Air Guide 31
Implementation of Part 201 and Part 212 Permitting and Reasonably Available Control Technology Requirements for Bakeries
The 1994 amendments to Part 201 removed the exemption for wholesale bakeries form the requirements to obtain permits to construct and certificates to operate for air emission points. The section 201.6(l) exemption now reads: "process, exhaust or ventilating systems in bakeries or restaurants preparing food only for on-site human consumption or on-site retail sale". Hence, Part 212 now applies to facilities generating VOC emissions that result from baking of certain goods for off-site consumption or wholesale commerce. These changes were made to comply with the 1990 clean Air Act Amendments which require reasonably available control Technology (RACT) for major facilities throughout New York State which emit volatile organic compounds (VOC).
- Applicability of Part 212 RACT
In the New York City and Lower Orange County Metropolitan Areas, major facilities are defined as those with an annual potential to emit 25 tons or more of VOC. In upstate New York, major facilities are defined as those with an annual potential to emit 50 tons or more of VOC.
The term potential to emit means that an emission point with no enforceable restrictions on its hours of operation is allowed to operate 24 hours per day over 365 days per year, or a total of 8760 hours per year. The potential to emit is calculated by multiplying the maximum hourly emission rates in pounds per hour from all Emission points at a give facility by 8760 and then dividing by 2000 to determine tons per year. A facility with 5.8 pounds per hour emitted would be a 25 ton per year potential facility, and one emitting 11.5 pounds per hour would be a 50 to per year potential facility.
A potential major facility may be able to eliminate RACT applicability by using enforceable conditions on certificates to operate that reduce potential emissions below the 25 or 50 ton threshold. Air Guide 10 contains acceptable procedures to reduce a facility's potential to emit.
regions 1, 2, and 3 should not require RACT evaluations pursuant to Table 3 of Section 212.9 if the facility is not a major potential facility or has enforceable conditions to reduce its potential emissions below 25 tons per year.
- Emission Rates
The Environmental Protection Agency (EPA) has produced an alternative Control Technology (ACT) Document for Bakery Oven Emissions (EPA 453/R-92-017). This document includes a formula for predicting VOC emissions from bread ovens on page 2-19. The formula yields a VOC emission factor per ton of bread baked. The amount of VOC generated is a function of the amount of yeast added to the formula and the amount of time the yeast is allowed to ferment before the bread is baked. Almost all of the VOC emitted from bakery ovens is ethanol (CAS #00064-17-5).
VOC Emission Factor = 0.95Yi + 0.195ti - 0.51S - 0.86ts + 1.90
VOC E.F. = pounds of VOC per ton of baked bread
Yi = Weight in pounds of yeast added initially for each 100 pounds of flour in the recipe (known as baker's percent) to the nearest tenth of a pound.
ti = Total yeast fermentation time in hours to the nearest tenth of an hour.
S = Weight in pounds of yeast added in during a remix ("spike") stage for each 100 pounds of flour in the recipe to the nearest tenth of a pound.
ts = Secondary ("spike") yeast fermentation time in hours to the nearest tenth of an hour.
Note that the formula allows two different fermentation times. This allows for more accurate emission estimates of the "sponge and dough" process, which is a two phase mixing and fermentation process used for half of the white bread produced in the United States.
Fermentation can be suspended if the dough is held below 50°F. Some products, such as bagels, danish, or raisin bread, may have special ti values because a refrigeration phase is part of the process.
Once the VOC emission factor is calculated, multiply that value By the amount of bread produced per hour (oven capacity) as follows:
VOC emissions per hour = VOC E.F. (lb VOC/ton bread baked) x bread baked (ton/hr)
In the "straight dough" method, all of the ingredients are added at once, so only the Yi percent and the ti time factor are used. The fermentation time starts when yeast comes in contact with water and ends when the bread Enters the oven. The VOC produced during fermentation is mostly ethanol bound in the dough, and it remains inside the loaf until The internal temperature of the loaf reaches the vaporization temperature of alcohol, 174°F. The calculations for the straight dough method are as follows:
VOC E.F. = 0.95Yi + 0.195ti + 1.90
VOC emissions = VOC E.F. x bread baked (ton/hr) per hour
Here is an example of the use of the emission factor formula.
- The bakery provides the following information.
Oven bread production capacity is 2.88 tons / hour of finished product.
Yi = 4.0 pounds initial yeast / 100 pounds flour
ti = 5.7 hours
S = 0.5 pounds of "spike" yeast / 100 pounds flour
ts = 1.3 hours
- The bakery calculates the emission factor.
VOC E.F. = 0.95 (4.0) + 0.195 (5.7)
- 0.51 (0.5) - 0.86 (1.3) + 1.90
= 3.8 + 1.11 - 0.25 - 1.11 + 1.90
= 5.45 LB VOC / ton bread
- The bakery calculates hourly emissions using the emission factor.
VOC emission rate = 5.45 lb/ton bread x 2.88 ton bread/hr
= 15.6 lb VOC/hr
- The bakery provides the following information.
- Oven Design
Ovens are either directly fired or indirectly fired. Direct fired units would use natural gas burners within the oven, and products of combustion would be exhausted out of the oven stack along with the VOC from the baking process. Indirectly fired ovens use a fire tube system with a separate exhaust for products of Combustion, and distillate oil could be used as fuel. The region should not require a separate form for combustion emission stacks on indirect ovens. Fuel use should be indicated in Section G of the process form.
Ovens can be built with differing bread flow patterns. In a tunnel oven, dough is conveyed from the front entrance to the rear exit. In a lap oven, dough is loaded and unloaded from the front of the oven after travelling the length of the oven and back. In A spiral oven, the dough circles the oven latitudinally several Times.
Ovens often have multiple stacks with unequal emissions due to the length of the ovens. A review of stack test data by major bakeries indicates that the following emission splits are typical.
- Single-lap or double-lap oven
These types of ovens usually have two or three stacks. For baked foods including buns, rolls, bread and other yeast leavened products, assume that 70% of the ethanol is emitted from the first stack and 30% from the second stack of a three stack oven. Assume that 90% is emitted from the first stack and 10% from the second stack of a two stack oven. The first stack is the stack closest to the oven exit.
- Tunnel Oven
This type of oven usually has two or three stacks. For three stack ovens, assume 20% emission from the second or middle stack and 80% emission from the third or last stack. For two stack ovens, assume 10% from the first stack and 90% from the second stack.
- Spiral Oven
These ovens typically have only one stack.
- Single-lap or double-lap oven
- Non Yeast Products and Non Bread Emissions
Products such as cakes and cookies typically use baking soda, Not yeast. Ovens which bake these products exclusively have negligible VOC emissions. The Part 201 exemption for these ovens continues in new subdivision 201.6(cc).
Some products called breads, such as corn bread and soda bread, use baking powder, not yeast. Some sweet goods, such as danish pastry, use yeast, so the fact that a product is a sweet good does not mean that it has no VOC emissions. Yeast content is the Determining factor.
Less emission data is available on other products which use yeast, such as English muffins or bagels. The bread formula from the ACT may overestimate emissions from these products. Bakeries may submit data which supports using other emission formulas, such as the American Institute of Baking (AIB) formula on page 1-4 of the ACT document. A bakery always has the option to conduct a stack test to determine oven Emissions for a product, but the Department does not expect a major testing program from any facility. The bakers believe the EPA formula yields reasonable results for most yeast leavened products.
- Control equipment
The ACT document makes the following bakery oven VOC control equipment assessments.
- Thermal Oxidizers
Thermal oxidizers are technically feasible, but suffer from high fuel costs.
- Regenerative Thermal Oxidizers
These units are also technically feasible, and because of their ceramic bed heat retention capabilities, are more fuel efficient than a straight thermal unit.
- Catalytic Oxidizers
These units are the most common bakery VOC control devices by far. However, some users have expressed concern that catalysts may need frequent replacement or the catalyst must be washed at intervals to retain effectiveness.
- Carbon Adsorption
Carbon units are not recommended on bakery ovens because fats and oils may clog the carbon pores, and ethanol is difficult to strip from the carbon.
Scrubbers are not recommended because of the multimedia water pollution produced by the scrubber.
Condensers are not technically feasible because Airflow rates are too high and condensate disposal costs would be high.
Use of microbes in a media to consume VOC from bakery ovens is not technically feasible because oven exhaust temperatures are too high. However, the bakers may be able to use this technology if moisture, oxygen, and temperature are adjusted appropriately.
- Thermal Oxidizers
- Oven heat input versus bread production rate
The ACT document shows on page 4-5 that an average of 520 BTU of Heat is required to bake one pound of bread. A typical direct fired oven, operating at a 50% efficiency level, will require Approximately 1000 BTU of heat input per pound of bread. Operating efficiencies could vary significantly from oven to oven. An indirect fired oven would tend to require more heat input per pound of bread due to its lower heat transfer efficiency.
- Product Reformulation
The bakery industry may be able to reformulate bread recipes to reduce VOC emissions, but the ACT says these low or modified yeast Content products have not been demonstrated to provide taste Acceptable to consumers. Future prospects are promising, but the reformulated products are not currently feasible as an emission reduction strategy.
Variances from the Part 212 81% overall capture and control Requirements for large emission points at major facilities will be reviewed and processed pursuant to Air Guide 20. DAR is reviewing information that appears to indicate that sources emitting less than 15 tons downstate or 25 tons upstate will likely be eligible for a variance pursuant to Air Guide 20. DAR will share this information with the regional offices, the Small Business assistance Program and applicants. None-the-less, no blanket variances are to be issued. Each source subject to Part 212 will Have to seek a variance so as to allow case by case review by DEC and EPA. DEC's Bureau of Technical Services will, however, assist in securing group or batch review by EPA of the variances.
- Enforcement Guidance
The Commissioner will be issuing an Enforcement Guidance Memorandum to deal with the application of the Department's enforcement discretion for instances of non-compliance with Part 212. The expected issuance date is November 1, 1994. Until issuance of that document or another statement by the Commissioner concerning the enforcement consequences of failing to meet regulatory deadlines, DEC staff should encourage expeditious compliance and point out the regulatory and statutory deadlines, but commence no actions for non-compliance. Through its enforcement, DEC will seek strict compliance and allow reasonable schedules of compliance.
Thomas M. Allen