This page provides a brief
introduction to ecosystem
goods
and
services,
their accounting in existing life
cycle
oriented
methods, and the techniques
available
in
Eco-LCA.
Eco-LCA is a physically-based approach
to account for the role
of ecosystem services.
Resources that it accounts for are shown in Table
1.
These resources are
represented in their original units and
combined to yield a hierarchy of metrics.
- Raw and normalized data. The raw data are in a
variety of units and may be normalized to permit their comparision. The
current Eco-LCA implementation uses the total consumption or flow of
each resource in the U.S. economy for normalization.
- Classification. Classification schemes in Eco-LCA
include,
renewable versus nonrenewable, biotic versus abiotic,
materials versus energy, or in terms of their originating ecosphere
(lithosphere, biosphere, hydrosphere, atmosphere, and other services).
- Aggregation. Eco-LCA includes various aggregation
schemes that are based on thermodynamic concepts.
- Energy includes
renewable and nonrenewable
energetic sources including fossil fuels, sunlight and wind.
- I Exergy is
Industrial Cumulative Exergy
Consumption, which includes material and energy resources extracted
from nature and consumed in industrial activities. This approach is
similar to exergy analysis used in engineering (Szargut
et
al.,
1988).
- I+E Exergy is
Ecological Cumulative Exergy
Consumption, which extends I
Exergy by also accounting for the exergy
consumed in ecosystems. This approach is closely related to emergy
analysis developed in systems ecology (Odum,
1996).
- Metrics. Various metrics such as renewability
index, return on investment, etc. may be calculated based on these
results.
The Eco-LCA software
is based on an integrated ecological-economic model of the U.S. economy
( Zhang
et al., 2010), and is best
suited for assessment at the scale of economic sectors. Data at the
process scale can also be combined with the input-output model to
result in a tiered hybrid life cycle study. Such studies are described
in published papers ( Urban
and Bakshi, 2009; Baral
and Bakshi, 2010).
Ecosystem Goods and
Services
Ecosystem goods and services are broadly classified into the
following
categories.
- Supporting services, such as biogeochemical
cycles, support all other services.
- Regulating services, such as flood protection and
climate and disease regulation, are benefits from the regulation of
ecosystems.
- Provisioning services, such as food and genetic
resources, are obtained directly from ecosystems.
- Cultural services are spiritual and recreational
benefits that people obtain from ecosystems.
The millennium ecosystem assessment
identified that state of many of these
services continues to deteriorate due to anthropogenic pressures.
Life Cycle Oriented
Methods for Sustainable Engineering
Despite much effort, as discussed in the
critical review by Zhang
et
al. (2010),
none
of
the
existing life cycle oriented methods, including life cycle
assessment, ecological footprint, emergy analysis, human appropriation
of net primary productivity, and others, account for all the ecosystem
goods and services. Even among the methods that account for some
ecosystem
services, the emphasis is on representing their contribution in common
units such as global hectares for ecological footprint, solar
equivalent joules for emergy, or dollars for methods based on monetary
valuation. Such univariate representation is appealing
due to easier interpretability of the results, but assumes
substitutability between the resources being aggregated, and
usually cannot account for many resources due to difficulties in
representing them in terms of the selected common unit.
References
-
Baral, A., B. R. Bakshi, R. Smith,
Assessing Resource Intensity and Renewability of Cellulosic Ethanol Technologies using Eco-LCA,
Environmental Science and Technology, accepted, 2012
-
Bakshi, B. R., M. J. Small,
Incorporating Ecosystem Services into Life Cycle Assessment,
J. Industrial Ecology, 15, 4, 477-478, 2011
-
Baral, A., Bakshi, B. R., Thermodynamic Metrics for
Aggregation of Natural Resources in Life Cycle Analysis: Insight via
Application to Some Transportation Fuels, Environmental
Science and Technology, 44, 2, 800-807, 2010
-
Odum, H. T., Environmental Accounting: Emergy and
Environmental Decision Making, John Wiley, 1996
-
Szargut, J., Morris, D. R.,
Steward, F. R., Exergy Analysis of
Thermal, Chemical and
Metallurgical Processes, Hemisphere Publishing, 1988
-
Urban, R. A., Bakshi, B. R., 1,3-Propanediol from
Fossils versus Biomass: A Life Cycle Evaluation of Emissions and
Ecological Resources, Industrial and Engineering Chemistry
Research, 48, 17, 8068-8082, 2009
-
Zhang, Y., Singh, S.,
Bakshi, B. R., Accounting
for
Ecosystem
Services
in
Life
Cycle
Assessment, Part I: A Critical
Review, Environmental Science and Technology, 44, 7,
2232-2242, 2010,
2010
-
Zhang, Y., Baral, A.,
Bakshi, B. R., Accounting
for
Ecosystem
Services
in
Life
Cycle
Assessment, Part II: Toward an
Ecologically-Based LCA, Environmental Science and Technology,
44,
7,
2624-2631,
2010
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