Milling & Baking News - December 9, 2014 - 26

Regulatory Affairs

Air emission calculation for
particulate matter: Flour
Particulate Matter (P.M.) is a pollutant according to the Clean Air Act
and the Environmental Protection
Agency (E.P.A.). The most common
particulate for bakers and snack food
manufacturers is flour.
Flour particles average about 80
microns (P.M. 80) in size with the
smallest about 10 microns (P.M. 10)
and the largest 300 microns. A micron is one millionth of a meter, or
about 0.000039 inch. A typical yeast
cell is 3 to 4 microns; 100 microns is
the average diameter of a strand of
human hair.
The E.P.A. has regulations for P.M.
10 and P.M. 2.5. Some applications
for an air permit require the estimation of the potential emissions of
P.M. 10 or P.M. 2.5. Flour milled to

For bakeries the potential particulate emissions are insignificant because the particles are too big to fit
through the filters. For regulatory
purposes, the emission would be
insignificant, in some areas at less
than 0.01 lbs per hour or in some areas less than 100 tons per year. For
example, a bakery uses 5,000 lbs of
flour per hour. Worst case, if 99.99%
is captured by the baghouse then 0.5
lbs per hour, or 2 tons per year (8,760
hours), is the potential release.
Note that flour that may escape
from an oven stack would be heavy
enough to fall on the roof and may
be a sanitation problem and a storm
water permit violation.
Some readers may be familiar
with the estimation of volatile organic compound air emissions of

less than P.M. 1 is no longer flour but
has been broken down into starch
granules and other molecules. About
6% of a load of flour may have particles smaller than 75 microns.
Flour usually is transferred pneumatically from trucks and rail cars
to silos. Flour then usually is transferred pneumatically to scales and
mixers in the facility. The transfers
are controlled with filters for loading and for the scaling hoppers in
the bakery. The filters will capture
particle sizes of 0.5 microns and
larger. Baghouses that are flour control fabric filter collectors are common silo controls and are 99.99%
capture efficient. Inside the bakery,
suction systems often keep flour
from circulating in the air.

ethanol from the baking of yeast
raised products found by going to
www.epa.gov, search for AP 42 Bakery Oven Emissions and then go to
Chapter 9.9.6.
There is no methodology for estimating potential emissions for flour.
For purposes of air permit compliance most companies use AP 42 Portland Cement, Chapter 11.6. Cement
kiln dust ranges from 5 microns to
greater than 50 microns. Use of this
substance is a conservative choice
but defensible and reasonable. The
emission factor from Table 11.6-2
Dry process kiln with fabric filter is
0.2 lbs per tons handled.
As background, in the E.P.A. document, "Technical background document on control of fugitive dust at

BY ANNE GIESECKE

26 / December 9, 2014

Milling & Baking News

cement manufacturing facilities,"
Chapter 3 is titled "Emissions estimation" and 3.1.1 is titled, "Description of cement kiln dust handling
processes at the sample factory."
In the E.P.A. document AIRS Source
Classification Codes and P.M. 10 Emission Factor Listing by Technology
Transfer, EPA-45014-89-022, Cement
Manufacturing, Dry Process, Raw Material Transfer the emission factor of
0.15 lbs per tons handled is used.
Some companies use AP 42 Concrete Batching, Chapter 11.12 Cement Unloading to elevated storage
silo, pneumatic, controlled. Note
that the particle size of the components is about 62 to 2,000 microns. In
Table 11.12-2 the emission factor is
0.00099 lbs per tons handled.
P.M. 2.5 particles are created by the
burning of fossil fuels. To estimate
emissions for P.M. 2.5 and other constituents from Natural Gas Combustion go to AP 42 Chapter 1.4. Small
Boilers.
The National Fire Protection Association Standards 61 for Dust from
Food Processing and 654 Combustible Particulate Solids set concentration levels low enough to avoid
explosions and fire (www.nfpa.org).
Inside the bakery, the Occupational
Safety and Health Administration
sets concentration levels low enough
to protect human health and for adequate sanitation standards. Other
federal and state regulations to control dust also apply.
Sosland Publishing has a database of
articles that I have written about calculating air and water emissions and sustainability. Go to www.bakingbusiness.
com and select either Milling & Baking
News or Baking & Snack, and search for
"Giesecke." Many bakers have said
that the information was very helpful.
This is my final column for Milling & Baking News as I am retiring
from the food industry at the end
of this year. It has been a pleasure
to work with so many wonderful people. Thanks to Sosland for
the writing opportunity. I will be
spending time with family and will
increase time in pursuit of land and
underwater archeology. MBN

Anne Giesecke, Ph.D., is
a contributing editor at
Sosland Publishing Co.
bakingbusiness.com / world-grain.com

http://www.nfpa.org http://www.bakingbusiness http://www.epa.gov http://www.bakingbusiness.com http://www.world-grain.com

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