Solar Emergy Research Articles

Environmental performance of a XIV Century water management system: An emergy evaluation of cultural heritage

In the late Middle Ages, the city of Siena (Italy) had a high population density and had to face the problem of supplying water within the city walls for housing, crafts, economic and commercial activities, as well as for the risk of fire. A network of underground drifts, namely “Bottini”, was then built, achieving a total length of about 25 km in the late XIV Century. The Bottini have been capturing and conducting rain water from the countryside to the fountains in the city centre for centuries, and still provide an average 9.5 L s −1 of clean water, though it is not drinkable nowadays. Currently, water provided by the ancient aqueduct is only used to fill a set of monumental fountains, and is then wasted. In this paper, we have investigated the environmental performance of the water supply in Siena, comparing results from the analysis of the historical Bottini and the contemporary water supply system. In particular, an emergy evaluation was developed in order to account for the environmental resource use of the water management system, considering both the historical and the modern aqueducts, and providing information on their “sustainability”. Specific emergy, measured in units of equivalent solar energy (solar emergy Joules – seJ) per liter of water provided, as well as the Environmental Loading Ratio and the Emergy Investment Ratio, were used as indices of environmental performance. Results have shown that the Bottini have a lower environmental impact in terms of rate of renewability with respect to the contemporary system. Based on statistics on water use in urban centres (drinking, washing, gardening, etc.), we argued that keeping the Bottini alive is not only a good practice for the conservation of a precious cultural heritage, but could be a potential opportunity for improving urban ecology.

Emergy Evaluation of Agro-ecosystem of Shiyang River Basin, Northwestern China

This paper presents an ecological analysis of agricultural systems in arid region of Northwestern China. Emergy analysis, a method for environmental accounting developed by H.T. Odum in the Eighties, is appropriate for this task because of its ability to transform different types of inputs to a common form (solar emergy) in order to allow scientific and objective comparisons across different period and regions. Taking Liangzhou and Minqin oases, located in the middle and lower reaches of the Shiyang River basin in Gansu province as a case study, the detailed structure of the agricultural process, input/output and emergy indicators of the systems are examined and compared for the years 1986 and 2000. Both the total emergy input and the total yield increased in the two oases. In Liangzhou Oasis the emergy of livestock production exceeded the traditional crop production, which still is the dominant production in Minqin Oasis. The emergy investment ratio, EIR, although increased in the investigated period, was less than 0.5 in both Liangzhou and Minqin oases, indicating that purchased materials and services were less than half the value of indigenous emergy sources exploited. As a consequence, the emergy yield ratio, EYR, was very high in both Liangzhou and Minqin oases. However, the increasing environmental loading ratio, ELR, and the decreasing environmental sustainability index, ESI, in the two oases illustrate a weakening sustainability of the two agro-ecosystems, and this tendency was more evident in the downstream Minqin Oasis, calling for more attention to the environmental degradation in the region.

Greenhouse gas emissions and natural resources use by the world economy: Ecological input–output modeling

For the world economy as a biophysical network associated with financial links, an ecological endowment inventory and corresponding ecological input–output modeling are presented to investigate the greenhouse gas emissions and natural resources use in 2000. A forty-sector global economic input–output table is constructed through an integration and extension of existing statistics which covers thirty-four countries accounting for about 80% of the world economy. Global inventories for ecological endowments of six categories, i.e., greenhouse gas emissions, energy sources, water resources, exergy resources, solar emergy resources, and cosmic emergy resources, are accounted in detail. As a result of the modeling, embodied intensities of different ecological endowments are obtained for all forty sectors, based on which the sectoral embodiments for consumptive and productive uses are presented separately. Results of this study provide a sound scientific database for policy making on global climate change mitigation as well as on global resources management.

Resources use and greenhouse gas emissions in urban economy: Ecological input–output modeling for Beijing 2002

The embodiment of natural resources and greenhouse gas emissions for the urban economy of Beijing economy 2002 by a physical balance modeling is carried out based on an extension of the economic input–output table into an ecological one integrating the economy with its various environmental driving forces. Included resources and greenhouse gas emissions belong to six categories as energy resources in terms of primary energy and secondary energy; water resource; emissions of CO2, CH4, and N2O; exergy in terms of energy sources, biological resources and minerals; and solar emergy and cosmic emergy in terms of climate resources, soil, energy sources, and minerals.

Solar emergy evaluation for Chinese economy

A unified evaluation integrating various forms of energy sources and natural resources, products and services, and imports and exports is carried out systematically at the national scale for the booming Chinese economy 1978–2005, based on the ecological measure of solar emergy. The development of the economy is shown heavily dependent on the consumption of nonrenewable natural resources. Of the total resources use, the indigenous resources contribute the most, along with the increasing imports of nonrenewable resources. The development of the Chinese economy is characterized with the recovery stage during 1978–1981, transformation stage during 1981–1991, steady growth stage during 1991–2000, and accelerated increase stage after 2000, with specific distinctive systems indications.

Ecological input–output modeling for embodied resources and emissions in Chinese economy 2005

For the embodiment of natural resources and environmental emissions in Chinese economy 2005, a biophysical balance modeling is carried out based on an extension of the economic input–output table into an ecological one integrating the economy with its various environmental driving forces. Included resource flows into the primary resource sectors and environmental emission flows from the primary emission sectors belong to seven categories as energy resources in terms of fossil fuels, hydropower and nuclear energy, biomass, and other sources; freshwater resources; greenhouse gas emissions in terms of CO 2 , CH 4 , and N 2 O ; industrial wastes in terms of waste water, waste gas, and waste solid; exergy in terms of fossil fuel resources, biological resources, mineral resources, and environmental resources; solar emergy and cosmic emergy in terms of climate resources, soil, fossil fuels, and minerals. The resulted database for embodiment intensity and sectoral embodiment of natural resources and environmental emissions is of essential implications in context of systems ecology and ecological economics in general and of global climate change in particular.

Emergy-based Simulation to Assess Brazil’s Long-term Carrying Capacity: Environment, Electricity and Population

A macroscopic mini-model of Brazil’s electrical generating capacity (BRAZELECTRIX, Brazilian Electricity Matrix) was developed using the Energy Systems Language and simulated with iconographic Extend® software to explore long-term (200 years) population carrying capacity. South American reserves of natural gas (NG) and Brazilian stream hydro-power potential were assumed as the main inputs to electric power production. Energy values (e.g., kWh, joules) for fuels, electricity and environment were transformed to solar emergy (i.e., solar equivalent joules) to simplify cross comparison with a single metric. BRAZELECTRIX was calibrated using a holistic method that used mean component life-times and conservation of material and energy for each individual unit. Validation of BRAZELECTRIX, based on historical data, gave a root mean square error of 8% for hydroelectricity and 28% for natural gas use. Investments in natural gas infrastructure (e.g., contracts, pipelines, processing plants and electric power plants) accelerated Brazil’s expansion of electrical generating capacity for a finite period, allowing the country to reach its renewable (hydro-power only) carrying capacity 100 years sooner than without (2040 vs. 2140). Brazil has a total of 560 zetta-solar equivalent joules per annum (1 Zseja = 1 ×1021 sej per year) of stream hydro-power potential; 170 Zseja is currently used for electricity generation. According to BRAZELECTRIX, eventually 390 Zseja will be tapped for hydroelectricity. The standard of living, as measured by annual per capita electrical solar emergy, had risen 680% from 166 tera-solar equivalent joules (Tseja) to 1130 Tseja during the 35 year period following 1965 and was predicted to increase another 75% to its maximum (1973 Tseja) in 2050. By comparison, an urbanizing state of the United States (North Carolina) had an annual per capita electrical solar emergy of 7815 Tseja in 1992, indicating that Brazil could reach a living standard, as measured by per capita electricity usage, equal to one-forth the level of United States. Macroscopic mini-models combined with emergy accounting evaluated long-term paths for Brazil’s electricity supply and related it to natural environment trade-offs to demonstrate how sustainable carrying capacity of a developing nation can be forecast.

Dynamic emergy accounting for assessing the environmental benefits of subtropical wetland stormwater management systems

An eco-hydrological model of a subtropical urbanizing watershed in south Florida, USA was developed to simulate solar emergy using H.T. Odum's energy systems language as programmed in an iconographic simulation software (i.e., Extend ®) to provide dynamic valuation of a wetland stormwater management system (WSMS). The solar emergy (i.e., ultimate amount of solar energy required to produce another form of energy) and emdollar (EM$, value an energy flow contributes to an economy based on its proportion of total emergy flow) values of watershed transpiration (a measure of productivity), surface discharge and change in landscape water storage were quantified for various ratios of wetland to upland areas, valuing wetlands in EM$ ha −1 y −1. Simulation results indicated that integrating a WSMS into the watershed increased landscape productivity, decreased surface discharge and increased surface water storage. The eco-hydrological value of watershed productivity was 367 EM$ ha −1 y −1 when 10% of the watershed was wetland, which was an increase of 65 EM$ ha −1 y −1 (based on Florida's emergy-to-dollar ratio in 1985, 2 × 10 12 sej $ −1). The annual contribution of this extra ecological productivity to public welfare was 12 million EM$, which was estimated from the product of eco-hydrological value and local emergy investment ratio of south Dade County (18:1). Average emdollar value of water saved per unit of wetland was 343 EM$ ha −1 y −1. Dynamic emergy accounting provided distributions of solar transformities of hydrologic variables as opposed to more commonly used point estimates. Our work advances the temporal dynamic principles of emergy accounting by demonstrating how solar emergy may be continuously tracked through an ecosystem to estimate the value of nature's life-support services.

Towards the Understanding of Embodied Energy in Buildings: Emergy of Construction and Demolition

This paper presents the study of embodied energy use throughout the construction and demolition as a tool to indicate embodied energy efficiency and environmental inputs of buildings and building materials in Thailand. Emergy 26 Journal of Architectural Research and Studies Volume 2 2004 Faculty of Architecture Thammasat University Analysis Technique is used to calculate the amount of energy required to make something expressed in units of the same form of energy, called Solar Emergy. And Emergy of money, called Embath has also been evaluated. The objectives are to evaluate and compare Emergy and Embath of buildings to help determining the Emergy saving and the environment benefits of buildings and building materials during construction and demolition. The method is to collect and analyze data inputs of cost and quantity from bill of quantity; BOQ of buildings: residences, schools, offices and hospitals for construction and 2 types of structure, halftimber and concrete structure for demolition. Materials during construction and demolition of each building are evaluated. This study examines all factors, which are Emergy, masses and cost, and environmental inputs to create Emergy index and environmental index as well. Four influencing factors effecting Emergy values are found: Renewable resource or structure, non-renewable resource or decoration, building system and labor. Structure is the major factor of residential buildings, schools and office buildings. Decoration is the major factor of hospital buildings. In demolition stage, structure is also the main factor. In demolition stage, Emergy value of half-timber structure buildings is the same as 7 years of energy consumption. Whereas Emergy value of concrete structure building is the same as 19-30 years of energy consumption. Therefore, structure materials should be used in as small amount as possible, especially the high transformity materials. Eventually, the environmental index suggested that using more renewable than non-renewable resource would be appropriate to the environment and the world resource. The building usable life is depend on materials, the more non-renewable resource, the longer life of the materials should be used.

Promise and problems of emergy analysis

Solar Emergy is the available solar energy used up directly and indirectly to make a service or product. Although this basic concept is quite straightforward, its implications are potentially profound. H.T. Odum pioneered the development and use of emergy, and presented it as a way of understanding the behavior of self-organized systems, valuing ecological goods and services, and jointly analyzing ecological and economic systems. Unfortunately, like many groundbreaking ideas, emergy has encountered a lot of resistance and criticism, particularly from economists, physicists, and engineers. Some critics have focused on detailed practical aspects of the approach, while others have taken issue with specific parts of the theory and claims. This paper discusses the main features and criticisms of emergy and provides insight into the relationship between emergy and concepts from engineering thermodynamics, such as exergy and cumulative exergy consumption. This reveals the close link between emergy and ecological cumulative exergy consumption, and indicates that most of the criticisms of emergy are either common to all holistic approaches that account for ecosystems and other macrosystems within their systems boundaries, or a result of misunderstandings derived from a lack of communication between various disciplines, or are not relevant for engineering applications. By identifying the main points of criticisms of emergy, this paper attempts to clarify many of the common misconceptions about emergy, inform the community of emergy practitioners about the aspects that need to be communicated better or improved, and suggest solutions. Further research and interaction with other disciplines is essential to bring one of H.T. Odum’s finest contributions into the mainstream to guide humanity on “the prosperous way down.”

EMERGY-based environmental systems assessment of a multi-purpose temperate mixed-forest watershed of the southern Appalachian Mountains, USA

Emergy (with an ‘m’) synthesis was used to assess the balance between nature and humanity and the equity among forest outcomes of a US Forest Service ecosystem management demonstration project on the Wine Spring Creek watershed, a high-elevation (1600 m), temperate forest located in the southern Appalachian mountains of North Carolina, USA. EM embraces a holistic perspective, accounting for the multiple temporal and spatial scales of forest processes and public interactions, to balance the ecological, economic, and social demands placed on land resources. Emergy synthesis is a modeling tool that allows the structure and function of forest ecosystems to be quantified in common units (solar emergy-joules, sej) for easy and meaningful comparison, determining ‘system-value’ for forcing factors, components, and processes based on the amount of resources required to develop and sustain them, whether they are money, material, energy, or information. The Environmental Loading Ratio (ELR), the units of solar emergy imported into the watershed via human control per unit of indigenous, natural solar emergy, was determined to be 0.42, indicating that the load on the natural environment was not ecologically damaging and that excess ecological capacity existed for increasing non-ecological activities (e.g. timbering, recreation) to achieve an ELR of 1.0 (perfect ecological–economic balance). Three forest outcomes selected to represent the three categories of desired sustainability (ecological, economic, and social) were evaluated in terms of their solar emergy flow to measure outcome equity. Direct economic contribution was an order of magnitude less (224×10 12 solar emergy-joules (sej) ha −1) than the ecological and social contributions, which were provided at annual rates of 3083 and 2102×10 12 sej ha −1, respectively. Emergy synthesis was demonstrated to holistically integrate and quantify the interconnections of a coupled nature-human system allowing the goals of ecological balance and outcome equity to be measured quantitatively.

Emergy indices and ratios for sustainable material cycles and recycle options

Emergy (spelled with an m) is the energy required to make a service or product expressed in energy of one form. The emergy used in the life cycles of major building materials as well as the emergy inputs to waste disposal and recycle systems were evaluated. Emergy per mass (expressed as solar emergy per gram [sej/g]) for building materials varied from a low of 0.88 E9 sej/g for wood to a high of 12.53 E9 sej/g for aluminum. Generally, emergy per mass is a good indicator of recycle-ability, where materials with high emergy per mass are more recyclable. Recycling added between 1 (cement) and 234% (wood) to the emergy inputs per gram of building materials. The analysis of materials suggested that recycle of wood may not be advantages on a large scale, but metals, plastic, and glass have very positive benefits. Two types of solid waste disposal systems were evaluated: municipal solid wastes (MSW), and construction and demolition wastes (C&D wastes). Expressed as emergy, the costs of collecting, sorting and landfilling (for 25 years) MSW were 251.0 E6, 8.2 E6 and 37.9 E6 sej/g, respectively. The costs of demolition, collection, sorting and landfilling C&D wastes were 49.0 E6, 21.7 E6, 6.7 E6, and 11.7 E6 sej/g, respectively. Three different recycle trajectories were identified and analyzed: (1) material recycle (the ‘standard’ recycle of a material where it is used again as the same material [i.e. glass bottles recycled and made again into glass bottles]); (2) by-product use (where a by-product from some process is used to make something entirely different [i.e. flay ash in concrete]); and (3) adaptive reuse (where a material after recycle is reused for an entirely different purpose [i.e. plastic milk cartons are converted into plastic lumber]). Three recycle indices measuring the benefits of various recycle systems suggested that materials that have large refining costs have greatest potential for high recycle benefits and that highest benefits appear to accrue from material recycle systems, followed by adaptive reuse systems and then by byproduct reuse systems.