EMERGY

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

Bastianoni, S. and Marchettini, N., 2000. The problem of co-production in environmental accounting
by emergy analysis. Ecol. Model. 129: 187-193.

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 a6erage 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. © 2000 Elsevier Science B.V. All rights reserved.

Emergy Evaluation of Reforestation Alternative in Puerto Rico

Odum, H.T., Doherty, S.J., Scatena, F.N., Kharecha, P.A., 2000. Emergy
evaluation of reforestation alternatives in Puerto Rico. Forest Science
46 (4), 521–530.

Abstract: 
Six alternative ways of reforesting degraded lands in Puerto Rico were evaluated using emergy (spelled with an “m”). Emergy and its economic equivalent, emdollars, put the contributions of environmental work and human services on a comparable basis. This article shows the emergy method for evaluating forest contributions to public benefit and its use to select alternatives for reforestation. Emdollar values were compared for six scenarios for reforestation of degraded land in Puerto Rico: (1) the natural succession within or adjacent to mature forest; (2) reforestation from the spread of the exotic tree siris (Albizia lebbek); (3) reforestation with plantations of siris and mahogany for harvest; (4) reforestation by leaving plantations unharvested; (5) direct planting of seedlings of many species; and (6) starting patches of forest by massive transfer of topsoil, seed bank, and roots. After energy systems diagrams were made for each reforestation alternative, data were assembled and evaluation tables prepared that estimated the emergy required for: (1) canopy closure and (2) developing species complexity if left unharvested. To explain the method, detailed calculations were included for one of the alternatives, exotic Albizia lebbek plantation on 11 yr harvest cycle. All alternatives generated net public benefit (emdollar yield ratios 4.2 to 24.3). The emdollar value of a closed canopy developed in 10 to 20 yr ranged from 20,000 to 48,000 em$ /ha, whereas the economic costs were $1200 to $9700. For complex forest development in 25 to 60 yr, values ranged from 63,000 to 118,000 em$ /ha, much higher than economic costs of $4000 to $12,000/ha. Highest public benefit per dollar cost came from succession (24.7 em$/$) and exotic colonization (19.1 em$/$). Highest potential monetary returns were from exotic spread (15.1 $/$) and plantations (17.9 and 14.5 $/$). Stand quality after 60 yr, as measured by the transformity (emergy/energy), was largest in mahogany plantation (6.4 × 10 4 sej/J) and succession forest (3.9 × 104 sej/J).

An EMERGY Evaluation of Puerto Rico and the Luquillo Experimental Forest

Scatena, F.N.; Doherty, S.J.; Odum, H.T.; Kharecha, P. 2002. An EMERGY
evaluation of Puerto Rico and the Luquillo Experimental Forest. Gen. Tech. Rep.
IITF-GTR-9. Río Piedras, PR: U.S. Department of Agriculture, Forest Service,
International Institute of Tropical Forestry. 79 p.

Abstract: 
The many functions of Puerto Rico and the Luquillo Experimental Forest (the Forest) were evaluated in units of solar EMERGY, an energy-based measure of resource contribution and influence, defined as the energy of one type required to produce a flow or storage of another type. Rainfall and tectonic uplift are the largest environmental inputs into the Forest. The interaction of these inputs results in an erosional landscape where the EMERGY of biological processes is less than the EMERGY associated with the physical and chemical sculpturing of the landscape. The environmental work that built the natural capital of these forests is 9 to 50 times their current dollar market values. Of the investments evaluated in this study, the effects associated with water extraction are the largest. Tectonic inputs and the hydrologic cycle also provide most of the environmental EMERGY flows in the island of Puerto Rico. The ratio of societal inputs to environmental inputs, however, is 45 for Puerto Rico and 3.5 for the Forest. Per capita EMERGY- use is typical of moderately developed economies, but the island has one of the most investment-intensive, least self-sufficient economies known and an EMERGY signature that resembles a city-state.
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