Biodiesel Standards & Properties

Hannu Jääskeläinen

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Abstract: Two major specifications establishing the quality requirements for alkyl ester-based biodiesel fuels are the ASTM D6751 in the USA and the EN 14214 in Europe. This paper includes a summary of these standards, compares the US and EU specifications and test methods, and discusses the underlying issues.

Standard Specifications

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 [767]. 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.

Table 1
US and EU Biodiesel Specifications

PropertyASTM D975-08aASTM D6751-12EN 590:2004EN 14214:2012
Flash point, minNo 1D 38°C
No 2D 52°C
D9393°CD9355°CEN 22719101°CEN ISO 2719
Water & sediment, max0.05% volD27090.050% volD2709
Water, max200 mg/kgEN ISO 12937500 mg/kgEN ISO 12937
Total contamination, max24 mg/kgEN 1266224 mg/kgEN 12662
Distillation temperature (% vol recovered)90%:
1D 288°C max
2D 282-338°C
D8690%: 360°C maxD116065%: 250°C min
85%: 350°C max
EN ISO 3405
Kinematic viscosity1D 1.3-2.4 mm2/s
2D 1.9-4.1 mm2/s
D4451.9-6.0 mm2/sD4452.0-4.5 mm2/sEN ISO 31043.5-5.0 mm2/sEN ISO 3104
Density820-845 kg/m3EN ISO 3675
EN ISO 12185
860-900 kg/m3EN ISO 3675
EN ISO 12185
Ester content5% vol. maxEN 140785% vol. max FAMEEN 1407896.5% minEN 14103
Ash, max0.01% wtD4820.01% wtEN ISO 6245
Sulfated Ash, max0.020% massD8740.02% massISO 3987
Sulfur, max (by mass)1D and 2D:
S15 15 mg/kg
S500 0.05%
S5000 0.50%
D5453 D2622 D1292Two grades:
S15 15 ppm
S500 0.05%
D5453Two grades:
50 mg/kg
10 mg/kg
EN ISO 14596
EN ISO 8754
EN ISO 24269
10.0 mg/kgEN ISO 20846
EN ISO 20884
EN ISO 13032
Copper strip corrosion, maxNo 3D130No 3D130class 1EN ISO 2160class 1EN ISO 2160
Cetane number, min40D61347D61351.0EN ISO 516551.0EN ISO 5165
Cetane index, min46.0EN ISO 4264
One of3:
- cetane index
- aromaticity

40 min
35% vol max

PAH, max11% wtIP 391
EN 12916
Operability, one of:
- cloud point
ReportD2500 D4539 D6371
Cloud pointReportD2500Location & season dependantEN 23015Location & season dependantEN 23015
CFPPLocation & season dependantEN 116Location & season dependantEN 116
Carbon residue on 10% distillation residue, max1D: 0.15% wt
2D: 0.35% wt
D5240.050% wt5D45300.30% wtEN ISO 10370
Acid number, max0.50 mg KOH/gD6640.50 mg KOH/gEN 14104
Oxidation stability3 hrs minEN 1411225 g/m3 maxEN ISO 122058 hrs minEN 14112
Iodine value, max1201 g Iod/100gEN 14111
EN 16300
Linolenic acid methyl ester, max12.0% wtEN 14103
Polyunstatured methyl esters, max1.00% wtEN 15779
Alcohol control0.2% wt methanol max, orEN141100.20% wt methanol maxEN 14110
130°C flash point minD93
Monoglycerides, diglycerides & triglycerides, maxMG
0.40% wt
D6584MG 0.70% wt
DG 0.20% wt
TG 0.20% wt
EN 14105
Group I metals (Na + K), max5 mg/kgEN 145385.0 mg/kgEN 14108
EN 14109
EN 14538
Group II metals (Ca + Mg), max5 mg/kgEN 145385.0 mg/kgEN 14538
Free glycerin, max0.020% wtD65840.02% wtEN 14105
EN 14106
Total glycerin, max0.240% wtD65840.25% wtEN 14105
Phosphorous, max0.001% wtD49514.0 mg/kgEN 14107
prEN 16294
Lubricity, max520 µmD6079460 µmISO 12156-1
Conductivity, min25 pS/mD2624 D4308
Cold soak filtration time (CSFT), max360 s4200 sD7501
(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 [1849]. These guidelines bear some resemblance to EN 14214 but there are some notable differences including: