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Report on the Technical Feasibility of Integrating an Annual Average 2% Renewable Diesel in the Canadian Distillate Pool by 2011

2  Fuel Technology Readiness

2.1  Key Factors
2.2  Main Findings
2.3  Analysis

For the purposes of this report, fuel technology readiness is defined as properties of renewable diesel required to operate under the range of Canadian conditions having been assessed and demonstrated including an assessment of the fuel properties of renewable diesel in relation to conventional diesel. Fuel properties include oxidative stability during long-term storage and cold weather operability, including the crystallization of renewable diesel blends in fine fuel filters (as measured by the cloud point, pour point and cold soak filtration test). Where possible, a range of Canadian conditions means extreme winter conditions of down to -37°C, and where appropriate and possible, seasonal temperature variations. The assessment of these properties would be performed for renewable diesel from a variety of feedstocks at blend levels of up to B5.

Fuel Quality

High quality fuel is a key requirement in order to avoid operational issues. The quality requirements for fuels are set through specifications defined by stakeholders through technical committees and adopted by standards-setting bodies.

2.1  Key Factors

A detailed study of the available literature and results obtained from the NRDDI projects, supplemented with consultations with industry, have shown that the following factors need to be considered before confidence in renewable diesel fuel technology readiness can be established:

  • Cold flow operability;
  • Long-term storage;
  • Formation of sediments;
  • Microbial growth; and
  • Engine lube oil dilution.

These key factors are described below.

2.1.1  Cold Flow Operability and Formation of Sediments

The low temperature properties of the fuel are extremely important for proper operability in the Canadian climate. Unlike gasoline, petroleum diesel and renewable diesel can freeze or gel as the temperature drops. If the fuel begins to gel, it can clog fuel filters and could eventually become too thick to pump. The cold flow requirements of diesel fuel vary considerably by season and region. Important low temperature performance metrics for handling diesel and blends with renewable diesel are as follows:

  • Cloud point: The temperature at which small solid crystals are first visually observed as the fuel is cooled. Below cloud point, these crystals might plug filters or could drop to the bottom of a storage tank. However, fuels can usually be pumped at temperatures below cloud point.
  • Pour point: The temperature at which the fuel contains so many agglomerated crystals that it is essentially a gel and will no longer flow. Distributors and blenders use pour point as an indicator of whether the fuel can be pumped, even if it would not be suitable for use without heating or taking other steps.7

Tests commonly used to characterize the low temperature operability of middle distillate fuels are described in more detail in Appendix 1 (Section 8). Petroleum companies and fuel distributors manage cold flow requirements of all middle distillate fuels by adding low cloud point fuels, such as kerosene or arctic diesel, to ensure the final fuel blend meets the cold temperature requirements, based on regional historical weather data. In Canada there are two types of diesel fuels used in transportation: Types A and B. In general, Type B diesel fuel will cloud at warmer temperatures than Type A.

In the case of biodiesel, the cloud point is significantly higher than that of petroleum diesel. Due to this higher cloud point, B100 is commonly stored in heated tanks for blending in winter. Blending biodiesel with diesel will therefore increase the cloud point of the blended fuel. Naturally, the higher the biodiesel blend level, the more the cloud point will be raised. The same applies to HDRD. However, commercially available HDRD generally has a much lower cloud point than biodiesel. As is the case with petroleum diesel fuel, the cloud point of a biodiesel blend should be adjusted to meet the recommended Canadian General Standards Board (CGSB) cloud point temperature. Low temperature cloud point fuels, such as kerosene or arctic diesel, must be considered depending on the base fuel properties to ensure the final fuel blend meets the requirements in cold conditions.

Precipitate formation above the cloud point is considered an important factor for the assessment of biodiesel blend suitability use in cold climates. Over time, insoluble materials can form and sediments can build up at the bottom of the fuel tank, from where the fuel is drawn. A fuel filter is normally present between the tank and the engine to prevent unwanted material from reaching the engine. These sediments can plug the fuel filter and may result in the engine not receiving any fuel and shutting down. For this reason, OEMs recommend fuel filter changes for their vehicles at pre-defined intervals. Reports of field issues with biodiesel blends in cold conditions in the United States and Europe underscore the need to better understand the phenomena associated with the formation of sediments. Standard-setting bodies are currently evaluating testing methodologies to identify potential problematic biodiesel blendstock characteristics to prevent their use in winter season blends.

2.1.2  Long-term Storage

All fuels have a limited shelf life. Long-term storage and storage with temperature variations lead to fuel oxidation, causing the fuel to degrade. Although biodiesel has been known to have a shorter shelf life than most petroleum diesels, fuel standards specify long-term stability requirements for both B100 and blended fuels to ensure all fuels have adequate long term performance.

2.1.3  Microbial Growth

Regardless of how well a fuel storage system is maintained, water will accumulate in the storage tank, forming a water bottom. As a general rule, wherever fuel and water come into contact in a fuel storage or distribution system, microbial contamination is likely to occur. For many of the species present in the water bottom, liquid hydrocarbon fuels represent an excellent nutrient source. As a result, microorganisms proliferate at the fuel/water interface, surviving in the water phase while feeding on the fuel. Microbial contamination is not specific to any one fuel type; marine, aviation, automotive and home heating fuels are all susceptible, although certain applications pose a higher risk for contamination. Similarly there is no single specific organism that can be identified as being responsible for degradation and spoilage. Possible problems that might arise as a result of microbial growth include increased filter plugging8 and tank metal corrosion.9

Concerns have been raised about the potential for greater microbial contamination with biodiesel blends because biodiesel attracts water more than petroleum diesel. Biocides have been recommended in certain reports as a remedy for both conventional fuels and renewable fuel blends wherever microbial growth has been problematic.

2.1.4  Engine Lube Oil Dilution

Engine lubrication is an important factor for engine reliability and durability. Maintaining lube oil quality is a key consideration when introducing changes in engine technology systems. Due to the severe operating load, speed and temperature of diesel engines, the introduction of unwanted substances into the lube oil system will gradually lower the lube oil quality resulting in harmful engine operation. At a minimum, oil dilution could impact the interval requirements for oil changes, the effectiveness of additive packages, sump capacity and performance of after-treatment systems. Therefore, it is always necessary to identify and analyze the possible sources of contamination and monitor them. Possible sources of contamination include unburnt fuel, carbon, water, acid, solid impurities, etc. Biodiesel has a higher flash point than petroleum diesel, which can lead to an increased level of unburnt fuel in the lube oil.

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2.2  Main Findings

The findings below have incorporated information from demonstrations and research identified in Exhibits 1 and 2 to gather evidence regarding cold flow operability, sediment formation due to long-term storage, microbial growth and engine lube oil dilution. The most significant findings are summarized below.

2.2.1  Cold Flow Operability and Formation of Sediments

Several projects described in the literature have demonstrated that renewable diesel blends can be made to conform to the latest CGSB standards and cloud point schedules for a large variety of Canadian conditions. The Renewable Diesel Characterization Study (RDCS) carried out by Climate Change Central10 and partners aimed to evaluate the feasibility of obtaining CGSB compliant renewable fuel blends, with primary emphasis on cold weather operability, and to provide more baseline information on renewable diesel blends compared to petroleum diesel. The analysis included blends of biodiesels from a variety of feedstocks and HDRD, with Ultra-Low Sulphur Diesel (ULSD) as the base fuel. However, not all biofuels or ULSD fuels available in Canada were investigated. All fuels were tested in their neat form as well as in renewable diesel fuel blends from 2 to 5%. The biodiesel blends were evaluated against the latest CGSB B1-5 specification. This study provided no ‘rules of thumb’ for changes in cold weather fuel characteristics attributable to the renewable diesel, ULSD, or kerosene, but rather presented the actual results of tests conducted on available fuel samples. The study showed that a variety of renewable diesels, both methyl esters and HDRD fuels, made from a variety of feedstocks, can be blended with petroleum diesel components to produce CAN/CGSB-3.520 compliant fuels that meet all quality criteria including cloud points.

In addition to the RDCS study, data from several cold weather operability demonstration projects were used to inform this section. The Alberta Renewable Diesel Demonstration (ARDD) project11 and the NRDDI Manitoba Hydro project12 found that winter season operability was achieved by reducing the biodiesel content of the biodiesel blend in the seasonally adjusted petroleum diesel to B5 or B2 in various feedstocks, and by adding Ultra-Low Sulphur Kerosene (ULSK) to adjust the finished fuels’ cloud point. The ARDD project found that in order to meet the CGSB cold operability specifications from December 2007 to March 2008, for a B2 canola methyl ester (CME) blend, additional ULSK was required. Less ULSK was found to be required for the 2% HDRD since the cloud point of this renewable diesel was significantly lower. In the NRDDI Manitoba Hydro study on B5 blend usage in gensets with outdoor fuel storage tanks in northern Manitoba, it was also demonstrated that kerosene can be used to achieve the CGSB cold operability specifications. Other NRDDI projects13,14, used low cloud point ULSD, instead of ULSK, to achieve CGSB cloud point compliant biodiesel blends which worked well in cold weather.

Imperial Oil carried out a laboratory test program under the NRDDI15 assessing low temperature storage stability of 57 biodiesel blends (primarily B5 and B20). Results showed that precipitates form in some of the fuel blends after ten days of storage at 2-4°C above its cloud point. These precipitates were found to be enriched in saturated monoglycerides (SMGs), and the sediment did not easily re-dissolve. The results confirmed previous reports16,17,18 in literature regarding the potential filter plugging impacts of SMGs formed above the cloud point during low temperature operations. The study led to the suggestion to use a modified filter blocking tendency (FBT) test as a means to evaluate the potential of this type of sediment formation. The project also concluded that additional work to improve the correlation between SMG and the FBT as well as a fundamental study of the kinetics of SMG precipitation and re-dissolution, including the impact of base fuel aromatic content, would be very valuable.

The NRDDI Manitoba Hydro Fleet project performed additional work on the subject and found that the correlation between SMG and FBT is not as strong as suggested in the Imperial Oil study, but that the modified FBT test is useful to monitor fuel quality for biodiesel blends. It also found that for the blends investigated in the project, any precipitate formed re-dissolved after one hour at room temperature.

In the NRDDI Royal Military College (RMC) project, particle formation kinetics for B100 CME and tallow methyl ester (TME) as well as their B20 and B5 blends were studied19 following a cold soak at 3°C above the fuel blends’ cloud point. Gas chromatography performed on the particulate collected showed that they contained SMG, glycerol and biodiesel. The project found that the interaction between the biodiesel and the diesel is a contributor to the formation of these sediments. The project also found that agitation can significantly improve re-dissolution of precipitates formed above the cloud point.

Results from the NRDDI Imperial Oil project, in particular, has led CGSB to investigate a new test method, based on the FBT with a pre cold-soak, to evaluate biodiesel suitability for cold weather operability. The Imperial Oil and Manitoba Hydro Fleet projects showed that base diesel aromaticity affects solubility of biodiesel trace components such as SMG.

A recent issue in Minnesota20 regarding fuel filter plugging in cold weather resulted in the temporary suspension of the B5 mandate for No. 1 (Type A in Canada) ULSD from January 15, 2010 through March 31, 2010. The B5 mandate remains in effect for No. 2 ULSD (Type B in Canada). Prior to increasing the state mandate to the 5% level, 2% biodiesel blends were successfully used in both No. 1 and No. 2 diesel all year round. The temporary waiver was in response to a request by the Minnesota Biodiesel Council after some rare incidences of filter clogging were observed with fuel containing 5% biodiesel and 95% No. 1 ULSD. These incidences occurred during a cold temperature spell in the Great Lakes region, only in tank dispensing filters and with this particular fuel blend. The fuel met the appropriate standards at the time of the incident and the filter plugging precipitates formed at temperatures significantly higher (~ -28°C) than the cloud point of the fuel blend (~ -38°C). The precipitate formation is suspected to be linked to the level of aromaticity of the petroleum diesel fuel, due to aromaticity being a main difference between No. 1 and 2 ULSD. Work is ongoing to determine the cause, however, it does not seem to be linked to the sediment formation described above and the issue does not appear to be feedstock specific. Conclusions from laboratory work currently being undertaken in Minnesota to identity the possible causes of the filter plugging is pending.

2.2.2  Long-term Storage

Results from NRDDI studies indicate that low-level biodiesel blends could still meet current fuel standards’ specifications after several months of storage.

The Prairie Agricultural Machinery Institute (PAMI) conducted a biodiesel demonstration involving farmers in Manitoba in 200821. Soy methyl ester (SME) blends were used in harvest equipment for the 2008 farming season with fuel left in the equipment over the non-harvesting season (about nine months). Under the NRDDI, low-level biodiesel blends from three combines were analyzed after this storage period. All samples met the current CGSB biodiesel specifications for B1-5 blends. More detailed analysis was performed on all samples to further evaluate their quality and no concerns were raised. PAMI also investigated un-additized CME blends of B5, B10 and B20, which had been stored for approximately two years in outdoor above-ground storage tanks. These fuels also met applicable standards. These results suggest that storing biodiesel blends for periods of up to two years, under real world conditions, does not necessarily adversely impact the quality of the biodiesel to the point where it fails to meet fuel specifications.

The NRDDI Imperial Oil thermal/oxidative storage stability test program22 investigated the oxidative stability of 54 biodiesel blends (primarily B5 and B20) with and without an antioxidant additive during 12-weeks of accelerated storage, simulating 12 months of storage at 17°C, without temperature variations, according to ASTM test method D-4625. Oxidative stability was assessed before and after the storage term, and total insolubles and FBT were assessed after the storage term. The study showed that the use of antioxidant additives improved the long-term storage stability as measured by the test methods. The results confirm that antioxidants can be used to ensure adequate long-term storage stability of biodiesel fuels. The research23,24, also indicates that limiting the level of sediments in biodiesel is important for low-temperature storage and operating furnaces as well as motor vehicles.

The NRDDI Manitoba Hydro Genset project also investigated storage stability by accelerated testing, using the same methodology as the Imperial Oil thermal/oxidative storage stability test program and also concluded that one year of biodiesel blend storage could be achieved. This project also examined the real world effects of long-term cold temperature biodiesel storage. Phase one of the demonstration project was conducted prior to the NRDDI. SME B5 blends made in January 2008 were shipped to Brochet, Manitoba in February via ice roads and stored in outside storage tanks from February 2008 to November 2009. Phase two of the project was conducted at the same location from November 2009 to May 2010, using a CME B5 blend made in November 2009. The fuel quality was monitored throughout the project for potential degradation and the B5 blends remained suitable for use following long-term storage over the course of the project. This project did not identify any operability issues or additional maintenance requirements for operation on B5 blends.

2.2.3  Microbial Growth

Biodiesel testing in marine applications has demonstrated that severe microbial growth can occur using B20 in these applications. For example, during the Washington State Ferries biodiesel project25, excess sludge formed in the fuel purifier of one of the three vessels operating after one month with a B20 blend. Researchers found active bacteria present in the sludge samples from the purifier, and bacteria was found to play a key role in the sludge formation that resulted in filter clogging. Discussions with operators uncovered that sludge formation from microbial growth has been encountered with conventional diesel fuel also. The excessive sludge problem was solved by the application of biocide in the fuel during the studied period.

British Columbia (BC) Ferries launched a marine biodiesel demonstration project in September 2009 running B5 CME blends in their Queen Alberni vessel for six weeks. Since no problems were encountered, the demonstration project was expanded and currently most of their vessels are running on B5. Closer monitoring of water levels and fuel handling practices has been a focus, but overall, operators have hardly noticed any difference from operation with diesel fuel. It was reported that to date26 none of the fleet running on B5 has experienced problems with the solvent effect of biodiesel or increased microbial growth.

2.2.4  Engine Lube Oil Dilution

A National Renewable Energy Laboratory (NREL) study27 investigating B20 blends in engines with advanced after-treatment systems showed that there were “no obvious biodiesel specific effects on used lube oil properties, and most changes appeared to be consistent with normal lube oil aging”, even though some biodiesel oil dilution was detected.

The NRDDI FPInnovations project28 included a minor engine lube oil dilution testing component. Selected forestry equipment, running on B5 blends, were monitored for lube oil deterioration through engine oil sampling and testing. The protocol involved sampling engine oil several months prior to the use of biodiesel blends (during routine oil change), halfway through the service life of the oil, and once again at the time of the next oil change. Wear metals (from engine part friction or oxidization) and oil condition were tracked before and after the use of biodiesel blends. The results indicated that all oil samples were still fit for service, with no significant differences between engines running on ULSD and B5, even after a few unintentional extended oil drain intervals of 450 to 600 hours in a few instances. Based on these results, it was shown that B5 and lower blend ratios are perfectly acceptable with regular oil services every 300 hours.

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2.3  Analysis

Several projects have shown that renewable diesel blends can be made to conform to the latest industry accepted standards under a variety of Canadian conditions.

Care must be taken with regard to managing the cloud point of all fuels and fuel blends. Fuel blendstock components need to be chosen and adjusted to meet the CGSB recommended temperature specifications for the season and region of use.

As such, in cases where the fuel distribution chain involves more than just the main fuel supplier, it is essential to ensure that key information on properties of the base diesel fuel is considered. The dealer may not always have full access to information regarding the properties of their diesel fuel supply, and may rely on its supplier to ensure that the fuel received meets the required specifications. Depending on the point of blending, independent dealers may need to become better informed about certain biodiesel and base diesel fuel properties.

NRDDI studies have shown that the use of commercially available additives can improve the long-term storage oxidative stability of the fuel, but are not always necessary to achieve adequate storage stability. Additive suppliers should be consulted to evaluate the additives needed and to establish dosage rates that are appropriate for the application.

Work is on-going to improve the understanding of sediment formation during storage of renewable diesel blends, including the base fuel interaction and impact of aromatic content. Investigations of precipitate formation above the cloud point, through a more comprehensive understanding of the scientific basis, are being conducted by standards-setting bodies with the aim of assessing what type of new specifications will be needed in renewable diesel blend standards.

The nature of the Minnesota incident (described in section 2.2.1) is being actively investigated by the authorities and is being monitored in Canada to avoid similar occurrences. The diesel aromatic level and use of Type A versus Type B USLD in the Canadian diesel pool is also an important consideration pertaining to this issue.

Controlling free water levels can help prevent incidences of microbial growth. The use of biocides can mitigate problems with microbial growth should they arise, and is a practice that has been around for some time.

For low-level biodiesel blends, no obvious biodiesel specific effects on lube oil properties are expected.

Finally, fuel supply is an ever-evolving field. As fuel sources are increasingly diversified, there is a need for continuous evolution of fuel standards to address new and emerging issues. All stakeholders, including fuel suppliers, users and regulators, have a role to play in ensuring the fuels being sold in Canada are fit for purpose.

Currently in Canada, there is one approved renewable diesel standard: CGSB standard for 1 to 5% biodiesel blends29. This standard relies on the requirements described in the ASTM30 or CEN31 B100 standards for the biodiesel blendstock used to create the low-level blend. There is ongoing work at CGSB to develop a Canadian B100 blendstock standard as well as one for 6% to 20% biodiesel blends. An updated CGSB heating oil standard32, allowing for up to 5% biodiesel, is expected to be published next year.

Although there are no current standard development projects in North America for HDRD (or other emerging diesel fuel replacements), the European Committee for Standardization has released a Workshop Agreement that specifies requirements and test methods for marketed and delivered paraffinic diesel fuel, such as HDRD, from synthesis or hydrotreatment processes for use in diesel engines. The document describes the quality for use as automotive fuel at 100% concentration. This “pre-standard” can be used on a voluntary basis for engine clearance, fuel acceptance and fuelling station allowance, supporting both local regulations and international trade. In the longer term, further work in this area, including the move toward a more formal standard, will depend on whether paraffinic diesel becomes widely available as a general automotive fuel. Therefore there may potentially be the need for modifications to the CGSB diesel standards to allow for the use of this product as a blendstock.

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7 National Renewable Energy Laboratory, “Biodiesel Handling and Use Guide”, Fourth Edition, Revised December 2009.

8 Washington State Ferries, “Biodiesel Research & Demonstration Project”, April 2009.

9 Conservation of Clean Air and Water in Europe (CONCAWE), “Guidelines for Handling and Blending FAME”, Report 9, November 2009.

10 Climate Change Central, “Renewable Diesel Characterization Study”, August 2008.

11 Alberta Renewable Diesel Demonstration, “Final Report”, February 2009.

12 Manitoba Hydro, “Demonstration of the Use of Biodiesel in Electric Generators in Remote Canadian Locations and Long Term Storage in Gensets”, June 2010.

13 Saskatchewan Research Council, “Off Road Biodiesel Demonstration Agricultural Sector”, Interim Report, May 2010.

14 Manitoba Hydro, “Long Term Storage and Use of Biodiesel in Fleets “, June 2010.

15 Imperial Oil, “Low Temperature Storage Test, Phase II – Identification of Problem Species”, November 2009.

16 M. Brewer, “Identification of Precipitate Found in Depot Storage Tanks Containing Swedish Klass1 B5 Fuels”, International Congress on Biodiesel, Vienna, Austria, November 2007.

17 R. Faucon, A.Gendron, and O. Cottalorda, “Diesel Fuel B7 Specifications Need to be Reinforced for Cold Weather Conditions”, World Refining Fuels Conference, Brussels, May 2009.

18 Charley Selvidge, Scott Blumenshine, Kurt Campbell, Cathy Dowell and Julie Stolis, “Effect of Biodiesel Impurities on Filterability and Phase Separation from Biodiesel and Biodiesel Blends”, IASH 2007, the 10th International Conference on Stability, Handling and Use of Liquid Fuels, Tucson, AZ, October 5-11, 2007.

19 The Royal Military College of Canada, “Particles Formation Kinetics in Biodiesel and Petrodiesel Blends above the Cloud Point”, May 2010.

20 Natural Resources Canada’s Communication with MEG Group Fuel Consultant, May 2010.

21 Prairie Agricultural Machinery Institute, “Effects of Long Term Storage on Biodiesel Quality”, March 2010

22 Imperial Oil, “Thermal/Oxidative Storage Stability of Bio-diesel Fuels”, November 2009

23 Imperial Oil, “Low Temperature Storage Test, Phase II – Identification of Problem Species”, November 2009

24 Important Research Provides Assurances for Bio Heating and Transportation Fuels, January 2010 Press Release, Canadian Petroleum Products Institute.

25 Washington State Ferries, “Biodiesel Research & Demonstration Project”, April 2009.

26 Natural Resources Canada’s Communications with BC Ferries, April 2010.

27 National Renewable Energy Laboratory, “Impacts of Biodiesel Fuel Blends Oil Dilution on Light-Duty Diesel Engine Operation”, Presented at the 2009 SAE International Powertrains, Fuels, and Lubricants Meeting, June 2009.

28 FPInnovations, “Demonstration of the Potential Use of Biodiesel for Off-Road Machinery in Canadian Highway Construction and Forest Operations”, June 2010.

29 Canadian General Standards Board, “CAN/CGSB-3.520; Automotive (On-road) Diesel Fuel Containing Low Levels of Biodiesel Esters (B1-B5)”, 2005

30 American Society for Testing and Materials (ASTM), “ASTM D6751: Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels”, 2009.

31 European Committee for Standardization, “EN 14214: Automotive Fuels – Fatty acid methyl esters (FAME) for diesel engines – requirements and test methods”, November 2008.

32 Canadian General Standards Board, “CAN/CGSB-3.2: Heating Fuel Oil”, 2007