what is the difference between diesel and biodiesel

what is the difference between diesel and biodiesel


Biodiesel is a liquid gasoline that’s created by chemically processing vegetable oil and altering its properties to make it carry out extra like petroleum diesel gasoline. It was first evaluated significantly within the late Nineteen Seventies however was not broadly adopted at the moment.

The subject of biodiesel gasoline has been receiving a substantial amount of curiosity not too long ago, and each large- and small-scale producers have began manufacturing at places all through the state. Nonetheless, many individuals are nonetheless unsure about whether or not biodiesel is a dependable, protected gasoline to make use of for diesel engines.

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This truth sheet explains the main variations between biodiesel and petroleum diesel (additionally known as petrodiesel), together with details about biodiesel components and blends. The companion truth sheet on this sequence Utilizing Biodiesel Gasoline in Your Engine explains the efficiency you’ll be able to anticipate when operating an engine on biodiesel.

Properties of Biodiesel Versus Petroleum Diesel

The sizes of the molecules in biodiesel and petroleum diesel are about the identical, however they differ in chemical construction. Biodiesel molecules consist nearly completely of chemical substances known as fatty acid methyl esters (FAME), which comprise unsaturated “olefin” elements. Low-sulfur petroleum diesel, however, consists of about 95 % saturated hydrocarbons and 5 % fragrant compounds.¹

¹If the biodiesel is made utilizing ethanol slightly than methanol, the ensuing molecules are”fatty acid ethyl esters”(FAEE).

The variations in chemical composition and construction between petroleum diesel and biodiesel lead to a number of notable variations within the bodily properties of the 2 fuels. The seven most vital variations are as follows:

  1. Biodiesel has larger lubricity (it’s extra “slippery”) than petroleum diesel. It is a good factor, as it may be anticipated to scale back engine put on.
  2. Biodiesel incorporates virtually no sulfur. That is additionally factor, as it may be anticipated to lead to lowered air pollution from engines utilizing biodiesel.
  3. Biodiesel has a better oxygen content material (normally 10 to 12 %) than petroleum diesel. This could lead to decrease air pollution emissions. However, relative to petroleum diesel, it causes barely lowered peak engine energy (~4 %).
  4. Biodiesel tends to thicken and “gel up” at low temperatures extra readily than petroleum diesel. Some forms of oil are extra of an issue than others. It is a concern, particularly for the chilly winters which can be typical to Pennsylvania.
  5. Biodiesel is extra more likely to oxidize (react with oxygen) to type a semisolid gel-like mass. It is a concern, particularly for prolonged gasoline storage and when utilizing engines which can be solely operated sometimes (resembling standby energy mills). technique for storage is to make use of a dry, semi-sealed, cool, light-tight container.
  6. Biodiesel is extra chemically lively as a solvent than petroleum diesel. Because of this, it may be extra aggressive to some supplies which can be usually thought of protected for diesel gasoline.
  7. Biodiesel is far much less poisonous than petroleum diesel. This could be a actual profit for spill cleanups.

The standard of petroleum diesel gasoline tends to be extra uniform and dependable, particularly when in comparison with small-scale manufacturing of biodiesel the place high quality management might or might not have been good. Petroleum diesel can range in high quality from plant to plant or from area to area, however the variations are sometimes a lot smaller. Poor-quality biodiesel gasoline can result in many issues in engine efficiency, and care ought to be taken to make sure that your gasoline is of fine high quality (see the Renewable and Different Vitality Reality Sheet: Utilizing Biodiesel Gasoline in Your Engine). Biodiesel that conforms to ASTM normal D6751 ought to be of a constant, prime quality.

In all equity, we must always point out that petroleum diesel has additionally demonstrated issues with oxidative stability and low-temperature efficiency, though biodiesel, at current, appears to be extra inclined.

Does the Kind of Vegetable Oil Used Matter?

A typical query relating to biodiesel that comes up is “which oil crop leads to the most effective biodiesel?” There are particular variations from crop to crop, nevertheless it’s not a simple matter to decide on a “finest” one, particularly when the price of rising or shopping for oil can range fairly a bit from crop to crop as properly.

Totally different vegetable oils have larger or decrease concentrations of various chemical elements (fatty acids, for essentially the most half), which impacts their efficiency when they’re made into biodiesel. As well as, the chemical construction of the alcohol that’s reacted with the oil to create biodiesel also can have an effect on the properties of the gasoline. Typically, the chemical properties that matter essentially the most are the size of the biodiesel molecule, the quantity of “branching” within the chain, and the diploma of “saturation” of the molecule.

As proven in Desk 1, these properties have each optimistic and destructive results on biodiesel, so it’s not actually attainable to decide on a “good” oil for biodiesel. As if this wasn’t difficult sufficient, we have to additionally keep in mind that cold-starting properties could be important throughout winter in chilly climates however unimportant in summertime or in heat elements of the world. On high of all that, it’s attainable to purchase components that enhance among the less-than-ideal properties of biodiesel.

Desk 1. Common comparability of various oil chemical properties associated to their use as newurbanhabitat.comertyPositive effectsNegative effectsLength of moleculeIncreases the cetane quantity, warmth of combustion; decreases NOx emissionsIncreases viscosityAmount of branchingDecreases the gel pointDecreases the cetane numberSaturationDecreases NOx emissions, improves oxidative stability, reduces depositionIncreases melting level and viscosity; reduces lubricity*

*Technically, the discount in lubricity is because of the elimination of polar compounds containing sulfur which can be pure components by hydrogenation and the formation of saturated compounds.

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Typically, longer molecules with extra branching are helpful to the efficiency of biodiesel however are seldom current in FAME. Excessive unsaturation (excessive iodine quantity) results in poor oxidative stability and is undesirable in bio- diesel. Of the various forms of fatty acid present in vegetable oils, oleic acid might be finest, whereas linoleic is much less fascinating and linolenic acid is most undesirable.

With all this in thoughts, it seems that canola oil, with its excessive proportion of lengthy, unsaturated fat (a lot of oleic acid), could also be barely higher for biodiesel gasoline high quality than among the different oilseed crops, though this has not been conclusively confirmed with cautious testing. Tropical oils resembling palm oil, with their excessive proportion of saturated fat, are inclined to have vital issues with cold-weather efficiency, as they have an inclination to solidify extra readily than many different oils.

Making Biodiesel Higher with Components

A few of the properties of biodiesel gasoline should not best from an engine efficiency perspective. Fortunately, components can be utilized to counteract these issues and enhance the general high quality of the gasoline.

  • Chilly-flow improvers: these components enhance the cold-weather efficiency of biodiesel by limiting its capacity to gel. They have a tendency to solely enhance the working vary by about 5 levels.
  • Gasoline stabilizers: these components act as “antioxidants” to scale back the opportunity of oxidation degradation of the gasoline.
  • Antimicrobial components: it’s attainable for microbes to develop in biodiesel, leading to clogged traces and fouled gear. Antimicrobial components stop this by killing off any present microbes and stopping them from returning.
  • Detergent components: these assist cut back the formation of deposits on engine elements by forming a protecting layer on the elements and dissolving present deposits from the surfaces throughout the engine.
  • Corrosion inhibitors: these additionally defend the engine by forming a protecting layer on the elements, thus stopping corrosive chemical substances from reaching the floor.

A big selection of components is accessible available on the market at this time, and they are often bought at an automotive store or on the Web. Usually, a single product will be bought that mixes many or all the above components. The precise composition of those components is normally a carefully guarded commerce secret, and never all components carry out the identical. Customers ought to maintain monitor of how properly a particular additive is working for them and take care to comply with the producer’s suggestions for the focus and correct use of the additive. Understand that there are various “snake oil” salesmen out there at this time. Solely cope with respected firms and suppliers which can be authorized by your engine’s producer.

What About Blends?

Biodiesel gasoline blends very simply with petroleum diesel. These blends are described by their share of biodiesel (e.g., “B20” has 20 % biodiesel, 80 % petroleum diesel). Typically, the properties of a mix will lie someplace between the properties of the biodiesel and the petroleum diesel. Blends are typically used to enhance the lubricity of petroleum diesel or cut back its sulfur content material.

In all probability essentially the most helpful cause for a biodiesel producer to mix could be to enhance cold-operating traits through the winter. A mixture of 70 % biodiesel and 30 % petroleum diesel has been reported to be efficient for delicate winter situations. Kerosene, often known as #1 diesel gasoline, is mixed with normal (#2) petroleum diesel throughout winter months (normally ~40 % kerosene, 60 % #2 diesel) to enhance its cold-weather efficiency. This strategy might be the simplest method to make biodiesel usable throughout harsh midwinter situations in Pennsylvania. Nonetheless, remember that solely low-sulfur kerosene that’s authorized as an engine gasoline ought to be used.


Biodiesel and petroleum diesel are very comparable fuels, however they aren’t an identical. Nonetheless, the variations are remarkably small after we take into account the radically totally different process for making biodiesel as in comparison with petroleum diesel. Many components can be found that may modify the properties of biodiesel gasoline, and biodiesel will be simply blended with petroleum diesel gasoline if desired.

What's So Different about Biodiesel Fuel?

For added data, please confer with the next Penn State Extension truth sheets and experiences:

  • Biodiesel: A Renewable, Home Vitality Useful resource
  • Renewable and Different Vitality Reality Sheet: Utilizing Biodiesel Gasoline in your Engine
  • Making Your Personal Biodiesel: Temporary Procedures and Security Precautions
  • Biodiesel Security and Finest Administration Practices for Small-Scale Noncommercial Manufacturing


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Penn State Biomass Vitality Heart

Ready by Daniel Ciolkosz, extension affiliate, Penn State Biomass Vitality Heart and Division of Agricultural and Organic Engineering

Reviewed by Joseph Perez, Division of Chemical Engineering, Dennis Buffington, Division Agricultural and Organic Engineering, and Glen Cauffman, Penn State Farm Companies

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