Emergy evaluation and economic analysis of three wetland fish farming systems in Nansi Lake area,China

Emergy and economic methods were used to evaluate and compare three fish production models, i.e., cage fish farming system, pond intensive fish rearing system and semi-natural extensive pond fish rearing system, in Nansi Lake area in China in the year 2007. The goal of this study was to understand the benefits and driving forces of selected fish production models from ecological and economic points of view. The study considered input structure, production efficiency, environmental impacts, economic viability and sustainability. Results show that the main difference among the three production systems was the emergy cost for fish feed associated with their feeding system, i.e., feeding on natural biomass such as plankton and grass or on commercial feedstock. As indicated by EYR, ELR and ESI, it can be clearly shown that the intensive production model with commercial feed is not a sustainable pattern. However, the point is that more environmentally sound patterns do not seem able to provide a competitive net profit in the short run. The intensive pond fish farming system had a net profit of 2.57E+03 $/ha, much higher than 1.27E+03 $/ha for cage fish farming system and slightly higher than 2.37E+03 $/ha for semi-natural fish farming system. With regard to the drivers of local farmer’s decisions, the accessibility of land for the required use and investment ability determine the farmer’s choice of the production model and the scale of operation, while other factors seem to have little effect. Theoretically, the development of environmentally sustainable production patterns, namely water and land conservation measures, greener feed as well as low waste systems is urgently needed, to keep production activities within the carrying capacity of ecosystems. Coupled emergy and economic analyses can provide better insight into the environmental and economic benefits of fish production systems and help solve the problems encountered during policy making.     

Technologies,challenges and perspectives of biogas production within an agricultural context. The case of China and Africa

Environment, Development and Sustainability - The use of fossil fuels in modern economies has been a success because of the low cost of fossil resources. However, the depletion of fossil reserves,...     

Material, energy and environmental performance of technological and social systems under a Life Cycle Assessment perspective

Selected energy and material resource conversion systems are compared in this paper under an extended LCA point of view. A multi-method multi-scale assessment procedure is applied in order to generate consistent performance indicators based on the same set of input data, to ascertain the existence of constraints or crucial steps characterized by low conversion efficiency and to provide the basis for improvement patterns. Optimizing the performance of a given process requires that many different aspects are taken into account. Some of them, mostly of technical nature, relate to the local scale at which the process occurs. Other technological, economic and environmental aspects are likely to affect the dynamics of the larger space and time scales in which the process is embedded. These spatial and time scale effects require that a careful evaluation of the relation between the process and its surroundings is performed, so that hidden consequences and possible sources of inefficiency and impact are clearly identified. In this paper we analyse and compare selected electricity conversion systems, alternative fuels and biofuels, waste management strategies and finally the time evolution of an urban system, in order to show the importance of a multiple perspective point of view for the proper evaluation of a system's environmental and resource use performance.     

Understanding the global economic crisis: A biophysical perspective

The recent economic meltdown worldwide has reinforced our understanding of the effects of decoupling economic growth, monetary policy, and resources. Concern for peak oil and suggestions that it may have contributed to the global economic woes as well as over concern for the banking fraud may be adding confusion over the underlying causes and sending a misleading message to the public and ultimately to policy makers. Viewing the economy as simply a circulation of money that can be manipulated to increase spending and therefore consume our way out of the current economic situation, is courting disaster by deluding the public that the solution lies in simple adjustments to the current monetary system. Similarly, emphasizing that energy is the problem and that the solution can be found with another energy source is probably counterproductive in the short run and may be disastrous in the long run. The recent nuclear accident in Japan seriously calls into question increased dependence on nuclear energy and renewable energy sources, in the majority, have low net yields and are unevenly distributed worldwide.In this paper we frame the economic system as a subsystem of the larger more encompassing geobiosphere and suggest that within this context, neoclassical economics is unlikely to provide sufficient explanation of the recent economic melt-down. From a biophysical perspective, increasing the amount or speed of money circulation as well as extracting more energy from whatever source is available will only compound the problems and relying on growth as the solution to what ails the global economy is not a desirable nor a tenable solution.     

Assessing geobiosphere work of generating global reserves of coal, crude oil, and natural gas

A teacher of ours used to say, “Like ice in a fire, something for nothing you will never acquire”, which is a poetic equivalent of “there is no such a thing as a free lunch”. Human economies are dependent on high quality fossil fuels and will likely continue depending on them for some time to come. Value of a resource is not only what one pays for it, or what can be extracted from it, but also value can be attributed to the “effort” required in its production. In this analysis we apply the emergy synthesis method to evaluate the work invested by the geobiosphere to generate the global storages of fossil energy resources. The upgrading of raw resources to secondary fuels is also evaluated. The analysis relies on published estimates of historic, global net primary production (NPP) on land and oceans, published preservation and conversion factors of organic matter, and assessments of the present total global storages of coal, petroleum, and natural gas. Results show that the production of coal resources over geologic time required between 6.63E4 (±0.51E4) seJ/J and 9.71E4 (±0.79E4) seJ/J, while, oil and natural gas resources required about 1.48E5 (±0.07 E5) seJ/J and 1.70E5 (±0.06E5) seJ/J, respectively. These values are between 1.5 and 2.5 times larger than previous estimates and acknowledge a far greater power of fossil fuels in driving and shaping modern society.     

Emergy-based urban health evaluation and development pattern analysis

The objective of this study is to measure and evaluate the ecosystem health levels of 31 Chinese capital cities in 2004 through an emergy synthesis framework. A system of indicators was developed corresponding to the four factors of urban ecosystem health including efficiency, structure, impact and flux. Furthermore, combined with individual indices, an emergy-based urban ecosystem health index (EUEHI) was proposed to measure and evaluate the health levels among various typical cities in China, which offers an integrated evaluation tool in view of urban production, trade and consumption. The results showed that there are intrinsic differences among six clusters associated with driving mechanisms distinguishing the rankings of urban health levels. After lining the cities of similar health levels with cluster map, the spatial distribution of the urban health is found to be arch-shaped, increasing initially and then decreasing from coast to inner land. This kind of spatial hierarchy is per se compatible and consistent with the hierarchical theory of emergy synthesis. The results also revealed double restrictions of urban health between economy and environment. Moreover, the interaction analysis was used for mirroring the driving mechanism of urban ecosystem health. Three conclusions were arrived at. Firstly, environmental health is inversely related to the economic health in China, indicating that cities cannot achieve win–win between environment and economy in the current urban development mode. Secondly, based on economy-driven mode, four quadrants were divided in the city division map, wherein 43.33% of the concerned cities developed in high economy-restriction mode, which means low economic level is still an important limiting factor for the major cities of China. Finally, based on environment-driven mode, two sections were divided, of which weak environmental dominance mode expounds the special characteristics of urban environment with obvious fragility. 23.33% of the 30 cities were in the intermediate state, which means a few correspondingly unhealthy cities should develop concrete polices for the urban ecosystem restoration.     

Updated evaluation of exergy and emergy driving the geobiosphere: A review and refinement of the emergy baseline

Crucial to the method of emergy synthesis are the main driving emergy flows of the geobiosphere to which all other flows are referenced. They form the baseline for the construction of tables of Unit Emergy Values (UEVs) to be used in emergy evaluations. We provide here an updated calculation of the geobiosphere emergy baseline and UEVs for tidal and geothermal flows. First, we recalculate the flows using more recent values that have resulted from satellite measurements and generally better measurement techniques. Second, we have recalculated these global flows according to their available energy content (exergy) in order to be consistent with Odum's (1996) definition of emergy. Finally, we have reinterpreted the interaction of geothermal energy with biosphere processes thus changing the relationship between geothermal energy and the emergy baseline. In this analysis we also acknowledge the significant uncertainties related to most estimates of global data. In all, these modifications to the methodology have resulted in changes in the transformities for tidal momentum and geothermal energy and a minor change in the emergy baseline from 15.8E24 seJ/J to 15.2E24 seJ/J. As in all fields of science basic constants and standards are not really constant but change according to new knowledge. This is especially true of earth and ecological sciences where a large uncertainty is also to be found. As a consequence, while these are the most updated values today, they may change as better understanding is gained and uncertainties are reduced.     

Energy and land use in worldwide agriculture: an application of life cycle energy and cluster analysis

Agriculture is expected to provide food in a sustainable manner while also partially contributing to the energy problem as well as to bio-material supply. Moreover, fossil fuels scarcity calls for an increase of energy efficiency in agricultural processes. This study evaluates patterns, trends, driving factors and trade-offs of energy use in selected agricultural systems and aims at grouping them into clusters with similar energy and social performances. Results show that in 2010 the highest power densities and energy intensities of production are found by crop sector of cluster 5 (China: 59.19 GJ/ha, 15.29 MJ/kg dm) and cluster 3 (Japan: 50.11 GJ/ha, 12.32 MJ/kg dm) as well as by livestock sector of cluster 3 (Japan: 328.47 GJ/ha, 103.08 MJ/kg dm), while the lowest values in clusters 2 and 4, including selected developing countries and USA. Cluster 3 (Japan) also shows the lowest energy intensity of economic value of crops (2.75 MJ/$), while cluster 5 (China) the highest one (23.96 MJ/$). Cluster analysis also sheds light on trends, identifying two groups: cluster 1*, gathering most European countries, USA and Japan, characterized by a decreasing trend of all energy indicators; and cluster 2*, including developing countries, the Netherlands and Spain, characterized by an increasing trend of indicators. Results highlight the importance of an integrated framework for evaluating energy use as well as of a multi-criteria approach to understand the trade-offs and interplay of performance indicators.     

Economic and environmental performance of electricity production in Finland: A multicriteria assessment framework

Meeting environmental, economic, and societal targets in energy policy is complex and requires a multicriteria assessment framework capable of exploring trade-offs among alternative energy options. In this study, we integrated economic analysis and biophysical accounting methods to investigate the performance of electricity production in Finland at plant and national level. Economic and environmental costs of electricity generation technologies were assessed by evaluating economic features (direct monetary production cost), direct and indirect use of fossil fuels (GER cost), environmental impact (CO₂ emissions), and global environmental support (emergy cost). Three scenarios for Finland's energy future in 2025 and 2050 were also drawn and compared with the reference year 2008. Accounting for an emission permit of 25 €/t CO₂, the production costs calculated for CHP, gas, coal, and peat power plants resulted in 42, 67, 68, and 74 €/MWh, respectively. For wind and nuclear power a production cost of 63 and 35 €/MWh were calculated. The sensitivity analysis confirmed wind power's competitiveness when the price of emission permits overcomes 20 €/t CO₂. Hydro, wind, and nuclear power were characterized by a minor dependence on fossil fuels, showing a GER cost of 0.04, 0.13, and 0.26 J/J_e, and a value of direct and indirect CO₂ emissions of 0.01, 0.04, and 0.07 t CO₂/MWh. Instead, peat, coal, gas, and CHP plants showed a GER cost of 4.18, 4.00, 2.78, and 2.33 J/J_e. At national level, a major economic and environmental load was given by CHP and nuclear power while hydro power showed a minor load in spite of its large production. The scenario analysis raised technological and environmental concerns due to the massive increase of nuclear power and wood biomass exploitation. In conclusion, we addressed the need to further develop an energy policy for Finland's energy future based on a diversified energy mix oriented to the sustainable exploitation of local, renewable, and environmentally friendly energy sources.