minimize the SEEL of the HM system, which is a critical approach to promote the coordinated development of the hydropower and ecological environment in the Yangtze River basin. This study helps to understand the complex relationship between human and water systems and provides a novel framework that can be used as an evaluation index and insights for hydropower sustainability assessment.

Availability and 6E assessment and optimal design of a novel cogeneration system based on integrated turbo compressor station - SOFC-solar-geothermal-steam and organic Rankine cycles with machine learning

A novel integrated cogeneration system for a real gas turbocompressor station has been proposed. Also, a new systematic approach has been introduced for analysis and optimization of the considered system based on using energy, electrochemical, exergy, exergoeconomic, exergoenvironmental, emergoeconomic, and emergoenvironmental analyses along with advanced exergy, economic and environmental evaluations, and availability assessment. In addition, a powerful machine learning tool has been employed to reduce optimization algorithm computational time.To show the ability of the proposed system and systematic approach, a gas injection station with three gas turbine (GT) drivers have been studied. To improve the performance from the thermodynamic, economic, and environmental points of view and to the application of renewable energies, the integrated system includes turbocompressors with solid oxide fuel cells (SOFC), steam, and organic Rankine cycles (SORCs) while using solar and geothermal energies has been proposed for the power and steam production. In addition, six-objective optimization has been done with a genetic algorithm, and finally, the availability assessment was applied for basic (turbocompressors) and the proposed cycle. To reduce the computational time of the optimization algorithm, the machine learning method has been employed to generate 6E objective functions.Results show the power generation is increased by about 60%, and 6370kg/h of process steam is produced. Five organic fluids were examined, and among them, R11 was found to be the best selection. Energy and exergy efficiencies increased by 12.8% and 10.8%, respectively, compared to the base cycle. Also, the results show that cost, environmental impact, and total emergy of electricity generation are 49.59 $/MWh, 26.99 Pts/MWh, and 4.09e12 sej/MWh. The advanced analysis states that REC1, LPSUP, and REC2 have the greatest potential for energetic, economic, and environmental improvements. In the optimal conditions, the results of the 6E analyses indicate that thermal and exergy efficiencies of 3.06% and 2.84%, and perspective of economic, environmental, and emergy per unit of power generation, 9.54%, 8.86%, and 9.05% of improvement is achieved, respectively. The availability of the proposed system was obtained at 87.28%, and the probability of failure of a GT is reduced by 0.14% compared to the base cycle, indicating the proposed plan's attractiveness.

Emergy evaluation of a solar-powered cascade system for dehumidification, cooling and heating in hot summer and cold winter areas of China

A solar-powered cascade system is proposed for dehumidification, cooling and heating in hot summer and cold winter areas of China. To evaluate the energy, environmental and economic sustainability of the system, the emergy evaluation of the proposed system is analyzed and compared with different energy sources. The effects of solar radiation intensity, air temperature and relative humidity on the emergy performance of the system are discussed. The results show that the input total emergy and transformity of the proposed system are 9.88 × 1016 sej/y and 4.75 × 105 sej/J, which are lower than that of the systems powered by other energy. The environmental load ratio and emergy sustainability index are the highest when the system is powered by solar energy, with the value reaching 1.33 and 1.66, respectively. According to parameter sensitivity analysis, the total emergy input decreases by 6.31% and the emergy saving ratio increases by 29.09% as the increase of solar radiation intensity. The system has the best emergy performance at air temperature of 26.18 °C. The system has lower environmental load and higher sustainability in lower relative humidity climate. This work proves the viability and sustainability of the novel cascade system.

Which rice farming system is more environmentally friendly in Khuzestan province, Iran? A study based on emergy analysis

This research was conducted with the aim of (i) evaluating the sustainability of three rice production systems (DBS: dry bed seeding, TP: transplanting, and WBS: wet bed seeding) in Khuzestan province, Iran, (ii) introducing the most cost-effective and sustainable system, and (iii) providing solutions to increase the systems' sustainability and efficiency. In order to analyze the studied systems during the 2020–2021 growing season, several emergy-based and economic indicators were analyzed. The total emergy inputs supporting the systems are estimated to be 2.69E+16, 4.16E+16, and 3.17E+16 sej ha−1 yr−1 for DBS, TP, and WBS, respectively. The three studied farming systems were determined to be inefficient and unsustainable due to their reliance on purchased resources including labor, fossil fuel, and seed/transplant. According to the environmental loading ratio and modified environmental loading ratio indicators, the WBS and TP systems exerted less pressure on ecosystems and were more sustainable than the DBS system due to the greater quantity of purchased renewable flows (labor and seed/transplant). The results of the emergy renewability, emergy sustainability index, and modified emergy sustainability index indices indicated that the three investigated systems were not sustainable, indicating that high energy consumption in rice farming systems resulted in a significant environmental burden. The economic analysis of rice production systems revealed that the DBS system was economically superior due to its lower total production costs, especially labor costs, when compared with the other two systems. In light of the water scarcity crisis in Iran, the DBS method is recommended due mainly because of its ability to save 30–60% of irrigation water in the studied areas compared with the other two systems that have high water consumption. Due to the lower sustainability and greater environmental pressure of the DBS method compared with the two studied farming systems, it is also recommended to decrease the proportion of nonrenewable inputs (fossil fuel, chemical fertilizers, and herbicides) and increase the proportion of renewable inputs (organic fertilizer).

Integrated emergy and economic evaluation of the dominant organic rice production systems in Jiangsu province, China.

Changing from conventional to organic farming might have fewer negative environmental impacts because of the avoidance of synthetic fertilizer and chemical pesticides. In this study, the economic viability and environmental and sustainability performance of the four dominant organic (rice-green manure rotation (RG), rice-duck co-culture (RD), rice-crayfish co-culture (RCF) and rice monoculture (RM)) and one conventional (rice monoculture (CRM)) rice production modes were evaluated in Jiangsu Province, China. Compared with the CRM mode, organic rice production increased economic benefits density and improved the economic benefit of crop land and irrigation water use. With the lowest total emergy input and the highest rice yield, the CRM mode showed the highest ecological efficiency in converting resources to total available energy content and nutrition density unit among the five rice production modes. However, the RCM mode showed higher environmental pressure and lower sustainability than the four organic modes due to the larger proportion of nonrenewable emergy input. The RM mode was the most uneconomic organic rice production mode with the highest cost input and the lowest product output but had relatively higher sustainability due to the higher proportion of renewable resources to total emergy inputs. Compared with the RM mode, the value-to-cost ratio, economic benefit density and benefit-cost ratio were increased in the RG, RD and RCF modes. Although the RD and RCF modes had higher efficiency in converting resources to total nutrition density units and monetary value, they imposed higher environmental pressure with a lower renewable fraction and emergy sustainability index than those in the RM mode. The RG mode had higher emergy utilization efficiency and the highest renewable fraction and emergy sustainability index among the four organic rice production modes. Considering the ecological and economic effects, the RG mode was conducive to improving the economic viability and sustainability of organic rice production.

Valuing the Natural Capital of Sea Areas Based on Emergy Analysis

Marine natural capital is an important component of natural capital yields goods and service flows benefiting the human being. The emergy analysis method allows one to account for mass, energy and money flows in an ecosystem, providing technical support for assessing its broader value regarding our economic dependence. Thus, we used this method to evaluate the natural capital of the Zhoushan archipelago sea area from 2011 to 2016 and proposed a formula to estimate the marine organism’s transformity. The average total emergy of our study area was 6.93 × 1022 sej and emdollar was about 9.20 billion yuan, which is equivalent to 9.3% of the average regional GDP of 98.5 billion during the same period. The Zhoushan archipelago sea area has high emergy density (ED) and low emergy self-sufficiency ratio (ESR), which shows low input–output efficiency for local use. In addition, the high purchased emergy (PR), high emergy exchange ratio (EER) and low renewable resources emergy ratio (%R) imply an increasing dependence on the outside social and economic inputs. Overall, Zhoushan sea area was in an early but steady state of development. The results can serve as a benchmark for policy making and implementation to achieve local sustainable development. As a tool for emergy-based sea area capital assessment, the model is of great significance for quantifying the ecosystem service value and accounting for marine/land natural capital value.

Sustainability evaluation of protected vegetables production in China based on emergy analysis

Protected vegetables have undergone rapid development in recent decades in China, accompanied by high resource consumption and environmental load. This study adopts emergy synthesis to evaluate the sustainability of protected vegetable production system (PVPS) in China. The emergy input structure and emergy flow of the PVPS were first determined to reveal its unique artificial environment from the perspective of facility structure and internal environment. Then, a new emergy indicator of artificial environment sustainability (EIAS) and conventional emergy-based indicators were proposed to evaluate the regional heterogeneity of PVPS in China's four major producing regions. Finally, six hypothetical scenarios were designed to explore the future development direction and sustainability of the PVPS. The results showed that the total emergy input for PVPS was 3.79E+22 sej in 2018, which mainly depended on non-renewable purchase emergy, such as labor and services (41.67%), artificial environment construction (23.35%), and land cost (10.83%). The provinces with the highest emergy inputs were concentrated in the Huang-Huai-Hai temperate region, followed by the subtropical region of the Yangtze River Basin. The proportion of artificial environment construction input in the northeast temperate region was the largest, while that in the subtropical region of the Yangze River Basin was the smallest. Compared with the baseline scenario, emergy input can be reduced by 1.79%, and sustainability can be improved by 1.96%, by reducing artificial environment construction input by 2030, with a limited optimization effect. Integrated technological improvements, such as advanced farmland management, water-saving irrigation technology, and energy-efficient utilization, can improve the sustainability of PVPS by 5.99% without sacrificing vegetable yield. This study provides a better understanding of the sustainable management of PVPS.

Emergy analysis and optimization for a solar-driven heating and cooling system integrated with air source heat pump in the ultra-low energy building

In this paper, a solar-driven heating and cooling system integrated with air source heat pump is designed and applied to the ultra-low energy building. The heat and electricity from the compound parabolic concentrated-photovoltaic thermal collector are fed to air source heat pump to increase the efficiency of the air source heat pump. Integrating energy, social, environmental, and economic benefits of the system in the whole life cycle, an emergy-based optimization method is adopted to obtain the optimal configuration of the compound parabolic concentrated-photovoltaic thermal collector. Under the optimal configuration, the emergy performance of the designed system is analyzed, and the monthly emergy performance and the influence of investment cost and solar irradiation on the emergy performance are discussed. The optimization results show that when the photovoltaic coverage ratio is 1.0, the total emergy consumed by the designed system is the lowest, 2.64 × 1016 seJ/y, which saves 9.96% of emergy compared with the reference system. The environmental load ratio, emergy sustainability index, emergy investment ratio, and emergy yield ratio under optimal configuration are 126.62, 0.021, 0.62, and 2.64, respectively. The emergy investment ratio and environmental load ratio in January are the highest, which are 0.28 and 100.09, respectively, while the emergy yield ratio and emergy sustainability index in May are the largest, which are 15.02 and 0.179, respectively. The environmental load ratio and emergy investment ratio are positively correlated with the annual investment cost, while the emergy sustainability index and emergy yield ratio are negatively correlated with the annual investment cost. The emergy optimization facilitates a better selection of building energy supply systems.

Sustainability of agroecosystems by indices: A comparative study between indicators of ecological footprint sustainability and emergy analysis; a case study in Dez catchment, Iran

Efficient farm management is one of the most important issues in achieving Sustainable performance. Ecological Footprint (EF) measurement and Emergy Analysis (EA) are appropriate tools to achieve the principles of sustainability in different ecosystems. This study aimed to compare the indicators and determine the ecological sustainability of two cropping systems of irrigated wheat and grain maize using ecological footprint evaluation and emergy analysis in the catchment area of Dez in Iran in the crop year 2019–2020. For this purpose, a total of 400 questionnaires from wheat and maize farmers were collected based on a simple random sampling method. The results of evaluating the ecological footprint method of wheat and maize cultivation in the study area at the level of one hectare were 3.50 and 4.66 global hectares, respectively. Also, the results of total emergy inputs for the ecological system of wheat and maize production were 1.60E+16 and 2.55E+16 sej ha−1 per year, respectively. This study showed that the two methods EF and EA are complementary. The evaluation results of both sustainability indices were very close to each other so both cultivation systems were environmentally unsustainable. We also found that the ecosystem of the irrigated wheat production system is more desirable than the ecosystem of the maize production system in terms of yield, renewability, and environmental sustainability. Since both cropping systems are strongly affected by the purchased inputs (more than 95%), as a result, they create a high environmental pressure, which shows the apprehensive condition of the current agricultural production systems in Iran. This study is the first study from Iran that uses these two tools simultaneously to determine the sustainability assessment of two strategic products of the region.

Can additional agricultural resource inputs improve maize yield, resource use efficiencies and emergy based system efficiency under ridge-furrow with plastic film mulching?

Water scarcity is a major constraint for maize production in drylands. As an efficient water-saving technology, the ridge-furrow with plastic film mulching (RM) system has achieved success in dryland farming. The efficiency of the rainwater-harvesting system in RM is greatly affected by erratic precipitation, and water absorption by crops is influenced by nutritional availability. Whether the additional supply of irrigation and nitrogen (N) resources under the RM system could influence the resource use efficiencies, emergy flows, and system efficiency of agricultural products is unclear. Therefore, a 3-year field study on maize plants consisting of four planting patterns (CP: conventional planting; RM; RM + SI: RM plus supplementary irrigation; RM + SI + N: RM + SI plus additional N fertilizer) was conducted from 2018 to 2020 in the Loess Plateau of China to determine resource use efficiencies, emergy flows, and system efficiency through emergy evaluation. In this study, we demonstrated the high efficiency of the micro-field rainwater-harvesting system of RM by collecting more rainwater and improving soil hydrothermal conditions. For example, the soil temperature and moisture of topsoil at seedling stage were increased by 4.3 °C and 13%, respectively, under RM compared with CP. The soil hydrothermal conditions in RM further improved maize yield (+35%), water use efficiency (+32%), N partial factor productivity (+37%), radiation use efficiency (+10%), and system efficiency (8%, from an emergy perspective), compared to CP. However, the additional supply of N or irrigation in RM + SI or RM + SI + N planting patterns failed to increase resource use efficiency, although the maize yield was increased by 9%. Furthermore, although the total emergy input was increased by 19%, it did not significantly increase energy output, and thus decreased the resource efficiency by 9% through emergy evaluation, compared to RM. Overall, RM without additional agricultural resource input could be recommended as a sustainable and cleaner production strategy for maize in drylands to address the issues of ever-increasing food demand and declining availability of production resources.