Paint & Coating Manufacturing (Liquid): P2 Opportunities
Regulatory developments, R&D, and the continuing market trends toward water-based/lower-emitting coatings, and other coating technologies, have contributed to reductions in air emissions, heavy metal use, and wastes from this industry. Of regulatory importance, the EPA’s National Emission Standards for Hazardous Air Pollutants (NESHAP): Miscellaneous Organic Chemical Manufacturing and Miscellaneous Coating Manufacturing; Final Rule was adopted in 2003, which requires many pollution prevention and controls and measures for specific processes in the coating manufacturing industry, to comply with the air regulations.
Many of the opportunities listed below may already be in place at many paint production facilities. Any suggestions that are new to a manufacturer, may require specialized training upon implementation, to achieve the benefits of improved material and energy and water efficiency, and reduced worker illnesses relating to exposure.
Paint Formulation and Mixing
- Reformulate safer paints that have less toxic constituents: heavy metals, NPEs, triclosan (as an antibacteria), and higher-toxicity or higher-volatility solvents. Regulated hazardous air pollutants (HAPs) like toluene and xylene can be replaced in some paint formulations, by non-HAP and/or low-emitting alternatives. Some effective substitutes include: ester solvents, selected ketones, aliphatic hydrocarbons, and selected alcohol solvents (such as acetone). An industry representative from the ACA suggests that solvents in use are increasingly “low vapor pressure,” resulting in lower air emissions throughout the manufacturing process.
- Replace powder pigments with paste-based, or pre-dispersed form.
- Use computerized programming for spot-on color match, minimizing mistints and off-spec products. Ask customers to supply a substrate sample with their color-match requests.
- Formulate custom orders in lab in small quantities to confirm proper constituents and processing parameters.
- Especially for custom orders, produce batch sizes in exact amounts ordered.
- Order raw materials as needed to minimize expiration.
- Check materials for damage and expiration date upon receipt.
- Offer mis-tints and off-spec products to non-profit organizations – such as schools, low-income developments, and charities.
Process Water (Also see Equipment Cleaning)
- Dedicate separate equipment to a product or family of products to reduce the need for cleaning and the generation of wash solvent or wash water. Hard plumbing of solvent distribution systems can also reduce solvent waste.
- Recirculate and filter wash water. Some plants have onsite wastewater treatment which may allow dedicated streams to be treated for re-use in vessel cleaning or if pure enough and the right color, directly back into the next batch, or into primer products that do not have strict color requirements. Columbia Paint began using white wash water in new batches of paint, and added a raw material code to the reusable wash water going into new product. (See this opportunity and rest of case study here).
- Minimize cleaning water use with mechanical and manual methods prior to water cleaning (see equipment cleaning).
- Minimize use of solvent-based cleaners, with mechanical and manual methods first, before solvent use, and or identify safer solvents that can do the same job.
- Clean water-based mixing vessels before the residual paint dries so solvents are not necessary to remove cured paint. Based on a case study by the Institute for Research and Technical assistance (IRTA), manufacturers can save significant costs by cleaning the paint tank immediately after use, before the paint has cured. Cleaning with plain water or a pressure washer are significantly cheaper and less hazardous options than cleaning with methylene chloride, which is a carcinogen. According to the IRTA study, the most cost-effective washing method is to use power washing.
- Test and implement safer solvent cleaning alternatives especially for xylene, toluene, methylene chloride, and any containing N-methyl pyrrolidone (NMP).
- Use high-efficiency solvent-water separation system or modify equipment to improve the recovery rate. Increasing solvent recovery may enhance wastewater quality by reducing chemical oxygen demand (COD) (Durson, et al, 2006).
- If spills occur, use manual cleaning methods to collect prior to washing down.
- Implement spill prevention measures and training. When spills occur, use manual /dry clean up prior to washing down, creating additional wastewater or hazardous material.
- Ensure all floor drains route to catchment or sump where spill and washwater is collected for treatment.
Equipment Cleaning and Maintenance
- Clean vessels immediately before residuals begin to dry on the sides of the vessel.
- Clean out tanks as much as possible, with gravity, mechanization, and/or manual methods prior to using solvent or water wash.
- If water-based paints cure before removal, try alternatives to solvents first, such as physical abrading with sanding discs, or high-pressure/low-volume water spray. If solvent is needed, according to an IRTA study, benzyl alcohol strippers are generally much safer for workers than methylene chloride. Additionally, avoid strippers containing N-methyl pyrrolidone (NMP) due to its reproductive and developmental toxicity.
- Always comply with regulatory and best management practices for working in confined spaces when staff must be inside a vessel to clean.
- Use high pressure nozzles and wash systems to reduce the amount of water or solvent needed to clean.
- Collect the rinse solvent/ water for treatment and reuse onsite or movement to another treatment facility (See Process Water above)
- Sludge – dewater with flocculation, filtration or centrifuge to remove water before disposal.
- If caustic solution is currently used for equipment cleaning, evaluate the use of alkaline cleaners instead.
- Where possible, replace filter cartridges with bag filters, and/or reusable wire screens that can be washed and reused indefinitely.
- Collect equipment waste oils and maintenance fluids for recycle or waste-to-energy.
- Institute a “make to order” production system to minimize expirable and excess raw material and finished goods onsite.
- Use inventory tracking systems and visual controls on the inventory itself, to streamline the storage management of raw materials and finished goods.
- (If not already present), Install floor scales to accurately weigh raw material addition amounts, in lieu of eye-balling or measuring by height of the material in a container.
- Separate raw materials for solvent and water-based batches, if both are produced in the same facility.
Exterior Air Pollutants
- Use low sulfur-content fuels for machinery/facility operation.
- Proactively maintain combustion systems to minimize carbon dioxide and nitrogen dioxide emissions.
- Use efficient combustion and dust filter systems.
- Monitor air emissions with automated systems and use data to ensure proper control.
Indoor Air Pollutants
According to a 2006 study, reducing or controlling organic emissions inside the plant is important due to the typical ‘open design’ of production facilities. In the paint industry, 99% of indoor particles are in non-visible range (< 30 um), and are low density, making them difficult too separate. These suspend in air and can easily be inhaled into lungs.
- Comply with the NESHAP 5H provisions. See Implementation Tool for the Miscellaneous Coating Manufacturing NESHAP for process vessels, storage tanks, equipment leaks, wastewater and heat exchange systems, transfer operations, and closed vent systems/control devices.
- Use air tight covers to cover paint tanks during blending, mixing, and storage. Install floating lids on solvent storage containers.
- Use conservation vents and carbon adsorbents to reduce emissions.
- Optimize dust collection equipment and ventilation systems to minimize exposure.
- Use paste or liquid pigment instead of dry powders.
- Do not allow solvent-based paints to “dry” in the plant because solvents will evaporate to air, essentially releasing solvent vapors to indoor air.
- Use automated controls to ensure timely filter replacement as soon as specified limits are identified.
- If pigment additives are hazardous due to metal or other constituents, purchase in drums instead of bags, because those residual powder means the bags are also hazardous waste. (Drums can be rinsed out and reused or recycled, however additional washwater is generated from cleaning).
- If pigment feedstock is NOT hazardous, segregate that packaging and dispose of as solid waste rather than including it with any contaminated packaging.
- Dispose of solvent still bottoms as hazardous waste, unless they test non-hazardous.
- Evaluate the possibility of reusing collected pigment dust in future production. If feasible, install separate baghouse dust collection systems for powder loading areas if the material can be recycled for future production.
- Ensure chemicals are segregated, have secondary containment, and are stored away from regular sewer system discharge portals.
- Decrease the amount of shrink or stretch wrap used in final packaging. Consider mechanizing stretch wrap application, or find other alternatives to sheet plastic to stabilize products on outbound pallets.
- Use product stewardship and/or material exchange services to sell or give away unused resins, pigments, and other raw materials to another manufacturer, and/or to find potential raw materials from other manufacturers to use in production.
- Recycle kraft bags, plastic buckets, and other raw material packaging.
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