WAC 173-408-980:

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173-408-190 << 173-408-980 >> 173-408-990

1.0 Calculate Heat Input Capacity

Equation 1

Where:
	Collection Efficiency	=	The landfill gas collection efficiency in percent (%), which is 75 percent.
	GHV (Gross Heating Value)	=	Gross heating value of methane, which is 1,0121 in units of British thermal units per standard cubic feet, or Btu/scf.

1	Landfill Methane Outreach Program (LMOP) Interactive Conversion Tool

2.0 Methane Gas Generation

CH4 Generation is calculated using the following equation:

Equation 2

Where:
	CH4 Generation	=	CH4 generated in the inventory year (Mg of CH4).
	FCH4	=	Fraction of decomposing carbon converted into CH4 (Default = 0.5).2
	ANDOCyear-start	=	ANDOC in place at the beginning of the inventory year.
	ANDOCdeposited-last year	=	ANDOC deposited during the previous inventory year.
	ANDOCdeposited-same year	=	ANDOC deposited during the inventory year.

2	2006 IPCC Guidelines for National Greenhouse Gas Inventories

3.0 To Convert Methane Generated from Mg of CH4 to SCFM

Equation 3

4.0 Define ANDOC%

Equation 4

Where:
	WIPFRACi	=	Fraction of the ith component in the waste in place.
	TDOCi	=	Total Degradable Organic Carbon fraction of the ith waste component (Mg of that component/Mg of Total waste in place).
	DANFi	=	Decomposable Anaerobic Fraction of the ith waste component, that fraction capable of decomposition in anaerobic conditions (Mg of decomposable carbon for that component/Mg TDOCi for that component).

5.0 Define ANDOC

Equation 5

Where:
	ANDOC	=	Anaerobically Degradable Organic Carbon, carbon that is capable of decomposition in an anaerobic environment (Mg of carbon).
	WIP	=	Waste in place estimate of all the landfilled waste (wet weight) as reported to Ecology's Solid Waste Management Program (tons).

6.0 Calculate ANDOCyear-end

Equation 6

Where:
	ANDOCyear-end	=	ANDOC remaining undecomposed at the end of the inventory year.
	ANDOCyear-start	=	ANDOC in place at the beginning of the inventory year.
	ANDOCdeposited-last year	=	ANDOC deposited during the previous inventory year.
	ANDOCdeposited-same year	=	ANDOC deposited during the inventory year.
	M	=	Assumed delay before newly deposited waste begins to undergo anaerobic decomposition (Months, Default = 6).
	k	=	Assumed rate constant for anaerobic decomposition; k = ln2/half-life (years); half-life is the number of years required for half of the original mass of carbon to degrade.

Table 1 lists the accepted constant values for the anaerobic decomposition rate ("k").

Table 1: K Values

K for Average Rainfall (Inches/Year)
Inches Rain	<20	20-40	>40
K Value	0.02	0.038	0.057

[Statutory Authority: Chapter 70A.540 RCW. WSR 24-11-052 (Order 22-15), § 173-408-980, filed 5/13/24, effective 6/13/24.]

Reviser's note: The brackets and enclosed material in the text of the above section occurred in the copy filed by the agency.