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Prepared by Meinhardt Infrastructure & Environment Group
The aim of this chapter is to estimate the quantities of oil consumed during use and thus the quantity of used oil generated. The consumption of oil during its use directly affects the amount of residual oil generated and available for recovery and collection after use. For the purpose of this report, consumption during use is considered to be synonymous with loss of oil resulting from its use, and as such refers not only to direct forms of consumption such as combustion but also to minor leaks and spills of lubricants at the point of use. This determination appears to be in accordance with the scope set by previous studies.
This chapter reviews those previous studies that have been identified and the information available for each DISR category to determine the volume of oil available for collection.
A small number of previous studies have investigated the consumption of particular oil categories during their use, leading to the development of 'generation factors'. These generation factors are subsequently used to estimate the proportion of virgin lubricants available for recovery and collection after use; this is equivalent to the amount of used oil generated.
It has been previously asserted that Australian generation factors have not been the subject of direct studies (AIP 1998), however there have been limited studies conducted in Europe and the US. Consultation with stakeholders and review of relevant literature has failed to identify any Australian studies in this field.
Franklin Associates conducted a landmark study of the generation and flow of used oil in the US (US EPA 1984). Whilst the study is of some significance, it has been recognised that its estimates were tentative (Australian and New Zealand Environment Council 1991; Pennsylvania Department of Environmental Protection 1996). As it was found that data regarding collection, reprocessing and reuse of waste oil was not documented, the study relied extensively on estimates yielded through telephone interviews and site visits (Mueller 1989). Estimates for the US were updated in 1996 using 1991 statistics, however, they are still regarded as tentative and the study notes that better baseline survey data are needed (Pennsylvania Department of Environmental Protection 1996).
A study of used lubricating oil in Australia conducted in 1991 for the Australian and New Zealand Environment Council used the US EPA generation factors with minor adaptations to reflect categories supplied by the Department of Primary Industries and Energy (Australian and New Zealand Environment Council 1991).
More recent work by the Australian Institute of Petroleum (AIP 1998) adapted generation factors prepared by the oil companies' European organisation for environment, health and safety (CONCAWE 1996). Adjustments to generation factors for automotive lubricant categories reflected the relatively older vehicle fleet in Australia, whilst base stocks were allocated a generation factor in line with their assumed normal use for automotive lubricants. These adjustments were best estimates based on industry knowledge.
Generation factors estimated in these previous studies are outlined in Table 4.1. It must be noted that each study reported generation factors against different sets of lubricant categories. Factors posited by AIP and ANZEC match the DISR categories, and CONCAWE categories have previously been translated to match DISR categories by AIP. The factors posited by US EPA were made against more specific categories that related to the lubricants' use. These have been condensed to match DISR categories, resulting in a numeric range being presented for some categories rather than single values. Note that categories that have not been specifically addressed by a particular study are marked "N/E" for "not estimated".
Table 4.1 Used Oil Generation Factors Estimated by Previous Studies
|Automotive Petrol Engine Oils||60||65||64||59 - 67|
|Automotive Diesel Engine Oils||60||65||64||59 - 67|
|Hydraulic brake fluids||N/E||N/E||-||10 - 75|
|Industrial gear oils||75||75||N/E||59|
|Industrial hydraulic oils||50||70||76||76|
|Industrial metalworking oils||20||20||0||10 - 100|
|Industrial other||61||50||33||32 - 73|
|Process oils||0||0||0||10 - 27|
Source: AIP (1998), ANZEC (1991), CONCAWE (1996), Mueller Associates (1989)
Comparison of the generation factors estimated by each study indicates a degree of variation within all categories except automotive specialty oils and greases. The two studies that published a factor for base stocks are in reasonable agreement. There is considerable difference between the factors posited for aviation oils and marine oils by CONCAWE and US EPA, however the factors were not altered by either AIP or ANZEC respectively. By contrast, factors for other industrial oils vary significantly between studies.
There is also a fair level of agreement between estimates for both automotive engine oils, however there does not appear to have been any distinctions made between petrol and diesel-fuelled engines. The most detailed estimates were those made by US EPA, which posited generation factors for automotive engine oil according to vehicle type and either personal or commercial use; the average of these values was subsequently used by ANZEC.
Information collected from stakeholders and other sources relating to lubricant consumption rates was used to review the estimates posited by previous studies. There is a paucity of data relating to lubricant consumption, which has particularly acute effects on the ability to review some categories. The findings are presented according to DISR lubricant category.
Automotive Petrol Engine Oils
Previous studies have estimated that approximately 8 litres of lubricating oil are used per year per passenger vehicle (CONCAWE 1996). If this estimate was applied to the number of passenger vehicles registered in Australia in 1999 (ABS 2000), then the quantity of virgin lubricating oil sold for use in 1999 would be approximately 78 megalitres. Given that passenger vehicles account for over 80% of road vehicles and that approximately 90% of household vehicles use petrol (ABS 2000, 2001a), then this estimate would roughly agree with the quantity of automotive petrol engine oil sold in 1999, as indicated in Table 3.6 (96.5 megalitres).
Adjustments made by AIP (AIP 1998) to CONCAWE estimates reduced the percentage of used oil available for collection to 5-10% below the CONCAWE estimates; this was in order to account for the older age of the Australian vehicle fleet. The average age of passenger vehicles in Australia in 1999 was 10.3 years, compared to 7 years in France and between 3 to 10 years in Great Britain (ABS 2000, CCFA c.2001, DETR 2001). Adjustments by AIP would therefore appear to assume that the rate of oil consumption increases significantly after 10 years of operation.
Advice provided by one stakeholder indicates that most cars are unlikely to burn large amounts of lubricants until they have travelled from 100,000 to 200,000 kilometres. Given that the average annual distance travelled per passenger vehicle in Australia in 2000 was approximately 14,000 kilometres (ABS 2001b), the period of 10 years posited by AIP appears plausible.
The average vehicle age varies across Australia, ranging from approximately 9 years in Northern Territory to approximately 12 years in South Australia in 1999 (ABS 2000). It is therefore important to note that the AIP adjustment will not reflect the varying rate of consumption between States and Territories.
Consumption of oil and lubricants by automobiles is likely to vary significantly from one vehicle to another. Factors that influence the rate of consumption include not only vehicle age but also driving conditions, frequency of servicing, engine design (e.g. size), physical properties of the oil being used and usage patterns.
One of the key physical properties of automotive engine oil is viscosity. The viscosity of an oil influences the likelihood that it will leak past piston heads into the combustion chamber of an engine, particularly in hot operating temperatures. Whilst a more viscous oil is less likely to enter the combustion chamber, it will also impose more friction on moving parts. Reducing the friction between moving parts is a desirable outcome with regards to fuel efficiency. The adoption of less viscous oils in order to improve fuel efficiency may therefore result in a higher percentage of oil being lost through combustion. One stakeholder from the motor industry advised that new vehicles may consume approximately half a litre for every 100,000 kilometres and that this value will increase proportionate to vehicle age.
Combustion is only one element of total oil consumption. Other factors, such as accumulation and seepage will also result in consumption. Advice from stakeholders indicates that one-quarter of a litre can be entrained in car oil filters even after they have been drained.
A survey of households with motor vehicles in March 2000 indicated that approximately 30% of households (or 1.9 million households) serviced their vehicles at least once every three months, and a further 48% (or 3 million households) serviced their vehicles once every six months (ABS 2001a). If it is assumed that all of these services included replacement of the oil filter, then the application of these statistics to the number of registered passenger vehicles in Australia in 1999 yields an estimate of the volume of oil lost through retention in the filters after draining of approximately 5.5 megalitres.
These issues suggest that the AIP generation factor has been posited with sufficient knowledge of the underlying issues and, with reservations regarding the applicability of Australia-wide average values to individual States and Territories, has been accepted for use by this study.
Automotive Diesel Engine Oils
There is considerably less information available regarding consumption of automotive diesel engine oils than there is for automotive petrol engine oils.
If it is assumed that the generation factors estimated by US EPA for trucks and buses, as well as off-road engine oils for farming, construction and mining equipment, are based on these vehicles being equipped with diesel engines, then this estimate indicates a distinct difference in consumption rates between petrol and diesel engines that is not reported by later studies.
Advice collected by one stakeholder indicates that it is considered acceptable for a well-maintained large truck towing two trailers to burn 1 litre of lubricant every 1,000 kilometres. The rate of consumption is likely to vary considerably and will increase with vehicle age, as suggested by anecdotal evidence that an 8-year-old vehicle burns 2 to 3 times the amount indicated above, and that some old trucks have been known to consume as much as 1 litre per 100 kilometres. These figures appear much higher than those cited for automotive petrol engine oils.
Depending on the type of truck (i.e. rigid trucks with gross vehicle mass (GVM) of 3.5 and less than 4.5 tonnes, rigid trucks with GVM of 4.5 tonnes or greater, articulated trucks and non-freight carrying trucks), the estimated average age of registered trucks in Australia in 1999 ranged from 11.6 to 15.4 years of age (ABS 2000). This may indicate that the average rate of consumption is greater than 1 litre per 1,000 kilometres.
Given that trucks in Australia in 2000 travelled a total of approximately 39,127,000,000 kilometres (ABS 2001b), then a rate of automotive diesel engine oil consumption of 1 litre for every 1,000 kilometres travelled yields a total of approximately 39 megalitres of oil consumed. This equates to a 36% consumption rate, which is in close agreement with generation factors posited by both ANZEC and CONCAWE.
If this consumption rate was adjusted to reflect advice regarding the increase of consumption concurrent with increasing vehicle age, then total consumption of all automotive diesel engine oil would occur at the rate of 2.75 litres per 1,000 kilometres. As it is known that automotive diesel engine oil is collected in significant volumes, it is unlikely that the average rate of consumption is higher than 1 litre per 1,000 kilometres.
Oil may also be retained in components after their use. Larger oil filters such as those in mining equipment may retain up to half a litre of engine oil after being removed and drained. Crankcase ventilation breathers may retain a further quarter of a litre, which will be lost to the system through capture in filters and formation of dusty sludges.
The information collected for review indicates that the rate of consumption of automotive diesel engine oil should not be regarded as synonymous with that for automotive petrol engine oil, however previous studies do not provide any evidence to suggest that the generation factor is likely to be lower than either 59 or 60 per cent. This being the case, the factor posited by AIP has been accepted for use by this study.
Transmission Fluids and Gear Oils
The adjustment of the CONCAWE generation factors for both transmission fluids and gear oils by AIP was on the same basis as for automotive petrol engine oils, being the difference in average age of the vehicle fleet. Given the comments regarding vehicle age above, the assertion made by AIP appears plausible. Consultation with stakeholders and literature searches did not yield sufficient information to critically review the rate of consumption for this lubricant category. In the absence of further information, the generation factor of 80% posited by AIP has been accepted for use by this study.
Specialty oils include coolants and shock absorber oils, and may also include two-stroke motor oil. Advice received from stakeholders indicates that oil is not recovered from used shock absorbers, and that two-stroke motor oil is totally consumed during use, primarily through combustion. This supports the generation factors posited by AIP, ANZEC and CONCAWE, and as such this study assumes that no specialty oils are available for recovery.
Hydraulic Brake Fluids
Only one previous study posited a generation factor for hydraulic brake fluids, ranging from 10% for on-road vehicles to 75% for off-road vehicles (US EPA 1984). The basis for the distinction between these two uses is not clear. Calculation of each generation factor against the proportion of new oil sold for each use yields a weighted average of 48%.
It is unlikely that the rate of consumption is solely attributable to system failure as hydraulic brake systems are not as susceptible to spillage as industrial systems, despite their degree of exposure and the pressure under which they operate. A stakeholder within the automotive recycling industry advised that hydraulic brake fluid is difficult to remove, even with pressurised evacuation systems.
Given that the majority of registered vehicles are expected to be for on-road use, it is reasonable to assume a generation factor of at least 10%. Note that this factor may understate the amount of oil available for recovery given the weighted average for factors posited by US EPA. It is also possible that technological and operational changes in the intervening years since the US EPA factors were determined may have contributed to an overall decline in the volume of fluid available for recovery.
However in the absence of definitive data, the AIP "non-estimate" has been accepted as 0%.
Information regarding the consumption of aviation oils is limited. Advice obtained from an Internet aviation information and news service (www.avweb.com) indicates that light aircraft are recommended to change their oil at least once every 4 months, and that it is considered acceptable for a light aircraft to consume approximately one litre of oil every 20 hours of flying time. However the average number of flying hours per light aircraft in Australia is not known. No advice was received with regards to commercial freight or passenger airline activities.
The extent of the discrepancy between estimates posited by US EPA and CONCAWE is cause for concern. It has been assumed that the difference in factors relates not to technological advancement during the intervening years between studies, but is rather the result of differences in data gathering and underlying assumptions. There is insufficient information to declare either estimate more reliable than the other. This study will employ a factor of 90%, which is the generation factor posited by AIP.
It has been assumed that all prior studies have focused upon marine engine oils only and exclude oil transported as a commodity by the marine sector.
The estimate posited by CONCAWE and adopted by AIP is in fact a "non-estimate" as CONCAWE were unable to assess a recovery percentage due to direct re-use of oil within ship engines. The basis for the different estimate posited by US EPA is not known. Consultation with stakeholders and literature searches did not yield sufficient information to critically review the rate of consumption for this lubricant category. As there is insufficient information to declare either estimate more reliable than the other, this study will employ a factor of 0%, which is the factor posited by AIP.
It has been assumed that this category refers solely to railroad diesel engine oils and excludes the use of oil for specialist applications within this sector. Specialist applications identified both in Australia and overseas include rail greasers on tight radius curves, railway switches, cog wheels, wheel flanges and packing in journal boxes (i.e. the boxes that hold the axles of wheel sets that are not equipped with roller bearings). All of these applications are assumed to involve total loss, and as such would reduce the percentage of oil available for recovery were they included in an estimate.
The basis for the difference between estimates posited by US EPA and AIP are not known. There is insufficient information to declare either estimate more reliable than the other. This study will employ a factor of 40%, which is the generation factor posited by AIP.
Industrial Gear Oils
The basis for the difference between estimates posited by US EPA and CONCAWE are not known. Consultation with stakeholders and literature searches did not yield sufficient information to critically review the rate of consumption for this lubricant category. In the absence of further information, the generation factor of 75% posited by AIP has been accepted for use by this study.
Industrial Hydraulic Oils
Hydraulic systems are susceptible to spillage as they are often exposed and operate under high pressure. For example, in the mining industry, applications where mechanical system failure may result in oil spillage have been provided by LaGanza (1998), and include mobile sources such as continuous miners, conveyor drive units and roof support systems, and stationary sources such as machine tools, and spillway gears for weirs and dams.
Advice provided by one stakeholder indicates that the quality of modern hydraulic hoses reduced the risk of failure, however the quantity of lubricant present in a large piece of equipment may result in the loss of a few thousand litres before the machine could be shut down. Another stakeholder advised that shut downs often did not occur due to the cost of machinery downtime, and that oil losses continued on a large scale until such time as a mechanic was available to fix the problem.
The basis for the difference between estimates posited by US EPA and CONCAWE are not known. The estimate posited by AIP after adjustment of the CONCAWE estimate suggests that there is a higher incidence of catastrophic loss in the Australian mining sector; this is supported by stakeholder advice discussed in the previous paragraph.
Consultation with stakeholders and literature searches did not yield sufficient information to verify that this is indeed the case. However in the absence of further information, the generation factor of 50% posited by AIP has been accepted for use by this study.
Industrial Metalworking Oils
There is a significant degree of variation between the generation factors posited by CONCAWE and USEPA. Calculation of each generation factor against the proportion of new oil sold for each use yields a weighted average of 77%.
Review of the explanatory information provided by CONCAWE and US EPA studies indicates that the principal cause for the difference in estimates is the inclusion by CONCAWE of cutting oils within this category. This inclusion appears to have been accepted by AIP, suggesting that factors used for this study must also account for the high losses associated with the high loss of cutting oil through mixing with water during use. The factor of 20% posited by CONCAWE (and subsequently used by AIP) has therefore been used for this study.
A number of applications for oil result in total loss (that is, the oil is completely consumed or cannot be recovered as a result of its use). These applications include but are not limited to:
The extent to which these incidences of total loss will affect the overall generation rate for recoverable oil depends upon the proportion of lubricants used in each application. Of the other industrial lubricants listed by US EPA, lubricants used in turbines accounted for over 60% of oil sales, and were assigned a generation factor of 59%. Comparable levels of detail were not available from other studies, so it is not possible to detect any changes over time in the proportion of lubricants used for each application.
There is a significant degree of variation between estimates posited by AIP, ANZEC, CONCAWE and US EPA for this lubricant category. The higher rate of recovery posited by AIP accounts for the inclusion of transformer oil within this category, which has been asserted to be almost entirely recoverable by CONCAWE, as well as compressor oil, which was also assigned a high recovery rate by CONCAWE. Consultation with stakeholders and literature searches did not yield sufficient information to verify this adjustment. Calculation of each generation factor against the proportion of new oil sold for each use yields a weighted average of 61%, which is the same as that proposed by AIP. A generation factor of 61% has therefore been accepted for use by this study.
Greases have been assumed to be totally lost through use by both the US EPA and subsequent ANZEC study. Use of grease commonly results in the smearing of relatively thin films of grease across moving parts, which may be difficult to remove in such a manner as to allow for recovery.
Some applications will also expose the grease to elements resulting in its removal during use, such as the continual removal by passing water of the grease used to lubricate wicket gate bearings in hydroelectric turbine power generators. It has been assumed that the quantity of grease available for recovery is negligible, and as such a factor of 0% has been used for this study.
Previous studies by ANZEC and CONCAWE have asserted that process oils are completely consumed as part of their use, either as the raw materials for particular products or as an element of production processes. Examples of the use of process oils include the production of agricultural sprays, explosives, ink, textiles, and the preparation of plasticisers, reinforcement and extension for rubber products. These uses would intuitively appear to result in the consumption of most, if not all, of the oils used.
By comparison, earlier estimates suggest that a small portion of process oil is available for recovery after use. The factors posited by US EPA range from 10% for white oils, rubber oils and other oils, to 27% for electrical oils. Calculation of each generation factor against the proportion of new oil sold for each use yields a weighted average of 14%. This compares well with an earlier study of waste oil, which asserted that 5-15% of process oils (e.g. flotation oils) generate waste oil (Kimball 1975).
It is unclear whether technological or operational changes in the intervening years since these latter factors were posited may have contributed to an overall decline in the volume of fluid available for recovery. In the absence of any additional information, the AIP position, based on CONWAVE information that oils are completely consumed as part of their use, is accepted.
Generation factors for base stocks have only been prepared by AIP and ANZEC, presumably arising from the existence of a distinct category in the DISR (and formerly DPIE) sales data. The reason for the comparative detail of the estimate posited by ANZEC is unclear, however it is sufficiently close to factors estimated for automotive engine oils to suggest that the factor is based on an assumption that the majority of base stocks are used to produce automotive lubricants. This has also been asserted by AIP.
As discussed in Section 3.3.1, base stocks are also used to prepare comparatively smaller volumes of industrial and mining lubricants. As the exact nature of the split between the two uses is not known, the impact of the latter use on the generation factor cannot be reliably estimated. In the absence of such information, the generation factor of 60% posited by AIP has been accepted for use by this study.
It is important to note that losses will occur at each stage of the supply chain, rather than solely at the point of use. Losses may be expected during the storage, handling, retailing, transport, collection and reprocessing of oil. Loss may result from spillage arising from either mechanical system failure or maintenance practices where used oil is not recovered.
Advice from the AIP indicates that the plastic bottles used for the majority of small packs may absorb approximately 2% of the product, and that a further 3% to 4% of product forms an oily sheen that cannot be drained from the container.
Maintenance of machinery may give rise to spillage, particularly in situations where recovery of the used oil is not considered practical. For example, the design of concrete mounting pads for farm irrigation pumps may not provide sufficient clearance to allow for the collection of oil drained during changes. Advice from one stakeholder indicates that oil in these pumps needs to be changed every 4 to 5 days when in continuous use, and that approximately 30% of the used oil is recovered.
Earthmoving equipment contractors operating in remote districts may bury used oil resulting from on-site oil changes due to the logistical difficulties of transporting used oil back to the home depot or workshop, which may be 500 kilometres or more from the site of use.
One stakeholder who both supplies new oil and collects used oil advised that the quantity of used oil collected from two major earthmoving contractors in his region was approximately 5% of sales of new oil. This may indicate that a significant proportion of used oil is disposed of by methods other than collection for recovery.
Similar observations were also made by another stakeholder, who commented that the top-up of hydraulic systems with worn seals, rather than shutdown and repair of the problem, was a potential cause of avoidable spillage. This scenario is likely to apply to users of older equipment for logging, excavation, earthmoving, haulage and farming.
Water infiltration due to diurnal temperature-related expansion and contraction of storage drums has also been posited as a source of system losses. It is possible that technical data regarding the magnitude of losses at each stage of the supply chain has been prepared previously by either individual companies or research agencies, however it is also likely that this data is dispersed and would not be readily available.
It can be seen from the preceding discussion that in some instances insufficient information is available to determine which of the posited used oil generation factors is most accurate. The AIP estimates, however, have most often been accepted when considered in conjunction with stakeholders' advice and other information sources relating to lubricant consumption rates.
In order to avoid compounding errors by the introduction of new waste oil generation factors based on a combination of the available data, it is considered that accepting one source of information is more beneficial. The AIP used oil generation factors have thus been accepted, with reservations, for the purposes of this study.
The following assumptions have been made in the determination of used oil generation factors.
Assumption 7: The used oil generation factors posited by AIP have been assumed to be correct for all DISR categories. This assumption is based on a consideration of all available information.
Assumption 8: To determine the used oil generation factors for the 'Automotive Petrol Engine Oils', 'Automotive Diesel Engine Oils, 'Transmission Fluids' and 'Gear Oils' categories, AIP adjustments appear to assume that the rate of oil consumption increases significantly after 10 years of operation.
Assumption 9: In the absence of an estimate by AIP, the used oil generation factor for the 'Hydraulic Brake Fluids' category is assumed to be 0% based on all information available.
Assumption 10: AIP have assumed a used oil generation factor for the 'Railroad' category. There is no information for the basis of this factor, which has been assumed to be correct by this report.
Assumption 11: AIP have assumed that there is a high incidence of catastrophic loss in the Australian mining sector and have thus decreased the CONCAWE used oil generation factor for 'Industrial Hydraulic Oils'.
Assumption 12: AIP have included transformer oil and compressor oil in the 'Industrial Other' category and thus assumed an increase in the CONCAWE used oil generation factor for this category.
Assumption 13: In the absence of an estimate by AIP, it is assumed that 'Greases' are totally lost through use as per information in the US EPA and subsequent ANZEC studies.
Assumption 14: AIP determined the used oil generation factor for the 'Base Stocks' category based on the assumption that the majority of base stocks are used to produce automotive lubricants.
If the generation factors discussed above are applied to DISR sales data for new oil for 2000, then the quantity of used oil available for recovery in Australia in 2000 is estimated to be 303 megalitres. The estimated volume of used oil available for recovery by oil type is indicated in Table 4.2.
Table 4.2 Volume of Used Oil Available for Recovery in Australia (2000)
|Used oil available for recovery
|Automotive Petrol Engine Oils||94.1||60||56.5|
|Automotive Diesel Engine Oils||107.3||60||64.4|
|Hydraulic brake fluid||0.4||0||-|
|Industrial gear oils||3.6||75||12.1|
|Industrial hydraulic oils||11.8||50||21.6|
|Industrial metalworking oils||2.4||20||1.8|
It is likely that application of the above factors to individual States and Territories will overlook regional variations, as those that are supported by statistical data are derived from Australia-wide statistics (e.g. average age of motor vehicles). It is therefore not considered prudent to generate estimates for individual States and Territories.
Table 4.3 indicates that the estimates prepared by this study, which is based mainly upon the AIP used oil generation rates, are greater than those that may be made by applying factors posited by previous studies.
Table 4.3 Comparison of Estimates Against Other Generation Factors
|Used Oil Available for Recovery
|Automotive Petrol Engine Oils||56.5||61.2||60.2||61.2|
|Automotive Diesel Engine Oils||64.4||69.7||68.7||69.7|
|Hydraulic brake fluid||N/E||N/E||N/E||1.0|
|Industrial gear oils||12.1||12.1||-||9.5|
|Industrial hydraulic oils||21.6||30.3||32.8||32.8|
|Industrial metalworking oils||1.8||1.8||-||7.1|
It must be noted that none of the previous studies originally reported against the same lubricant categories used for this study, and as such their application to current categories may not account for the entire total of new oil sold. This lack of complementarity may skew the comparison of estimates, depending on the number of categories not specifically accounted for by previous generation factors.
The estimates made through this study are based on estimates by AIP and, where necessary, statistical information and stakeholder advice. Many assumptions, as listed, have been made by in both the AIP and this study. The extent and quality of information relating to the generation of used oil for particular oil types varies significantly, but is very limited overall. This results in a very high level of uncertainty for the majority of generation factors. Care must therefore be taken when using these estimates to acknowledge their indicative nature.
The consequences of the lack of information regarding used oil generation rates is potentially significant as this data has been used to determine the amount of used oil available for recovery in Australia.