DNR Vehicle Maintenance Facility

DNR’s Bureau of Field Services Reduces Waste at Vehicle Maintenance Facility

Process Background

The Minnesota Department of Natural Resources (DNR) manages Minnesota’s natural resources. This includes: timber management and sales; mineral sales; reforestation of logged areas; operating fish hatcheries; protecting endangered species; establishing and enforcing hunting and fishing limits and seasons; and developing and maintaining wetlands, trails, campsites and recreation areas in state parks and forests.

The DNR’s Bureau of Field Services operates six vehicle maintenance facilities throughout the state. The number of vehicles serviced and the types of maintenance performed varies at each shop.

The vehicle maintenance shop that serves the greatest number of vehicles (300) in the DNR fleet and generates the most waste is in Grand Rapids, and it is the focus of this project. This shop employs four mechanics, two welders and a shop foreman.

The Grand Rapids facility is a Small Quantity Generator (SQG), generating between 220 and 2,200 pounds of hazardous waste per month. The wastes generated by this shop include: Stoddard solvent, antifreeze, motor oil, filters, tires, batteries, floor sorbent, engine fluids and various aerosol cleaners.

The Grand Rapids Vehicle Maintenance Facility primarily performs preventive maintenance and repairs, along with some predictive maintenance. The preventive or scheduled maintenance includes: oil changes; tune-ups; coolant changes and adjustments; fluids added/replaced (if dirty), tire rotation/inflation; and checks of brakes, belts, hoses, and shocks. Repairs range from replacing starters to overhauling engines. Predictive or conditioned-based maintenance is done as a result of testing that occurs during the preventive maintenance. For example, if transmission fluid appears dirty or smells burned, it is changed; if antifreeze is dirty, it is changed or restored to the proper freeze point.

Incentive for Change

The DNR is committed to protecting and managing natural resources. Its pollution prevention policy statement affirms this commitment: “Only by mitigating pollution as much as possible within our own organization can we truly foster an ethic of environmental protection, resource conservation and reduction in the economic burden of disposal.”

Although the Grand Rapids maintenance facility had used licensed haulers to recycle used oil, filters, antifreeze, batteries and tires, the DNR was eager to reduce: 1) the volume of waste it produced—particularly hazardous waste; 2) disposal costs; and 3) potential liabilities from transporting, off-site storing or disposing of waste.

In addition, the Governor’s Executive Order 91-17 (which provides for the implementation of pollution prevention by state government) requires that all state of Minnesota agencies reduce their generation of hazardous waste and use of toxic chemicals. To comply with this Executive Order and fulfill its mission to foster an ethic of environmental protection and resource conservation, the DNR requested assistance from MnTAP’s student intern program to evaluate ways to reduce waste and prevent pollution.

Intern Activities

A waste audit was prepared in 1994 by the Grand Rapids vehicle maintenance facility to determine the type and amount of waste it produced, and the cost of its disposal. The major waste streams evaluated included: used oil, automotive filters, antifreeze, parts-washing solvent, tires, batteries, floor sorbent and aerosol products.

The intern identified and evaluated the following options for the DNR to use: remanufactured parts, low sulfur diesel fuel, more efficient recycling systems, less hazardous and reusable materials, and materials available in bulk. Another option was to lengthen equipment maintenance or service schedules.

Research of viable alternative courses of action were the focus of this pollution prevention project. This was accomplished by surveying managers of similar fleets to learn of their pollution prevention steps, interviewing researchers in the petroleum and equipment manufacturing industries, and reading related academic and trade magazine articles.


Alternatives available to the DNR involve the simple substitution of a less hazardous material that works just as well as its hazardous counterpart. However, there are both benefits and disadvantages that must be balanced. All of the waste streams were analyzed and reduction options for each stream are proposed.

Option #1: Using Re-manufactured Parts


A remanufactured part is a used component or core that has been disassembled, cleaned, and inspected for worn or faulty components, and has had those components remachined or replaced, reassembled and tested. If a core frequently shows defects in a particular area, it may be re-engineered to prevent premature failure.

The remanufacturing process yields the following environmental, energy and economic benefits

  • Only 1/5 the amount of energy is needed to remanufacture a part as compared to manufacturing a new part.
  • Each pound of new material used in remanufacturing saves and reuses five to nine pounds of used core.
  • Top grade remanufactured parts are about half the cost of a new part.


Reliability of a re-manufactured part must also be factored into the overall cost. The part itself may be under warranty, but some costs cannot be recaptured (such as labor and downtime) if the re-manufactured part is not as reliable as a new part. To date, data is not available about the reliability of remanufactured parts.

Suggestions for using re-manufactured parts

  • Mandate the use of nonelectrical remanufactured parts, such as disk brake pads or drum shoes. Since electrical parts (such as starters, alternators, and generators) reputedly have a higher incidence of failure, their use should be optional.
  • Select high-quality remanufactured parts. The highest grade or line of parts that meet or exceed Original Equipment Manufacturer (OEM) specifications should be required.
  • Implement a pilot study to get a better idea of the cost and savings in using remanufactured parts.
  • Trade in all worn-out parts at the time that a replacement part is purchased. If the parts supplier will not accept a used part, a core broker should be located, since core supply is integral for remanufacturing capacity.

Option #2: Using Low-Sulfur Diesel Fuel


Amendments to the Clean Air Act of 1990 require that all highway diesel fuels have a maximum sulfur level of 500 parts per million (ppm); therefore, the use of low-sulfur diesel is not optional.


Since the federal rule became effective on October 1, 1993, there have been well-documented reports of fuel system failures (rotary fuel pumps and unit injectors). These reports of fuel system failures were followed by sales literature that stressed the need for additives or conditioners to increase the lubrication value of the new fuel.

Explanations for the fuel pump failures include:

  • Inherently reduced lubricity due to the hydrotreating process used to produce the fuel.
  • Initially poor-quality fuel.

The petroleum and engine manufacturing industries, along with regulatory agencies such as the Environmental Protection Agency (EPA), suggest that the problem was due to the incompatibility of old nitrile seals with the chemical composition of the new fuel.

Suggestions for Using Low-Sulfur Diesel Fuel

  • Contact a fuel supplier to determine whether the low-sulfur diesel fuel is sufficiently conditioned for lubricity and cold weather starts. If not, consider using an additive specified by the fuel supplier based on the characteristics of its fuel.
  • The DNR currently requires diesel engines in heavy trucks to reduce fuel consumption and increase equipment longevity. Similar purchasing requirements are recommended where diesel engines are available as options (since fuel system failures do not occur when low-sulfur fuel is used in new vehicles).

Option #3: Lengthening Equipment Service Cycles


The incentives for extending service cycles are both immediate and long term, and include the following:

  • Long-term costs are offset by reduced potential environmental impact and associated cradle-to-grave liability for the waste generated.
  • Short-term operating costs are reduced for used oil disposal, replacement oil and filter, labor and equipment down time when the elapsed time or miles between oil changes is extended.
  • Doubling the oil change interval (OCI) reduces by half the number of miles before overhauls are required. However, savings must be balanced with the potential shortening of equipment life.


Factors that impact OCI extension include: using synthetic oil, evaluating the effect of trip length on type of service, and using alternative filtration systems.

  • Synthetic Oil.
    Synthetic oil is superior to petroleum oil because it permits better cold weather performance and longer endurance. However, since synthetic oil has improved fluidity, oil loss will occur more quickly through leaks because the thinner fluid will flow through a bad seal or worn ring.
  • Trip Length
    Service or operating conditions conducive to extended OCI are long trips (>62 miles), not short trips or mixed-used service. Short trips or mixed use of a vehicle rapidly accelerates oil degradation and effectively prohibits the extension of OCI beyond that recommended by vehicle manufacturers.
  • Alternative Filtering Systems
    By-pass filtration systems remove small, solid contaminants with screens or centrifugal force without significantly reducing oil flow rate. A joint study by researchers at Fleetguard and Cummins Engine Company found that engine wear is directly related to the size of particles removed in filtration. They also concluded that the use of a combination by-pass and full-flow filter system reduces engine wear rate to less than one-half of what occurs when using a full-flow filter system. A cost analysis concluded that the costs of using by-pass filters is offset by extended engine life, assuming that equipment is kept longer than 3-8 years (90,000 mile maximum).

Manufacturers of by-pass filtration systems evaluated for this project included: TF Purifier, Fleetguard, Racor, and Enviro Filtration (this is not a complete list of manufacturers available, and is not an endorsement of these companies).

By-pass filtration systems are used alone or in combination with conventional full-flow filters. For example, Fleetguard’s system uses both by-pass filtration and full-flow filtration. First, the full-flow system removes larger particles from all of the oil. Then, some of the oil is diverted to the by-pass filtration system, which removes particles down to 3-20 microns in size.

Another by-pass filtration system (TF Purifier’s Mobile Oil Refiner) uses a cotton filtration system that removes particles down to one micron in size, along with acid and sulfur. It also removes fuel, water and antifreeze from oil in its evaporation chamber.

Some by-pass filtration systems (such as Racor’s permanent liquid filtration system) use a stainless steel wire-cloth filter, which may be cleaned with a solvent. More evaluation is necessary to ensure that contaminants cleaned off the filter may also be filtered or removed from the solvent in which it is cleaned or the resulting wastewater.

  • The cost of these bypass-filtration systems may be prohibitive for vehicles that are not owned or are replaced instead of overhauled when catastrophic engine failure occurs (as is currently the case with the majority of vehicles in the DNR fleet). The least expensive by-pass filtration system costs $166, which does not include shipping or installation.

Suggestions for Extending Oil Change Intervals:

  • Determine whether any of the filtering systems evaluated would be appropriate for vehicles in the DNR fleet. Consider the cost of the system and the pay-back period given the expected life of the vehicle in the fleet.
  • Set up a pilot study to examine extending OCI with testing and/or altered filtration systems to a small segment of the DNR’s fleet. Only test vehicles that show the greatest promise of success with minimal obstacles. This includes vehicles with diesel engines, that are: 1) no longer under a manufacturer’s warranty, 2) kept for longer periods of time, and 3) overhauled instead of replaced.
  • Consider using one vendor’s offer to prepare a cost-free survey of the fleet’s vehicle types and service use, fluids used, engine information and past maintenance history. This survey will provide a second opinion on the viability of extending OCI, since the vendor will recommend the optimal OCI and other maintenance schedules.

Option #4: Minimizing Oil Waste


Used oil generated by the Grand Rapids shop consists of petroleum and proprietary additives and may contain transmission fluid and power steering fluid. The DNR generated 1,300 pounds (or 179 gallons) of used oil in 1994. A contractor hauled the used oil to an offsite asphalt plant at no cost to the DNR.


Consolidating oil from other locations for an on-site, oil burning space heater is not cost effective, and would produce emissions that may require an air permit.

Suggestions for Minimizing Oil Waste

  • Mandate the use of re-refined oil in bulk quantities to create a market for recycling for reuse (currently diesel engines only; limited for gas engines).
  • Reduce the volume of used oil by extending service intervals where allowable.
  • Locate a used oil burning facility with dust collection equipment that can more effectively remove hazardous particulates from stack gases.

Option #5: Minimizing Antifreeze Waste


Spent antifreeze is composed of primarily ethylene glycol, proprietary rust inhibitors, lubricants and anti-foaming agents. It also may contain any of the following contaminants: benzene, lead, petroleum and proprietary petroleum additives. Spent antifreeze is considered hazardous due to the contaminants in, and the toxic nature of, ethylene glycol.

In 1994, 80 gallons of waste antifreeze were generated by the Grand Rapids shop and hauled off-site by a licensed hauler at a cost of $245. The shop replaces antifreeze only as testing indicates the need.

Suggestions for Minimizing Antifreeze Waste:

  • Mandate purchasing recycled antifreeze to create a market for recycling, if it is not recycled on-site.
  • Use a mobile on-site antifreeze recycling service, to provide immediate cost savings and drastically reduce the amount of waste generated.
  • Work with other state agencies to find ways to share equipment. Resolve issues relating to acquisition or inter-agency leasing, transportation, maintenance, general liability and accounting.

Option #6: Minimizing Solvent Waste


The Grand Rapids shop operates three parts-washing machines that use petroleum naphtha/Stoddard solvent to clean vehicle parts.

In 1994, the shop generated 358 gallons of spent solvent, which included: 18 gallons of solvent from the equipment dedicated to washing brakes, and 340 gallons of other parts-washing solvent. A licensed hauler charged $1,976 to dispose of the spent solvent and service the equipment.


Spent solvent may contain benzene, cadmium, trichlorethylene, tetrachloroethylene, lead and asbestos. Composition varies with the contaminants with which it comes in contact. It is deemed hazardous due to its constituents and combustibility.

Suggestions for Minimizing Solvent Waste

  • Negotiate a lease with a vendor to replace current systems with those that allow continuous filtration and reuse of solvent.
  • Request independent laboratory reports from a vendor, or a written warranty stating that its solvent meets the new National Emissions Standards for Hazardous Air Pollutants (NESHAP) rules as interpreted by the Minnesota Pollution Control Agency (MPCA).
  • In the absence of a warranty that assures compliance with NESHAP, apply for the necessary permits for use and disposal.
  • Switch to an aqueous system.

Option #7: Minimizing Used Filter Waste


Types of filters generated in this facility include oil, fuel tank, fuel line and automatic transmission filters. In 1994, the shop generated 800 pounds of used filters that were disposed of by a contractor at a cost of $150.


Filters may contain oil, fuel and automotive fluids, as well as the contaminants that they are designed to remove.

Suggestions for Minimizing Used Filter Waste

  • Purchase an oil filter crusher, if feasible, to consolidate the waste.
  • Extend OCI, if appropriate, to reduce the number of filters used.
  • Consider purchasing reusable air and oil filters when they become more widely available and cost effective.

Option #8: Minimizing Tire Waste


In 1994, 219 worn tires were hauled off-site by a contractor for recycling at a disposal cost of $276.


Used tires are not a problem unless they are mismanaged. Tires contain petroleum compounds, cadmium, natural or synthetic rubber, carbon black and ash. These materials are considered nonhazardous, but due to fire hazard and groundwater leachate, they may not be landfilled.

Suggestions for Minimizing Tire Waste:

  • Implement a policy for purchasing retread tires where feasible—which are half the cost and as durable as new—and products made from recycled materials to promote a market for recycling.
  • Optimize tire life through preventive maintenance:
    • Inspect for uneven wear every 4,000-6,000 miles. The type of wear may indicate that brakes or shock absorbers need maintenance.
    • Keep wheels balanced and aligned; correct for tire-wear problems such as feathering, cupping or one-sided wear.
    • Have drivers check tire pressure weekly.
    • Continue to re-align and rotate tires at a minimum of every 15,000 miles.
  • Optimize tire life by encouraging staff to avoid:
    • Overloading the vehicle, which may cut tire life by 30 percent.
    • Mixing tire size or construction.
    • Spinning the tires in mud or snow.
    • Exceeding the speed rating of the tire. (The tire’s load index as shown on the side of the tire specifies the maximum speed at which the tire is safe for extended use.)

Option #9: Minimizing Battery Waste


The DNR generated approximately 21 waste batteries in 1994. The lead from the batteries was reclaimed by a local recycler who paid the DNR $10.25 for the waste.


Used vehicle batteries contain lead and corrosive acid, and are deemed hazardous because of these components.

Suggestions for Minimizing Battery Waste

  • Store batteries in a room without a floor drain, or seal the drain or use curbing to prevent leaks from entering the drain.
  • Store batteries on a nonreactive surface made of chemically compatible materials. Wood shelving covered with heavy polypropylene is less expensive than a container or tray specifically made for battery storage.
  • Store cracked or leaking batteries in sealed plastic containers.
  • Keep a “Used Lead-Acid Battery Log” that records weekly inspections and final disposition of batteries.
  • If transporting the batteries is not done by a contractor, follow the transportation requirements as outlined in the MPCA fact sheet, Spent Lead Acid Batteries—Requirements for Transporters.

Option #10: Minimizing Floor Sorbent Waste


In 1994, the Grand Rapids shop generated 264 pounds of spent sorbent. This waste was landfilled with other solid waste at an unknown cost. Sorbent waste contains any of the materials spilled on the shop floor.


New state rules (effective October 1995) require testing and special handling of waste floor sorbent. It can be handled under applicable industrial solid waste rules only if it contains no free liquids, and has been tested and shown to be nonhazardous. New disposal options are to: launder and reuse, burn for energy recovery, or dispose of as hazardous waste.

Suggestions for Minimizing Sorbent Waste:

  • Encourage mechanics to practice good housekeeping by using drip pans, avoiding spills and minimizing trips and distance during material transfers in the shop.
  • Minimize sorbent use by first using tools and training to recover liquids as liquids, rather than using sorbent.
  • Use a wet/dry vacuum to clean up liquids.
  • Reduce the volume of sorbent that needs to be managed as hazardous waste by segregating any sorbents containing hazardous materials.
  • Label and place in the shop secondary sorbent containers for partially used sorbent that contains no hazardous materials. Encourage the reuse of this sorbent until it is saturated.
  • Continue to use newsprint-based sorbent until a better alternative is selected.

Option #11: Minimizing Aerosol Waste


In 1994, the Grand Rapids shop generated approximately 60, 10 to 13-ounce aerosol cans. The chemical composition of these aerosols depended on the application. Aerosol products used included: cleaners, lubricants, starting fluid, lock de-icer and coolant.


Aerosol containers generate more waste than refillable containers due to the packaging and material delivery problems. If aerosol cans are not “empty” and they contain hazardous materials, they must be managed as hazardous waste and disposed of with a licensed hauler.

Aerosol materials used in the shop were evaluated for hazardous characteristics, and if a suitable less hazardous material was available, it was identified.

The mechanic supervisor in the Grand Rapids shop proposed that aerosol cans be replaced with reusable atomizers charged with shop air. He was the recent recipient of a MN Great! Award for his work to replace single-use aerosols with reusable applicators using liquid products available in bulk quantities.

Suggestions for Minimizing Aerosol Waste:

  • Educate shop workers about the hazardous characteristics of materials. If no alternatives exist, encourage workers to use aerosols sparingly.
  • Create a shop policy of refusing free samples of aerosols that contain hazardous ingredients.
  • Replace hazardous materials with less hazardous counterparts.
  • Buy materials in bulk when available, or purchase in refillable pump bottles instead of aerosol.
  • Develop a purchasing guide that reduces the number of aerosol types used in the facility.
  • Reduce current inventory by using materials in stock instead of disposing of them.


It may not be possible to completely eliminate all hazardous wastes at the DNR’s Grand Rapids shop. However, there are immediate benefits to reducing hazardous waste by implementing the following suggestions:

  • Purchase re-refined oil for both gasoline and diesel engines.
  • Use an on-site antifreeze recycling service for replacing antifreeze and eliminating disposal costs. This service immediately provides reconditioned antifreeze at a cost savings of $3.50/gallon.
  • Implement preventive maintenance program to prolong life of tires.
  • Purchase retread tires when they are available. They are less expensive and more durable than new tires.
  • Purchase materials in bulk for use with reusable atomizers to reduce by half the cost of the raw material and disposal charges.
This project was conducted in 1995 by MnTAP intern Anne Lutz, a chemical engineering student at the University of Minnesota.