|Parnell, Jr., Calvin|
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/6/2006
Publication Date: 6/30/2006
Citation: Wanjura, J.D., Parnell, C.B., Shaw, B.W., Capareda, S.C. 2006. Source testing of particulate matter emissions from cotton harvesters - system design. In: Proceedings of the Beltwide Cotton Conference, January 3-6, 2006, San Antonio, TX. 2006 CDROM. p. 370-378. Interpretive Summary: Particulate matter (PM) emissions from agricultural operations, including cotton harvesting, have come under increased regulatory pressure in the U.S. Regulators in California calculate annual emissions from cotton production operations based on emission factors developed from protocols using ambient PM10 samplers and dispersion modeling. The samplers used in these protocols most likely reported PM10 concentrations that were in error due to the interaction of the sampler performance characteristics and the particle size distribution of the dust emitted from the operation. Agricultural dusts have particle size distributions characterized by mass median diameters in excess of 15um and geometric standard deviations in the range of 1.6 to 2.3. It has been shown that an ambient PM10 sampler sampling dust with these characteristics could report PM10 concentrations in excess of true PM10 concentrations by as much as 300 – 400%. The dispersion models used to develop the emission factors were state of the art at the time they were used, but later science has provided better methods to use in modeling the downwind impacts of emissions. This paper focuses on the development of a new system to measure emissions from cotton harvesting operations on a source testing basis. Preliminary design concepts are discussed and evaluated through the use of a simulation model to determine the feasibility of implementing the design in a new emission factor development protocol.
Technical Abstract: Recent air quality legislation has placed increased pressure on agricultural producers in several states across the U.S. In particular, California removed the exemption for agricultural sources from air quality permitting in 2003. Through the use of inaccurate particulate matter emission factors, agricultural operations have been targeted as significant sources of particulate matter emissions. The emission factors used by regulators in California were developed using techniques with high levels of uncertainty. The objective of this manuscript is to present a novel approach to measuring source emission concentrations from cotton harvesting operations. The proposed sampler design would collect all of the harvested seed cotton, trash, and conveying air at the exit of the conveying ducts used to transport the harvested material to the basket. The air and entrained particulate matter would be separated from the seed cotton and large trash inside a dropper box where isokinetic concentration measurements would be taken at a point just before the air and entrained particulate matter is exhausted to the outside. Subsequent particle size distribution analyses of the particulate matter collected from the isokinetic samples would be used to determine the corresponding PM10, PM2.5, and PM10-2.5 source emission concentrations. Finally, particulate matter emission factors would be calculated (for each size fraction indicator, i.e. PM2.5, PM10, or PM10-2.5) on both a lbs/acre and lbs/bale harvested basis. It is expected that the techniques discussed in this manuscript would yield more accurate science based emission factors than the emission factors currently in use.