Post on 24-Apr-2023
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).
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