DR. Don Research Update
Life cycle analysis of a crop system, Part 1
Dissecting the system designed to quantify the full environmental impact of productions systems

By Don Lotter

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 LCA methodology.

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:

Input related:

  • Depletion of abiotic resources
  • Land use

    and output related:
  • Human and eco- toxicity
  • Climate change
  • Ozone depletion
  • Acid rain
  • Eutrophication

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 score tallied.

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 LCA scores.

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

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