|January 22, 2004:
To evaluate the sustainability and environmental impact
of any production system, more has to be done than to
just look at the immediate, proximate impacts, such as
the effects of sprays and fertilizers on ecosystems. Life
cycle assessment (LCA) looks in depth at production systems
by assessing “embedded” environmental impacts
– the environmental impacts that occur in producing
and transporting the different components that go into
a production system, as well as the proximate impacts.
Researchers from Germany have developed a methodology
for doing LCA on crop systems and have done an initial
LCA on synthetic nitrogen fertilizer use in wheat. This
research is an important development, because no comprehensive
environmental analysis can be done of agricultural systems,
such as comparing the environmental impacts of organic
vs. conventional crop production systems, without some
form of LCA.
This and the next research update will look at the
two papers by Brentrup et. al., being published in the
European Journal of Agronomy, that describe their crop
The Europeans are far ahead of North American researchers
in developing methods for assessing the environmental
impacts of agriculture, due to the legislative mandates
laid down by the European Union.
The first step in developing a LCA is to select a reference
unit, in this case, the production of one ton of wheat
in Europe. Everything in the LCA is referenced to this.
Reasonable system boundaries are set to count only the
important components of production.
One of the fundamental divisions the authors make is
between impacts on ecosystems/humans and impacts due
to resource depletion. Resource depletion doesn’t
have an impact per se but has its own scarcity impact.
For example, the mining of phosphates causes impacts
on ecosystems/humans (i.e. pollution) and depletes a
resource as well.
A life cycle inventory is developed of all resources
that are used and all outputs generated by the wheat
production system, i.e. resources used in soil tillage,
fertilizer application, harvest etc.
Environmental impact categories were developed –
these will be somewhat consistent through all types
of human production. These are listed as:
- Depletion of abiotic resources
- Land use
and output related:
- Human and eco- toxicity
- Climate change
- Ozone depletion
- Acid rain
Each of the items in the life cycle inventory, i.e.
resources used in soil tillage, fertilizer application,
harvest etc. is given a score for each environmental
impact category. So in the climate change category,
CO2, N2O, and CH4 emissions are added up for the resources
used in each component in the inventory.
These are then weighted so that different impacts can
be put into the same quantification process and a single
This process has gaps and fuzzy areas that need to
be approximated, and the process of “fuzzy thinking”
(an area of science that deals with gray areas) is important
in the endeavor. The lack of complete data sets in LCA,
I believe, is one reason why U.S. scientists have not
developed the science of LCA. There are too many gray
areas in LCA work and U.S. scientists have trouble with
that, as well as trouble tackling whole systems.
The Europeans clearly seem to be more comfortable with
the concept of grasping the system as a whole, using
the data that exists in the system, and where there
is no data, making an approximation.
The next update will look at the wheat system and how
different levels of N fertilizer gave widely different
Brentrup, F. et al. 2004. Environmental impact assessment
of agricultural production systems using the life cycle
assessment methodology I. Theoretical concept of a LCA
method tailored to crop production. European Journal
of Agronomy. 20, 247-264.
Don Lotter has a Ph.D. in agroecology and has worked
in sustainable agricultural development in North America,
Latin America, and Africa over the past 25 years. He
can be contacted via his website www.donlotter.com