• Energy Research

Abstract In vivo NMR techniques and substrates selectively enriched with 13 C were used to follow the step-by-step metabolism of glucose and xylose, on their own or as mixed substrates in the ratio as they occur in hydrolysates from hemicellulose. The organism used was a newly isolated strain of Klebsiella planticola isolated from soil where maize has been cultivated for 30 years. Results suggest that glucose is converted to pyruvate via the Embden-Meyerhof pathway and then to lactate and ethanol. No evidence of 2,3-butandiol or formate metabolism was observed. This organism had a higher rate of uptake of xylose than previously studied microorganisms, resulting in ethanol, lactate, acetate succinate and formate as end products. Xylose metabolism in K. planticola G11, unlike that reported for many other organisms, was not inhibited by glucose. The addition of glucose, after 2 h of xylose fermentation, did not change the rate of xylose metabolism.

Abstract Offshore cultivation of seaweed provides an innovative feedstock for biobased products supporting blue growth in northern Europe. This paper analyzes two alternative exploitation pathways: energy and protein production. The first pathway is based on anaerobic digestion of seaweed which is converted into biogas, for production of electricity and heat, and digestate, used as fertilizer; the second pathway uses seaweed hydrolysate as a substrate for cultivation of heterotrophic microalgae. As a result the seaweed sugars are consumed while new proteins are produced enhancing the total output. We performed a comparative Life Cycle Assessment of five scenarios identifying the critical features affecting resource efficiency and environmental performance of the systems with the aim of providing decision support for the design of future industrial scale production processes. The results show that all scenarios provide environmental benefits in terms of mitigation of climate change, with biogas production from dried Laminaria digitata being the most favorable scenario, quantified as −18.7*10 2 kg CO 2 eq./ha. This scenario presents also the lowest consumption of total cumulative energy demand, 1.7*10 4 MJ/ha, and even resulting in a net reduction of the fossil energy fraction, −1.9*10 4 MJ/ha compared to a situation without seaweed cultivation. All scenarios provide mitigation of marine eutrophication thanks to bioextraction of nitrogen and phosphorus during seaweed growth. The material consumption for seeded lines has 2–20 times higher impact on human toxicity (cancer) than the reduction achieved by energy and protein substitution. However, minor changes in cultivation design, i.e. use of stones instead of iron as ballast to weight the seeded lines, dramatically reduces human toxicity (cancer). Externalities from the use of digestate as fertilizer affect human toxicity (non-cancer) due to transfer of arsenic from aquatic environment to agricultural soil. However concentration of heavy metals in digestate does not exceed the limit established by Danish regulation. The assessment identifies seaweed productivity as the key parameter to further improve the performance of the production systems which are a promising service provider of environmental restoration and climate change mitigation.

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.

This paper evaluates the environmental pressure that is generated by the construction of two types of building, through the application of ecological footprint analysis. The appraisal of the impact of human settlement on the environment is of great concern and environmentally-friendly buildings are actually required. By considering the embodied energy of building materials and the “land area” required to sustain their assembly line, a comparison between the ecological footprint of two typical buildings in the context of Italy is presented. Finally, it is shown that the ecological footprint of building construction can be reduced by using environmentally-inexpensive materials, renewable energy resources and by optimizing bio-productive land use through the construction of multi-story buildings.

The allocation of emissions embodied in international trade is crucial to evaluate the real impact of countries in the climate change and their responsibility in greenhouse gas emissions. In this paper we apply a new theoretical framework that allocates the emissions embodied in international trade and computes the consequent carbon transferred across countries, according to a consumption-based accounting. The method uses the value of goods traded internationally and the respective carbon intensity as a average national emissions coefficient.. We analyze a trilateral trade system composed by Sweden, Italy and Poland during the period 2000-2008. We find that, with respect to the conventional greenhouse gas national inventory schemes, consumption-based accounting implies an increase of Italian and Swedish emission responsibility by 1.4% and 11.8%, respectively, and a decrease of Polish one by 2.81%. We also assess the relevance of this framework at the sectoral level by hypothesizing a shift of Italian imports of Machinery and Transport Equipment from Poland to Sweden. We deduce that, through appropriate policies, importer nations could be encouraged to find producers with the best environmental performances while exporter nations could be induced to reduce their carbon intensity to stimulate the international demand for their goods. Finally, we discuss some policy implications deriving from the application of the consumption-based accounting. The analysis performed in the paper suggests that the consumption-based accounting could be an important tool in the climate change challenge to reduce global emissions.

Abstract This paper aims to clarify some aspects of the discussion between “emergists” and “exergists”. First, we address the problem of the differences between energy-based emergy and exergy-based emergy: we show that the two are proportional, having the exergetic equivalent of solar energy as scale factor. In the second part, we show that emergy and transformity can be written as a function of exergy alone, in particular of “partial” efficiencies of the processes involved in a production system, from solar energy to the final product.

Dr. Maud’s letter introduces many interesting aspects andquestions that are worth clarification. The fact that a mereeconomic management of productive systems is leadinghumanity to the destruction of the planet is, in our opinion,quite clear. Sustainability is a complex concept that needs tobe addressed with a complex approach. One singularfunction, although very suitable, will never be exhaustiveand able to explain all the aspects of sustainability.1. AssumptionsThe authors agree with the two assumptions made by Dr.Maud:A. Emergy evaluation is the holistic approach mostappropriate for analyzing the systems that are at theinterface between natural and human systems. Agricul-tural and zootechnical systems are therefore those inwhich emergy evaluation best expresses its potential.Nonetheless, it is not an omni-comprehensiveinstrumentable to focus on every particular aspect of a system.B. Both poultry systems have a good economic response,the conventional for the lower cost of production, theorganic for the increasing demand of this type of food,especially in top level restaurants.One point, for which we have a different opinion, is abasic aspect of sustainability: according to Dr. Maud, itseems that sustainability is the sum of ecological andeconomic aspects, and that the two aspects should beconsidered separately. We think that the two aspects have adifferent hierarchical value: economic advantage can beinduced or driven by laws, social behaviors, politicaldecisions, etc., if (necessary condition) ecological–physicalsustainability is already achieved. If we consider a systemthat is not economically profitable but ecologicallysustainable, a change in the socio-economic frameworkcan (and should!) enhance economic performance, main-taining the same physical conditions. The contrary, however,is not true: if the goal is economic profit, someenvironmental aspects could be irreversibly damaged. Atmost, we may have a ‘‘compatible’’, but not a sustainable,development.2. The EmMoney use in Emergy evaluationFrom a theoretical point of view, a direct link betweenemergy and economic values is represented by the so-called‘‘emergy-to-money ratio’’ (EMR), which is calculated as theratio of the total emergy flow to the related monetaryevidence. It is expressed in sej/[currency]. Its expression isderived from a macro-systemic (i.e. a nation or a region)analysis by dividing the total annual emergy by the grossdomestic product (GDP). Therefore, EMR depends on thetotal emergy flow, GDP, prices and exchange rates amongcurrencies. Only emergy is directly related to physicalentities. The others are determined by market dynamics.Hence, when EMR is used as a conversion factor to measurethe emergy related to money flows, the market partiallyaffects the emergy content of some flows, arbitrarilyeliminating or creating a portion of emergy.