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A Comprehensive Environmental and Economic Assessment Method Applied to the Southwest Michigan Greenhouse Gas Mitigation Cropping Experiment Third USDA Symposium on Greenhouse Gases & Carbon Sequestration in Agriculture and Forestry March 21-24, Baltimore MD Susan Subak, Ph.D.

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Expanded Assessment for Alternative Practices: Environmental Comparison

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Expanded assessment for alternative practices environmental comparison

A Comprehensive Environmental and Economic Assessment Method Applied to the Southwest Michigan Greenhouse Gas Mitigation Cropping Experiment

Third USDA Symposium on Greenhouse Gases & Carbon Sequestration

in Agriculture and Forestry

March 21-24, Baltimore MD

Susan Subak, Ph.D.

Institute for the Study of Society and Environment


Expanded assessment for alternative practices environmental comparison

  • Expanded Assessment for Alternative Practices:

  • Environmental Comparison

  • - greenhouse gas emissions

  • - nitrogen loadings

  • chemical applications

  • Question: Do herbicides applied for No-Till represent a significant pollution trade-off for greenhouse gas abatement?

  • Does the benefit of nitrogen reduction for low-input agriculture surpass greenhouse gas benefits for No-Till?

  • Economic Comparison

  • - direct input cost savings

  • - greenhouse gas reduction value

  • (value of reducing nitrogen and chemicals not assessed)

  • - crop value (price x yield)


Expanded assessment for alternative practices environmental comparison

Kellogg Biological Station Cropping Experiments

NSF – LTER; Michigan State University

Data logs: 1991-1999

Corn/wheat/soybean rotation

T1: Conventional Tillage

T2: No-Till

T3: Low Input with Legume Cover

T4: Organic with Legume Cover

Robertson, G.P., Paul, E.A, Harwood, R.R.Greenhouse Gases in Intensive Agriculture: Contributions of Individual Gases to the Radiative Forcing of the Atmosphere. Science 289(5486): 1922-1925.


Expanded assessment for alternative practices environmental comparison

Greenhouse Gases:

From Robertson et al 2000:

Soil C

CO2 inputs to fertilizer, lime, fuel

N2O

CH4

Nitrogen Loadings:

Compiled from logbooks from KBS for fertilizer applications

Toxicity Index:

Derived by author based on logbooks from KBS for herbicide and pesticide applications


Expanded assessment for alternative practices environmental comparison

Toxicity Index:

I = a x b x 1/c x d x 1/e

a = volume chemical applied (liter/hectare/year)

b = % active ingredient

c = lethal concentration half life (LC50) for trout (mg/liter)

log 10 scaled 1 to 5

d = groundwater ubiquity index (GUS)

log 10 scaled 1 to 5

e = water degradation half life (days)

log 10 scaled 1 to 5


Expanded assessment for alternative practices environmental comparison

  • Value of alternative practices compared with Conventional Tillage:

  • Input Costs

  • Greenhouse Gas Emissions Abatement ($10 t CO2e)

  • Crop Value


Expanded assessment for alternative practices environmental comparison

Conclusions from KBS Example:

Environmental:

- Chemical impact (Toxicity Index) of CT, NT and Low Input/legume were similar

- Nitrogen loadings were very different for the low-input practices (compared with CT and NT) but importance depends on estimated local impact

- Environmental benefit from reduced GHG and/or nitrogen loadings compared with CT is clear

Economic:

- Higher crop yields from NT were canceled out by higher direct input costs

- Lower crop yields from Low-Input/legume were canceled out by lower input costs

- Greenhouse gas abatement value is low, under current assumptions, but can change the incremental value from negative to positive when comparing these alternatives to CT


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