Introduction Problem: (Dairy)-farming is messy! Agriculture: 6.3 % - - PDF document

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A linear programming model to optimize diets in environmental policy scenarios

Paper by: L.E. Moraes, J.E. Wilen, P.H. Robinson, J.G Fadel (2012) Presented by: Dan Jensen

Introduction

• Problem: (Dairy)-farming is messy!
• Goal: Tool for optimizing dairy cattle diet
• Status of this research: Preliminary!

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• Agriculture: 6.3 % total US GHG emissions (2009)
• Enteric fermentation (): 20 % of US human GHG
• Also nitrogen, phosphor, etc.
• Effect of emission taxes
• Forced (assumed) reduction
• Sensitive to constraints. E.g. feed prices

Methods General Background

• Linear Programming Model (LPM)
• Reminder - an LPM is:
• Method to achieve best outcome given certain

constraints

• Constraints are represented by linear

relationships

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Methods The models

• Three scenarios – three models:
• BASEM: Cheapest possible feed (baseline)
• TAXM: what if there was an emission tax?
• … of 5 $ per tonne?
• … of 17 $ per tonne?
• … of 250 $ per tonne?
• REDM: what if you were forced to reduce

emissions?

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Methods The models, Assumptions 1

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−

Methods The models, Assumptions 2

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Locally collected kg/kg DM $/kg DM − − −

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Methods The models, Assumptions 2.1

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Methods The models, specifics

• BASEM/REDM:

Remember: j = feed c = cost of feed

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Methods The models, specifics

• TAXM:

Remember: j = feed c = cost of feed Notice: e = expected emission (tonnes) p = tax price per tonne

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Methods The models, Outputs

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55.65 MJ/kg

• How big is the mess?

Feed composition – absorbstion Excrete composition

5 minute break

Methods The models, Constraints 1

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Nutrient req.

• Diet. Feet Limits

Methane Restrictions DMI Other Limits, 1

• Diet. Barley Limits

Other Limits, 2

• Diet. Forage Proportions

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Methods The models, Constraints 2

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Nutrient req.

Remember: j = feed a = cow category (7 kinds) i = nutrient (14 kinds)

Amount Nutrient content Requirement

7 x 14 = 98 eq.

Methods The models, Constraints 3

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• Diet. Feed Limits

Remember: j = feed a = cow category (7 kinds) l = limit (for 10 kinds of j)

≤ ∙

• 7 x 10 = 70 eq.

Methods The models, Constraints 4

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Methane Restrictions (REDM) Total feed (all cows, all feed) Methane predictions 1-Reduction BASEM emission Max. Emission

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Results

• REDM:

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↓ → ↓ ! ∴ ↓ → ↑ $%!

Results

• REDM:

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Crude protein consumption given Methane reduction For the 7 kinds of cows Metabolisable energy proportion given Methane reduction

Results

• REDM:

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Consumption Excretion

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Results

• Shadow prices, Feed stuff:

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%&! '( )*!%' )%!+:

• .)*!'* / -0 !(1*%'+

Results

• Shadow prices, Methane emissions:

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Conclusions

• Cost of low emission diet exceeds cost of taxes

TAXM ~ BASEM

• Reduction of emissions yields increase in

Nitrogen-excretion

• Further studies are needed!

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