FREQUENTLY ASKED QUESTIONS
What is Biodiesel?
Biodiesel is a clean-burning, renewable fuel made from vegetable oils, animal fats and recycled cooking oil and greases. Vegetable oils such as rapeseed, canola, soybean and palm oil are the most common raw material for commercial-scale biodiesel production. Biodiesel has physical and chemical properties similar to conventional petroleum-based diesel. The specification for biodiesel fuel is ASTM D6751.

The manufacturing process for biodiesel converts oils and fats into fatty acid methyl esters, which is commonly referred to as biodiesel. Biodiesel is produced by chemically reacting non-petroleum oils or fats with a methanol or other short chain alcohol in the presence of a catalyst such as potassium hydroxide or sodium methlyate. This chemical reaction is known as transesterification.

What is the ASTM D6751 specification for biodiesel?
B100 biodiesel fuel quality is governed by the ASTM D6751 specification. ASTM is a standards group comprised of engine and fuel injection equipment manufacturers, fuel producers, and fuel users whose standards are recognized in the U.S. by governmental entities, including state agencies responsible for ensuring fuel quality. The ASTM specification for biodiesel lists 18 parameters that all biodiesel fuels must meet in order to be legally sold in the United States. Learn more about Biodiesel Specifications.

Does biodiesel have any materials compatibility issues?
B100 Biodiesel is not compatible with certain hoses and gaskets because it can degrade certain types of rubber compounds, causing leaks or total inoperability. Likewise, B100 may over time permeate some types of plastics such as polyethylene or polypropylene. Older vehicles manufactured before 1993 are more likely to contain seals, gaskets, etc. that will be affected by B100 over long periods of time. B100 is also not compatible with some metals (i.e. brass, bronze, galvanized metal surfaces), which can result in the formation of high levels of sediment. B20 or lower biodiesel blends minimize most issues associated with material compatibility. According to the U.S. Department of Energy, "Experience over the last 10 years with B20 indicates compatibility with all existing elastomers in diesel fuel systems, even those that are sensitive to higher blends [of biodiesel] such as nitrile rubber." Learn more about Biodiesel Usage Guidelines in our Introduction to Biodiesel.

How should biodiesel be stored?
Biodiesel is best stored in tanks that do not have any residual water, sediments or other contaminants. Heat and sunlight can accelerate oxidation; therefore storage in clear totes is not advisable. The National Biodiesel Board recommends that B20 blends be used within six months, which is comparable to current practices recommended for conventional diesel. When storing biodiesel for longer periods, the use of nitrogen blankets and anti-oxidants and/or stability additives is suggested. Learn more about Biodiesel Usage Guidelines in our Introduction to Biodiesel.

What can be done to avoid cold weather performance problems with biodiesel?
Similar to conventional diesel, biodiesel fuels can also have cold weather performance limitations, but these limitations are more severe when using a pure biodiesel B100 fuel. The potential for cold flow problems in biodiesel fuels can be moderated by dilution via blending with conventional diesel, which also makes the use of cold flow additives practical. Thus, a B5 or B20 fuel will generally have very few cold flow issues beyond that normally experienced with conventional diesel fuel. When using B20 in below freezing temperatures, cold flow performance can be managed by i) using cold-flow additives, ii) ensuring that the conventional diesel used in the blend is a ‘winter diesel’ that has a sufficiently low cloud point, i.e. some winter diesel blends achieve very low cloud points by including No. 1 diesel. Learn more about Biodiesel Usage Guidelines in our Introduction to Biodiesel.

How are engine manufacturer’s warranties impacted by biodiesel use?
Using biodiesel fuel only impacts the warranty as it relates to fuel related problems directly attributed to biodiesel. According to the U.S. Department of Energy, "Federal law prohibits, the voiding of a warranty just because biodiesel was used – it has to be the cause of the failure." Most OEM dealers and customer service departments currently tell their customers that 5% biodiesel blends (B5) are acceptable, with the requirement that the pure biodiesel used in the fuel blend adheres to ASTM D6751. Some OEMs' warranties now cover the use of biodiesel blends up to B20 for certain engine models. For an updated list of OEMs and their position on warranty coverage for biodiesel usage, visit the National Biodiesel website at: http://nbb.org/resources/fuelfactsheets/standards_and_warranties.shtm.

What is Biomass Gasification?
Biomass such as firewood and agriculture-generated residues and wastes are generally organic. They contain carbon, hydrogen, and oxygen along with some moisture (in the case of animal wastes, moisture content can be very high). Under controlled conditions, characterized by low oxygen supply and high temperatures, most biomass materials can be converted into a gaseous fuel known as producer gas, which consists of carbon monoxide, hydrogen, carbon dioxide, methane and nitrogen. This thermo-chemical conversion of solid biomass into gaseous fuel is called biomass gasification.

Most of the inorganic constituents in the feedstock are chemically altered and either discharged as bottom ash, char, or entrained with the raw product gas as fly-ash. Depending on the type of biomass used, volatile and condensable organic and inorganic compounds may also be produced during gasification. The raw bio-gas, if not combusted immediately, can be cooled, filtered, and scrubbed to remove condensables and any carry-over particles. The raw bio-gas can also be processed to remove undesired components such as CO2 and H2S. When biomass is gasified with steam and/or oxygen a "synthesis gas," rich in CO and H2, is produced which can be catalytically converted to produce high-value fuels and chemicals².



What is Anaerobic Digestion?
Anaerobic digestion is a biological process that produces a gas principally composed of methane (CH4) and carbon dioxide (CO2) otherwise known as bio-gas. These gases are produced from organic wastes such as livestock manure, food processing waste, etc.

Anaerobic processes could either occur naturally or in a controlled environment such as a biogas plant. Organic waste such as livestock manure and various types of bacteria are put in an airtight container called a digester so that the process can occur. Depending on the waste feedstock and the system design, bio-gas is typically 55 to 75 percent pure methane. State-of-the-art systems report producing bio-gas that is more than 95 percent pure methane.


What is an Anaerobic Digester?
An Anaerobic Digester is a device for optimizing the anaerobic digestion of biomass and/or animal manure, and possibly to recover bio-gas for energy production. Digester types include batch, complete mix, continuous flow (horizontal or plug-flow, multiple-tank, and vertical tank), and covered lagoon.