Nadia Marchettini

Emergy-based indices and ratios to evaluate the sustainable use of resources

Abstract By means of a systemic analysis of the relationships among components of an ecosystems web, the flows of energy and other resources converging to produce the output (biomass, biodiversity, assets, etc.) can be evaluated on a common basis, i.e. the content of solar equivalent energy (emergy). Indices and ratios based on the emergy flows can be calculated and used to evaluate the behaviour of the whole system. In this paper, one of these indices, the emergy yield ratio η (total yield emergy per unit of emergy invested) is evaluated and suggestions made to modify it to account for present and future environmental damages due to the use of a given resource. The meaning of this index, with and without the proposed modification, is stressed illustrating the long-term effects of environmental pollution as well as some key uncertainty factors that are very often not taken into account. Odum, 1993

Sustainability assessment of a farm in the Chianti area (Italy)

Abstract In the study of agricultural systems, where land fertility and environmental conditions are primary factors, it is essential to consider both the efficiency and the environmental sustainability of processes. Emergy analysis, introduced by H.T. Odum [Science 242 (1988) 1132], is an approach developed at the interface between thermodynamics systems ecology. It was here used to obtain sustainability indicators and to assess the efficiency of a complex agricultural system, a farm in the Chianti area. The results for different crops were compared with Italian averages to obtain an idea of the long-term sustainability of this agricultural system. The cultivation of all the crops on the farm, except grapes, was more efficient and had less impact on the environment than the Italian standards. The Chianti grapes were compared not only with the Italian average but also with grapes of similar high quality, ‘Brunello di Montalcino’ and ‘Nobile di Montepulciano’, both grown in the same region. The production of grapes in the Chianti vineyard was more efficient and had an intermediate environmental impact, in the emergy sense, with respect to the other two systems. The proportion of emergy inputs to the farm that are local or renewable is quite high. Thus the emergy analysis demonstrated that the Chianti farm has a relatively good long-term sustainability considering both the whole system, and its individual crops.

Ethanol production from biomass: Analysis of process efficiency and sustainability

Bioethanol production from agricultural raw materials can be carried out to produce liquid fuels and reduce CO2 emissions from the combustion of fossil fuels and hence its impact on climate. Crop production and transformation processes have been investigated by the traditional energy and carbon analyses and the more recent emergy analysis. The latter is able to account for, on the same basis, both renewable and non-renewable inputs, including goods and labour involved in a process. The combination of such analyses provides a deeper insight into the problems of converting biomass to fuel. In particular it is shown that emergy analysis can evaluate long-term sustainability and comparisons of emergy-based indices can be used to compare efficiency and environmental input between various production systems.

The problem of co-production in environmental accounting by emergy analysis

Abstract This paper deals with the application of emergy analysis to systems with co-productions. Emergy is a measure of how much work the biosphere has done in order to provide a product, in terms of solar energy joules. For this reason, especially by means of the emergy-based indices, emergy analysis is a one of the key functions for assessing sustainability. However the application of emergy analysis to processes with co-production can be misleading. Usually some inputs have to be added in order to obtain a ‘useful’ product from a by-product. This would lead to penalizing a co-production with respect to two (or more) independent processes, since the fact of having another output is neglected in calculations. To have a better comparison, we introduce the concept of joint transformity and the weighted average of the transformities. The same reasoning is applied to other emergy-based indices. These new indexes should be added to the set of the existing ones to enlarge the possibilities of application. A case study of a dairy farm in Puerto Rico was analyzed from this viewpoint, showing that co-production of milk and methane (or electricity) is more efficient and less impacting on the environment with respect to separate productions, while two separate processes would be more effective in using local resources.

Emergy/exergy ratio as a measure of the level of organization of systems

Abstract Emergy and exergy have been developed as complementary goal functions. By definition, emergy is the solar energy directly and indirectly required to generate a flow or a storage. Exergy is a property of a system, measuring the maximum work that can be extracted from a system when it goes towards the thermodynamic equilibrium with a reference state. The concept of emergy contains the history, the time and all the different processes involved up to the present state of the system, while exergy is a measure of the actual state, of the level of organization and of the information content. These two approaches are very suitable for describing self-organizing systems such as ecosystems. The ratio of the emergy flow to the exergy can give further information on the state of a system, showing what concentration of solar energy equivalent, space and time (emergy) is required to maintain or create a unit of organization (exergy). The proposed index is related to the efficiency with which a system organizes itself or, if steady, maintains its complexity. To test this approach we considered three coastal lagoons. Two of them are artificial, built by man to purify sewage. One is a control pond fed with estuarine water and ‘clean’ water from the local sewage treatment plant, and one is a ‘waste pond’ fed with estuarine water mixed with more ‘polluted’ (i.e. richer in nutrients) effluent. The third system is the lagoon of Caprolace (Italy) a ‘natural’ system, placed in a national park. Experimental results show that the emergy/exergy ratio has the lowest value for the ecosystem of Caprolace. The waste pond has the highest environmental cost for the production of a unit of organization. Both the control and the waste ponds show a decreasing value of the emergy/exergy ratio with time, meaning that natural selection is organizing the systems.

Water: A medium where dissipative structures are produced by a coherent dynamics

The Belousov-Zhabotinsky phenomenon is analyzed in a framework where the dynamics of dissipative structures outlined by Prigogine is implemented through the collective dynamics produced in liquid water by Quantum Electrodynamics, which has received recently some experimental support. A mechanism allowing the appearance of self-produced oscillations is suggested.

Dynamics of pattern formation in biomimetic systems

This paper is an attempt to conceptualize pattern formation in self-organizing systems and, in particular, to understand how structures, oscillations or waves arise in a steady and homogenous environment, a phenomenon called symmetry breaking. The route followed to develop these ideas was to couple chemical oscillations produced by Belousov-Zhabotinsky reaction with confined reaction environments, the latter being an essential requirement for any process of Life. Special focus was placed on systems showing organic or lipidic compartments, which represent more reliable biomimetic matrices.

Importance of the Bradhyrizobium japonicum symbiosis for the sustainability of a soybean cultivation.

Abstract Economic development in agriculture is often accompanied by strong environmental pressures that present risks, which could lead to irreversible damage of the associated agro-ecosystem. A form of agricultural management that utilizes natural resources rationally yet maintains ecological stability is necessary. Ecologically sound, yet productive, use of resources requires indicators that assess not only productive and economic factors, but also environmental impact and ecological effects. Thus, to study an agricultural activity and its interaction with the environment, a holistic approach, capable of considering ecological, biophysical and socio-economic aspects is appropriate. Here we use emergy analysis and its indicators as given in Odum (Science 242 (1988) 1132–1139), to evaluate how sustainability of a soybean crop in south Tuscany (Italy) is increased using the specific bacteria inoculation to satisfy, through fixation, the nitrogen need of the crop. Cultivation was studied with two options: (1) utilization of chemical fertilizers to supply nitrogen needs as often done in the past, and as a viable present alternative and (2) the symbiotic activity of Bradyrhizobium bacteria, given as inoculum, to cover all nitrogen needs. This article shows that proper agricultural management should help maintain, and increase, system capacity, i.e. the quality of the system environment (soil, water,…), to sustain biomass, and prevent environmental degradation. For an Italian agro-ecosystem, the results demonstrate that agricultural production is more than doubled and the use of non-renewable and toxic inputs, such as chemical fertilizers, is reduced by use of the inoculum. The good results for soybean suggests development of analogous cultivation methods for other agricultural species, such as gramineous, for which different N-fixing bacteria such as Azospirillum, have been already identified.

A thermodynamic methodology to assess how different cultivation methods affect sustainability of agricultural systems

SUMMARY To evaluate environmental sustainability of complex systems, such as agricultural cultivation, it is necessary to adopt a systemic approach that considers all mass and energy flows that drive processes and that interlace, amplify, and influence each other. Emergy analysis, a thermodynamic-ecological methodology developed by Odum (1988), produces powerful indicators to evaluate process efficiency and to assess long-term sustainability. We performed a comparison among three cherry crops with different cultivation methods (traditional, biological and integrated) employing different inputs (natural and non-natural), in order to understand how agricultural systems should be developed in order to be economically successful with respect to the environment. Traditional methods using high quantities of non-natural inputs demonstrated unsustainability, while the integrated method of natural and purchased inputs turned out to be the best. The emergy approach demonstrated a powerful methodology to assess sustainability, and the indications obtained for cherry crops could be extrapolated to other types of cultivation.

Effect of temperature in a closed unstirred Belousov–Zhabotinsky system

Complex periodic and aperiodic behaviours are reported in an unstirred Belousov-Zhabotinsky oscillatory reaction performed at temperatures varying between 0°C and 8°C. A route to chaos following a Ruelle-Takens-Newhouse (RTN) scenario is identified. Thus, temperature effects on the coupling between chemical kinetics, diffusion and convection, seem to be responsible for the observed RTN scenario. In this Letter we demonstrate that the temperature is a bifurcation parameter for the sequence period-1 → quasiperiodicity → chaos.