In most situations a hazardous waste is generated as a recognizable by-product, spent material, sludge, or residue of a manufacturing process.  Typically, the the moment a hazardous waste is generated (its point of generation) it is immediately contained in a hazardous waste management unit and becomes subject to the RCRA regulations.  However, there are times when a hazardous waste’s point of generation may be within and/or part of a manufacturing process, such as in a process tank or pipeline.  In this case, must it be managed as a hazardous waste while it remains in the process tank or pipeline?    The answer is “no”, if you are able to use the Manufacturing Process Unit Exclusion at 40 CFR 261.4(c):

A hazardous waste which is generated in a product or raw material storage tank, a product or raw material transport vehicle or vessel, a product or raw material pipeline, or in a manufacturing process unit or an associated non-waste-treatment-manufacturing unit, is not subject to regulation under parts 262 through 265, 268, 270, 271 and 124 of this chapter or to the notification requirements of section 3010 of RCRA until it exits the unit in which it was generated, unless the unit is a surface impoundment, or unless the hazardous waste remains in the unit more than 90 days after the unit ceases to be operated for manufacturing, or for storage or transportation of product or raw materials.

The units the USEPA considers subject to the exclusion are identified in 40 CFR 261.4(c) as:  “…a product or raw material storage tank, a product or raw material transport vehicle or vessel, a product or raw material pipeline, or in a manufacturing process unit or an associated non-waste-treatment-manufacturing unit”.  A Manufacturing Process Unit (MPU) is further identified at RO 11935 as including:  distillation columns, flotation units, and discharge trays of screens.  It may also include tanks and tank-like units which are designed to hold valuable products or raw materials in storage or transportation or during manufacturing.  Any uncertainty you may have about the applicability of your unit to the Manufacturing Process Unit exclusion should be confirmed with your state environmental department or your regional USEPA office.

An MPU is not designed or managed by the generator as a waste management unit, but instead is part of a process where a hazardous waste may accumulate.  Since correct management of a hazardous waste inside a manufacturing process could be impossible, and since the USEPA did not intend to regulate product and raw material storage tanks, transport vehicles and vessels, or MPU’s, it created the Manufacturing Process Unit Exclusion (RO 14469).

The MPU Exclusion allows you to accumulate a hazardous waste in an authorized unit (see above) not subject to any of the RCRA regulations as long as the following conditions are met:

• The hazardous waste was generated in the MPU and remains in the MPU.
• The MPU does not cease operation for more than 90 days.  A temporary shut-down (eg. for maintenance or a slow down in production) may be OK, but you definitely don’t want anything that looks like you’ve “ceased operation” of the MPU.
• The MPU cannot be a surface impoundment.

This exclusion can continue indefinitely with the hazardous waste accumulating in the MPU, not subject to RCRA regulation, unless or until either of the following occur (RO 11899):

• The hazardous waste is removed from the MPU, or;
• The hazardous waste remains in the MPU more than 90 days from the date the MPU ceases operation.

So, if a Large Quantity Generator of hazardous waste removes a hazardous waste from an MPU he must immediately begin managing it according to the RCRA regulations which would include the 90-day on-site accumulation limit.  However, if the MPU ceases operation, the hazardous waste within the MPU does not become subject to RCRA regulation until more than 90 days have passed from the day the MPU ceased operation.  On the 91st day the hazardous waste (whether it remains in the MPU or not) becomes subject to full RCRA regulation, including the 90-day on-site accumulation limit (RO 11903).

The MPU Exclusion does not exclude the waste from the definition of a solid waste, however.  Therefore the waste in an MPU is a solid waste from the moment of its generation (RO 14309).  Since the management of a solid waste is regulated under Subtitle D of RCRA and largely left to the individual states, check with your state environmental agency to confirm its proper management.

Example:  A facility receives natural gas via pipeline to its facility.  Prior to combustion the natural gas is put through an on-site process to remove excess moisture.  The excess moisture accumulates in a tank that is integral to the delivery and combustion system.  Prior experience tells the facility operator that the moisture in the tank will exhibit the toxic characteristic for Benzene (D018).  It may take several years for the tank holding the D018 moisture to accumulate enough hazardous waste to justify its removal and disposal.

Question:  Must the hazardous waste in the moisture accumulation tank be managed according to the RCRA regulations pertaining to a generator of hazardous waste upon its initial accumulation in the tank?

Answer:  No.  If managed properly, the hazardous waste in the tank is subject to the Manufacturing Process Unit Exclusion @ 40 CFR 261.4(c).  It need not be managed as a hazardous waste until it is removed from the MPU or it remains in the MPU >90 days from the date the MPU ceased operation.

For more information about the Manufacturing Process Exclusion, refer to this RCRA Online FAQ:  What is the Manufacturing Process Unit Exclusion and When Does it Apply to a Wastestream?

Your interest in this question means you likely require HazMat Employee Training and Hazardous Waste Personnel Training.  Don’t hesitate to contact me with your questions about the MPU Exclusion or either training requirement.