7. Properties of Petrol
This section examines the main properties that specify petrol quality. These include:
- Properties specified in the current regulations;
- Other properties currently not specified.
These properties are presented generally in the order in which they appear in Schedules 1 and 2 of the Regulations. Each is examined under the following headings (as applicable):
- Property
What is it?
Why is it important (its effect on engine performance)?
How is it controlled? - Comparison of current New Zealand and international specifications
- Why regulate?
Why does this property need to be regulated?
Should the current specifications be changed? - Proposed changes
Proposed changes and timing
Implications of changes, potential costs and benefits
It is noted that for some properties of petrol, there is a high degree of interdependence - for example, volatility and distillation parameters, composition and density are all inter-related so it is not possible to change one in isolation and not affect the others. In refinery operations, where each crude oil produces a range of fuels, changing the properties of one product will also have flow on effects for other products - for example, changes required to meet new specifications for petrol may have an impact on production of diesel or other products. Therefore a broader view needs to be taken when considering the implications of any changes to specified quality properties.
Appendix C contains a description of how spark-ignition engines work, and the fuel characteristics that are relevant to petrol engine performance.
7.1 Properties Currently Specified
7.1.1 Octane Number
What Is It?
Octane Number is a measure of a petrol's resistance to auto-ignition. Auto-ignition in petrol engines can be classified into two types:
- Knock, caused by spontaneous combustion of a portion of unburnt air-fuel mixture ahead of the advancing flame front; and
- Surface ignition (pre-ignition or post ignition), where ignition is initiated by any hot surface in the combustion chamber rather than spark discharge at the spark plug.
Both processes result in uncontrolled combustion which, if severe, can cause major engine damage. Knock is generally the more common form of abnormal combustion. A significant defining feature of knock is that it is able to be controlled by ignition timing.
The higher the octane number of a petrol, the greater its resistance to knock. Iso-octane (octane number 100) and n-heptane (0) are used as the reference points for octane number. An octane number of 91 means that the fuel, when tested in a specified engine and procedure, has the same anti-knock quality as a mixture of 91% iso-octane and 9% n-heptane by volume.
There are two common measures of octane:
Research Octane Number (RON) is an indicator of the fuel's anti-knock performance at lower engine speed and typical acceleration conditions.
Motor Octane Number (MON) reflects the anti-knock performance of a fuel under high engine speed and higher load conditions.
The difference between them (i.e. RON - MON) is called the sensitivity and reflects the effect of changing operating conditions on the fuel's anti-knock performance.
In common usage, the term "octane", as in the 91 and 96 grades of petrol available in New Zealand, refers to RON, which for petrol, is always the higher value.
The specified test methods are ASTM D 2699 for RON and ASTM D 2700 for MON.
Why Is It Important?
Spark ignition engines are designed for a certain octane rating, corresponding to the compression ratio. Using a fuel of a lower rating may result in knocking, due to compression ignition occurring before spark ignition. In many modern engines, the spark occurs before the end of the compression stroke, to maximise the length of the power stroke, which requires the fuel to be resistant to compression ignition.
Many modern vehicles are designed with knock sensors which can retard the spark timing to accommodate conditions that would cause knocking. However, compensating for a low octane fuel by this mechanism results in loss of performance and efficiency. Using a petrol with a higher octane rating than specified will generally not improve engine performance.
As engine technology develops to achieve greater fuel economy, higher compression ratios may become more common in engine designs, necessitating higher octane fuel. A 95 RON/85 MON grade is seen as being the optimum octane rating, providing a balance between reducing fuel consumption and increasing the energy required to produce the fuel. Most Japanese cars are designed to run on 90 RON which is the regular grade standard in Japan, and these vehicles dominate the current New Zealand fleet. However, over the long term the demand for premium grade petrol worldwide is projected to increase.
Low speed knock during acceleration is generally audible and the driver can ease back on the accelerator if it is severe. This form of knock is influenced more by the RON than the MON. The MON will have more impact on high speed, high load conditions when knock may not be audible to the driver and is potentially more damaging. A greater sensitivity will mean a lower MON for a given RON and greater potential for the more damaging and less detectable high speed knock. Sensitivity should not generally exceed a value of 10 - 11, though for high octane petrols (97 - 98 RON) it may be higher.
How Is It Controlled?
Branched chain hydrocarbons, olefins and aromatics are high octane components of petrol and their presence tends to improve its anti-knock performance. These compounds have differing sensitivities and so their use will affect the balance between RON and MON. Octane enhancing additives (organo-metallic compounds such as lead alkyls and MMT) can be used to improve the octane number of petrol. High octane blending components (oxygenates such as MTBE and ethanol) can also be used.
All of these means of meeting octane rating specifications are constrained in New Zealand:
- The formation of branched chain hydrocarbons is achieved through alkylation and isomerisation during refining of the gasoline fraction of crude oil. While all the Australian refineries have some level of capacity for either one or both of these processes, the Marsden Point Refinery does not. Therefore improving octane rating via addition of branched chain hydrocarbons can only be achieved at Marsden Point by the use of imported blending stock containing high levels of these compounds.
- There is a trend worldwide to reduce the amount of aromatics and olefins in petrol because of the effects of some of their products of combustion on air quality. These are discussed in more detail in Sections 7.1.9 and 7.2.1 respectively.
- The use of lead alkyls has now been phased out in New Zealand because of the adverse environmental effects of lead discharged from vehicle exhausts. Lead in petrol is discussed in Section 7.1.8.
- Similarly, other organo-metallic compounds (such as MMT) are not favoured by the automotive industry as octane enhancers because of their effects on engine components and catalysts. Manganese is covered in Section 7.2.2.
- Oxygenates such as MTBE and ethanol have a strong affinity for water and can rapidly migrate from fuel spills into ground water. Also the majority of the New Zealand petrol distribution infrastructure is not completely water-free and is therefore not suited to the use of MTBE or ethanol. Oxygenates are discussed in more detail in Section 7.1.11.
Because of these constraints, the Marsden Point Refinery, which produces about two thirds of the gasoline used in New Zealand, has limited capacity for reducing the benzene and total aromatics content of petrol, with its current configuration and balance of feedstocks. Even production of premium grade currently requires the use of significant volumes of imported gasoline blendstocks to achieve octane targets. This has implications for other properties considered in the review.
Current New Zealand and International Specifications
Most petrol specifications in other countries state a minimum limit only for both RON and MON. International specifications for octane number are already closely aligned as shown below.
In the United States, an Anti-knock Index (AKI) is commonly used, which is the average of RON and MON i.e. (RON + MON)/2. USEPA regulations require a minimum anti-knock index of 87. The value of AKI for New Zealand's 91 grade is 86.5, and for premium grade is 90.
| Grade | Regular | Premium | 98 RON |
|---|
| Specification | RON | MON | RON | MON | RON | MON |
| New Zealand | 91 | 82 | 95 | 85 | | |
| Euro 3 (2000) | 906 | 807 | 95 | 85 | | |
| World-Wide Fuel Charter | 91 | 82.58 | 95 | 85 | 98 | 88 |
| Australia (from 1 January 2002) | 91 | - | 95 | - | | |
| Japan | 89 (No. 1) | - | 96 (No. 2) | - | | |
In 1998/1999, regular grade petrol sampled in New Zealand had an average RON of 91.7 and an average MON of 83.0. Premium grade had an average RON of 96.5 and an average MON of 86.2.
While the current statutory requirements for premium grade petrol are 95 RON/85 MON minimum, the supply specification used by the refinery and the four main oil companies (the NZRC and User Company specification) is actually 96 RON/86 MON minimum. Some companies (but not all) market premium grade specifically as 96 octane. This level is understood to have been adopted following "octane satisfaction surveys" carried out prior to the introduction of premium unleaded petrol (PULP) to establish the appropriate octane range for the premium grade to suit the vehicle fleet.
BP and Mobil are now both marketing high octane grades in New Zealand (nominally 98 RON).
Why Regulate?
The primary reason for continued regulation is to ensure that the consumer is able to buy petrol of known and consistent octane number.
Newer engine designs are less prone to higher speed knock. Given this, the recent Australian review of fuel quality (see Section 5.3) concluded that MON is an outdated parameter and it has not been included in the environmental specifications which come into effect next year. This effectively removes any direct control on sensitivity. However, it is important to maintain sensitivity control for older technology cars.In view of the make-up of the New Zealand fleet, it is considered that the maximum sensitivity still needs to be controlled through specifying minimum limits for both RON and MON.
The "boutique" high octane grades now available are of relatively small volume and because of this, it is not considered that their octane number specifically needs to be regulated, other than that they should meet the octane number being advertised. This is discussed in more detail in Section 10.
Changes Proposed to the Regulations
| Current Regulations | Proposed changes |
|---|
Octane number for regular grade petrol:
91 minimum RON; 82 minimum MON | No change |
Octane number for premium grade petrol:
95 minimum RON; 85 minimum MON | No change |
7.1.2 Colour
What Is It?
Petrol is normally colourless and a dye is added (usually at the refinery) to provide any required colour. Generally, colours are used to differentiate between grades during distribution, in particular between leaded and unleaded petrols. This dye does not affect vehicle performance.
Current New Zealand and International Specifications
International specifications do not stipulate any colour requirements for petrol. The New Zealand specifications currently only require that the colour of petrol ensures that it "not be mistaken for a harmless substance". The change from specifying particular colours was made in 1998 following concerns about the cost of compliance.
There is also no requirement for the two grades to be of different colours, and in fact the colour may vary depending on whether it comes from the Marsden Point Refinery or is imported. Currently regular grade from the Refinery is red. Regular grade in Australia is purple (leaded is red). Premium grade and the new higher octane grades now available are yellow.
It is understood that Australia proposes to continue with its standard colours.
Why Regulate?
Normally the consumer will not see the fuel that is being put into a vehicle, but the colour does allow the grade of petrol to be easily determined when it is sampled and for it to be readily distinguishable from diesel, which has no added colour.
The requirement for petrol "not to be mistaken for a harmless substance" - is primarily for consumer protection and child safety. However, the interpretation of a "harmless" colour is very subjective. Regulating the colour of petrol does not seem to achieve the original intention and the present requirement is considered to be unenforceable.
Changes Proposed to the Regulations
| Current Regulations | Proposed Change |
|---|
| Colour: not to be mistaken for a harmless substance | Immediate removal of requirement |
7.1.3 Volatility and Distillation Parameters
What Are They?
These properties characterise the volatility of the petrol, that is, its tendency to vaporise. This is critical to both engine performance, particularly starting, as well as vapour emissions from the fuel distribution system. As petrol is a mixture of a large number of different hydrocarbons, the boiling point is a temperature range rather than a single value, and so four main measures of volatility are commonly used.
E70, E100, E150 and E180
These are the percentages by volume of petrol that evaporate when it is heated to 70°C, 100°C and 180°C respectively. E70 is a measure of cold running performance. The distillation properties can alternatively be expressed as temperatures corresponding to different volumes, for example T10, T50 and T90. These are the temperatures at which 10%, 50% and 90% by volume of the petrol has evaporated.
Distillation End Point
This is the temperature beyond which all the volatile components have boiled off, leaving only a residue (see Section 7.1.4). These properties are illustrated in Figure 7.1 which shows a typical distillation curve for petrol.
Figure 7.1: Typical Distillation Curve for Petrol
Reid Vapour Pressure (RVP)
The vapour pressure is another measure of the volatility of the fuel and relates principally to the lighter components in the fuel such as butane. To measure the true vapour pressure is quite involved, so a simpler parameter, the Reid Vapour Pressure is used and is referenced to a standard temperature (37.8°C or 100?F).
Flexible Volatility Index (FVI)
This is a parameter calculated from the RVP and the measured value of E70, and is an indicator of the hot running performance (the tendency for vapour lock).
FVI = RVP + (0.7 x E70)
Vapour Lock Index (VLI) is used in European specifications and is essentially the same as FVI, though it differs by a factor of 10.
Another indicator of volatility is the Driveability Index or Distillation Index (DI) which is calculated from T10, T50 and T90 and also allows for the effects of oxygenates. The formula is:
DI = (1.5 x T10) + (3 x T50) + T90 + (11 x %O2 w/w)
DI is a measure of cold driveability. "T" numbers have traditionally been used in the USA, Japan and Australia although the USEPA is moving away from these in favour of % evaporation properties (E70 etc.) which behave linearly when blending different batches.
Why Are They Important?
Fuel must contain enough volatile components (light ends) to enable easy starting and acceptable driveability when an engine is cold, but not so much that it begins to vaporise in the fuel lines when the engine is hot (this is known as vapour lock and impedes fuel flow). The fuel must also not be so volatile that evaporation from the fuel tank is excessive - both for environmental and health reasons. Therefore, volatility must reflect not only the general performance requirements of spark-ignition engines but also the range of climatic conditions in which they must operate, so direct comparisons with other countries are not necessarily valid.
The high end of the distillation curve, that is the least volatile (heaviest) components, are important in contributing to deposit formation and exhaust emissions. These compounds may not fully vaporise before entering the combustion chamber, particularly under cold running operation. This can cause oil dilution and increased cylinder wear, and may lead to combustion chamber and inlet system deposits and spark plug fouling. Exhaust hydrocarbon emissions are also influenced to a small extent by the heavy compounds; reducing the fuel's T90 value leads to small reductions in hydrocarbon emissions, particularly under cold running conditions. The evaporative emission of VOCs is also reduced with decreased T90. These effects are generally fairly small.
The heavier compounds in petrol are generally those with the highest energy content and density, so their reduction will tend to reduce the energy content per litre of fuel slightly, thereby increasing fuel consumption.
How Are These Properties Controlled?
RVP is usually controlled during refining by adjusting the proportion of butane, the most volatile component, in the final blend. Reducing RVP reduces evaporative losses and the international trend is towards lower maximum RVP limits.
End Point is reduced by altering the cut point between the petrol fractions and heavier products during refining.
The other distillation properties are not usually controlled directly but reflect the composition of the petrol.
Current New Zealand and International Specifications
The following table compares the current New Zealand requirements with a range of volatility specifications used internationally. It is important to note that the values of these volatility properties must be set to suit the climatic conditions in which the fuel is used. The European specifications define volatility classes, based on climate which each EU country is able to assign on a seasonal basis. The World-Wide Fuels Charter volatility classes are based on minimum expected ambient temperatures.
| Parameter | E70 | E100 | E180 | End Point | RVP | FVI |
|---|
| Specification | Vol %
min | Vol %
max | Vol %
min | Vol %
max | Vol %
min | °C
max | KPa
max | |
| New Zealand | 25 | 45 | 45 | 67 | 90 | 220 | - | 77.5 - 115 |
| Euro 3 (2000)9 | 20 - 22 | 48 - 50 | 46 | 71 | 75 (E150) | 210 | 45 - 70 | 1250 max10 |
| World-Wide Fuel Charter11 | 20 - 25 | 45 - 47 | 50 - 55 | 65 - 70 | 90 | 195 | 55 - 7012
65 - 80 | |
| Australia | To be included in future operability standards (under development) | 210 (from 1 January 2005) | Controlled at state level | To be included in future operability standards (under development) |
| Japan | T10, T50 and T90 specified | 220 | 44 - 78 | |
| USA | | | Subject to control under RFG (reformulated gasoline) specifications. | |
Why Regulate?
Performance
After cold starting problems were encountered with a shipment of imported fuel in 1994, the specified minimum values for E70 and E100 in New Zealand were increased from 15% and 40% respectively to the current values of 25% and 45%. Some suppliers believe that that a minimum E70 value of 22% would be less constraining on refineries while not unduly affecting performance and similarly that E70 maximum could be increased to 50%. While changing the minimum E70 should not have any significant impact on engine performance, increasing the maximum will increase the evaporative losses.
The current specifications for FVI (77.5 min and 115.0 max) reflect the allowable seasonal variation but do not specify summer and winter requirements per se. If RVP limits were introduced, FVI might be considered superfluous. However, engines with carburettors are more susceptible to vapour lock than than those with fuel injection systems. As carburetted engines currently make up a significant proportion of New Zealand's petrol vehicle fleet, it is considered that the maximum limit on FVI needs to be retained, as has been done for the "shoulder seasons" in the United Kingdom. The minimum requirement is not seen as necessary to control engine performance and minimum FVI is not regulated elsewhere.
Reducing the end point will reduce smoke emissions due to reduced high molecular weight aromatics. Changing the distillation end point to 210°C will align with the Euro 3 standard and the current Australian proposals (to be implemented in 2005).
Evaporative Emissions
In order to reduce evaporative losses and resulting hydrocarbon emissions from vehicles and during bulk storage and distribution, there have been moves in many other countries to reduce the allowable vapour pressure. Many countries set maximum RVP limits in summer. In New Zealand, there are no direct limits on vapour pressure, though it is controlled indirectly through limits on FVI. Based on the current E70 limits, the FVI specifications allow RVP to range between 46 and 97.5 kPa, although other properties may be constraining. However, the NZRC and User Company specification does set seasonal limits for RVP (albeit at a high level).
RVP reduction is achieved by reducing the lighter ends such as butanes which in turn affect cold starting. Lower volatility fuels are less of a problem in fuel-injected engines common in many new vehicles but can cause difficulties with carburetted engines in older vehicles, which make up a significant proportion of the New Zealand fleet. Therefore RVP limits should not be set too low.
Harmonisation with Other Specifications
Volatility requirements set in international standards reflect a range of climatic conditions and care needs to be taken when identifying suitable values for use in New Zealand. It has been suggested that E100 limits be changed to 46% (minimum) and 71% (maximum) to align with Northern European volatility classes. However the benefits of this would be limited.
E150 is considered to provide better control of volatility and 75% (minimum) is an appropriate level to set. Specifying an E150 value instead of E180 will align with the Euro standard
It is considered that there is no benefit from adopting DI in favour of the current property/properties.
Changes Proposed to the Regulations
| Current Regulations | Proposed changes |
|---|
| E70: 25% minimum; 45% maximum | Immediate reduction of minimum E70 to 22% |
| E100: 45% minimum; 67% maximum | No change |
| E180: 90% maximum | Stage 1 replacement of E180 specification with E150, set at 75% maximum |
| Distillation end point: 220°C maximum | Stage 1 reduction of distillation end point to 215°C Stage 2 further reduction of distillation end point to 210°C |
| Reid Vapour Pressure: not currently specified | Immediate introduction of maximum RVP limits by season (see table below) (test method ASTM D 323) Stage 1 reduction of RVP limits Stage 2 further reduction of RVP limits |
| Flexible Volatility Index: 77.5 minimum; 115 maximum | Immediate removal of minimum limit on FVI |
Proposed RVP Limits by Season
| Season | Dates | Immediate | Stage 1 | Stage 2 |
|---|
| Summer: | 1 December - 30 April | 85 kPa max | 75 kPa max | 65 kPa max |
| Autumn: | 1 May - 31 May | 90 kPa max | 85 kPa max | 80 kPa max |
| Winter: | 1 June - 30 September | 95 kPa max | No further change | No further change |
| Spring: | 1 October - 30 November | 90 kPa max | 85 kPa max | 80 kPa max |
The test method for RVP is ASTM D 323 and is already specified in relation to FVI.
Implications of Proposed Changes
- Reducing the E70 minimum limit to 22°C will provide more flexibility for suppliers without compromising cold start performance.
- Lowering the end point to 210°C will have a minimal effect on petrol production at the Marsden Point Refinery. While this change is expected to deliver environmental outcomes in respect of reduced smoke emissions, the availability of sources outside New Zealand could constrain imports (Australia is not reducing until 2005). It is proposed that New Zealand follows a similar timetable to Australia in achieving this final step.
- The effect of reducing RVP on the operation of a refinery is to reduce the volume of petrol produced and create a surplus of butane. As the Marsden Point Refinery has no market for this butane it would be used as fuel with an associated impact on operating costs. Limiting the maximum summer RVP to 75 kPa and a subsequent further reduction to 65 kPa will therefore have economic penalties for the Refinery. There would also be some impact on blending as butane content has an impact on octane.
- The immediate RVP limits proposed reflect the current NZRC and Refinery Users specification limits. These limits will apply at the point of supply. For imported fuels, RVP limits already exist in most source countries.
7.1.4 Residue and Existent Gum
What Are They?
The residue is the percentage volume remaining after the distillation end point is reached and represents the proportion of non-volatile components in the fuel. This material, which is primarily waxes and gums, may form deposits in engine fuel inlet systems. The residue is determined as part of the standard distillation test using ASTM D 86.
The residue is then washed in a solvent before drying and weighing to determine the amount of gum present - the "Existent Gum". The test method is ASTM D 381.
These properties are a function of the petrol composition and distillation characteristics.
Current New Zealand and International Specifications
The current specification requires a maximum of 2% by volume residue after distillation which is almost universal in international petrol specifications. The specification for gum is 5 mg per 100 mls, which is in line with the European and Japanese standards as well as the World-Wide Fuel Charter.
No changes to either specification are considered necessary.
Changes Proposed to the Regulations
| Current Regulations | Proposed changes |
|---|
| Residue: 2% maximum by volume of petrol | No change |
| Existent gum (solvent washed): 5mg/100ml maximum | No change |
7.1.5 Copper Strip Corrosion
What Is It?
Corrosiveness in petrol is usually due to free sulphur or sulphur compounds which combine with water from combustion to form acids. The test procedure uses a strip of polished copper which is immersed in a sample of the fuel and heated to a specified temperature for a specified time. The degree of corrosion is measured by comparing the staining with a reference sample. The test method is ASTM D 130.
Current New Zealand and International Specifications
While the New Zealand specification calls for 2 hours at 100°C, this is now out of step with practice elsewhere (for example, in Europe and Australia) where a longer duration and lower temperature test (three hours at 50°C) is becoming more common. It is understood that the New Zealand test conditions may have originally been adopted to offer adequate corrosion protection for a particular type of dispenser pump.
The current test is considered more severe than that used elsewhere due to the higher temperature. While a test at 50°C for three hours would take longer, it would also be less hazardous to the technician carrying it out. On balance it is considered that a revised test will be safer, while offering adequate corrosion protection and aligning with international practice. For imported fuel, the standard test could be used, rather than having to perform a unique New Zealand one, thereby reducing compliance costs. No change to the test method or required corrosion test standard is proposed.
Why Regulate?
Some measure of the corrosivity of petrol needs to be retained to provide protection for fuel tanks, dispenser pumps and vehicle engine and fuel system components.
Changes Proposed to the Regulations
| Current Regulations | Proposed changes |
|---|
| Copper strip corrosion test: 100°C for 2 hours, then compare with a reference sample | Immediate: Copper strip corrosion test: 50°C for 3 hours, then compare with a reference sample |
7.1.6 Sulphur
What Is It?
Sulphur occurs naturally in crude oils and must be removed to an acceptable level during the refining process as it promotes corrosion and affects the performance of vehicle emissions control equipment.
Why Is It Important?
Sulphur does not affect engine performance directly but it reduces the efficiency of catalytic converters. Developing petrol engine technologies such as gasoline direct injection (GDI) and lean burn will require advanced catalyst technology in order to meet Euro 4 emission levels (in 2005) for CO, hydrocarbons and NOx. These technologies are very sensitive to sulphur and require levels at or below 50 ppm. Euro 5 (2008) emission standards are likely to require further reductions.
While there is no direct environmental benefit in reducing sulphur in petrol from the current levels, by enabling new engine and emissions control technology, it will have an indirect effect on emissions of CO, hydrocarbons and NOx.
Current New Zealand and International Specifications
| Specification | Maximum sulphur content |
|---|
| New Zealand | 500 ppm |
Euro 3 (2000)
Euro 4 (2005) | 150 ppm
50 ppm
10 ppm to be available from 2005 onwards, and required for all petrol by 2011 (proposed) |
| World-Wide Fuel Charter | 1000 ppm (Cat.1 ), 200 ppm (Cat.2), 30 ppm (Cat.3), none (Cat. 4) |
| Australia | 500 ppm in ULP and 150 ppm in PULP from 1 January 2002
150 ppm in all grades from 1 January 2005
50 ppm (proposed in future, (EA, 2000b)) |
| Japan | 100 ppm |
USA
(CaRFG only)13 | CaRFG2: 80 ppm (cap) - current
CaRFG3: 60 ppm (cap) from December 2002, 40 ppm (cap) from December 2004
Both flat limits and pool averages/cap specified |
The catalytic reforming process (platformer) used at the Marsden Point Refinery to upgrade naphtha to high octane gasoline blendstocks requires the sulphur in the feed to be removed before processing. As a consequence, the sulphur levels in petrol produced in New Zealand are very much lower than the current 500 ppm limit. The test method presently used can detect levels down to 100 ppm, but only 5% of samples collected in 1998 - 1999 contained detectable levels of sulphur.
Any sulphur in the petrol produced at the Marsden Point comes from the imported blendstocks required to boost the octane. A lot of these blendstocks come from Australia, and are produced by a catalytic cracking process which does not require the feedstock to be desulphurised. Last year blendstocks made up about 11% of the total volume of petrol produced at Marsden Point.
Similarly, imported petrol produced primarily from catalytically cracked spirit will also contain higher levels of sulphur than the Refinery's product.
Why Regulate?
- As noted, current sulphur levels in New Zealand petrol are already well below the 500 ppm maximum limit and in many cases below Euro 3 levels (150 ppm) and often Euro 4 levels (50ppm).
- Sulphur at this level in petrol does not currently present any environmental or health concerns and should not prove a barrier to engine or emissions control technology before at least 2005. However, it is evident that vehicle and emission control technology will ultimately require levels below 50 ppm and that New Zealand will have to cater for this (probably from 2007 onwards).
- When making decisions to introduce new technology, vehicle manufacturers will generally rely on regulated sulphur levels rather than actual sulphur levels. This is particularly so where this will affect equipment performance and warranties and therefore clear signals are needed regarding future sulphur levels in New Zealand petrol for the vehicle industry.
- Australian refineries currently cannot produce finished petrol or blendstocks with the same levels of sulphur that the Marsden Point Refinery can achieve, and will not be able to for some years. Australia is a major source of supply for imported regular and premium petrol, as well as blendstocks, and may become more so if benzene and aromatics limits are to be reduced. Early imposition of Euro 3 or even Euro 4 levels for sulphur on New Zealand petrol could constrain future supplies from Australia, however, other low sulphur supplies are available from Pacific Rim refineries.
- If New Zealand aligns its timetable for reducing petrol sulphur limits with Australia, there is a potential for actual levels to increase in the interim.
- On balance, there are benefits to going at least some way to locking in the current low levels of sulphur in New Zealand's petrol as soon as practicable and providing a clear signal on future direction.
As the current test method is not particularly suited to detection of low sulphur levels, adoption of a new method, ASTM D 5453, which is suitable for both petrol and diesel is proposed. This is currently used by refineries in California and is available at the Marsden Point Refinery as well.
Changes Proposed to the Regulations
| Current Regulations | Proposed changes |
|---|
| Sulphur: 500 ppm maximum (mg/kg) | Immediate reduction of maximum to 150 ppm (test method ASTM D 5453) |
| | Stage 2 further reduction to 50 ppm maximum |
| | Ultimate requirement for sulphur free petrol (less than 10 ppm). |
7.1.7 Oxidation Stability Induction Period
What Is It?
This test is a measure of the stability of the petrol during long term storage. Oxidation results in the formation of gums, deposits and sludges.
The test method is ASTM D 525. The sample is heated in a sealed vessel with oxygen and the time measured before it starts to absorb the oxygen (i.e. oxidise) and form gum. The induction period measured does not equate to the safe storage time. A figure of 240 minutes minimum usually ensures a satisfactory level of stability for normal storage and distribution and this is the current New Zealand specification.
Petrol containing sufficient straight-run naphtha contains naturally occurring anti-oxidants. However, some petrols require dosing with antioxidants to control oxidation.
Current New Zealand and International Specifications
The current level specified in New Zealand is 240 minutes, which is the same as in Japan. The Euro standards require a 360 minute induction period and the World-Wide Fuel Charter 480 minutes (for Category 2+ fuels).
The present requirement is considered to be somewhat outdated and is exceeded by a significant margin. A change to 360 minutes minimum would align with international practice. The test would, however, take longer (six hours vs. four hours).
No change to the test procedure is required.
Changes Proposed to the Regulations
| Current Regulations | Proposed changes |
|---|
| Oxidation stability induction period: 240 minutes. | Immediate: Oxidation stability induction period of 360 minutes. |
7.1.8 Lead
What Is It and Why Is It Important?
Previously lead was added to petrol in the form of compounds such as tetra-ethyl lead (TEL) to improve the octane rating. It does not affect engine performance as such but lead contamination accumulates in catalytic converters and poisons the catalyst. This effect is cumulative and irreversible. No reference has been found to the minimum level of lead required to avoid damage to catalysts but a standard of 5 mg/litre has become a common international standard for unleaded petrol.
Concerns over effects on human health have resulted in the phasing out of petrol additives containing lead in many countries over the last 10 - 20 years. As lead affects the performance of catalysts in vehicle emission control systems its withdrawal has been necessary to enable the introduction of catalyst technology in petrol vehicles. New Zealand petrol has been lead-free since 1996 and we are ahead of many other countries, including Australia, where leaded petrol is still available.
The current test method specified is IP 224.
Current New Zealand and International Specifications
The current New Zealand specifications set a maximum level of 13 mg/litre to allow for some level of minor contamination, though the test procedure used can detect down to 0.3 mg/litre. However measured lead levels are very low and often it is not detectable. Maximum levels measured do not typically exceed 3 mg per litre which is the level set by the NZRC and User Company specifications. Any lead detected will generally be due to contamination during transport in ships tanks which have previously been used for leaded fuels.
The European standard for unleaded petrol sets a maximum level of 5 mg/litre. Australia proposes to align with this by January 2002. The World-Wide Fuels Charter requires lead to be below detectable limits (though it does not define the test procedure to be used). The Japanese petrol specification requires 1 mg/litre. The basis for the current New Zealand figure is in line with the Toxic Substances Regulations, which also restrict the use of lead in petrol. Prior to 1994, the maximum limit for unleaded petrol was 50 mg/litre.
Changes Proposed to the Regulations
| Current Regulations | Proposed changes |
|---|
| Lead: 13 mg per litre maximum | Immediate reduction to 5 mg per litre maximum |
With progressive removal of lead from petrol in the main sources of imported supplies in the future (such as Australia), this should be readily achievable.
7.1.9 Total Aromatics
What Are They?
Aromatics are hydrocarbons with a molecular structure based on cyclic carbon (benzene) rings. Benzene itself is the simplest aromatic compound (discussed separately below) but others common in petrol include toluene and xylene. Some, particularly benzene, are known to be carcinogenic. Aromatics containing multiple benzene rings are known as polycyclic aromatic hydrocarbons or PAHs (also referred to as PCAs). Many PAHs detected in exhaust emissions display some mutagenic and carcinogenic activity.
Aromatics occur naturally in crude oil. They are also produced as part of the catalytic cracking and reforming processes used in refining and are used to increase the octane rating of petrol.
The aromatic content is determined by gas chromatography, using test method ASTM D 5580.
Why Are They Important?
Aromatics are high octane constituents of petrol, and therefore any reductions in levels need to be made up with some other high octane constituents or octane improving additives. With the move to the wider use of unleaded petrol, refiners have tended to increase the level of aromatics to meet octane requirements, particularly for premium grades.
As they are solvents, at high concentrations aromatics can affect some of the elastomers used in seals and gaskets in pumps and fuel lines, particularly on older vehicles. The problems encountered following the introduction of PULP in 1996 were attributed in part to a particular shipment of imported fuel that contained a high level of toluene. At that time there were no limits on total aromatics; this lead to the current limit of 48% by volume of total aromatics being imposed.
However, sudden large reductions in aromatic levels or low levels can also cause loss of elasticity or shrinkage in some elastomers "acclimatised" to higher levels. This can also be a problem in diesel fuels.
The heavy compounds, particularly PAHs, can be more difficult to combust; this may lead to combustion chamber and inlet system deposits and spark plug fouling. Exhaust hydrocarbon (HC) emissions are also influenced to a small extent by these heavy compounds; reducing the fuels aromatics content (manifesting as a reduced T90) leads to small reductions in the HC emissions, particularly under cold running conditions.
Current New Zealand and International Specifications
Total aromatics levels in New Zealand petrol currently average around 44% by volume for premium grade and 35% for regular grade. The NZRC and User Company specification also has a limit on toluene + xylenes, which was established following the introduction of premium unleaded petrol in 1996. However this is not regulated.
The current maximum allowable level of aromatics in Europe is 42%, with a move to a 35% limit proposed for 2005 (Euro 4).
The USEPA and South Australia (since March 2001) have adopted air toxics models for regulation of emissions which allow some flexibility in setting limits on benzene and total aromatics. Australia is not targeting 42% aromatics until 2005 and even then this will be a pool average, with a cap set at 45%. There are no plans at present to move to the Euro 4 target of 35%.
| Specification | Total aromatics |
|---|
| New Zealand | 48% max by volume |
Euro 3 (2000)
Euro 4 (2005) | 42% max by volume
35% max by volume |
| World-Wide Fuel Charter | 40% max by volume reducing to 35% for Category 3+ |
| Australia | 45% pool average over 6 months with a cap of 48% (from 1 January 2002)
42% pool average over 6 months with a cap of 45% (from 1 January 2005) |
| Japan | Not specified |
| USA14 | CaRFG2: 22% average by volume, cap 30%, flat 25%
CaRFG3: 22% average by volume, cap 35%, flat 25% |
Why Regulate?
The control of aromatics levels in petrol is the most direct way of limiting evaporative losses and exhaust emissions of these compounds, thereby reducing human exposure to them. Hence in recent years international standards have focused on progressively reducing allowable aromatics levels. Attention originally focused on benzene because of its carcinogenic properties and higher volatility.
As previously noted, sudden changes in aromatics levels can affect elastomers in engines and too low a level may also cause shrinkage in seals in older vehicles in the New Zealand fleet which have always operated on higher levels. It is noted that Japan, the major source of our vehicles, has no aromatics limit.
A lower limit for aromatics could be imposed immediately for regular grade petrol which would reflect actual levels and lock them in, without significantly affecting production. Regular grade accounts for around 75% of New Zealand's petrol consumption at present. However, it is not international practice to impose different limits for regular and premium grades.
The benefits of an early reduction in aromatics levels are less obvious than reductions in benzene. Unless the use of oxygenates such as MTBE are permitted, it will be extremely difficult to meet the octane requirements for petrol produced at Marsden Point if aromatics levels are restricted to less than 42%. At this stage it proposed to restrict the use of MTBE until the environmental case is established (see Section 7.1.11) so a less aggressive timetable for reduction of aromatics is proposed.
Changes Proposed to the Regulations
| Current Regulations | Proposed changes |
|---|
| Total Aromatic Compounds: 48% maximum by volume (including benzene). | For regular grade: Immediate reduction to 40% maximum by volume |
| | For premium grade: Stage 2 reduction to 42% maximum by volume |
Implications of Proposed changes
The impact of any reduction in total aromatics cannot be assessed in isolation as it is very dependent on what changes are made to other specifications, including benzene, sulphur, oxygenates and olefins. These last two are alternative sources of octane.
A 42% limit on aromatics with the current configuration of the Marsden Point Refinery would impose restrictions on the feedstocks and blendstocks that can be used. A reduction to 35% is at the limit of what could be accommodated without major investment. Plant modifications to achieve reductions by 2006 would require major investment and would still be quite limiting in terms of requiring suitable blendstocks (i.e. an additional operating cost).
7.1.10 Benzene
What Is It and Why Is It Important?
Benzene is the simplest aromatic compound and the one that has received most attention due to its known carcinogenic properties. The benzene content is determined by the same test method used for total aromatics.
Vehicles emit benzene through evaporation from their fuel systems and through exhaust emissions. International practice in recent years has been to set lower limits on benzene in petrol in response to health and air quality concerns.
The benzene content does not directly affect engine performance, but like other aromatics, it is a good source of octane.
Current New Zealand and International Specifications
| Specification | Benzene |
|---|
| New Zealand | 5% max by weight (approximately 4.2% by volume) |
| Euro 3 (2000) | 1% max by volume |
| World-Wide Fuel Charter | 2.5% max by volume reducing to 1% for Category 4. |
| Australia | 1% max by volume in all grades from 1 January 2006
No earlier mandatory reduction is proposed as industry averages are already low as required by state regulations |
| Japan | 1% max by volume since January 2000 |
| USA15 | Ca RFG2: 1% by volume (flat)
Ca RFG3: 0.8% (flat) |
Benzene levels in New Zealand petrol have risen slightly in the last 3 - 4 years and currently average (1998-1999) around 4% (by weight) for premium grade and 3.3 % for regular, still below the specified maximum of 5%. This value was set in the original specifications in 1988 and has remained unchanged since then.
The maximum allowable benzene concentration is the regulations is currently expressed as a percentage by weight rather than a percentage by volume which is out of step with most international specifications. The limit of 5% by mass is roughly equivalent to 4.2 % by volume.
As noted previously, some jurisdictions use air toxics models for setting limits on benzene in petrol.
Why Regulate?
Benzene levels have historically been regulated to control both evaporative emissions and exhaust emissions. Population exposure assessments indicate that current benzene levels in New Zealand's air would result in an annual exposure level which is commensurate with current, risk-based, guidelines (see Section 4.2). However, it is proposed to reduce the ambient air quality guidelines for benzene in 2010, hence reducing the additional lifetime cancer risk. The population exposure data indicate that most New Zealanders living and working in urban and suburban areas are currently exposed to higher levels than this criterion. Exposure levels are likely to increase even more with increased vehicle movements and congestion.
While for many other air contaminants, such as particulates, exposure comes from a number of different sources, for most people, motor vehicles are the primary route of exposure to benzene.
Controlling Evaporative Losses
The evaporation of volatile components from petrol can be reduced by minimising the concentration of those components in the fuel and by minimising the exposure of the fuel to air. Reduction of benzene levels achieves the first objective; modern vehicle fuel systems design (including absorption traps on fuel tank breathers and fuel injection systems instead of carburettors) achieves the second.
Vehicle Exhaust Emissions
Benzene emissions in vehicle exhausts arise from benzene in unburned fuel, and from pyrolysis and partial combustion of heavier aromatics and possibly some other hydrocarbons, therefore reducing total aromatics also reduces benzene levels in exhaust from vehicles. 3-way catalytic converters are therefore the most effective way to reduce benzene in exhaust emissions. Other newer measures to further reduce hydrocarbon emissions, such as better control of the air-fuel ratio, improved catalysts and reducing the light-off time (how quickly the catalyst heats up and starts to operate effectively) will also reduce benzene concentrations in exhausts.
However, with the current fleet turnover and replacement trends it will be a number of years before this technology becomes dominant in the New Zealand fleet. The same applies to control technology for evaporative emissions from petrol. There are no plans at present to introduce vapour recovery for bulk transfer and distribution in New Zealand.
It is therefore proposed that benzene levels in petrol be managed downwards, and that New Zealand moves to align with the limits already adopted in Europe, Japan and the USA. Australia proposes a 1% limit by 2005 which would mean that from that time, imported product could be sourced and would not restrict supply.
Changes Proposed to the Regulations
| Current Regulations | Proposed changes |
|---|
| Benzene: 5% maximum by mass (equivalent to around 4.2% maximum by volume) | Immediate change to specifying benzene content as % by volume; set at 4% maximum |
| | Stage 1 reduction to 3% maximum by volume |
| | Stage 2 reduction to 1% maximum by volume |
Implications of Proposed changes
As for total aromatics, any reduction of benzene limits will require the octane to be made up from other sources. If the use of oxygenates or octane-enhancing additives are precluded, then the octane has to be made up with olefins, alkylates or isomerates. For the Marsden Point Refinery operation, some reduction in benzene levels can be achieved by appropriate selection of crudes and blendstocks. The alternative is adding further processing capability to convert benzene and other aromatics to other octane-boosting compounds.
As noted previously, significant quantities of imported blendstocks are already required to produce the current grades, and much of this is sourced from Australia. The high octane petrol currently being marketed by BP is sourced directly from Australia and contains 2% max by volume benzene.
A 3% limit could be achieved for New Zealand produced petrol by appropriate selection of feedstocks and blendstocks but this would impose significant costs on the Refinery as well as well as the users. Other constraints on the petrol specifications would make these costs higher. Fuel could be imported to meet the 3% limit, but it would depend on availability (such as timing of changes in Australia) and any change to the level of imports would also affect the Refinery operation.
A 1% limit for New Zealand produced petrol would require major capital investment with a significant lead time, so that implementation earlier than 2006 would be unlikely. Under current proposals, 1% benzene petrol should be available from all Australian producers by 2005.
The approach of using pool averages (as proposed for Australia) or an air toxics formula (USA, South Australia) can provide more flexibility for the refiners in achieving the targets. While such an approach focuses on controlling effects rather than absolute limits it is potentially difficult to administer in a small market like New Zealand and may lead to significant variations in petrol properties. A further discussion of pool averaging is given in Section 9.6.1. This type of model is not proposed at this stage.
7.1.11 Oxygenates
What Are They?
Oxygenates are organic compounds containing carbon, oxygen and hydrogen. They can be added to petrol as a blending component and to increase octane. Their use in petrol effectively increases the available oxygen for combustion which has the effect of reducing CO formation and hydrocarbon emissions. The two main groups are alcohols (such as ethanol and methanol) and ethers (such as methyl tertiary-butyl ether (MTBE)). Blends containing up to 11% MTBE are common and for ethanol, 10% or higher.
Why Are They Important?
Driveability
The use of oxygenates can induce a "lean shift" in the fuel/air stoichiometry thereby reducing CO in vehicle exhaust emissions (CO occurs when there is insufficient oxygen for complete combustion to CO2). This tends to benefit mostly older carburetted engines as modern electronic engine management systems monitor the oxygen content of the exhaust gases and adjust the air/fuel ratio accordingly.
Oxygenates in petrol can cause over-leaning depending on how the engine management system is calibrated, leading to drivability problems and increasing emissions of NOx. For MTBE, the effect is quite small - 15% MTBE results in a change in the stoichiometric air/fuel ratio of only 2%. Ethanol requires more heat to vaporise than ethers and this can also affect the drivability of petrol/ethanol mixtures.
Volatility
Blending oxygenates into petrol can increase the vapour pressure of the fuel and significantly modify the volatility and distillation characteristics, resulting in increases in evaporative emissions. Methanol has the most dramatic impact - small amounts (in the order of 2%) can cause 35% increases in vapour pressure. Ethanol can also have significant effects on vapour pressure, whereas for MTBE, the effect is much smaller (around 5% max at 4-5% concentrations) and can drop to zero at higher concentrations.
Exhaust Emissions
PM emissions from petrol engines, while already low compared with diesel engines, can be reduced by up to 50% with the addition of oxygenates to petrol.
Octane Enhancement
Oxygenates are good sources of octane but also have high sensitivities (see Section 7.1.1) which can limit their application for octane enhancement. MTBE does not appear to deteriorate high speed octane performance, while methanol may do. Generally, the effects will vary with the base fuel and specific vehicles, however MTBE appears to be more effective in providing octane enhancement.
Current New Zealand and International Specifications
Many new specifications allow oxygenates to be added but place a limit on the overall oxygen content of the final blend. A limit of 2.7% max by mass is common, which is equivalent to around 7.5% by volume ethanol and 15% by volume MTBE. A number of countries allow exemptions and/or place limits on specific types of alcohols and ethers.
The use of oxygenates was made mandatory by Federal law in the United States in 1990 on the grounds of its air quality benefits (primarily reduced CO emissions). Because of its lower volatility and cost, MTBE has generally been more attractive as an oxygenate than alcohols or other ethers, and its use increased significantly in the United States with the subsequent introduction of the reformulated gasoline (RFG) programme (see Section 5.3). It is also used widely in Europe and parts of Asia. However MTBE has a strong affinity for water and has been found at low levels in groundwater both in the USA and the United Kingdom. As a result, California has now banned the use of MTBE and other ethers in petrol from the end of 2002 and other states have followed. The issue is under close scrutiny in the United Kingdom as well.
| Specification | Oxygenates | Oxygen |
|---|
| New Zealand | 0.1% max by weight for any oxygenates but up to 11% by volume MTBE may be added. (This is equivalent to around 0.1% by volume ethanol). | Not specified |
| Euro 3 (2000) | Max allowable content determined by type (3% v/v methanol, 5% ethanol). Oxygenate boiling point must not exceed specified FBP of overall fuel. Ethers must contain 5 or more carbon atoms, up to 15% MTBE allowed. | 2.7% max by mass. |
| World-Wide Fuel Charter | | 2.7% max by mass. Up to 10% ethanol subject to quality requirements. No methanol permitted. |
| Australia | All specified ethers - max. 1%
(MTBE from 1 January 2004, others from 1 January 2002). Limit still to be set for ethanol. | 2.7% max by mass from 1 January 2002 (ethanol exempt). |
| Japan | 7% max by volume MTBE | Not specified |
USA
(California) | Certain exemptions - MTBE to be progressively phased out in response to environmental concerns. | 2.7% max by mass. |
Petrol sold in New Zealand does not generally contain MTBE at present, although the current specification allows it, by means of an exemption. The maximum oxygenate limit in New Zealand effectively precludes the use of alcohol blends or other ethers.
Low levels of MTBE may occur from time to time in imported fuel due to contamination from previous cargoes. MTBE and other oxygenates have an affinity for water and the New Zealand distribution infrastructure is generally not set up to allow water-free operation. Hence, the use of MTBE is avoided. Some of the major oil companies have also taken a position against the use of MTBE until the environmental case for its use is conclusively proven.
Why Regulate?
Both environmental and consumer concerns suggest that the use of oxygenates needs to continue to be regulated. The particular issues relating to MTBE and ethanol are discussed separately below.
MTBE
Environmental Issues
The main route for environmental impact of MTBE is via leakage of petrol from storage tanks.
MTBE has a strong affinity for water (MTBE solubility in water is 4.3%, water in MTBE 1.4%). While levels found in groundwater in the United Kingdom and United States do not appear to pose a significant health risk as such, MTBE has a distinctive taste and smell and will taint water groundwater supplies, even at very low concentrations. Groundwater is an important resource in New Zealand and contamination of the resource from leaking storage tanks does occur. The main benefits of MTBE are the reduction of CO emissions and its use as a source of octane, thus allowing for reduction of the level of benzene and aromatics in petrol. A more detailed discussion of water quality issues is given in Section 4.3.
Consumer Issues
Like all oxygenates, the addition of MTBE can reduce the volumetric energy content of petrol, as the oxygen portion does not combust. This can have the effect increasing fuel consumption (litres per 100 km) slightly. As noted, the effect of MTBE on volatility of petrol blends is generally not significant.
Ethanol
With the use of MTBE now being phased out in some parts of the United States because of concerns over groundwater contamination, the use of ethanol as an oxygenate is expected to increase.
Ethanol-blended petrol is sold in parts of Australia and its use has been reviewed as part of the preparation of the new environmental standards (EA, 2000c). At this stage, no standard for ethanol content in petrol has been agreed, but it is likely that at least 10% ethanol blends will be allowed (EA, 2001a,b). The Australian Government, in response to submissions from the domestic ethanol industry, is in the process of determining whether a higher volume of ethanol would be appropriate for their climate conditions and vehicle fleet.
Environmental Issues
Ethanol is completely soluble in water and is not considered toxic. However, it can increase the solubility of other hydrocarbons in water and increase the mobility of hydrocarbon plumes from subsurface spills in the soil, so there are some environmental concerns.
Vehicles in the United States and Europe, where oxygenated fuels are widely used, are mandated to have advanced emissions control systems. New Zealand does not have a similar requirement, and many of our vehicles lack even basic emissions control devices. Due to these differences in vehicle technologies, it is difficult to predict with certainty the changes in tailpipe emissions that would result from using ethanol-blended petrol. There is general agreement that oxygenated fuels reduce CO emissions. However, results of studies examining the effects of ethanol-blended petrol on exhaust emissions of hydrocarbons, volatile organic compounds, and oxides of nitrogen have been mixed.
In terms of other air emissions, combustion of ethanol produces acetaldehyde, a toxic air contaminant, and peroxyacetyl nitrate, an eye irritant and cause of plant damage. Acetaldehyde is included on the Ministry for the Environment's proposed list of air contaminants. The amount of these pollutants that will be emitted from a vehicle burning ethanol-blended petrol will depend on the emissions control technologies incorporated into the vehicle.
A further area of concern in terms of air quality is evaporative emissions from the carburettor, fuel tank, or other part of the fuel system. Ethanol-blended petrol may lead to increases in evaporative emissions because rubber, plastics, and other materials in the fuel system are permeable to ethanol.
The mixing of ethanol-containing and ethanol-free petrol in vehicle fuel tanks may also increase evaporative emissions. The relationship between vapour pressure and ethanol content of a blend can be non-linear so that the mixture may have a higher vapour pressure than either product alone. Any use of ethanol should be subject to the fuel meeting all the volatility properties (distillation, RVP, FVI) for unoxygenated fuel.
If ethanol is produced from biomass or as a by-product of the dairy industry (as it is in New Zealand) then there are clear benefits from the perspective of greenhouse gases.
Consumer Issues
10% ethanol blends have been shown to perform well without any detrimental effects on vehicle performance. However it should be noted that much of the operating experience supporting this contention comes from the USA where all vehicles have been designed to run on oxygenated fuels since they were first mandated in 1990. The implications on driveability and materials performance need to be carefully considered if its use is to be permitted in New Zealand.
Driveability
Generally, in order to meet regulated vapour pressure limits, petrol blended with ethanol will contain less butane, which is itself volatile and has a high energy content. Like any oxygenated fuel, ethanol-blended petrol, because of its oxygen content, contains less total energy than unblended petrol. This means that the air-fuel mixture coming from the carburettor is "leaner" with ethanol-blended petrol than with petrol alone. For this reason, cold starting and cold weather driveability may be problematic for some cars in the New Zealand fleet.
Cold starting depends on vaporisation of the petrol, and more heat is required to vaporise blends containing ethanol. In addition, when ethanol-blended petrol is used, the vapour contains a greater concentration of alcohol than its concentration in the petrol. As a result of these factors, cold starting may be difficult.
The mixture of air and ethanol-blended petrol from the carburettor may be so lean that it causes "lean misfire"; that is, the mixture may be too lean to combust. Lean misfire causes one or more cylinders to pass unburned fuel into the exhaust system. Symptoms include a rough idle and hesitation or stumble on acceleration.
Mixing ethanol-blended petrol with regular petrol in a vehicle's fuel tank may also cause driveability problems. Older cars are more likely to have water in their fuel tanks, and this water may cause the alcohol in the blended fuel to separate from the fuel and mix with the water. If this happens, layering may occur in the fuel tank; the petrol-rich upper layer may no longer have a sufficiently high octane number to operate the engine properly and the alcohol rich aqueous layer may cause rough running or complete stoppage of the vehicle.
Effects on Fuel System Materials
Ethanol in petrol can cause the elastomers in vehicle fuel systems to swell and lose strength, leading to failures of critical components such as fuel pumps and hoses and the risk of fire. The result could be similar to the situation encountered with the introduction of unleaded petrol, when fuel system leaks were attributed to high aromatics levels in petrol.
There may also be problems for motorists switching between ethanol-blended petrol and regular petrol, as elastomers that swell with ethanol use would subsequently shrink with petrol, potentially causing fuel system leaks. This effect could be especially pronounced in vehicles that are more than 10 years old.
There may be other proprietary components in fuel systems that are also susceptible to damage from exposure to ethanol, particularly in non-automotive engines such as lawnmowers.
Manufacture and Distribution of Ethanol-Blended Petrol
Because of the effect that ethanol has on petrol properties, particulary on vapour pressure, the preparation of blends must be carefully managed. Ideally, blending would take place at a facility that is capable of performing product quality tests and correcting any deficiencies in the fuel. Blending at ports or in tankers would be difficult logistically, as it would require special petrol blendstocks that are then mixed with ethanol to produce a blend that complies with all the regulated properties. The quality of ethanol used for blending is also critical and properties such as water content and acidity need to be specified.
As ethanol can separate out on contact with water, ethanol blends must be transported through a completely water-free system. Although international practice is moving away from the use of "wet" distribution systems, some of New Zealand's fuel distribution infrastructure is not water-free. Ethanol blends would therefore not be able to be made at the Refinery and shipped throughout the country in tankers, as is the case for unoxygenated petrol. In addition, older storage tanks at service stations may contain some water and would need testing and upgrading before they could be used with ethanol-blended petrol. However, Gull Petroleum's distribution system, which is all relatively new, is dry and therefore suitable for ethanol blends.
While some smaller operators may been keen to pursue the use of ethanol-petrol blends in New Zealand if permitted in the future, operational requirements and cost implications suggest that their widespread adoption will not occur in the short term.
Changes Proposed to the Regulations
Given environmental concerns about contamination of groundwater in other jurisdictions, it is proposed that the use of MTBE and other ethers in petrol be banned until the environmental case is proven. This would be achieved by removing the exemption for MTBE from the oxygenates limit. This decision should be subject to review as more information becomes available, and may have an impact on the timetable and ultimate reduction of aromatics levels.
Given that MTBE is still in widespread use in some countries which are sources of imported petrol for New Zealand, maximum limits of 1.0% vol. for MTBE and 0.1% vol. for all other oxygenates would be included to allow for contamination from previous cargoes.
A significant amount of research into the use of ethanol blends was done in New Zealand back in the 1980s, but this was not progressed for various reasons, including difficulties in sourcing long-term supplies of ethanol. Interest has been expressed recently in the possibility of supplying ethanol-blended petrol to the New Zealand market. Given that the use of ethanol-blended petrol could assist New Zealand to meet climate change responsibilities to reduce greenhouse gas emissions, there is merit in providing for the possibility of petrol blended with up to 10% ethanol. However, there are significant risks associated with the use of ethanol-petrol blends as highlighted above, and these risks would need to be carefully managed.
One approach would be to allow the sale of ethanol-blended petrol for a limited amount of time on a test basis. A decision on the sale of ethanol-blended petrol on a permanent basis could then be based on the outcome of a New Zealand-based trial. There would need to be a clear framework for this testing and approvals process. A test period of 6 to 12 months would probably be needed. The test would need to demonstrate clearly that it had involved a large number and range of vehicles and that no adverse effects on engine performance had occurred. Consumers taking part in the test would need to be fully informed and agree to their participation. It should be noted that such an approach may require an amendment to the legislation under which the Regulations are made.
These considerations form the basis for the proposed changes.
| Current Regulations | Proposed changes |
|---|
| Oxygenates: 0.1% maximum by mass on total oxygenates, excluding MTBE. | Immediate: 0.1% maximum by mass applies to all petrol. Changes to ethanol and MTBE as below. |
| MTBE: Up to 11% by volume | Immediate limit of 1% maximum by volume, applying to all petrol |
| Ethanol: limited as per total oxygenates | Immediate: Allow addition of ethanol to petrol up to 10% by volume, subject to a testing and approval process. |
The Regulations currently require only petrol sold by retail sale to meet the specified limit. It is proposed the restrictions on MTBE and other oxygenates (other than ethanol) apply to all petrol.
Implications of Proposed Changes
Limitations on oxygenates severely restricts the options and increases the costs for reducing benzene and aromatics levels in petrol. While the costs of ethanol are an issue for the market, not for this review, it is generally accepted that with the current tax regime, it is too expensive to use for blending in New Zealand. However, recent moves in Australia suggest that there may be more widespread adoption of ethanol blends there in the next few years.
Making provision for ethanol blends in New Zealand will allow these fuels to be tested on a commercial scale and enable consumers to make an informed choice regarding its use. Controls on the use of ethanol blends will need to include requirements that :
- All fuels containing ethanol be labelled at the pump;
- Blends meet all other specified properties of petrol, including limits on volatility;
- The quality of ethanol used for blending be subject to suitable controls; and
- Consumer information on ethanol blends be provided.
7.2 Properties Currently Not Specified
The following properties for petrol are not currently included in the New Zealand specifications but have appeared in specifications elsewhere or are under discussion. Therefore their significance is discussed here.
7.2.1 Olefins
What Are They?
Alkenes and cycloalkenes are referred to as olefins in the oil industry. They have double bonds (i.e. are unsaturated) and are not normally present in crude oil, but are created during cracking and other refinery processing.
The olefin content of petrol will depend on source refinery configurations and feedstocks. Catalytically cracked petrols (such as produced in Australian refineries) tend to be higher in olefins.
Why Are They Important?
Olefins are often good octane components. However they are thermally unstable and this can lead to gum formation or deposits in engine intake systems. Very high levels of olefins could create problems similar to toluene - this could occur if maximum limits on benzene and total aromatics are reduced without regulating olefins at the same time.
Olefins are also formed during combustion of fuel. Their evaporation into the atmosphere has been established as contributing to ozone formation and their combustion products form toxic dienes such as 1,3-butadiene. Environmental concerns are the main basis for limiting their content in petrol, although some recent studies indicated that olefins may not be the only contributor to these emissions.
Current New Zealand and International Specifications
Environmental concerns have increased the focus on olefin content of petrol, and limits have been imposed or suggested in several jurisdictions as shown below. The current levels in New Zealand petrol are believed to be below 25%.
| Specification | Max % by volume |
|---|
| Euro 3 (2000) | 21% |
| World-Wide Fuel Charter | 20% (Cat. 2), 10% (Cats. 3 & 4) |
| Australia (proposed) | 18% pool average over 6 months with a cap of 20% (from 1 January 2004)
18% max. (from 1 January 2005) |
| Japan | Not regulated |
| USA | CaRFG2 & 3:
6% flat, or 4% average, 10% cap. |
Why Regulate?
Ambient butadiene levels in New Zealand are low and are not considered to be a significant environmental concern at present. Therefore there is no clear justification for reducing levels from this perspective. The greater imperative is likely to be engine performance, particularly the need to control against petrol with a very high olefins content.
A maximum limit of 25% by volume is proposed immediately to limit olefins at current levels and control against excessively high olefin cargoes. Australia proposes to adopt an 18% max limit by 2005, though this has not yet been agreed. New Zealand could follow a similar timetable with a two-stage reduction to 21% initially (aligned with Euro 3) and ultimately to 18% allowing for alignment with Euro 4 and Australia. A proposed test method has been specified.
New Regulations Proposed
| Current Regulations | Proposed changes |
|---|
| Olefins: Not currently regulated | Immediate limit of 25% maximum by volume, to apply to all petrol (Test method ASTM D 1319) |
| | Stage 1 reduction to 21% maximum by volume |
| | Stage 2 reduction to 18% maximum by volume |
As olefins have relatively high octane ratings, any reduction will necessitate replacement with some other more acceptable octane components so the implications of imposing limits on olefins content will be similar to those from aromatics limits.
The above timetable should not be constraining for the Marsden Point Refinery but it does remove one source of octane. A phased reduction as above would align with Australia so should not constrain imported fuel from there.
7.2.2 Manganese
What Is It?
The use of the organometallic compound methylcyclopentadienyl manganese tricarbonyl(MMT) as an octane booster in petrol is somewhat controversial. It has been used in Canadian petrol for a number of years but was later banned for a time (the ban has subsequently been lifted). The current New Zealand specification does not exclude its use.
Why Is It Important?
MMT is added in low concentrations (typically 18 mg Mn/litre) to boost octane. Engine manufacturers are strongly against the use of metal-based fuel additives from the perspective of potential ash formation, and there is significant uncertainty and disagreement about its environmental and health impacts. Higher concentrations (>165 mg Mn/litre) can cause problems with fuel instability, deposit build up and can adversely affect catalyst performance, particularly for hydrocarbon oxidation.
Current New Zealand and International Specifications
The use of MMT or compounds containing manganese in petrol is not currently regulated in New Zealand. It is understood that New Zealand petrol does not contain MMT at present.
The World-Wide Fuel Charter specifically bans the use of MMT. In the USA, although MMT is permitted for use in petrol, the EPA is requiring further study to determine whether or not manganese can have any cumulative effect on human health by building up in the bloodstream, and whether there is any need for future regulatory action. In Australia, it has been decided not to regulate at this stage pending the outcome of the USEPA process and assessment of the chemical hazards. MMT has also been the subject of much litigation in Canada. The European and Japanese specifications do not include any controls on manganese addition.
Why Regulate?
The case against MMT from an environmental and health perspective is unclear. However there is a perception in some quarters that its use as an octane enhancer in place of lead or benzene would be merely substituting one hazardous substance for another. The Toxic Substances Board (now dissolved) previously reviewed its use under the Toxic Substances Act 1979 (see Section 4.5), and raised some concerns. However as it was not a scheduled poison, there was no requirement to obtain formal approval.
The major fuel suppliers in New Zealand do not currently use MMT in petrol because of the objections of the automotive industry. In the light of these objections and concerns from environmental regulators elsewhere, a precautionary approach is proposed with a limit on manganese content and a test method being included in the regulations immediately. If other sources of octane are to be further constrained (benzene, aromatics, olefins and oxygenates) suppliers may see MMT as one means of meeting octane requirements, and if the Regulations do not specifically address it, there will be no means of controlling its use.
New Regulations Proposed
| Current Regulations | Proposed changes |
|---|
| Manganese: Not currently regulated | Immediate limit of 0.25 mg per litre maximum, to apply to all petrol
(test method ASTM D 3831) |
7.2.3 Phosphorous
What Is It and Why Is It Important?
Phosphorous was used in the past as an additive in petrol to prevent pre-ignition and spark plug fouling when fuel contained high levels of lead. It is understood to be a component of Valvemaster, an after-market additive (one that is added after the fuel is sold) used for older vehicles which were designed to run on leaded petrol.
Phosphorous can degrade the performance of catalysts in catalytic converters.
Current New Zealand and International Specifications
The European specifications and the World-Wide Fuel Charter prohibit the use of phosphorus containing compounds in petrol. The Australian review proposes a limit of 1.3 mg/litre from 1 Jan 2002. It is currently not covered by the New Zealand specifications.
Why Regulate?
Given the concerns about effects on engines, some level of consumer protection is considered necessary. This should take the form of a maximum limit on phosphorous content and a suitable test method, in line with that agreed in Australia.
New Regulations Proposed
| Current Regulations | Proposed changes |
|---|
| Phosphorus: Not currently regulated | Immediate limit of 0.20 mg per litre maximum, to apply to all petrol
(test method ASTM D 3231) |
7.2.4 Density
What Is It?
Density is a measure of a fuel's mass per unit volume. Density is a function of fuel composition, which is constrained by volatility parameters and aromatics content. Aromatics typically have densities of 880 kg/m³, C6+ naphthenes 780 kg/m³ and paraffins 700 kg/m³ or lower.
Why Is It Important?
The requirement to narrow the density range of petrol is driven largely by the desire of the engine manufacturers to improve fuel economy and improve combustion through improved fuel management systems.
As fuel is sold by volume not mass, fuel injection systems meter fuel volumes and consumption is measured on a volumetric basis, so any significant reduction in density could effectively increase fuel consumption. Narrowing the limits will allow better control of fuel/air ratio in new engine designs.
Current New Zealand and International Specifications
The World-Wide Fuel Charter and the European standard have both set density limits (minimum and maximum) on petrol. Japan has a maximum limit. There are no such proposals in Australia as yet.
The density range of petrol in New Zealand is typically 729 - 750 kg/m³ for regular grade and 740 - 760 kg/m³ for premium grade. The WWFC limits for Category 4 (the most stringent) are 715 - 770 kg/m³.
Does It Need to Be Regulated?
The benefits for the New Zealand fleet are not clear - the lack of density limits on petrol is not believed to be a barrier to new engine technology in the foreseeable future, nor does it directly affect emissions. Density is already constrained to some degree by other properties. It is generally considered that direct limits on petrol density would be an unnecessary constraint for refiners and not provide any significant benefit to users.
No change is proposed at this stage.
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