Mid Sweden University

Emergy accounting (also named emergy analysis or emergy synthesis) is a method developed from systems science and systems ecology. Emergy is a measure appearing when applying the energy hierarchy principle to natural (e.g. forests and lakes) or human (e.g. cities, regions and countries) systems. The principle postulates that energies in any system will self-organize in hierarchical patterns given time to do so (Odum 1994, 2007). Emergy is expressed in relation to one type of energy occurring in the hierarchy, almost always solar emergy Joules, seJ. In the context of economy, emergy values can alternatively be expressed in a currency related unit, for example Em€ or Em$ (proportional to values in seJ). The significance is that Em€ or Em$ measures the contribution different items gives to the whole system, rather than how individuals value different items on the market; a donor value approach rather than a receiver (market) value approach (Grönlund et al., 2015).

Emergy accounting has similarities with ecological footprint (EF) accounting. EF in principle accounts for the area of productive land needed to produce what we consume (measured in a unit called global hectares, a normalized hectare that takes into account different productivity and production methods–agriculture, forestry, and fishing–in different countries). By comparing this to the productive hectares available in the biosphere, the annual overshoot can be calculated. In the latest presentation the annual overshoot is calculated to be at least 50%. The EF method has met some methodological criticism based for example on the problems to include fossil fuels, water use, nuclear power, and toxicity aspects into the calculations. Emergy accounting has solved at least the two first of these problems.

Similar to ecological footprint (EF) accounting Emergy accounting use a global baseline for comparison. However, when EF uses the productive capacity of biological production in the biosphere (biocapacity), Emergy accounting instead use the renewable energy flows (solar, tide, and deep heat energies) driving the biosphere the investigated year. The comparison with the global baseline has made the two methods useful to evaluate activities covering large land areas as nations and regions, and of course the full biosphere. Cities have also been possible to evaluate since they generally depend on large production areas (EF) in the countryside or use a large share of the annual driving energies of the biosphere (Emergy accounting).

Many regions have been evaluated with Emergy accounting. For example several counties in Florida (Odum, 1994), the Caribbean island of Bonaire (Abel, 2000), the U.S. National forests (Brown and Campbell, 2007), the regions of  Nyando and Kerisho in western Kenya (Cohen, 2003), the Rolling Pampas in Argentina (Ferreya, 2001), the Siena region in Italy (e.g. Pulselli et al., 2008), the Okavango delta in Botswana ( Lehmensiek, 2004), and the Yancheng Biosphere Reserve in subtropical China (Lu et al., 2006). Some of the evaluation has also explicitly addressed regional sustainability, for example Dan Campbells (1998) “Emergy analysis of human carrying capacity and regional sustainability: an example using the state of Maine”.

Emergy accounting of urban areas during the period 1971-2015 have been reviewed by Grönlund et al. (2015). They found that sustainability became the main focus from approximately 2008 and up today. Investigated urban areas with a sustainability focus has been Macao (e.g. Lei et al. 2014), Beijing (e.g. Zhang et al., 2011), Rome (Ascione et al., 2009), Shenyang (Liu et al., 2014), and Montreal (Vega-Azamar et al., 2013).

Central in the sustainability assessment has been emergy indices of different kinds, e.g. Emergy Yield Ratio, Environmental Loading Ratio, Emergy Investment Ratio, Empower Density, Renewability, Emergy Intensity of currency, Emergy Exchange Ratio, Emergy/capita, Emergy-based Urban Ecosystem Health Index, Waste to emergy ratio, Waste to renewable, Emergy use purchased ratio, and Metabolic dependence (Grönlund et al. 2015).

Emergy accounting delivers something new to science: a quantitative method that claims to be able to handle flows of both energy and matter, sometimes said to represent the economy of nature, and economic flows, said to represent the economy–“living”–of human systems, like e.g. cities. This will open up for creative new ideas. When environmental economics was an emerging field within economics a couple of decades ago, a phase of creativity started with a wide flora of hypothesis’ emerging on how to put value on environmental issues outside of the traditional scope of neoclassical economic theory (“internalize the externalities”). A similar phase is likely to emerge now in the field of ecology, where emergy accounting will open up for new creative applications of how to incorporate economic flows and values into systems including both nature and society.

References

Brown, M. T., & Ulgiati, S. (2004). Emergy Analysis and Environmental Accounting. In C. J. Cleveland (Ed.), Encyclopedia of Energy (pp. 329-354). New York: Elsevier.

Campbell, D. E. (1998). Emergy analysis of human carrying capacity and regional sustainability: an exampel using the state of Maine. Environmental Monitoring and Assessment, 51, 531-569.

Grönlund, E., Fröling, M., & Carlman, I. (2015). Donor values in emergy assessment of ecosystem services Ecological Modelling, 306, 101-105.

Grönlund, E., Fröling, M., & Skytt, T. (2015). Energy, Emergy and the City. Paper presented at the Energy and Urban Systems. 9th Biennial International Workshop Advances in Energy Studies, Stockholm 4-7 May, 2015.

Odum, H. T. (1994). Ecological and general systems - an introduction to systems ecology. Niwot, CO, USA: Univ. Press of Colorado.

Odum, H. T. (2007). Environment, power and society for the twenty-first century : the hierarchy of energy. New york: Columbia University Press.