Biodiesel Specifications, Fuel Quality and Technical Overview National Biodiesel Board Diesel Technician Outreach Program 2010
Quality, Quality, Quality
B100 must meet D 6751 prior to blending to insure trouble-free use of B20 and lower blends
BQ-9000 fuel quality program helps to promote high quality fuel from producers and marketers
B20 and lower blends are recommended since most of the research and successful use of the fuel has been with these blends
See NBB Toolkit document “Use of Biodiesel Blends Up to B20” for more information
Blends over B20 require special precautions and should only be used by knowledgeable and experienced users
See NBB document “Guidance on Biodiesel Blends Above B20” for more information: http://www.biodiesel.org/pdf_files/fuelfactsheets/Use_of_Biodiesel_Blends_above_%2020.pdf
Why care about biodiesel quality?
Off specification biodiesel can cause engine operability problems
Quality is critical to continue to grow the industry
There is NO room for off-specification fuel
Customers need to receive consistent quality from lot to lot, batch to batch
Must be on-spec for tax credit and to be legal fuel
Biodiesel production review
Key elements in ASTM Specifications and Standard Test Methods
ASTM Specification D 6751 – 09, the specification of
B100 (biodiesel) fuel is described in detail.
Key properties of B 100 are discussed in terms of their tests and specifications.
Alternative testing procedures
Other issues affecting fuel quality
Review of the Production Process
Biodiesel is produced by a chemical reaction between methanol (or ethanol) and an oil or fat, in the presence of a catalyst.
Requires a strong basic catalyst (NaOH or KOH)
The reaction is called “Transesterification”
Changing one ester (vegetable oil) into another ester (biodiesel)
Oil + Alcohol yields Biodiesel + Glycerol
Transesterification (the biodiesel reaction) Fatty Acid Chain Glycerol Methanol (or Ethanol) One triglyceride molecule is converted into three mono alkyl ester (biodiesel) molecules Biodiesel Triglyceride
Potential Impurities: in Biodiesel
Methanol – Degrades some plastics and elastomers, corrosive; Can lower flashpoint to unsafe levels (fire safety)
Unconverted/partly converted oils (bound glycerin) – Results in very poor cold flow properties, injector and in-cylinder deposits, potential engine failure
Free Glycerin – Results in injector deposits, clogged fuel filters, deposit at bottom of fuel storage tank
Catalyst (caustic, NaOH) – Excessive injector, fuel pump, piston, and ring wear, filter plugging, issues with lubricant
All are limited by ASTM D6751 specification
ASTM Standards for Biodiesel
ASTM D6751 is the approved standard for B100 for blending up to B20, since 2001
Performance-based standard: Feedstock and Process Neutral
D975 – Add up to 5% biodiesel in Petrodiesel
D396 – Add up to 5% biodiesel in Heating Oil
D7467 – New standard for on/off road blends of B6 to B20
B100 Blending Component Specification
Major steps forward for passage of biodiesel blend specifications
Critical for obtaining OEM approval
Critical for ensuring that biodiesel performs as advertised so market can grow
D6751-09 Requirements McCormick, R.L, Westbrook, S.R. “Biodiesel and Biodiesel Blends” Standardization News , page 28, April 2007
B6-B20 Blend Specification
Oxidation Stability is 6 hours
Cold Soak Filtration Test included
Acid Number Reduction
Impact of Blended Specs
More large fleets are using B20
Nearly 55% of OEMs in the U.S. now support B20 or higher blends in at least some of their equipment
Biodiesel blends are the only non-petroleum diesel substitute to have officially sanctioned ASTM specifications
Quality is further improved, fuel specs can be enforced by regulatory bodies (supported by NBB)
Biodiesel companies have made process changes in order to meet D6751
Biodiesel Pump Labeling
No Label Required:
Fuel blends containing no more than five percent biodiesel and no more than 5 percent biomass-based diesel and that meet ASTM D975.
Fuel blends containing more than five but no more than 20 percent biodiesel or biomass-based diesel.
Fuel blends containing more than 20 percent biodiesel or biomass-based diesel.
Separate Labels for Biodiesel (Blue Labels) and
Biomass-Based Diesel (Orange Labels)
BQ-9000 Fuel Quality Program
Biodiesel Industry’s equivalent to an ISO 9000 program for biodiesel production & distribution companies as well as testing labs
BQ-9000 works hand-in-hand with the ASTM specifications for biodiesel
Quality Control System covers biodiesel manufacturing, sampling, testing, blending, storage, shipping, distribution
ASTM Grade Fuel, BQ-9000 Companies
Since 2005, there has been a substantial increase in interest in the NBB’s BQ-9000 Quality Program
There are now three BQ-9000 designations:
Producer (make it to spec)
Marketer (buy spec, keep it in spec, blend it right)
Certified Laboratories (test it to ensure it is in spec)
We now have 60 total companies BQ-9000 certified (37 producers, 23 marketers)
75-80% of the biodiesel volume in the U.S. is now made by BQ-9000 producers, and more certifications are in process
Many OEMs are now either requiring or strongly encouraging BQ-9000
2004 B100 Quality Survey
Under guidance of B20 Fleet Evaluation Team (OEM’s, NREL, NBB)
Samples obtained nationwide from biodiesel blenders (27 samples)
85% of samples tested met the ASTM D6751 specification
Four samples failed with high levels of:
phosphorus (lube oil contamination?)
acid number and total glycerin
2006 B100 Quality Survey
A subcontractor visited the site of a biodiesel blender, usually a terminal operator or jobber, to collect the B100 sample
32 B100s, 6 B99s, and 1 B50
59% of B100 samples tested fail the D6751 specification
Importantly, 30% fail total glycerin – immediate operational problems in cold weather
Other issue of concern is 20% failure rate for Na+K
Compares to 15% failure rate in 2004 survey
Samples were collected randomly, not on production volume basis
Biodiesel, based on production volume, may have different failure rate
Poor quality batch may have contaminated larger fuel lot
2007 B100 Quality Survey
Collect B100 samples directly from producers and analyze for properties most likely to impact engine performance and emission control systems
Flash point, oxidation stability, acid value, free and total glycerin, cloud point, Na+K, Ca+Mg, P, water & sediment
First survey that will link test results to production volume
Results presented at recent NBB meeting
56 out of 107 producers participated in 2007 survey or 70% of the 2007 US market –Reasons for not participating are likely due to lack of feedstock availability
Wide variety of feedstocks represented
Meeting the specification is independent of producer size or feedstock
Small producers failed specifications more often than medium or large producers
– Small producers: 28% of samples passed –Medium producers: 68% of samples passed –Large producers: 94% of samples passed
How do you ensure quality?
Biodiesel Fuel Quality is determined by:
1. Feedstock quality
2. Production process
3. Post-Reaction monitoring
4. Analytical Capability
5. Handling and Storage **CRITICAL
Acid Number, mg KOH/g
Total and Free Glycerin, % mass
Water and Sediment, volume %
Cloud point, °C
Oxidative Stability, hr
Method ASTM D 93
Changed 2007- Limit: 93ºC minimum
A sample is heated in a close vessel and ignited. When the sample burns, the temperature is recorded.
One of the following must be met:
1. Methanol content EN 14110:
0.2 max % volume
2. Flash point D 93 : 130 min °C
Flash Point Testing
Water and Sediment
Method D 2709
Limit of 500ppm, examining the free water content
100 mL of sample are centrifuged at 800 rcf for 10 min at 21° to 32°C in calibrated tube.
Water and Sediment
Biodiesel can absorb 1500 ppm of water while diesel only 50 ppm.
Free water can cause corrosion of fuel injection parts.
Precipitates above cloud point
Karl Fischer : Moisture Determination
Test Method ASTM D 664
Limits: 0.5 mg KOH/g maximum
pH sensitive electrode
May also be determined using indicators
Test Method ASTM D 874
Limits: 0.020 % mass maximum
Sample ignited and burned
Ash + carbon (C removed by H 2 SO 4 )
Indication of concentration of metal additives (Ba, Ca, Mg, Na, K, Sn, Zn)
More than 0.020 % indicates residual soap & catalyst
Free and Total Glycerin
Test Method ASTM D 6584
Limits: 0.020 % mass free glycerin
0.240 % mass total glycerin
Gas Chromatography with FID detection
Quantifies glycerol, mono-, di- and triglycerides
Production Factors: Total Glycerol
Measured with gas chromatograph (ASTM D6584) and requires a skilled operator.
Saturated monoglycerides have very low solubility in biodiesel.
If too high, there may be problems with fuel filter plugging and fuel stability.
Test Method ASTM D 5453
Limits: 0.05 % mass maximum
S oxidized to SO 2 at high temperatures
UV fluorescence of emitted gases SO 2 SO 2 * SO 2
S limits dictated by environmental considerations (S15 or S500)
Test Method ASTM D 2500
Limits: No established limits
Reported in ºC
Sample cooled and examined visually until first cloud appears.
Indicates the lowest temperature at which fuel is usable.
Generally higher than diesel.
Wax molecules in diesel fuel and biodiesel tend to crystallize at low temperatures.
Crystals agglomerate to form large masses.
This can cause filter plugging and eventually the fuel will become a solid mass.
Soy biodiesel gels at approximately 32 °F
#2 petroleum diesel fuel gels at 10 to 14 °F.
Biodiesel from saturated/tallow feedstocks can gel as high as 50-55°F.
In contrast , petroleum diesel fuel is a mixture of hundreds of different compounds that solidify at very different temperatures. So, even if some compounds crystallize at a relatively high temperature, many other compounds will stay liquid to a much lower temperature.
Watch your soap & water content!
Cloud Point & CFPP
Cold Soak Filtration Test
Developed in response to questions about precipitates above the cloud point
Character of precipitates may vary with feedstock
Method is now incorporated in the D6751
Method will be mandatory annex in D6751 until test method is balloted and written
ASTM Subcommittee 14 is working to further develop test method
Cold Soak Filtration Test Method
Preheat fuel at 40 ° C for 3 hours to remove thermal memory then hold at room temp for 24 hours
Soak 300 mL sample at 4 ° C for 16 hours and let return to room temperature
Time will vary with degree of saturation of feedstock
Filter fuel using 0.7 m filter and constant vacuum
Record time to filter fuel
If fuel does not filter, record time stopped and volume filtered
Equipment: Rancimat or OSI
Method: EN 14112; 3 minimum hours
Equipment cost: approximately 17- 20k
Recent addition to ASTM 6751
Products of oxidation in biodiesel are various acids or polymers, can cause fuel system deposits and lead to filter plugging & fuel system malfunctions.
Additives can improve the oxidation stability performance of biodiesel.
Biodiesel will react with oxygen from the air to form polymers, acids, etc.
Presence indicated by increasing Acid Value
Cause corrosion of metal components
Corrosion can be aggravated by water
Sediments that can plug fuel filters and coat metal surfaces
Class I & II metals: Ca/Mg/Na/K
Calcium & Magnesium & Sodium & Potassium can be in biodie sel as abrasive solids or soluble metallic soaps.
Solids contribute to injector, fuel pump, piston, and ring wear, & engine deposits.
Soluble metallic soaps have little effect on wear, but filter clogging & engine deposits
These compounds may also be collected in exhaust particulate removal devices
Less Critical Parameters
Copper Strip Corrosion
Fleet and Distributor Biodiesel Testing
Completeness of Reaction (3/27 Methanol Test)
Soap test: AOCS method
Wika Water test
Microbial growth, algae-x
Completion of Reaction
Dissolve 3 ml of biodiesel in 27 ml of methanol.
The biodiesel should be fully soluble in the methanol forming a clear bright phase.
If you observe un-dissolved material at the bottom of the sample the reaction did not proceed to completion
Each ml of undissolved material corresponds to 4% by volume.
0.2139 Bound Glycerin Although cloudy, there were no droplets of precipitate. 0.0900 Bound Glycerin Crystal clear, no cloudiness or precipitate. Samples Passing 3/27
0.9256 Bound Glycerin Note the falling droplets of unreacted oil. Samples Failing 3/27 1.8260 Bound Glycerin
Biodiesel Conversion Test
Acid Number Qualitative Tests
Soap- AOCS test method
Gels at ambient temperature as little as 5%
Cause problems with glycerol separation and washing
Soap can be split by acidulating
Soap is usually clear and very viscous
Methanol will act as a cosolvent and keep soap in solution with the biodiesel
High soap levels = high sulfated ash number
High FFA and water content lead to soap formation in process
Soap Test Titrating from blue/green to straw yellow….
Wilkes InfraSpec measures percent biodiesel in diesel fuel, ethanol in gasoline, water in ethanol as well as total glycerides during the biodiesel pass/fail determination in less than 5 minutes.
Paradigm Sensors * Paradigm Sensors’i-SPEC™ tests TOTAL GLYCERIN in blended fuels (B6-B20), which is in accordance with ASTM proposal that the biodiesel portion of the fuel must meet ASTM 6751 prior to blending.
Wika Water Test
Certain varieties of bacteria and fungi can grow in diesel fuel tanks.
Growth occurs at the interface of the fuel and water at the bottom of the fuel tank.
Water must be drained from tank bottoms on a regular basis.
Biocides are available to control microbial growth.
Dead microbes can still plug filters.
Water elimination and prevention is preferred over treatment.
Bacteria Growth Fungal Growth
Microbial growth – ULSD & moisture
Treat your storage tanks for moisture/biocide
Low energy content (not harmful)
Fuel filter plugging is the most common operational issue
Certificate of Analysis
Biodiesel Quality Standard
ASTM D 6751 Standards
Fuel quality is critical for proper functioning
Standards ensure satisfactory operation in diesel engines
BQ 9000 Certification
Certifies biodiesel producers and markers
Feeling of confidence for:
Engine and Vehicle Manufacturers
Purchase fuel from known quality producer
On-site and in-process analysis is essential
Watch for residual contamination
Correct product handling and storage procedures is essential
Final product must meet the current revision of ASTM D 6751
Biodiesel Fuel Quality Resources
http://www. uidaho . edu /bioenergy/index.html
Biodiesel Training Toolkit
News Releases & Information Resources
Technical Library, Spec Sheets & Videos
OEM Warranty Positions on Biodiesel
U.S. Diesel Vehicle List
Listing of BQ-9000 Certified Companies
Listing of BioTrucker retail sites
Biodiesel merchandise, literature, pump labels and more!