Mr. Howard compared alternative fuels on the following evaluation criteria; vehicle cost, infrastructure cost, safety, operating cost, reliability, customer acceptance, funding assistance, training costs, fuel availability, fuel quality, and fuel price stability. Fuels were evaluated on a scale of 1 to 10 with 10 being most desirable. The following table compares B20 with diesel fuel, compressed natural gas, liquefied natural gas, methanol, and ethanol.

Table 3.

Vehicle Performance
Emissions and performance data on several medium and heavy duty engine families fueled with B20, including the Detroit Diesel Series 60, 6V-71, 6V-92, 8V-71, Cummins L10, Cummins 5.9 B, and the Navistar 7.3 HEUI. Emissions data from these tests demonstrate that particulate matter, opacity, carbon monoxide and hydrocarbons are reduced. Oxides of nitrogen are slightly increased with some engines. Operating performance parameters, such as fuel consumption, power, and torque were similar to diesel fuel for these tests.

CONSIDERATIONS FOR B100 USE
Infrastructure
In general, the standard storage and handling procedures used for petroleum diesel should be used for B100. The fuel should be stored in a clean, dry, dark environment. Temperature extremes should be avoided. Acceptable storage tank materials include mild steel, stainless steel, fluorinated polyethylene, and fluorinated polypropylene. B100 has a solvent effect which releases the deposits accumulated on tank walls and pipes, which previously have been used for diesel. These deposits can be expected to clog filters initially and precautions should be taken to allow for this.

Materials Compatibility
B100 over time will soften and degrade certain types of elastomers and natural rubber compounds. Precautions are needed when using high percent blends to ensure that the existing fueling system, primarily fuel hoses and fuel pump seals, do not contain elastomer compounds incompatible with B100. Manufacturers recommend that natural or butyl rubbers not be allowed to come in contact with neat B100. B100 will lead to degradation of these materials. If a vehicle's fuel system does contain these materials, replacement with B100 compatible elastomers such as Viton® B is recommended. The recent switch to low sulfur diesel fuel has caused most original equipment manufacturers (OEMs) to switch to components suitable for use with B100, but users should contact their OEM for specific information. (Viton B is a registered trademark of DuPont Dow Elastomers.)

Cold Flow Properties
As with any diesel fuel, cold flow properties are important. A 20% blend of B100 will increase the cold flow properties (cold filter plugging point, cloud point, pour point) of petrodiesel approximately 1 to 3 degrees Celsius. Thus far, no precautions have been needed for fueling with 20% blends. Operation of neat (100%) B100 in cold weather, however, will experience gelling faster than petrodiesel. The solutions for this potential issue are much the same as that with low-sulfur diesel (i.e. utilization of fuel heaters and storage of the vehicle in or near a building). B100 appears to be largely unaffected by conventional pour point depressants.

B100 ATTRIBUTES
Emissions Reductions
The use of B100 in a conventional diesel engine results in substantial reduction of unburned hydrocarbons, carbon monoxide, and particulate matter. Emissions of nitrogen oxides are either slightly reduced or slightly increased depending on the duty cycle and testing methods. Particulate emissions from conventional diesel engines can be divided into three components. Each component is present in varying degrees depending on fuel properties, engine design and operating parameters.

The first component, and the one most closely related to the visible smoke often associated with diesel exhaust, is the carbonaceous material. This material is in the form of sub-micron sized carbon particles which are formed during the diesel combustion process and is especially prevalent under conditions when the fuel-air ratio is overly rich. This can occur as a result of insufficient combustion air, overfueling or poor in-cylinder fuel-air mixing. The second component is hydrocarbon material which is absorbed on the carbon particles, commonly referred to as the soluble fraction. A portion of this material is the result of incomplete combustion of the fuel, and the remainder is derived from the engine lube oil. Finally, the third particulate component is comprised of sulfates and bound water. The amount of this material is directly related to the fuel sulfur content.

The use of B100 decreases the solid carbon fraction of particulate matter (since the oxygen in B100 enables more complete combustion to CO₂), eliminates the sulfate fraction (as there is no sulfur in the fuel), while the soluble, or hydrocarbon, fraction stays the same or is increased. Therefore, B100 works well with new technologies such as catalysts (which reduces the soluble fraction of diesel particulate but not the solid carbon fraction), particulate traps, and exhaust gas recirculation (potentially longer engine life due to less carbon).

Health Effects
Evidence does exist which indicates that diesel particulate matter is a potential carcinogen. In 1988, the US National Institute for Occupational Safety and Health (NIOSH) recommended that whole diesel exhaust be regarded as "a potential occupational carcinogen", as defined in the Cancer Policy of the Occupational Safety and Health Administration. The use of B100 does result in decreases in most regulated emissions. Relative to health effects, research results indicate that particulate matter, specifically the carbon or insoluble fraction, is significantly reduced. In addition to reducing the overall levels of pollutants and carbon, the compounds that are prevalent in B100 and diesel fuel exhaust are different. Preliminary research on the speciation of diesel and B100 particulate indicates that B100 exhaust has less harmful impacts on human health than petrodiesel.

The United States Bureau of Mines (USBOM) has completed Ames mutagenicity testing of the diesel particulate matter (DPM) and exhaust gases from engines fueled with B100 to better understand how the use of B100 may impact the health of miners. Samples were taken from the exhaust of a Caterpillar 3304 PCNA equipped with an exhaust catalyst. Test results documented that the use of B100 reduced the Ames mutagenicity of DPM by 50% over conventional diesel fuel. In addition, the gas phase mutagenicity of B100 was negligible. USBOM researchers believed the strong reduction in mutagenicity may be due to the lack of aromatics or polycyclic aromatic hydrocarbons (PAH's) in the B100 fuel and, subsequently, in the exhaust gases. Tests from Europe confirm the reduction in DPM PAH using B100 blends as outlined below:

Table 4. Gaseous PAH levels of diesel fuel and a 50% B100 blend.

Lubricity
With the low-sulfur, low aromatic diesel fuel emerging on the market, fleet operators began to encounter premature wear and/or failure of injector pumps in increasing numbers.

Stanadyne Diesel Systems on October 15, 1993 and Bosch Diesel Fuel Injection Service on December 3, 1993 issued Service Letters to distributors and dealers concerning the lack of lubricity caused by hydroprocessing to reduce the sulfur content in the new low-sulfur diesel. The pump manufacturers recommended use of lubricity additives to alleviate the serious damage occurring to their injection pumps.

Testing at labs such as Southwest Research Institute, Stanadyne Automotive, and Engineering Testing Services has demonstrated that B100 shows significant lubricity improvement compared to diesel fuel. Two methods of analysis were utilized; the "Scuffing Load Ball On Cylinder Lubricity Evaluator" and the high frequency rotating rig (HFRR).

Table 5. Lubricity Results of B100 and Petroleum Diesel Using High Frequency Reciprocating Rig*

Table 6. Lubricity Results using Scuffing Load Ball on Cylinder Lubricity Evaluation, (SLBOCLE)*

Flash Point and Sulfur Content
The flash point of a fuel is defined as the temperature to which the fuel must be heated to produce a mixture that will ignite when exposed to a spark or flame. If the flash point of a fuel is too low, the fuel is considered a fire hazard which is prone to flashing, possible ignition, and even explosion. The flash point of B100 has been tested and reported by various sources. Specific testing at Southwest Research Institute concluded that the flash point of B100 blends increases as the percentage of B100 increases. Therefore pure B100 or blends of B100 with petroleum diesel is safer to store, handle, and use than conventional diesel fuel. In addition, pure B100 is essentially sulfur free and results in a total reduction of SO₂ emissions as well sulfate aerosols in particulate matter. These reductions should assist in increasing both vehicle and catalyst life over time.

Neat B100 has a flash point over 148°C, well above the flash point of conventional diesel fuel. Detailed below are the results from research for the flash point of B100 and B100 blends:

Table 7.

The diesel fuel, B25, and B50 were testing using the ASTM D93 Pensky-Martens closed cup method. The B100 blend containing 75% and 100% B100 did not flash using D93, therefore ASTM D92, the Cleveland open cup method, was used. The flash point of B100 blends increase and the percentage of B100 added increases. Other tests have confirmed this data and suggest that most of the flash point benefits occur at blends levels of 85% and greater.