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Development of biodiesel standards started in the 1990s, to support the increasing use of alkyl esters-based biodiesel and its blends as automotive fuels. ASTM International (formerly American Society for Testing and Materials) adopted a provisional specification PS121 for biodiesel in 1999. The first ASTM standard (ASTM D6751) was adopted in 2002 . In Europe, EN 14214 biodiesel standard (based on former DIN 51606) was finalized in October 2003. The US and EU standards have international significance; they are usually the starting point for biodiesel specifications developed in other countries (see also Fuel Regulations).
Approaches to US and EU standards for biodiesel differ. In the USA, ASTM D6751 establishes specifications for a biodiesel blend stock for middle distillate fuels. While the specification was written for B100, it is not intended for neat biodiesel used as automotive fuel. Rather, it is for the biodiesel component that is to be blended to produce biodiesel/diesel fuel blends. Since 2012, the ASTM D6751 standard defines two grades of biodiesel: grade 2-B (identical to biodiesel defined by earlier versions of the standard) and grade 1-B with tighter controls on monoglycerides and cold soak filterability. Two automotive standards for biodiesel/diesel fuel blends have been published by ASTM:
In Europe, standard specifications have been developed for unblended FAME diesel fuel as well as for certain higher level biodiesel blends, while low level blends are covered by EN 590, the European diesel fuel specification:
Biodiesel specifications and test methods according to ASTM D6751 and EN 14214 are compared with those of petroleum diesel in Table 1. Both ASTM D6751 and EN 14214 establish specifications for key fuel properties for biodiesel—the former for the biodiesel blend component, the latter for both blend stock and neat biodiesel automotive fuel.
|Property||ASTM D975-08a||ASTM D6751-12||EN 590:2004||EN 14214:2012|
|Flash point, min||No 1D 38°C|
No 2D 52°C
|D93||93°C||D93||55°C||EN 22719||101°C||EN ISO 2719|
|Water & sediment, max||0.05% vol||D2709||0.050% vol||D2709|
|Water, max||200 mg/kg||EN ISO 12937||500 mg/kg||EN ISO 12937|
|Total contamination, max||24 mg/kg||EN 12662||24 mg/kg||EN 12662|
|Distillation temperature (% vol recovered)||90%:|
1D 288°C max
|D86||90%: 360°C max||D1160||65%: 250°C min|
85%: 350°C max
|EN ISO 3405|
|Kinematic viscosity||1D 1.3-2.4 mm2/s|
2D 1.9-4.1 mm2/s
|D445||1.9-6.0 mm2/s||D445||2.0-4.5 mm2/s||EN ISO 3104||3.5-5.0 mm2/s||EN ISO 3104|
|Density||820-845 kg/m3||EN ISO 3675|
EN ISO 12185
|860-900 kg/m3||EN ISO 3675|
EN ISO 12185
|Ester content||5% vol. max||EN 14078||5% vol. max FAME||EN 14078||96.5% min||EN 14103|
|Ash, max||0.01% wt||D482||0.01% wt||EN ISO 6245|
|Sulfated Ash, max||0.020% mass||D874||0.02% mass||ISO 3987|
|Sulfur, max (by mass)||1D and 2D:|
S15 15 mg/kg
|D5453 D2622 D1292||Two grades:|
S15 15 ppm
|EN ISO 14596|
EN ISO 8754
EN ISO 24269
|10.0 mg/kg||EN ISO 20846|
EN ISO 20884
EN ISO 13032
|Copper strip corrosion, max||No 3||D130||No 3||D130||class 1||EN ISO 2160||class 1||EN ISO 2160|
|Cetane number, min||40||D613||47||D613||51.0||EN ISO 5165||51.0||EN ISO 5165|
|Cetane index, min||46.0||EN ISO 4264|
- cetane index
35% vol max
|PAH, max||11% wt||IP 391|
|Operability, one of:|
- cloud point
|Report||D2500 D4539 D6371|
|Cloud point||Report||D2500||Location & season dependant||EN 23015||Location & season dependant||EN 23015|
|CFPP||Location & season dependant||EN 116||Location & season dependant||EN 116|
|Carbon residue on 10% distillation residue, max||1D: 0.15% wt|
2D: 0.35% wt
|D524||0.050% wt5||D4530||0.30% wt||EN ISO 10370|
|Acid number, max||0.50 mg KOH/g||D664||0.50 mg KOH/g||EN 14104|
|Oxidation stability||3 hrs min||EN 14112||25 g/m3 max||EN ISO 12205||8 hrs min||EN 14112|
|Iodine value, max||1201 g Iod/100g||EN 14111|
|Linolenic acid methyl ester, max||12.0% wt||EN 14103|
|Polyunstatured methyl esters, max||1.00% wt||EN 15779|
|Alcohol control||0.2% wt methanol max, or||EN14110||0.20% wt methanol max||EN 14110|
|130°C flash point min||D93|
|Monoglycerides, diglycerides & triglycerides, max||MG|
|D6584||MG 0.70% wt|
DG 0.20% wt
TG 0.20% wt
|Group I metals (Na + K), max||5 mg/kg||EN 14538||5.0 mg/kg||EN 14108|
|Group II metals (Ca + Mg), max||5 mg/kg||EN 14538||5.0 mg/kg||EN 14538|
|Free glycerin, max||0.020% wt||D6584||0.02% wt||EN 14105|
|Total glycerin, max||0.240% wt||D6584||0.25% wt||EN 14105|
|Phosphorous, max||0.001% wt||D4951||4.0 mg/kg||EN 14107|
|Lubricity, max||520 µm||D6079||460 µm||ISO 12156-1|
|Conductivity, min||25 pS/m||D2624 D4308|
|Cold soak filtration time (CSFT), max||360 s4||200 s||D7501|
(1) Spain’s Royal Decree 1700/2003 sets the maximum iodine value at 140 to facilitate the use of soybean oil as a feedstock.|
(2) D129 is only applicable to S5000 grades.
(3) Limits only apply to S15 and S500 grades.
(4) 200 s if fuel temperature ≤ -12°C.
(5) Tested on 100% sample but reported using 10% residual calculation.
The US specification, ASTM D6751, defines biodiesel as mono-alkyl esters of long chain fatty acids derived from vegetable oils and animal fats. The type of alcohol used is not specified. Thus mono-alkyl esters could be produced with any alcohol (methanol, ethanol, etc.) so long as it meets the detailed requirements outlined in the fuel specification. By requiring that the fuel be mono-alkyl esters of long chain fatty acids, other components, with the exception of additives, would inherently be excluded.
The European biodiesel specification, EN 14214, is more restrictive and applies only to mono-alkyl esters made with methanol, fatty acid methyl esters (FAME). The minimum ester content is specified at 96.5%. The addition of components that are not fatty acid methyl esters—other than additives—is not allowed.
Guidelines for B100 used to make biodiesel/diesel fuel blends have also been adopted by automobile and engine manufacturers from North and South America, Europe and Asia . These guidelines bear some resemblance to EN 14214 but there are some notable differences including: