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August 2012 A Deeper Shade of Green 26
Appendix A. Basis for and Sources of Key Variables and
Equations
1. Formula for ECM
The equation to calculate “Energy Corrected Milk,” or ECM is –
ECM (kgs or pounds/day) = (UMPD x 0.323) + (7.13 x Protein Content) + (12.82 x Fat Content)
Where:
UMPD is unadjusted milk production per day
Protein content is kgs/pounds of protein
Fat content is total kgs/pounds of fat.
Source: Washington State University Extension, 2008; http://www.extension.org/faq/27579.
2. EPA Method for Calculating Enteric Methane Emissions per Cow
The EPA-recommended formula for estimating enteric methane emissions from a cow is –
Enteric Methane (kg/day) = (GE x Ym)/55.65
Where:
GE is Gross Energy intake,
Ym is a constant, and refl ects the portion of GE converted to methane
55.65 converts millijoules to kilograms
3. EPA Method for Manure Methane Emissions
The method used by EPA to project manure methane emissions is –
Manure Methane (kg/day) = VSP x Bo x MCF x 0.662
Where:
VSP is Volatile Solids Produced
Bo is the methane producing potential of waste
MCF is the Waste Management System Methane Conversion Factor (MCF), composed of a weighted average of the
MCFs associated with the different methods used on a farm to manage manure.
For full discussion of these and all other equations and data sources used in the SOG Version 1.2, see the SOG User
Manual. http://www.organic-center.org/SOG/Home