B20 and B100: Alternative Fuels

Growing interest in biodiesel as an alternative transportation fuel stems mainly from its renewable, domestic production; its safe, clean-burning properties; and its compatibility with existing diesel engines.

Biodiesel can be legally blended with petroleum diesel in any percentage. The percentages are designated as B20 for a blend containing 20% biodiesel and 80% petroleum diesel, B100 for 100% biodiesel, and so forth. B100 and blends of B20 or higher qualify for alternative fuel credits under the Energy Policy Act of 1992 (http://www.afdc.energy.gov/afdc/laws/key_legislation#epact92) for more information.

B20
Twenty percent biodiesel and 80% petroleum diesel—B20—is the most common biodiesel blend in the United States. Using B20 provides substantial benefits but avoids many of the cold-weather performance and material compatibility concerns associated with B100.

B20 can be used in nearly all diesel equipment and is compatible with most storage and distribution equipment. B20 and lower-level blends generally do not require engine modifications. Not all diesel engine manufacturers cover biodiesel use in their warranties, however. See the National biodiesel Board's Standards and Warranties page to learn more about engine warranties. Because diesel engines are expensive, users should consult their vehicle and engine warranty statements before using biodiesel. biodiesel blends between B6-B20 must meet prescribed quality standards—ASTM D7467. 

Biodiesel contains about 8% less energy per gallon than petroleum diesel. For B20, this could mean a 1 to 2% difference, but most B20 users report no noticeable difference in performance or fuel economy. Greenhouse gas and air-quality benefits of biodiesel are roughly commensurate with the blend; B20 use provides about 20% of the benefit of B100 use and so forth. Low-level biodiesel blends also provide benefits, but users are encouraged to experiment with higher biodiesel blends to maximize benefits.

B100
B100 or other high-level biodiesel blends can be used in some engines built since 1994 with biodiesel-compatible material for parts such as hoses and gaskets. However, as biodiesel blend levels increase significantly beyond B20, a number of concerns come into play. Users must be aware of lower energy content per gallon and potential issues with impact on engine warranties, low-temperature gelling, solvency/cleaning effect if regular diesel was previously used, and microbial contamination. To avoid engine operational problems, pure biodiesel (B100) must meet the requirements of ASTM D6751-09, Standard Specification for biodiesel Fuel (B100) Blend Stock for Distillate Fuels.

B100 use could also increase nitrogen oxides emissions, although it greatly reduces other toxic emissions. All these issues can be handled, but currently B100 use might be best for professional fleets with maintenance departments prepared to deal with this fuel.

ASTM biodiesel Specifications
The tables below show selected requirements for B100 and B6 to B20 blends. 

B100
The table below shows selected requirements for 100% biodiesel (B100) as listed in ASTM D6751.

Requirements for biodiesel (B100) Blend Stock ASTM D6751

Property	Test Method	Limits	Units
Calcium and magnesium combined	EN14538	5 max	ppm
Flash point	D93	93.0 min	°C
Water and sediment	D2709	0.050 max	vol %
Kinematic viscosity, 40°C	D445	1.9-6.0	mm2/s
Sulfated ash	D874	0.020 max	% mass
Sulfur	D5453	0.0015 max (S15) 0.05 max (S500)	% mass
Copper strip corrosion	D130	0.020 max	-
Cetane number	D613	47 min	-
Cloud point	D2500	Report to customer	°C
Carbon residuea	D4530	0.050 max	% mass
Acid number	D664	0.50 max	mg KOH/g
Free glycerin	D6584	0.020	% mass
Total glycerin	D6584	0.240	% mass
Phosphorus content	D4951	0.001 max	% mass
Distillation temperature, 90% recovered (T90)b	D1160	360 max	°C
Oxidation stability	EN14112	3 min	hours
Cold Soak filterability	Annex A1	360 maxc	seconds
Alcohol control - One of the following must be met:
(1) Methanol content	EN14110	0.2 max	vol %
(2) Flash point	D93	130 min	°C

 a Carbon residue shall be run on the 100% sample.
 b Atmospheric equivalent temperature.
 c B100 intended for blending into diesel fuel that is expected to give satisfactory vehicle performance at fuel temperatures at or below 10°F (-12°C) shall comply with a cold soak filterability limit of 200 s maximum.

B6 to B20
The table below shows requirements for 6% to 20% biodiesel (B6-B20) ASTM D7467.

Requirements for biodiesel B6-B20 ASTM D7467

Property	Test Method	Limits	Units
Acid number	D664	0.3 max	mg KOH/g
Viscosity at 40°C	D445	1.9-4.1a	mm2/s
Flash point	D93	52b	°C
Cloud point	D2500	Report to customer	°C
Distillation temperature, 90% evaporated	D86	343	°C
Ramsbottom carbon residue on 10% bottoms	D524	0.35 max	% mass
Sulfur	D5453	0.0015 max (S15) 0.05 max (S500)	% mass
Cetane number	D613	40 minc	-
Ash content	D482	0.01	% mass
Water and sediment	D2709	0.050 max	% mass
Copper corrosion 3 h at 50°C	D130	No. 3	-
biodiesel content	DXXXXd	6-20	% (V/V)
Oxidation stability	EN14112	6 min	Hours
Lubricity at 60°C	D6079	520 maxd	micron
One of the following must be met:
(1) Cetane index	D976-80	40 min	-
(2) Aromaticity	D1319-88	35 max	-

 a. If Grade No. 1-D or blends of Grade No. 1-D and Grade No. 2-D diesel fuel are used, the minimum viscosity shall be 1.3 mm2/s.
 b. If Grade No. 1-D or blends of Grade No. 1-D and Grade No. 2-D diesel fuel are used, or a cloud point of less than -12°C) is specified, the minimum flash point shall be 38°C.
 c. Low ambient temperatures as well as engine operation at high altitudes may require the use of fuels with higher cetane ratings. If the diesel fuel is qualified under Table 1 of D975 for cetane, it is not necessary to measure the cetane number of the blend. This is because the cetane number of the individual blend components will be at least 40, so the resulting blend will also be at least 40 cetane number.
 d. Where specified, the blend level shall be +/- 2% volume unless a different tolerance is agreed to by the purchaser and the supplier.
 e. If the diesel fuel is qualified under Table 1 of D975 for lubricity, it is not necessary to measure the lubricity of the blend. This is because the lubricity of the individual blend components will be at least 520 microns, so the resulting blend will also be at least 520 microns.