Summary. There is currently no published data on particulate matter (PM) emission rates (factors) from dairies. The philosophy of some State Air Pollution Regulatory Agencies (SAPRA's) is to use the emission factor that had been published in AP-42 for cattle feedyards of 280 lbs/1000 head per day (lb/1000hd/d) total suspended particulate (TSP) matter or 70 lb/1000hd/d PM10 for permitting and emissions inventory purposes. Prior to EPA removing this cattle feedyard emission factor from AP-42, the Department of Biological and Agricultural Engineering at Texas A&M University had determined that a more appropriate emission factor for cattle feedyards in the relatively arid west Texas area was 19 lb/1000hd/d (uncorrected for rainfall and snow events). The source of PM from cattle feedyards and dairies is the open surface of the pens (manure pack). The major difference between dairies and cattle feedyards is the fraction of time the dairy herd is in contact with the manure pack relative to cattle on feed. It is assumed that because of the relative small fraction of time that the dairy herd is on the manure pack, the dairy PM10 emission factor will be less than 19 lb/1000hd/d. The goal of this research is to obtain a science based emission factor for dairies that can be used for SAPRA permitting purposes.

Keywords. PM10, PM2.5, total suspended particulate, air sampling, emission rate, Freestall dairy, emission factor, emissions inventory

Introduction:

The agriculture industry is coming under increased scrutiny as a pollution source. This is especially true in non-attainment areas. The San Joaquin valley in California is classified as serious non-attainment for PM10. State Air Pollution Regulatory Agencies (SAPRA's) are required to include in their respective State Implementation Plans (SIP) procedures whereby non-attainment areas will be brought into attainment. These procedures are based upon emissions inventories, permitting, and emission factors. This is a problem specifically in California due to the dairies location in PM10 non-attainment areas. The focus of the SIP is on reducing pollution from the largest sources. If the dairy emission factor is grossly in error, the emissions inventories for PM10 from dairies will be in error. If the SIP plan for bringing the PM10 non-attainment areas into attainment is based upon erroneous emissions inventories, it is unlikely the area will be brought into attainment. In order to reduce PM10 emissions from dairies, the SAPRA will likely require that additional controls be installed with the permitting process. The economic burdens of reducing PM10 emissions from dairy operations will likely result in more dairies being forced out of business. It is imperative that accurate PM10 emission factors be used by SAPRA's for emissions inventory and permitting purposes. Peters and Blackwood (1978) developed an emission factor of 127 kg/1000hd/day total suspended particulate (TSP) matter (280 lb/1000hd/d TSP) for feedyards. This work was done using sampling data from Algeo et al., (1972) which represented the only data available at the time. Sweeten et al (1989, 1998) demonstrated that 25% of the TSP emitted by cattle feedyards was PM10. EPA accepted this PM10/TSP ratio. Hence, the PM10 emission factor used by SAPRA's for permitting and emissions inventory purposes was 32 kg/1000hd/d (70 lb/1000hd/d PM10) The errors associated with the AP-42 emission factor based upon Peters and Blackwood's study were documented by Parnell et al (1999). Subsequent work by Texas A&M University (Parnell et al., 1999) has shown that a more appropriate number would be 6.8 kg/1000hd/day PM10 (15 lb/1000hd/day PM10).

Feedlots for beef cattle are open pens with the pen surface serving as the manure pack. The action of the cattle on the manure pack is the source for PM emissions from the facility. Conversely, freestall dairies will keep the lactating portion of their herd in freestall barns with the rest of the cattle being kept in pasture areas or open pens similar to feedlots. A typical freestall barn consists of a feed alley down the center with feed bunks on each side. The exercise pens are only used during nighttime hours, and have the same surface composition as the open pens. Manure primarily accumulates in the alleys and is removed in one of two ways: flushing or scraping. Flushing involves introducing a large volume of water into the alley which flows into a collection system. The second method used for removing manure from the alley and the open pens is to use a mechanical scraping system. The flushing is performed multiple times daily in order to minimize manure accumulation in the alleys (EPA, 2001). Scraping of the pens is a control method used to reduce PM emissions. the frequency of scraping will vary from dairy to dairy. The frequency of manure removal in the free stall alleys minimizes PM entrainment from this section of the dairy.

Conclusions

From sampling conducted at a single central Texas dairy in the summer of 2002, a preliminary emission factor of 2.0 kg/1000hd/day PM10 (4.4 lb/1000hd/d) was determined. This number does not represent the variation that will occur throughout the year as ground conditions change, though it is much more representative of PM10 emissions from a freestall dairy than the current feedyard emission factor of 32 kg/1000hd/day PM10 (70 lb/1000hd/d) that has been used by some SAPRA's. The process described in this paper represents one of several methods that can be used to calculate emission factors from measured net PM concentrations. There is significantly more work that needs to be completed before a final emission factor can be published.

The measured concentrations were for 2 to 4 hour periods. In effect, the individual emission factors corresponded to the time period when sampling occurred. For comparison purposes, all emission factors were converted to a 24-hour basis.

For more information on this project, please contact:

Calvin B. Parnell
c-parnell@tamu.edu
979-845-3985
207-D Scoates Hall
2117, TAMU
College Station, Texas 77843-2117
USA.

Saqib Mukhtar
Mukhtar@tamu.edu
979-458-1019
303-B Scoates Hall
2117, TAMU
College Station, Texas 77843-2117
USA.