by Dr. Calvin B. Parnell, Jr.

The following are specific comments on GHG reporting for fugitive emissions from cattle feed yards surfaces:

• EPA specified in the proposed GHG emissions reporting rule that the mandatory reporting in 2010 should only include CH₄ and N₂O from manure management. CH₄ from enteric fermentation was not included in the mandatory reporting proposal. This action can be interpreted as EPA deciding that enteric fermentation will not be regulated.  The justification for excluding reporting emissions of CH₄ from enteric fermentation of beef cattle emissions is not clear and should be addressed.  The most likely control for this source is reducing the number of cattle on feed which may be politically unacceptable. According to the EPA emissions inventory estimates, 17% of the total agricultural emission of CH₄ is attributed to beef cattle enteric fermentation. This is in contrast to less than 0.5% of the total U.S emissions of CH₄ from manure management. If the goal is to significantly reduce GHG emissions to slow the global warming process,  there is very little benefit to  requiring all beef cattle feeding operations to report their emissions of CH₄ from manure management

·         Likewise, the magnitude of the N₂O emissions in units of CO₂e from manure management for beef cattle feed yards are very small relative to the total U.S. emissions of N₂O (2.2%) and relative to the total emissions from all agricultural sources (3%). (These emissions take into account the global warming potential of 310.) The determination of emission factors for N₂O for fugitive sources is very difficult. The protocol of measuring concentrations downwind, subtracting upwind (background) and calculating fluxes will not work for this species. Background N₂O concentrations are reported to be 319 ppm. Based upon our engineering calculations, the downwind concentrations of N₂O will be approximately 20 to 30ppb (0.02 to 0.03ppm). The measurement uncertainty associated with the resulting emission fluxes (factors) is too large.

 

Calculations: (Reference EPA. 2009. Emissions Inventories)

GHG emissions of CH₄ with a global warming potential of 21 using 2005 as the reference year:

1.      Total emissions (CO₂e) from all sources of CH₄ in the U.S. in 2005= 562 million metric tons (10⁶ tonnes);

2.      Total agricultural emissions (CO₂e) from all sources of CH₄ in 2005= 186*10⁶ tonnes;

3.      Total enteric fermentation emissions (CO₂e) from all sources of CH₄ from all beef cattle on feed yards in the U.S. in 2005=98*10⁶ tonnes

4.      Total beef cattle manure management CH₄ emissions (CO₂e) from all beef cattle on feed yards in the U.S. in 2005=2.4*10⁶ tonnes

 

GHG emissions of N₂O with a global warming potential of 310 using 2005 as the reference year:

1.      Total emissions (CO₂e) from all sources in the U.S. in 2005=316*10⁶ tonnes)

2.      Total agricultural emissions of N₂O (CO₂e) from all agricultural sources in 2005= 223 million metric tons (10⁶ tonnes)

3.      Total manure management beef cattle emissions (CO₂e) from all sources of N₂O from all beef cattle on feed yards in the U.S. in 2005=6.5*10⁶ tonnes

 

Table 1. Mass fractions of GHG emissions in units of CO₂e from beef cattle operations. (Reference EPA. 2009. Emissions Inventories)

 

 

·         EPA selected a mandatory reporting threshold of 25,000 metric tons (10³ tonnes) for all sources. This threshold was justified using an economic approach. The data used to calculate the costs included many assumptions and estimates that are questionable. With the EPA’s published emissions inventory (April 15, 2009), an alternative means for determining mandatory reporting thresholds is available and could provide a more logical means for determining which facilities should be required to report.

·         The regulation of GHG emissions is limited to emissions inventories (annual emissions). The goal is to find ways to reduce annual emissions of GHG to slow down the increase in CO₂e to prevent climate change or global warming. Forcing small emitters to report their emissions when reduction of their GHG emissions would have little impact on the increase in the concentration of CO₂e in the atmosphere is illogical.

·         Using 2005 as the base year, the total GHG emissions from all sources were 7,110*10⁶ tonnes. The total mass of CO₂e emitted by cattle feed yards of CH₄ and N₂O were (2.4+6.5)*10⁶ = 9 million tonnes. It is assumed that CO₂ emitted by cattle feed yards will not be regulated because it is CO₂ that has been sequestered in the feed. Hence, only emissions of CH₄ (562*10⁶ tonnes) and N₂O (316*10⁶ tonnes) from manure management must be reported. These emissions amount to only 0.43% and 2.1% of the total emissions of CH₄ and N₂O emitted, respectively.

·         The 25,000 tonnes mandatory emission threshold for reporting relative to the total mass of GHG emitted in 2005 is very low threshold. The reductions by 2020 mandated by the H.R.2454 are approximately 2 billion tons (2*10⁹ tonnes). 25,000 tonnes are less than 0.2% of the total reduction mandated by 2020. Why has EPA listed such a low threshold? The many “small emitters” of GHG will be spending much effort to comply with no net benefit to the goal of reducing the atmospheric concentration of CO₂e.

·         The number of cattle on feed yards that would result in required mandatory reporting was listed as 89,000 head. This number is incorrect. Using the data in table 1 and the reported 14 million (10⁶) head as the total number of head on feed yards in the U.S., the 25*10³ tonnes corresponds to 37,600 head not 89,000 head.

 

Calculations: (Reference Table 1)

Beef Cattle Manure Management Emissions (BCMM)

BCMM = [2.4 (CH₄) + 6.5 (N₂O)]*10⁶tonnes/year = 9*10⁶tonnes/year

Emission Factor (EF) = 9*10⁶tonnes/year/14*10⁶ head of cattle on feed

EF = 0.665 tonnes/hd-yr

Number of head on feed to emit 25*10⁶tonnes = 25,000/0.665= 38,000 head on feed.

 

Summary of Comments:

 

1.      GHG emissions should not be regulated as a “regulated” pollutant under the CAA. There are no direct health effects associated with breathing concentrations of CO₂e in the atmosphere. The costs in terms of Title V permitting and associated Title V fees would be overwhelming.

2.      The magnitude of manure management (CH₄ and N₂O) CO₂e emissions from cattle feed yards is very small relative to other sources. It is unlikely that any significant reductions of GHG will be obtained from regulating this source.

3.      The magnitude of enteric fermentation (CH₄) CO₂e emissions from cattle feed yards is significant and is not included in the mandatory reporting. Environment special interests will insist that this source be regulated. This should be addressed by EPA in the proposed rule. How will belching and passing gas be regulated? It seems that the only method to reduce this source of GHG will be to limit the number of cattle on feed yards. This may be unacceptable to the public.

4.      The method used to have all sources emitting 25*10³ tonnes required to report GHG emissions is flawed. It is recommended that some means of exempting small sources of GHG using EPA’s emissions inventories would be a better method. 25*10³ tonnes of CO₂e is less than 0.0000035% of the total GHG emitted in 2005.

5.      The mandatory reporting threshold for cattle on feed yards should be corrected. It is not 89,000 head.

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