Free & Total Glycerin (processing specification):

Perhaps the most important quality test for biodiesel is the measure of glycerin content. The key reaction in biodiesel production, transesterification, involves converting oils and fats to fatty acid methyl esters (FAME). Glycerin is the major byproduct and is higher in density and more polar than the FAME. Glycerin may be present in free form or bonded (mono, di and triglycerides). Measurement of both is necessary to determine how the conversion reaction proceeded. For producers, high glycerin content indicates the reaction has not proceeded to completion or the catalyst concentration is low. For distributors and end-users high glycerin may separate out in storage, plugging pumps and filters. It can also contribute to dirty injectors or the formation of deposits on nozzles, pistons, and valves causing poor combustion conditions. ASTM D6751 Requirement: a maximum for free glycerin of 0.020% by mass and a maximum for total glycerin of 0.240% by mass.

Kinematic Viscosity (processing specification):

Kinematic viscosity is the resistance of a fluid to flow under gravity. The viscosity is important in determining optimum handling, storage, and operational conditions. Fuels must have suitable flow characteristics to ensure that an adequate supply reaches injectors, at different operating temperatures. For producers and blenders, the kinematic viscosity verifies that the transesterification reaction is adequate; high viscosity may require producers to reprocess the batch. For distributors and end-users high viscosity can cause fuel flow problems and lead to stall out or fuel pump failure. ASTM D6751 Requirement: viscosity value from 1.9 to 6.0 mm²/s (cSt). Visual Appearance (quality specification): This standardized test supports specifications that fuel is clear and bright and free of visible particulate matter. Biodiesel fuels with these physical qualities will increase the confidence of distributors and endusers. No ASTM requirement, yet this is a BQ9000 expectation for each production lot.

Description Test Method	Test Method	Volume Required	Price
Cetane Index (calculated): Indicates ignition quality of fuel. (Also requires API gravity and Simulated Distillation)	ASTM D975	5mL	$20.00
Cloud Point: Indicates the point at which hydrocarbon clusters appear upon cooling under prescribed conditions.	ASTM D2500	100mL	$25.00
Ethanol: Indicates ethanol content of a sample. (Also requires Karl Fischer determination).	ASTM D5501	20mL	$125.00
Flash Point (Pensky-Martens Closed Cup): Measures the lowest temperature at which a specimen will ignite under specified conditions.	ASTM D93	300mL	$35.00
Free and Total Glycerin: Measures mono-, di-, and tri-glycerides as well as free glycerin.	ASTM D6584	5mL	$125.00
Free Fatty Acids by Titration: Determines the mass percent of free fatty acids in crude vegetable oils.	AOCS Ca 5d-01	50mL	$25.00
Karl Fischer Moisture Determination: Measures the amount of water in a sample.	ASTM D6304	5mL	$20.00
Methanol: Determination by gas chromatography of the methanol content of a sample.	EN 14110	20mL	$120.00
Pour Point: Measures the lowest temperature at which movement of the sample is observed under prescribed conditions.	ASTM D97	100mL	$20.00
Simulated Distillation: Determines the composition of feedstocks and products related to the production of fuels	ASTM D2887	5mL	$200.00
Soap and Catalyst by Titration: Determines the concentration of soap and catalyst in a biodiesel sample.	AOCS Cc 17-95	50mL	$25.00
Total Acid Number: Determines the content of acidic constituents in a sample of fuel.	ASTM D664	50mL	$25.00
Viscosity, Kinematic at 40ºC: Measures the resistance to flow of a fluid sample under gravity.	ASTM D445	50mL	$20.00
Visual Appearance: Provides an estimate of the presence of suspended free water and solid particulate indistillate fuels.	ASTM D4176	1L	$15.00
Water and Sediment: Determines the volume of free water and sediment in a fuel sample.	ASTM D2709	200mL	$20.00

 

Water & Sediment (quality specification):

Though water is always present in fuel, it is important to control its content. The water and sediment test relies on a centrifuge to vigorously separate out free water and any trace sediment present in the fuel. Water can be detected visually if gross contamination is present (cloudy appearance). For producers and blenders, excessive water may indicate the water wash/removal process is not performed correctly. For distributors and end-users, improper storage may be the reason for elevated water and sediment percentages, and poor ignition, filter clogging, and fuel pump problems can result. Sediment in storage tanks can obstruct the flow of fuel from the tank to a combustor. Water in middle distillate fuels can cause corrosion and growth of microorganisms. ASTM D6751 Requirement: a maximum for water and sediment of 0.050% by volume.

Total Acid Number (quality specification):

The acid number is a sum parameter for all acidic components to indicate the level of free fatty acids (FFA) present in biodiesel, as well as the presence of process acids and degradation by-products. The acid number correlates to the fuel’s long-term stability and corrosiveness; the smaller the value, the higher the quality. Regulators require non-aqueous potentiometric acidbase titration for determining the acid number. For producers and blenders, a high acid value for feedstock indicates unrefined or poorly refined product. Typical problems associated with a high acid number include poor process control, such as methanol carryover, when converting the oils and fats to fatty acid methyl ester (FAME) fuel. For distributors and end-users, a high acid number fuel can have a strong solvency effect on rubber seals and hoses in the engine, thereby causing premature failure. It may also leave deposits, which can clog the fuel filter or drop fuel pressure. ASTM D6751 Requirement: a maximum total acid number of 0.50 mg KOH/g.

Methanol Concentration (processing specification):

Methanol is a primary raw material reactant used in the production of biodiesel. Methanol content of biodiesel fuel is an important factor in determining the tendency of the fuel to exhibit flammable characteristics. Additionally, a key quality factor for the alcohol reactant material is water content; methanol is hygroscopic to some degree. Water affects the extent and rate of the esterification reaction. Producers will value methanol purity tests to assure that water content is negligible at the start of production. Additionally, excess alcohol used during the production reaction can be recovered to minimize operating costs and environmental impacts. Evaluating the purity of recovered methanol enables the determination of reuse suitability. Lastly, the evaluation of methanol in a glycerin byproduct enables producers to market this fuel byproduct as a commodity rather than manage it is a waste. ASTM D6751 Requirement: maximum methanol content of 0.2% by mass in biodiesel product.

Simulated Distillation (property specification):

The distillation test is used to determine the boiling range characteristics of a hydrocarbon sample. The boiling point range has an important effect on the performance, storage, and safety of the fuel. Biodiesel is fundamentally different than petroleum-based diesel, and it is especially evident with distillation. Biodiesel has a fairly homogenous consistency of straight chain hydrocarbons, all with 16 to 18 carbons. Consequently it exhibits a boiling point rather than a distillation curve. For producers, high distillation values may indicate the conversion reaction has not gone to completion (flash point may also be high); low values indicate methanol carryover. For users, high distillation values lead to poor starting, especially in cold weather; low values can lead to poor timing and seal material failure. ASTM D6751 Requirement: 90% distilled at a maximum temperature of 360˚C.

Flash Point (processing specification):

The lowest temperature at which the vapor of a combustible liquid can be made to ignite momentarily in air is identified as the flash point and correlates to the ignitability of the fuel. For producers and blenders a low flash point can indicate residual methanol remaining from the conversion process. A high flash point can mean the reaction has not proceeded to completion. For distributors and end-users, a low flashpoint in biodiesel can result in premature ignition, causing irregular timing, excessive fuel blow by into the crankcase oil, and excessive emissions. A high flash point can lead to poor ignition, resulting in inconsistent firing, and variable engine performance. It can also indicate potential clogging of fuel lines, filters and injector clogging in cold climates. ASTM D6751 Requirement: minimum 93°C.