Material Flow Analysis ofLubricating Oil Use in

CaliforniaBrandon Kuczenski†

Roland GeyerTrevor Zink

Ashley Henderson

Bren School of Environmental Science and ManagementUniversity of California, Santa Barbara

Resources, Conservation, and Recycling vol. 93, pp. 59-65, December 2014doi: 10.1016/j.resconrec.2014.10.001Originally submitted October 1, 2013

Revised August 11, 2014Second Revision October 3, 2014

Accepted October 4, 2014

† address correspondence to this author: bkuczenski@bren.ucsb.edu

AbstractPetroleum lubricating oils, used throughout the economy, are distinct among petroleum products in their capacity to be recovered and recycled at the end of their useful life. Used lubricating oil is regulated at the state and federal level because of concerns about environmental impacts arising from improper disposal, although rates of recovery are not known. We present a material flow analysis of lubricants through California's economy in the years 2007-2012. We introduce a novel technique for computing aggregate waste generation from a collection of hazardous waste manifest records, and apply it inorder to determine a recovery rate for used oil and to estimate the quantity of oil managed informally in the state. The records also offer a detailed view of the fate of used oils after they are recovered. We find that around 62% of lubricants are recoverable at end of life, of which 70-80% is being recovered. This rate shows a slight downward trend. If the trend is accurate, measures should be

taken to improve the performance of the used oil management system. Policy opportunities exist to reduce the quantity of oil managed informally through improving access to responsible used oil managementmethods. These include increasing the collection of used oil from industrial sources as well as “do it yourself” oil changes, expanding in-state reprocessing capacity, and promoting increased out-of-state reprocessing of used oil. Our methods introduce new possibilities to make use of direct observation in material flow analysis, potentially improving data availability and quality and increasing the relevance of material flow methods in policy applications.

KeywordsLubricants, Petroleum Lubricating Oil, Industrial Oil, Used Oil,

Material Flow Analysis, Hazardous Waste

1 INTRODUCTIONPetroleum products are among the most significant material flows in

the economy by magnitude and by environmental impact (Adriaanse et

al., 1997). In 2010 the world production of crude oil was 3.97 Gt, of

which 0.85 Gt was consumed in the United States (International Energy

Agency, 2011). The vast majority of this material is combusted in some

form as fuel. However, a fraction of crude oil is appropriated for

non-combustion uses including petrochemical production, asphalt and

paving materials, and lubricating and industrial oils known in

aggregate as “lubricants.” Because they are not consumed in use,

lubricants can be collected and recycled. Used lubricating oil can be

burned directly for energy recovery and can also be further processed

to produce distillate fuels or re-refined base lubricant (US

Department of Energy, 2006). Used oil management is subject to

regulations due to concerns about toxicity (US Environmental

Protection Agency, 1985). The most environmentally damaging aspect of

the used oil management system is the quantity of oil managed

informally, e.g. through on-site combustion or illicit dumping into

the environment (Lawrence Livermore National Laboratory, 2008; US

Department of Energy, 2006).

In California, used oil is considered a hazardous waste.

Consequently, as with other hazardous wastes, every shipment of waste

oil originating or terminating in California must be accompanied by a

hazardous waste manifest that reports the origin, destination,

quantity and disposition of the oil. Hazardous waste manifests are

nominally the responsibility of the generator; however, used oil-

containing wastes in California can be reported on a “consolidated

manifest” that is completed by a waste hauler operating a routine

collection route.

Despite significant policy interest, there are no recent estimates of

the quantity of used oil collected for recovery or the recovery rate

of used oil in California or the US, with the latest estimates based

on data from 1991-92 (Graziano and Daniels, 1995) and industry data

from 1997 (US Department of Energy, 2006). Neither is there an

established methodology for making such an estimate for a tracked

hazardous waste. Recent legislation in California called for a

"comprehensive life cycle assessment of the used lubricating oil

management system" in the state (Lowenthal, 2009). To support the life

cycle assessment (LCA), it was necessary to estimate the quantity of

used oil generated and collected through the formal waste management

process in California. In this paper we estimate these quantities in

California each year from 2007-2012 using publicly available data on

waste hauling. The difference between the expected amount of used oil

generated in a year and the amount in the formal management system

provides an estimate of used oil managed informally. Estimating the

quantity of oil undergoing informal management is the primary

motivation for the study.

Figure 1 Block diagram illustrating the lubricant material flow. PCMO = passenger car motor oil; HDMO = heavy duty motor oil; MWF = metal working fluids.

2 METHODS

2.1 Data SourcesNationwide production and trade in finished lubricants is tracked on a

monthly and annual basis by the US Energy Information Administration

(US Energy Information Administration, 2014); however, no public

resources exist that quantify demand at the state level. Under

contract to CalRecycle, a consulting firm developed an estimate of oil

demand in California by end-use application, along with the fraction

of each end-use that is expected to be recoverable at end of life

(Kline & Company Inc., 2012). That study used a proprietary survey

database of national lubricant demand along with a series of proxy

indicators to estimate California demand for each type of lubricant.

Loss rates are estimated based on technical modeling of lubricant use

processes and management practices. This model was used to estimate

the total quantity of recoverable used oil for each year of the study.

The quantity of oil actually collected was estimated from hazardous

waste hauling records (California Department of Toxic Substances

Control, 2013) as described below.

The life cycle of lubricating oil was represented as a series of

stocks and processes linked by flows, consistent with conventional

material flow analysis (MFA) practice (Brunner and Rechberger, 2003;

Kuczenski and Geyer, 2010). The system model and data sources are

summarized in Figure 1. Processes are represented by boxes; stocks

are represented by ovals; flows are arrows connecting them. Because

of the transient nature of the waste stream, all stocks are assumed to

have no accumulation or other net change in stock. The line style

indicates the source of data for each flow estimate. The quantity of

oil to informal management was computed as the difference between used

oil thought to be collectable based on the demand model, and used oil

actually collected in the formal management process. Because used oil

often has significant water content, it was necessary to compute the

portion of collected oil that was actually water (denoted "water

content feedback") and subtract this from the total oil formally

managed. The informal management estimate is the difference between

two independently estimated quantities, so the uncertainty in this

value will equal the sum of the uncertainties in those two estimates.

Figure 2 Detail of formal management model.

2.2 Management and Fate of Used OilFigure 2 shows a detail of the formal management model used in the

study and reports the six forms of disposition modeled. Three

California waste codes were regarded as containing used oil mixed with

varying quantities of non-oil (modeled as water): waste codes 221

“Waste oil and mixed oil,” 222 “Oil/water separator sludge,” and 223

“Unspecified oil-containing waste.” Table S1 in the supplementary

materials lists the three waste codes and the oil fractions assumed

for each. Facilities were classified as “generators” or

“consolidators” based on their industry classification. If a manifest

originated from a facility whose industry classification indicated it

was primarily concerned with waste collection, hauling, or oil

production, the oil on that manifest was considered to be collected by

a consolidator, with the actual generator being unknown. Manifests

originating from other types of facilities are assumed to originate

from the actual generator. The fate of oil disposed at each facility

was estimated based on a facility-specific basis, using permitting

records, company publications, and data provided by CalRecycle.

The highest-value fates of used oil are re-refining and distillation.

Distillation of recycled oil results in a distillate fuel, similar to

vacuum gas oil (VGO) produced in a refinery, and a heavy residue that

can be used as an asphalt modifier. The heavy metal contaminants in

the used oil are understood to be sequestered in the residual material

rather than the distillate, making the distillate cleaner-burning

(Brantley and Townsend, 1999; Legret et al., 2005; US Environmental

Protection Agency, 1992). The distillate can be burned as fuel or

further refined into secondary base oil. Both the distillate and the

secondary base oil can be regarded as equivalent to their primary

petroleum counterparts and use of them is likely to result in the

displacement of primary products (Fehrenbach, 2005; Pires and

Martinho, 2012). The asphalt modifier is used to adjust the physical /

mechanical properties of either roofing tar or road asphalt and may

displace primary road oil. Recycled fuel oil (RFO) is produced from

used oil with minimal treatment, including filtration and water

removal; it can then be combusted as a fuel. It is not straightforward

to determine if RFO combustion displaces an alternative fuel, or to

identify what fuel is displaced. Most RFO produced in California is

thought to be exported from the state for use either as a fuel or as a

feedstock for further reprocessing. Electrical process oils, also

called dielectric oils, are used as thermal and electrical insulators

and are not consumed in use. They can be drained, rejuvenated through

filtration and chemical treatment, and subsequently reused (Kajdas,

2000; Sabau, 2001). Oils that do not meet the requirements for the

above fates must be disposed in hazardous waste facilities or removed

from water in wastewater treatment.

Figure 3 Facility mass balance algorithm.

2.3 Mass Balance CalculationBecause used oil can be accumulated at transfer stations before being

delivered to its final disposition, a single quantity of oil can

appear on multiple manifests. Therefore a simple summation of all

manifested oil will result in an overestimation of the quantity of

used oil managed. Techniques to adjust for double-counting would

reduce the magnitude of this estimate. We constructed a network model

in which each facility handling used oil related waste was a node in

the network. By applying the mass balance principle, it was possible

to determine the apparent net generation or disposition of oil at each

facility. For each facility, all hazardous waste transfers involving

the facility as either origin or destination were identified. The

total inflow was computed as the sum of quantities over all manifests

listing the facility as destination, and the total outflow as the sum

of quantities over all manifests listing the facility as the origin.

Some transfers are considered to be "terminal" (i.e. disposed and not

recycled) based on the disposition code noted on the manifest; oil

reported on these manifests was assumed to meet its final disposition

at the destination facility. The net generation of oil at any given

facility is given by:

Gf=∑Mout,f–∑ (M¿,f−Mterm,f )

where Mout,f represents manifests originating at facility f, Min,f

represents manifests whose destination was facility f, and Mterm,f

represents terminal manifests. Gf>0 indicates a net generation of used oil; Gf<0 indicates a net disposition. This computation is illustrated schematically in Figure 3. Because each manifest has both

an origin and a terminus, the sum over all facilities must be zero.

We define the "aggregate material flow" as the smallest quantity of

material that can account for all observations. This value can be

computed as the sum of generated material over all generating

facilities (or the sum of consumed material over all consuming

facilities). The mass balance algorithm is stated precisely in Section

5.2 of the supplementary materials.

As each manifest had geographically explicit endpoints, the distance

from origin to destination could be computed and freight requirements

could be estimated based on that distance. Transport distance was

considered to be 120% of the geodesic distance between the two

facilities.

Used oil reported on a manifest was assumed to have a density of 0.899

kg/L, equivalent to 7.5 pounds per US gallon, a figure which is

consistent with state reporting practices. Dry used oil was assumed

to have an average density of 0.894 kg/L, consistent with the

assumption of 5% water content in bulk used oil. The same value

(0.894 kg/L) was assumed for finished lubricants. Base lubricants were

assumed to have a density of 0.875 kg/L. Sludge from oil-water

separators generated at primary refining facilities was considered to

be crude oil and not used lubricants, and was excluded from the

analysis. Oil-containing waste reported in terms of solid volumes was

considered to contain unrecoverable used oil and was excluded.

3 RESULTSThe two top-level categories of demand for lubricant products are

automotive and industrial uses. Automotive engine oils can be further

divided into passenger car motor oils (PCMO) and heavy duty or

commercial motor oils (HDMO), each of which includes engine

lubricants, transmission fluids, gear oils and greases. Heavy duty

uses include on-road heavy trucks and off-road uses such as in mining

and agriculture. Industrial demand includes process oils, stationary

engine oils, metalworking fluids, hydraulic fluids, turbine and

compressor oils, refrigeration and heat transfer fluids, and others

(Kline & Company Inc., 2012). While used oil can be recovered from

most engine lubrication uses, many other industrial uses result in

consumption through incorporation into products, or dissipative loss

of the oil.

3.1 Primary ProductionFigure 4 shows base lubricant production and trade from 1981-2013.

This chart presents domestic consumption, including imports, above the

horizontal axis and shows exports below the axis. The size of the

total base lubricant material flow can be described equivalently as

domestic consumption plus exports, or domestic production plus

imports. Domestic production has remained generally constant around

8--9 Mt (55—62 million barrels), while domestic consumption has fallen

modestly. This decline in consumption is consistent with a reduction

in vehicle miles traveled for both personal and commercial vehicles

over the last five years, as well as a gradual lengthening of oil

change intervals (Kline & Company Inc., 2012). As a result, lubricant

base stocks are currently oversupplied in the US market and US

lubricant manufacturing appears to increasingly supply the export

market. Imports, on the other hand, have also grown but represent a

smaller overall quantity. Imports are generally used to supply base

oil to geographic regions that lack domestic production capacity for

specific base oil groups (HSB Solomon Associates LLC, 2013).

Figure 4 US Production and trade of base lubricants, 1981–2013. (source: EIA 2014)

3.2 Demand and Recoverability by ApplicationDifferent lubricant applications have different rates of potential

recovery for used oils. Certain uses, such as engine lubrication, have

very high rates of recovery (as much as 90-95%), while other uses

result in total loss of the lubricant. Table 1 shows a summary of the

demand for lubricants by application, along with their estimated use-

phase loss rates. Aggregated loss rates are weighted averages based

on 2010 demand estimates for California. Total California sales and

use as well as quantity of recoverable lubricants for each year of the

study period are shown in Table 2. Demand quantities are reported on

a volume basis because primary data for this flow are reported in

terms of volume, and the densities of different products could vary.

Engine lubricating oils are lost through leaks and spills as well as

auto-combustion. Studies generally assume that older vehicles have

higher in-use loss rates (Norris et al., 2006; Spence, 2005). Two-

stroke engines do not have distinct lubrication systems. In these

engines, lubrication is provided by mixing the oil with the fuel;

consequently, all the oil is lost. Greases, while not strictly lost

during use, are assumed to be non-recoverable. Approximately 16% of

passenger car motor oils and 21% of heavy duty motor oils are lost.

The estimations are based on surveys of “quick lube” facilities and

modeling (Kline & Company Inc., 2012).

The landscape of industrial oil applications is more complex.

Lubricants used as process oils are often incorporated into products,

or are themselves the final product. Examples are oil used in the

production of rubber, in food or chemical products or as agricultural

sprays and pest suppressants. Dielectric oils, in contrast, can have

a loss rate as low as 13%, and account for the vast majority of

recoverable process oils. The overall loss rate for process oils is

estimated at 84%.

Metal working lubrication applications include cooling during metal

removal, high-pressure forming, and surface treatment or protection.

Fluids used in cooling are highly recoverable, although they are

likely to contain high concentrations of metal chips and dust, thus

requiring further processing prior to recovery. High pressure metal

forming fluids are also recoverable. However, they also present

environmental and toxicity problems, posing complications for used oil

recovery. Finally, fluids used in surface treatment are not

recoverable because they remain on the metal object. Overall loss

rates for metal working fluids are estimated at 31%.

Other industrial lubricant applications include railroad and marine

engines, turbines, refrigerators and compressors, and heat transfer

fluids. Lubricants for railroads and marine engines tend not to be

recoverable due to engine design and operating practices. The other

applications are recoverable in principle. The estimated aggregate

loss rate for these uses is roughly 53%. The overall loss rate across

all industrial applications is estimated to be 66%.

Table 1 Lubricant demand and loss fraction by application (Kline &

Company Inc., 2012).

2010 Demand -ML

loss fraction(CA)Category US CA

Automotive OilsPCMO 2419 265 0.16

Engine Oils 2008 225 0.14Other Oils 399 39 0.24Greases 11 1.1 1.00

HDMO 1989 151 0.21Engine Oils 1433 104 0.20Other Oils 498 43 0.15Greases 59 4.2 1.00

Total Automotive 4408 416 0.18Industrial OilsProcess Oils 2101 146 0.84

Dielectric 312 24 0.13Other 1789 121 0.98

Metal Working Fluids 569 25 0.31

Removal 261 13 0.10Forming 206 6.8 0.20Other 102 5.3 1.00

Industrial Engine Oils 693 73 0.80Other Oils 1291 64 0.19Greases 112 5.7 1.00Total Industrial 4767 313 0.66TOTAL 9175 729 0.38

3.3 Collection and Hauling in CaliforniaThis stage includes all processes related to collecting and

consolidating used oil and delivering it to facilities where it is

recycled or disposed. Flow magnitudes were estimated based on hauling

activity reported to the state on hazardous waste manifests. . The

net generation and disposal of used oil was computed from the mass

balances of all facilities as described in Section 2.3. Table 2 shows

the total quantity of each waste code collected during each year.

Approximately 250-270 kt/y (roughly 60% of used oil) was collected by

consolidators. This value is fairly consistent across all years of

the study, while the quantity of oil reported directly by generators

has declined. A “transfer” is a hauling trip departing from a non-

generating facility, i.e. a transfer facility. “Total Transfers” in

Table 2 indicates the total amount of oil undergoing such a transfer

in the year specified. The ratio of total transfers to total

collections provides a proxy measurement for the number of times a

quantity of waste is transferred prior to its final disposal. This

quantity is slightly greater than 1, meaning that the average reverse

logistics of used oil involves just over two trips. For waste code

221, the ratio is about 1.09--1.20, showing that most used oil

shipments are bulked and transferred at least once even after

consolidated collection. In contrast, the ratio is only 0.25-0.45 for

waste code 223, and roughly 0.04 for waste code 222, indicating that

these loads are not often hauled to transfer facilities between

generation and disposal.

Of the collected material, about 18--20% is finally disposed as

hazardous waste, treated as wastewater, or delivered to another

unknown fate. Most of this loss comprises waste that was treated at a

wastewater treatment facility and subsequently released to publicly

owned water treatment. Other waste fates during collection included

deposit in a hazardous waste landfill, destructive incineration, and

losses during transfer or handling.

Table 2 Material Flow Analysis results for California (italic values

represent projections).

Indicatorunit 2007 2008 2009 2010 2011 2012

Sales and Use - Automotive kg

4.36E+08

3.91E+08

3.70E+08

3.72E+08

3.82E+08

3.81E+08

Sales and Use - Industrial kg

2.98E+08

2.83E+08

2.65E+08

2.80E+08

2.84E+08

2.88E+08

Total Sales and Use kg

7.34E+08

6.74E+08

6.36E+08

6.52E+08

6.66E+08

6.69E+08

Recoverable dry oil kg

4.60E+08

4.21E+08

3.95E+08

4.02E+08

4.13E+08

4.13E+08

Total Collections - WC 221 kg

3.72E+08

3.58E+08

3.27E+08

3.28E+08

3.17E+08

3.05E+08

Total Collections - WC 222 kg

1.85E+07

1.52E+07

1.67E+07

1.65E+07

1.55E+07

1.62E+07

Total Collections - WC 223 kg

3.92E+07

3.89E+07

3.72E+07

4.20E+07

4.52E+07

4.48E+07

Total used oil collected kg

4.29E+08

4.13E+08

3.81E+08

3.87E+08

3.78E+08

3.66E+08

Direct from kg 1.64E+08

1.42E+08

1.32E+08

1.33E+08

1.26E+08

1.30E+08

Generator

Consolidated kg2.66E+08

2.70E+08

2.49E+08

2.54E+08

2.52E+08

2.36E+08

Total Transfers kg4.18E+08

4.31E+08

4.11E+08

4.14E+08

4.10E+08

3.83E+08

Waste Water kg7.29E+07

6.50E+07

6.62E+07

7.62E+07

7.28E+07

7.39E+07

Hazardous Waste kg4.29E+06

8.44E+06

4.55E+06

3.38E+06

2.74E+06

4.04E+06

Other / Unknown kg1.02E+07

8.22E+06

6.06E+06

8.08E+06

5.43E+06

3.91E+06

Waste Fraction of used oil collected 0.20 0.20 0.20 0.23 0.21 0.22

Dry used oil collected kg

3.49E+08

3.37E+08

3.10E+08

3.06E+08

3.03E+08

2.91E+08

Recovery Rate / Sales 0.48 0.50 0.49 0.47 0.46 0.43

Recovery Rate / Recoverable 0.76 0.76 0.80 0.78 0.76 0.73

Dry used oil exported kg

7.86E+07

6.30E+07

4.56E+07

4.25E+07

4.92E+07

5.47E+07

Oil to Informal Management kg 1.1E+0

88.4E+07

8.5E+07

9.6E+07

1.1E+08

1.2E+08

Total Freighttkm

1.56E+08

1.49E+08

1.42E+08

1.44E+08

1.39E+08

1.38E+08

Average Distance km 362 361 373 372 367 378

Collected used oil with hazardous waste separated and water removed,

called “dry used oil recovered,” forms the input for reprocessing.

The recovery rates for the used oil management system were estimated

based on this quantity. The analysis shows that 70--80% of

recoverable used oil is being recovered, or 44--50% of estimated

lubricant sales. The difference between the estimated amount of used

oil available for recovery and the actual quantity reported recovered

is the amount of oil disposed of through informal management.

Different routes for informal management include dumping directly to

the environment, combustion on-site either with or without energy

recovery, and any sale to a “gray market” for used oil that may exist

outside of regulatory supervision. Use of waste oil as a dust

suppressant, herbicide, or pesticide is considered to be a form of

dumping.

Total freight was the sum over all manifests of load mass times

transport distance. The average distance traveled by a given quantity

of used oil during reverse logistics was computed by dividing total

freight by total used oil collected (including wastes and losses).

This distance was found to be 360--380 km.

Figure 5 Recoverability and Collection of California used oil by reprocessingfate, 2007–2012.

3.4 Used Lubricant End-use DispositionThe overall disposition of recovered used oil in California is shown

in Figure 5 against estimates of demand and recoverability. The

overall used oil flow declined steadily, from 349 kt in 2007 to 291 kt

in 2012. The disposition route assigned to each shipment was based on

the receiving facility identified on the manifest. Around 170-190 kt

per year of oil was delivered to the state’s distillation facility for

production of distillate fuel and asphalt additives. Around 60-65 kt

of oil per year was delivered to the re-refining facility for

reprocessing into base lubricant, asphalt additives, and some fuels.

This quantity is lower in 2011-2012, around 40-50 kt per year, due to

repair and maintenance at the facility. These observed quantities are

consistent with the facilities’ operating capacities as described on

permitting documents and other communication with regulators, and

indicate operation at relatively high utilization, excepting the

periods of repair and maintenance noted.

Oil delivered on a manifest to a facility known to be engaged

primarily in transformer maintenance or transformer oil rejuvenation

was designated as dielectric fluid for rejuvenation. The quantity

reported ranged from 3.5-6 kt per year. This quantity is likely an

under-estimate because transformer oil processing may occur at

facilities that were not identified as such, and because some

rejuvenation is thought to occur on-site, thus not resulting in a

manifest.

Oil disposal at any other facility was interpreted as entering the RFO

market. The magnitude of this flow ranged from 60-105 kt per year.

Most of these facilities were outside of California. Part, though not

all, of the reduction in throughput at the re-refinery in 2011-2012 is

made up for in increased RFO production. Because used oil meeting the

“recycled oil” specification can be exported without a manifest,

available data do not support making any distinction between in-state

use as RFO and export from the state. Some RFO originating in

California was sold as feedstock for used lubricant distillation or

re-refining facilities outside the state; the remainder was burned or

used as a fuel cutting stock in cement kilns, asphalt plants, and

industrial and utility boilers.

4. DISCUSSION

4.1 Recovery and Disposal TrendsThe purpose of this study was to estimate the quantity of used

lubricating oil improperly disposed to the environment in California

by comparing records of used oil hauling against a demand-based

estimate of recoverable oil. The results show a recovery rate in

excess of 70%, a generally higher rate than most recyclable materials

such as plastic, copper, and steel. However, the recovery rate

exhibits a gradual decline over the study period even as the estimates

of lubricant demand and recoverability increased from their 2009 lows.

The total quantity of dry oil collected each year shows a monotonic

decline over the study period.

The widening gap between the estimate of recoverable used oil and

actually collected used oil must be explained by a combination of

informal management of used oil and uncertainties in the

recoverability model and the manifest data. Because manifest reporting

is mandatory and strictly enforced, it is unlikely that used oil

collected through formal management is significantly under-reported.

Assuming that the recoverability model also has small errors,

increasing informal management is the most likely explanation. Further

research is needed to determine whether demand for lubricants has

actually increased in California over the past few years, which would

confirm that the recovery rate for used oil is declining.

The bulk of oil reprocessing occurs at facilities in California that

hold state permits authorizing the reprocessing of oil. The combined

capacity of these facilities is less than the quantity of oil

recovered in a typical year, meaning that the state relies on the

export market to process some portion of its used oil. Exports

declined early in the study period, while in-state reprocessing

remained roughly constant. When in-state capacity is interrupted by

external events, as occurred during 2011-2012, it is necessary for the

export market to absorb the unprocessed oil. The observed decline in

oil collected during those years, against an expected increase in

collectable used oil, suggests that the export mechanism may not be

able to adequately accommodate these events.

It is difficult to compare the recovery rate in California against

other states or regions. In general, very little is known about the

recovery rate and reprocessing fate of lubricants in the broader US

market. Although increased investment in re-refining capacity

indicates that a market exists, there are no available statistics to

estimate a national recovery rate or to estimate the amount of used

oil that is improperly disposed. This detailed information is only

available in situations with relatively intensive regulatory

frameworks for used oil. No other US states require used oil transfer

to be reported on a manifest, and the regulatory and reporting

programs in other states are limited in scope (US Department of

Energy, 2006).

4.2 Observations of Material FlowsTraditionally, MFA is performed on an aggregated basis using large-

scale estimates and models of regional production and consumption

behavior. In contrast, the core of this study is based on direct

observations of the waste flow in the form of hazardous waste manifest

reports. Therefore the recovery portion of this MFA can be considered

a measurement, as opposed to an estimate based on models or survey

data. Hazardous waste manifests are legally binding regulatory

documents prepared by the persons responsible for handling the waste.

Because hazardous waste hauling is a commercial enterprise, they also

often represent commercial transactions. Thus the data contained in a

manifest are agreed upon by multiple entities and are likely to have

low uncertainty. Because of this empirical basis, the estimate of the

quantity of oil recovered is likely to be more accurate than an

estimate based on indirect information.

We suggest that a hazardous waste manifest provides a template for a

canonical observation of an industrial material flow, which we define

as the observed transfer of a quantity of well-defined material from

one facility or location to another. We identify six principal

components of such an observation:

Description of the substance being observed (in this case, the

California waste code provides a legal definition);

quantity of the substance;

originating facility or location;

destination facility or location;

fate of the substance upon arrival at the destination;

Time period during which the flow occurred.

Given a corpus of observations matching this definition, the

methodology developed for this study provides a link between the

observations and a macro-scale material flow estimate. The mass

balance algorithm is based on an interpretation of each observation as

a link on a directed graph in which the individual facilities are

nodes. The scope of such a measurement can be defined by the set of

facilities included and the time period. If the set of observations

includes all facilities in a region and all flows over a year, the

aggregate material flow measurement corresponds to the traditional MFA

model. Though the data requirements are greater, computation of an

aggregate material flow from direct observations is likely to result

in a more precise result than “top-down” estimation.

5. CONCLUSIONS

5.1 Policy ImplicationsDespite the presence of a widespread recovery infrastructure supported

by a strong regulatory regime, there is still a significant quantity

of oil thought to be recoverable whose fate is unknown, amounting to

as much as 20-30% of recoverable oil. If any significant portion of

this quantity is improperly disposed to soil or waterways, the

potential environmental impacts could be severe. Moreover, the

recovery rate appears to be declining. If this decline is in fact

occurring, it suggests the need for improvement in the state’s used

oil management system.

Policy makers could achieve reduced environmental impacts by further

incentivizing responsible management of waste oil. One approach would

be to promote measures that would increase in-state reprocessing

capacity or improve the access to California used oil by reprocessors

located out-of-state. These measures could increase demand for used

oil and inspire renewed collection efforts. Alternatively, policy

measures could be designed to pursue application-specific improvements

in used oil collection. The greatest sources for potential improvement

are the dwindling number of do-it-yourself oil consumers and

industrial oil consumers. Previous analysis by CalRecycle suggests

that industrial oil recovery is considerably lower than automotive oil

recovery (CalRecycle, 2008). This observation may be explained by the

existence of industrial oil recovery systems that operate

independently of commercial engine lubricant recovery services

(Organization for Economic Cooperation and Development, 2004; Taylor

Nelson Sofres Consulting, 2001).

5.2 Scientific ImplicationsThis study is distinct in the area of material flow analysis because

the main result derives from a collection of direct observations, as

opposed to traditional MFA's reliance on statistical accounts and

model-based approximation. We have identified the necessary elements

of a material flow observation and defined an aggregate material flow

as the smallest quantity of material that can account for all

observations. We provided an algorithm for synthesizing a collection

of discrete observations into a large-scale measurement of this

quantity.

This approach results in a measurement that is both more accurate and

more verifiable than traditional MFA results. It relies on a large

corpus of data which, at the regional level, is typically only

available under intensive regulatory regimes, such as California's

hazardous waste management program. However, at the firm level there

is considerable private data about material flows that could be used

to perform internal MFAs, or brought to bear on regional MFA if

questions of data privacy are addressed. Moreover, the observation

and measurement of material flows could be performed by individuals as

an industrial ecology application of “small-scale science” or citizen

science (Conrad and Hilchey, 2011; Kolok and Schoenfuss, 2011). Such

"crowd-sourced" data could be used to supplement traditional MFA

approaches at the product use-phase where there is significant public

interest or where national statistical accounts may encounter data

gaps. Some examples of related applications include the use of varied

plastic disposal data to make estimations about marine plastic debris

(Ryan et al., 2009) and the use of crowd-sourced data to calibrate

home energy consumption models (Mills et al., 2014). In all, the use

of direct observation in MFA can improve the availability and quality

of material flow data, potentially increasing the relevance of MFA

methods in policy applications.

AcknowledgmentsWe acknowledge the valuable contributions of the California Used Oil

LCA Stakeholder Team informing all aspects of the study. We thank Ian

Moncrieff (Kline & Company) for development of the California used oil

recoverability model. We thank James Brunk (HSB Solomon Associates,

LLC) for information about the California base lubricant market. We

thank Bob Boughton , Kenneth Bradshaw, Ann Carberry (CA Department of

Toxic Substances Control) for access to and interpretation of the used

oil manifest data. We thank Robert Carlson and Shirley Willd-Wagner

(CA Department of Resources Recycling and Recovery “CalRecycle”) for

coordinating the study and Emily Wang (CalRecycle) for access to and

interpretation of the CalRecycle data. This work was funded by

CalRecycle grant #DRR10063 (2011).

References

Adriaanse, A., Bringezu, S., Hammond, A., Moriguchi, Y., Rodenburg, E., Rogich, D., Schutz, H., 1997. Resource flows: The material basis of industrial economies. World Resources Institute, Washington, DC.

Brantley, A.S., Townsend, T.G., 1999. Leaching of Pollutants fromReclaimed Asphalt Pavement. Environ. Eng. Sci. 16, 105–116. doi:10.1089/ees.1999.16.105

Brunner, P.R., Rechberger, H., 2003. Practical Handbook of Material Flow Analysis. CRC Press.

California Department of Toxic Substances Control, 2013. Hazardous Waste Summary Report (Tanner Report) [WWW Document]. URL http://www.dtsc.ca.gov/HazardousWaste/HW_Summary/index.cfm (accessed 6.6.12).

CalRecycle, 2008. Used Oil Recycling Rate Annual Report: 2008.

Conrad, C.C., Hilchey, K.G., 2011. A review of citizen science and community-based environmental monitoring: issues and opportunities. Environ. Monit. Assess. 176, 273–91. doi:10.1007/s10661-010-1582-5

Fehrenbach, H., 2005. Ecological and energetic assessment of re-refining used oils to base oils: Substitution of primarily produced base oils including semi-synthetic and synthetic compounds.

Graziano, D., Daniels, E., 1995. Assessment of opportunities to increase the recovery and recycling rates of waste oils.

HSB Solomon Associates LLC, 2013. Rerefining Used Lubrication andIndustrial Oils: Effects on Virgin Crude Oil Refining.

International Energy Agency, 2011. Key World Energy Statistics. Paris.

Kajdas, C., 2000. Major pathways for used oil disposal and recycling. Part 2. Tribotest 7, 137–153. doi:10.1002/tt.3020070205

Kline & Company Inc., 2012. Lubricant Consumption and Used Oil Generation in California.

Kolok, A.S., Schoenfuss, H.L., 2011. Environmental scientists, biologically active compounds, and sustainability: the vital role for small-scale science. Environ. Sci. Technol. 45, 39–44. doi:10.1021/es100455d

Kuczenski, B., Geyer, R., 2010. Material flow analysis of polyethylene terephthalate in the US, 1996–2007. Resour. Conserv. Recycl. 54, 1161–1169. doi:10.1016/j.resconrec.2010.03.013

Lawrence Livermore National Laboratory, 2008. Improving Used Oil Recycling in California, History.

Legret, M., Odie, L., Demare, D., Jullien, a, 2005. Leaching of heavy metals and polycyclic aromatic hydrocarbons from reclaimed asphalt pavement. Water Res. 39, 3675–85. doi:10.1016/j.watres.2005.06.017

Lowenthal, 2009. California Senate Bill No. 546.

Mills, E., Bourassa, N.J., Rainer, L.I., Homan, G., Merket, N., Parker, D., Dickey, G., Glickman, J., 2014. Asset rating withthe home energy scoring tool. Energy Build. 80, 441–450. doi:10.1016/j.enbuild.2014.05.044

Norris, J., Stewart, R., Passant, N., 2006. Review of the fate oflubricating oils in the UK.

Organization for Economic Cooperation and Development, 2004. Emission Scenario Document on Lubricants and Lubricant Additives.

Pires, A., Martinho, G., 2012. Life cycle assessment of a waste lubricant oil management system. Int. J. Life Cycle Assess. 18, 102–112. doi:10.1007/s11367-012-0455-2

Ryan, P.G., Moore, C.J., van Franeker, J.A., Moloney, C.L., 2009.Monitoring the abundance of plastic debris in the marine environment. Philos. Trans. R. Soc. Lond. B. Biol. Sci. 364, 1999–2012. doi:10.1098/rstb.2008.0207

Sabau, J., 2001. On-Line Reclamation of Aged Transformer Oils, in: Electrical Insulation Conference and Electrical Manufacturing & Coil Winding Conference Proceedings. IEEE, Cincinnati, OH, pp. 557–565. doi:10.1109/EEIC.2001.965759

Spence, R., 2005. Consumed in Use Study.

Taylor Nelson Sofres Consulting, 2001. Literature Review of European Waste Oil Regeneration and Incineration.

US Department of Energy, 2006. Used Oil Re-refining Study to Address Energy Policy Act of 2005 Section 1838.

US Energy Information Administration, 2014. Lubricants Supply andDistribution [WWW Document]. Pet. Prod. Supply Dispos. URL http://www.eia.gov/dnav/pet/pet_sum_snd_a_eppl_mbbl_a_cur.htm

US Environmental Protection Agency, 1985. Hazardous waste management system; burning of waste fuel and used oil in boilers and industrial furnaces. Fed. Regist. 50, 49166.

US Environmental Protection Agency, 1992. 40 CFR 279: Recycled Used Oil Management Standards. Fed. Regist. 57, 41575.