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Sawmills and Lumber Yards

8/9/11 AG Annual Report

Sawmills and lumber yards can have multiple environmental rules affect them, depending on the operations performed at the facility. A sawmill may need a few different permits as listed below:

  • Air permit for particulates from sawing logs into lumber
  • Air permit for engines if the saw is operated by a fuel driven engine
  • Industrial storm water permit for water running off the yard which may carry sawdust, oils, or chemicals leached from sawdust into nearby streams
  • Possible air permit for wood fired boilers
  • Possible air permit for kiln drying
  • Possible air permit for pressure treating due to chemicals used
  • Possible hazardous waste generator notification for pressure treating

As pressure treating is an uncommon operation, it will not be touched on here. If a facility needs assistance regarding permitting for pressure treating, please contact the Small Business Environmental Assistance Program (SBEAP). The SBEAP is available to assist in all areas of permitting, including assistance with calculations as described below.

Air permitting: Sawmill

The most common emission from sawmills is sawdust. Most sawdust is fairly large and drops out of the air quickly. For many facilities, this sawdust is collected and sold as a by-product or given away to offset disposal costs. It may also be burned in boilers for facility heating, either comfort heating or as part of a process such as a drying kiln. However, some percentage of sawdust will be finer, especially if more precision sawing using finer toothed saw blades such as on a bandsaw or sanding is being done. This finer sawdust can become airborne and is considered an air pollutant.

Air permit applications in relation to sawmills consist of several parts. The first is the APC 100 Facility Identification form. This form collects general information about the facility, especially contact information. One of the key parts of this form is identifying the different air sources at a facility. This may include a ripsaw (especially if operated by a non-electric engine), a dust handling system that could include cyclones or baghouses, boilers, kiln dryers, or other operations.

The second form is the APC 101 Emission Point. If your facility has a cyclone that controls all the dust collected, use the APC 113 Cyclone form instead. The unique source ID is based on what the specific source was called on the APC 100 in order to provide consistency. A facility may need to complete multiple APC 101 forms as each should be for a specific source such as just the sawing or just the boiler. The APC 101 can be the most complicated as it requests information on emissions from the source. This can be difficult to calculate, especially as Air Pollution Control (APC) usually requests
information in terms of lbs./hour of emissions or materials processed. Sawmills can utilize boardfeet as this is the common measurement that they keep track of in terms of production or materials processed. A calculator was developed by the State of Oregon which is in common usage by different state agencies to help calculate particulate
emissions from sawmills. To use the calculator, the facility would need to know their production amounts for bark, chips, lumber, and any boilers or engines. It also includes the ability to calculate emissions from kilns and planers if those are present. For certain operations such as the main sawmill, if a cyclone or baghouse is used for dust collection that should be noted. The bark and chips should be entered as tons/hour of production. This might be estimated by knowing how much a trailer or other collection point can contain and then dividing by how long it takes to fill it up. For example, if the trailer holds 20 tons of chips and it takes 10 hours of the sawmill operating to fill it, then it is producing 2 tons/hour of chips. For the saw mill itself, the measurement should be in thousands of boardfeet/hour (Mbf/hr.).

Once the information for production and controls is input into the tab, the calculator will give the results on the output tab. For the sawmill itself, this should be particulates (PM). This calculator should be used with two different numbers. The first would be the average amount processed at the sawmill. The second would be the maximum amount that could be processed per hour. Each amount will be calculated as PTE which stands for Potential to Emit. This amount is calculated as if the facility operated continuously all year long which is 8760 hours/year. For the APC 101, the facility should take the PTE number and divide by 8760. This will give the lbs./hour amount that is requested on the APC 101. The average number should then be multiplied by the yearly operating hours of the sawmill and divided by 2000 to find the average tons of emissions/year. The maximum amount will give the PTE as requested by the form, but it should also be divided by 8760 to give the maximum emissions/hour.

APC 102 is used for how much lumber is processed (use boardfeet) and if a boiler is used. If the facility only has one cyclone and all the dust is controlled by it, the APC 102 is not needed. If there are several cyclones or parts of the facility not controlled by a cyclone, then an APC 113 would be needed for each cyclone and an APC 101 for each non-cyclone
controlled emission source.

Air permitting: Boilers and kilns

For facilities that have a boiler, if it is a natural gas fired boiler and is under 10 MMBTU/hour, then a letter or email to Air.Pollution.Control@tn.gov  with this information and a request for a determination of exemption may suffice. If the natural gas boiler is above 10 MMBTU, then it would need to be permitted. If the boiler is fired by wood or other biomass, it would need to be permitted. Refer to the SBEAP Boiler page for more information on Boilers.

Kilns for wood drying would be very similar to boilers. Sometimes boilers are used to provide indirect heating for the kilns to dry the wood. Emission calculations for kilns would be similar to that for boilers depending on the fuel source. Emissions are calculated using emission factors found in the EPA publication AP 42 for External Combustion Sources. This is an area in which the SBEAP commonly assists facilities.

Air permitting: Engines

Similarly, if the sawmill or even the entire facility is operated off of a generator that is gasoline or diesel fueled, then it would need to be permitted. The SBEAP Stationary Internal Combustion Engines page has more information concerning
engines. If the engine is only used as an emergency engine, then it could be permitted under Permit-by-Rule rather than going through a standard permitting application process. If it is instead the primary source of power for the sawmill, it would not be considered an emergency engine and would need to go through the standard permitting process. EPA publication AP 42 for Stationary Internal Combustion Sources has emission factors for engines, but a facility may also be able to get more specific data from the manufacturer of the engine. The manufacturer tests engines and can supply emissions data for that model of engine by request if it is not already part of the engine owner’s manual.

Water Permitting

There are two areas of water permitting that would typically impact a sawmill. The first would be during construction. If an area of 1 acre or more is being disturbed, then a Construction Stormwater permit is needed. This may require maps of the area, outfall locations (where water will run off the area), and could include requirements for silt fences, retention ponds, and water monitoring. If the construction might alter a nearby stream, lake, or wetland, an Aquatic Resource Alteration Permit (ARAP) would be required. As many sawmills are located in rural areas, it is possible they may have a septic system installed or need a water well drilled. A Septic System Construction permit would be required to have a septic system installed by a licensed septic system installer. The installer should know about the requirements of the construction permit and be able to assist during the planning stages of the facility. Well drillers and installers are also required to be licensed by the state. The state maintains a list of licensed well drillers and installers.

Once constructed, a sawmill would potentially need an Industrial Stormwater permit. This is also known as the Tennessee
Stormwater Multi-Sector General Permit (TMSP). As such, most of the requirements in the permit are general conditions that apply to many different types of facilities. This may also require retention ponds and water sampling, in part due to the leaching of tannins from sawdust. This is what turns the water that has a lot of sawdust in it dark brown. Other pollutants may be carried by the stormwater run-off from the sawmill and lumber yard, which is why the need for the Industrial Stormwater permit. Typically, an Industrial Stormwater permit would require annual sampling and testing of each outfall and a Stormwater Pollution Prevention Plan (SWPPP). The SBEAP has a web page with some basic information on Storm Water Runoff Management. This includes a sample SWPPP that though it is for an auto salvage yard, provides the basics that could be used for a sawmill or lumber yard.