a

14.2

41.4

150.4

559

2.9

303

1,502

190.5

182

148.1

6,000
21

Median values, obtained from a review of current literature.

Flash point of 100-percent waste oil is higher than either distillate or residual oils, indicating that no additional safety requirements are necessary for fuel handling. Heating value of waste oil varies slightly due to presence of bottom sludge and water (BS&W), but waste oil blends up to 25 percent were found to vary insignificantly in heating value from virgin distillate and residual oils.

Sediment and water content of waste oil/distillate residual oil blends is noticeably greater than virgin fuels, even at low blending ratios. Presence of water and sediment can cause certain operational problems such as strainer clogging, excessive wear of positive displacement pumps, erosion of burner nozzle tips, and burner flameout. These potential problems have been avoided by wide orifice nozzles with steam atomizing, flame sustaining torches, and minor redesign of fuel straining and fuel lines. As an alternative, waste oil can be pretreated to reduce or remove water and sediment.

Sulfur content of waste oil is low, and blending with high-sulfur residual oils can appreciably reduce both emissions of sulfur oxides and corrosion of internal boiler surfaces.

Ash content of waste oil/distillate-residual oil blends increased significantly above blending ratios of 5 percent for waste oil/distillate oil and 10 percent for waste oil/residual oil blends. Sediment in waste oils contain ash-forming materials which contribute to increased deposition on internal boiler surfaces and increased particulate emissions. Soot blowing, water washing, and manual cleaning are used to

effectively remove internal ash deposits; particulate emissions are regulated by local and Federal agencies.

Lead in waste oils was found to be 0.1 to 1.0 percent by weight and, consequently, lead content of waste oil/virgin fuel blends increases appreciably with blending ratio. This is an area of concern as lead has been identified as a hazardous air pollutant and will be discussed further under environmental effects. Lead also contributes to deposition on internal boiler surfaces through fouling of heat exchange surfaces.

Other trace elements are present in waste oil in higher concentrations than in virgin fuels. Blending waste oil with virgin fuels may somewhat increase deposition on boiler surfaces of sodium, calcium, barium, zinc, and phosphorus, depending on blending ratios. Small increases in vanadium and iron could also cause increased corrosion of internal boiler surfaces. However, negative impacts of these elements in waste oil blends of 5 percent are considered minimal.

Environmental Impacts of Untreated Waste Oil Fuel Combustion

Blending waste oil with residual oil will reduce air emissions of sulfur, silicon, sodium, vanadium, and nickel. Emissions of other trace metals will be slightly increased: magnesium, calcium, iron, copper, barium, zinc, phosphorus, silver, tin, chromium, and lead. Increased emissions of trace elements were determined to be minimal with small blending ratios of waste oil (less than 5 percent), except for lead. Lead has been identified by the Environmental Protection Agency as a hazardous pollutant, and ambient air standards for lead will soon be promulgated.

Lead content of untreated waste oil varies widely from about 0.1 to 1.0 percent by weight, a result of leaded automotive fuels. Increased use of unleaded gasoline is expected to reduce lead content of waste oils, but no appreciable decrease has been measured to date.

To evaluate the potential lead emission problem, ground-level lead concentrations were calculated for a 560 megawatt power plant firing a blend of 5 percent waste oil and 95 percent No. 6 fuel oil. The "worst case" situation was assessed by computer diffusion modeling based on a lead content of 1.0 percent and the highest percent of lead emissions reported in the literature: 50 percent of lead present in the fuel. Isopleths of average ground level lead concentrations for typical December wind patterns at a New England power plant site are shown in figure 1. Maximum calculated lead concentrations are 0.15 μg/m3, an order of magnitude less than 1.5 ug/m3 lead standard under consideration by the Environmental Protection Agency. However, the safe level of lead in ambient air is unknown, and the 1.5 μg/m3 level has only been proposed as a possible safe level. The diffusion modeling does indicate that lead emissions are not a substantial problem with low blending ratios.

Ground-level lead concentrations shown in figure 1 were calculated for a power plant with no air pollution control devices. Lead particles in flue gas are submicron in size, and a very efficient particulate control device would be necessary to significantly reduce lead emissions. High-efficiency electrostatic precipitators or fabric filters can provide high particle removals necessary to control lead emissions. These control devices are not commonly required for power plants burning oil, but are normally installed on newer, coal-fired boilers.

Reducing Technical and Environmental Impacts

Adverse technical impacts of combusting waste oil can be reduced by either modifying boiler fuel handling equipment or by improving waste oil quality by pretreatment. Potential environmental effects of increased particulate and lead emissions can also be reduced by pretreatment techniques or use of high-efficiency air pollution control devices. It is unlikely that any utility would install expensive pollution control devices solely to control emissions from waste oil combustion. However, when such control devices are already installed, environmental impacts of waste oil reuse as fuel will be substantially reduced.

Commercially available, high-level pretreatment processes--vacuum distillation or solvent extraction--can remove essentially all waste oil contaminants, including lead and other trace elements. Conventional acid-clay re-refining was not considered in this analysis of high-level treatment because of disposal problems associated with lead-containing waste products. Total costs for high-level vacuum distillation or solvent extraction pretreatment were estimated at $0.19 per gallon (updated to 1977)

Figure 1. Isopleths of average ground-level concentration of lead at a large New England power plant burning a 5-percent waste oil/residual oil blend. Units are ug/m3.

by appropriate cost index). Since these processes are generally capable of restoring the quality of waste oil to the virgin state, they would be most likely employed for re-refining waste oil to lubricating oil, not fuel.

Low-level pretreatment techniques include gravity settling and centrifugation for reduction of unbound water and sediment. Trace metals, including lead, are present as very small particles which are virtually unaffected by gravity settling. Centrifugation, preferably preceded by addition of a demulsifier, can improve removal of sediment and water over gravity settling to about 1.5 percent from the typical 5 to 10 percent levels found in untreated waste oil. Total costs were estimated at $0.15 to $0.17 per gallon (updated to 1977) for either settling or centrifugation.

Study Conclusions

The GCA study identified three options for reuse of waste oil as fuel which would add to energy supplies while minimizing adverse environmental and technical impacts:

Large users, especially utilities, could blend small quantities

(5 percent) of either untreated or low-level treated waste oil
with existing energy sources.

Medium-sized users with existing high-efficiency emission control
equipment could blend higher amounts of high-treated or low-
treated waste oil with existing fuel sources.

High-treated waste oil could be combusted by itself by small users.

Evaluating Reuse of Waste Oil on the Local Level

In recent years, a number of Federally sponsored research programs have identifie and discussed reuse options for waste oil. Most of these programs, including the GCA study, are general feasibility studies which compare merits of each reuse option on a national basis. The next logical step is an evaluation at the local level since waste oil reuse policy is normally formulated and implemented on a Statewide or regional basis.

GCA is conducting a study for the State of Massachusetts to document and evaluate existing barriers to effective waste oil reuse specific to Massachusetts. Potential waste oil supply is under evaluation through an updating of earlier studies [3,4], evaluation of permitted waste oil collectors, contact with industry representatives, and analysis of current trends of waste automotive oil generation. Recovery and reuse mechanisms which are practicable in Massachusetts will be identified, focusing on existing facilities and distribution patterns. Specifically, re-refining as lube oil and reuse as fuel in several new municipal, steam-generating incinerators, appear to be viable alternatives in Massachusetts.

The major thrust of the ongoing program will identify technical, institutional, environmental, and economic barriers which currently restrict effective reuse of waste oil in Massachusetts. Technical barriers are analogous to problems identified in the general, nationwide study described in this paper, but the Massachusetts study will document the extent to which these problems have/will occur in local facilities burnin waste oil. Through contacts made with waste oil haulers and users during the Massachusetts Hazardous Waste Survey, GCA will document the extent to which technical problems actually do occur in facilities burning or re-refining waste oil in Massachusetts. Waste oil haulers often mix oil from several sources. Efforts will be made to correlate the extent and types of process upset with various waste oil sources

The technical applicability of waste oil reuse as fuel in existing municipal incinerators in the State will be investigated by contact and personal interviews at these facilities and the responsible engineering firms and/or manufacturers of combuston equipment. This option may be important in the future as the State proceeds with plans for regional resource recovery plants for municipal refuse.

Institutional barriers to effective resource recovery from waste oils in Massachusetts will be identified and evaluated. For example, marketability and public acceptance of re-refined lube oil have been hampered in the past by Federal labeling requirements. Safety codes and Occupational Safety and Health Administration (OSHA) regulations may restrict use of unprocessed waste oils as fuel, and this possibility will be investigated through contact with the OSHA, operators of boilers, and consulting local city safety ordinances or codes. GCA will determine whether insurance policies covering either capital equipment or employee safety would be violated by use of unprocessed waste oil by contact and/or interviews with the Massachusetts Insurance Commissioner's Office, insurance companies, and the responsible personnel at several institutions which are using, or may use, waste oil as fuel. Also to be assessed is the effectiveness of public automotive waste oil receiving stations. The establishment of these stations has been specified by State law as a way of providing the public with a means of recycling the waste oil from "do-it-yourself" automotive oil changes. The program has maintained a low profile within the State, and its adequacy has not been formally evaluated.

Re-refining waste oils to form lube oils and pretreatment prior to use as fuel will generate an oily sludge which requires proper disposal. Of greater environmental importance is burning of untreated waste oil in combination with distillate oil; unprocessed waste oil is relatively dirty and, thus, particulate emissions will be somewhat increased. This increase must be assessed with respect to current air pollution regulations and ash content of local waste oil.

A major problem in Massachusetts is a strong economic incentive for waste oil reuse as fuel. Waste haulers pay service stations $0.03 to $0.07 per gallon for waste oil and sell collected oil locally as fuel for $0.20 to $0.30 per gallon. Unfortunately, little regard is given to the aforementioned problems with burning untreated waste oil: safety, burner maintenance and operation, and increased air pollution. A nearby facility is capable of restoring waste oil to virgin quality, but can only pay waste collectors about $0.10 per gallon. In the long run, it may be more desirable to re-refine waste oil instead of burning as fuel, but existing pricing structure is currently limiting re-refining. The GCA study will investigate mechanisms for promoting re-refining through a program of interviews with waste collectors and re-refiners and through a study of incentives which could be enacted by the State to promote the favored use option.

The final portion of this study will formulate recommendations to improve reuse of waste oil based on information obtained through the research program. Examples of possible action by the State include:

• require State vehicles and buildings to use recycled petroleum oils to set an example and stimulate the market;

• stimulate reuse by State tax incentives and alteration of any laws or regulations currently restricting reuse as fuel or re-refining as lube oil; and

• implement a program for improved public education and awareness concerning benefits of recycling lube and fuel oil.

References

[1]

[2]

Chansky, Steven, et al., Waste Automotive Lubricating Oil Reuse as Fuel, prepared by GCA/Technology Division for the U.S. Environmental Protection Agency, Publication Number EPA-600/5-74-032 (Sept. 1974).

Environmental Quality Systems, Inc., Waste Oil Recovery Practices, State-of-theArt (1972), Maryland Environmental Service and U.S. Environmental Protection Agency (Dec. 1972).

[3] Fennelly, P. F., Chillingworth, M. A., Spawn, P. D., and Bornstein, M. I., The Generation and Disposal of Hazardous Waste in Massachusetts, GCA Report No. GCA-TR-76-29-G (Oct. 1976).

[4]

Arthur D. Little, Inc., Study of Waste Oil Disposal Practices in Massachusetts, prepared for Massachusetts Division of Water Pollution Control (Jan. 1969).