v>EPA
United States
Environmental Protection
Agency
National Health and Environmental Effects
Research Laboratory, Atlantic Ecology Division
Narragansett, Rl 02882
Research and Development EPA/600/S-08/003
March 2008
ENVIRONMENTAL
RESEARCH BRIEF
Emergy and Its Importance
Daniel E. Campbell1
In ordinary commercial dealings among people, the
value of a product or service within the economy of a
state or nation is determined by what someone is willing
to pay for it. Payment is usually made with money, for
example, dollars when U.S. currency is used. Markets
and agreements between people on prices govern these
economic exchanges. The governance of small-scale
economic transactions in markets is not affected by this
discussion; however, the value of the environment needs
to be considered in a different way when setting public
policy.
People know that money is paid for their work
and that money is not paid to the environment. Yet the
environment does important work that is essential for all
economic activity. When people take products from the
environment, such as water, wood or animals, they do
so without paying for nature's work in providing those
products. Anything taken without payment becomes a
debt or liability on the financial balance sheets used by
all human enterprises. At present modern society owes
a tremendous debt to the environment, but this debt is
not entered on the books kept by government, industry,
and commerce. As a result our present environmental
debt is not being counted, controlled, and serviced in a
reasonable way. One problem is that up to this time, we
have not had an adequate method of accounting for these
debts.
1ORD, NHEERL Atlantic Ecology Division, Narragansett, Rl 02882
Only people can accept money for products and
services, so the environment can not and does not use
money as a measure of value. Value in an ecosystem
is measured not by money, but by flows of available
energy. Available energy is energy with the potential to
do work. All natural systems maximize flows of available
energy to compete effectively for resources. The
capacity to maximize current energy flow is determined
by innovations and changes that have occurred in the
past. Changes, which result in higher energy flows in the
present, are often carried forward into the future. When
everything required for an energy flow is considered,
scientists find that it is actually the sum of the flows of the
past and present available energy within a system that
is maximized. However, both the available energy used
in the past to make the inputs required for a product and
the available energy transformed in the present during
its production must be measured using a common unit to
account for the fact that energies have different qualities,
i.e., different ability to do work when used in a system.
The truth of the statements in the last paragraph can
easily be verified by each individual by considering their
own past. We all know that what we do today and what
we get paid for doing it, in large part, depend on what we
have learned and what we have experienced in the past.
Without our past use of food, shelter, books, and without
our families to support our learning and teachers to impart
their knowledge to us we would not be what we are today
or be able to do the work that we do in our jobs.
In the latter part of the 20th century, H.T. Odum and
his colleagues found and tested a way to quantify the past
Printed on 100% recycled paper
-------
use of available energy of all kinds on a common basis. They
defined the new quantity that accomplished this and called it
emergy. Emergy is all the available energy of one kind used-
up both directly and indirectly in the past to make a product
or service that exists in the present (Figure 1). Emergy is
expressed in its own unit, the emjoule, which connotes the
energy (joules) used in the past, as compared with joules
of energy available in the present in those products and
services. For most evaluations of environmental systems,
we use solar joules as the base unit. The solar energy used
in the past to make a joule of available energy in the present
is called the transformity of the product. Transformity is the
amount of energy of many kinds that is used-up in making
a unit of available energy in something else. It has units of
solar emjoules per joule of available energy (sej/J).
The definitions of emergy and transformity above give
rise to the Fundamental Equation of Emergy Evaluation:
Emergy (solar emjoules, sej) = Transformity (sej/J) x
Available Energy (J)
Emergy allows the work that the environment contributes
to economic activity to be quantified; and since all activities
are based on the transformation of available energy
in some process, economic and social quantities can
also be documented in terms of their emergies. When
all environmental, social, and economic quantities are
expressed in emergy and placed on a single balance sheet,
they are directly comparable and we have a comprehensive
measure of the condition of the system. The balance of
these factors will tell us whether our current system is
operating in a sustainable manner, i.e., the emergy assets
of the environment, economy, and society of a nation,
region or business must exceed their liabilities for the entity
to be healthy and sustainable.
In summary, emergy can be thought of as a kind of
energy memory that is carried forward in the capacity of
each individual thing to do work, when it is used for its
intended purpose within a system. It is important because
maximizing emergy flows is hypothesized to be the criterion
that determines success in evolutionary competition.
Therefore, we must understand and use nature's value
system if we hope to assess the environment fairly for
accounting purposes and discover the information that we
need to make wise public policy decisions.
Potash
1.71X109sej/g
Lime
.8X10s sej/
Phosphorus
2.16X1010sej/g
Nitrogen
2.36X1010sej/g
Pesticides
1.42X1010sej/g
Herbicides
Electricity
1.70X105 sej/J
Labor
4.41 E6 sej/J
'5.71X104g /1.69X103g
1.31X105g/4.23X103g
1.12X105g,3.73X105g
1.09X105g ,0
9.98X103g, 0
7.85X108J
5.91X107J
5.91X107J
2.11X104g
4.69X104g
7.83X103g
.32X108 J
5.78X10s J
1.16X107 J
Services
3.17X1012sej/$
7.23X1012sej/$
3.17X1012sej/$
8.12X109 J
6.82X109 J
9.96X108 J
Soil Loss
72400 sej/J
Evapo-
Transpiration
28100 sej/J
4.25X1010J
9.92X108 J
1.11 X1010J
6.05X1010J
1.48X1010 J
2.55X1010 J
Corn Production
FL Emergy = 9.28X1015 sej
AR Emergy = 4.66X1015 sej
MN Emergy = 4.43X1015 sej
FL Transformity = 5.21X105 sej/J
AR Transformity = 6.71X104 sej/J
MN Transformity = 6.50X104 sej/J
4.39X1O2 $
3.53X102$
6.27X102$
Corn Yield
1.81x1010J
6.95x1010J
6.81x1010J
The Emergy in Grain Corn
Inputs per ha pery
FL, AR, MN
To the Main
Economy
Figure 1. Emergy can be calculated for anything for which the production process is known. The main emergy inputs required for grain
corn produced on a hectare of land in Florida, Arkansas, and Minnesota are given along with the energy yield of corn and the
emergy (sej) and transformity (sej/J) of the yield. Florida and Minnesota use Brandt-Williams (2002) as a template. Arkansas
uses Odum et al. (1998) as a template, and thus a few inputs are summed but not shown for this state.
References
Brandt-Williams, S.L. 2001 (revised 2002). Handbook of Emergy
Evaluation. Folio #4. Emergy of Florida Agriculture. Center for
Environmental Policy, Environmental Engineering Sciences,
University of Florida, Gainesville, FL. 40 p.
Odum, H.T., Romitelli, S., Tigne, R. 1998. Evaluation Overview of
the Cache River and Black Swamp in Arkansas. Center for
Environmental Policy, Environmental Engineering Sciences,
University of Florida, Gainesville, FL, 1998.
------- |