Biodiesel is an alternative renewable fuel produced by chemical processing of vegetable oil or animal fats and changing its properties to make it suitable for diesel engines.
In recent years, biodiesel has gained a lot of interest owing to the high price of conventional fuels, environmental concerns, and diminishing oil reserves.
Out of the several cited reasons, biodiesel is preferred as it is a clean fuel, and its combustion yields a reduced amount of particulate matter and exhaust emissions.
The world’s biodiesel supply is expected to reach 41.4 billion liters in 2025, which was 3.9 billion liters in 2005.
India launched it’s National Biofuel Policy (NBP) way back in 2008 and achieved a production capacity of 660 million liters of biodiesel per year in 2019.
Although biodiesel’s stored energy content is equivalent to petroleum diesel, there are many differences in their physical & chemical properties and emissions rates.
This article will discuss the significant differences between biodiesel and diesel and see whether these two kinds of fuel compete with each other or complement each other.
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Biodiesel vs Diesel | Comparison & Differences
Owing to the differences in the chemical composition & structure of regular diesel and biodiesel, there are several notable variations in the two fuels’ physical properties.
The most significant differences are as follows:
1. Raw Materials & Manufacturing Process
Vegetable oils or animal fats are the primary raw materials for Biodiesel production through the transesterification process.
Fractional distillation of Crude oil at a temperature of 2000C – 3500C at atmospheric pressure produces petroleum diesel or regular diesel.
We get biodiesel from renewable sources that require less fossil energy (only 0.31 units) to make one unit of fuel.
2. Fuel Composition
Fatty acid methyl esters (FAME), is the main active ingredient in biodiesel whereas regular diesel fuel comprises pure hydrocarbons.
Biodiesel molecules contain unsaturated “olefin” components whereas petroleum diesel consists of approximately 95% saturated hydrocarbons and 5% aromatic compounds.
3. Fuel Lubricity
Biodiesel has higher lubricity than petroleum diesel due to the presence of Oxygen in ester molecules.
High lubricity is desirable as it reduces the failure of engine parts and lessens wear & tear.
Recent Ultra-low Sulphur diesel (ULSD) fuels demand removing the inherent sulfur-containing substances from petrodiesel by the hydrodesulfurization process.
This process yields ULSD with a lesser amount of Sulphur but also removes minor oxygen and nitrogen-containing compounds that are responsible for the lubricity of petrodiesel.
In this way, conventional diesel fuels possess poor lubricity but adding biodiesel at levels of 2% or above restores the lubricity of the former.
4. Environmental Concerns
The environmental impact of petroleum fuels such as diesel is well known but for biodiesel fuel, it depends on several factors such as raw material, production process, and final usage.
A work conducted by Knothe, Sharp, and Ryan. (2006) with a 2003 model year engine (14 L, six-cylinder, turbocharged, intercooled, exhaust gas recycling) showed that biodiesel fuel considerably reduces particulate matter emissions by 75%-83% as compared to the petroleum diesel base fuel.
Combustion of biodiesel and its blends produces the lowest GHG emissions so it can be considered as the best fuel for diesel engines.
Furthermore, biodiesel in blends reduces other emissions such as smoke, Odor, particulate matter, and Sulphur that are present in regular diesel fuel.
However, biodiesel can cause increased NOx emissions as compared to petrodiesel, but with new exhaust emissions control technologies, it will reduce with time.
5. Cetane Number
The cetane number of diesel fuel is an indication of its ignition delay.
A higher cetane number means short ignition delay and the fuel takes less time to burn.
Diesel fuels having higher cetane ratings allow easier engine start-up, which leads to less wear and tear.
Biodiesel fuel offers a similar and sometimes higher cetane rating than regular petroleum diesel.
The average cetane number of regular diesel fuel is 48 whereas pure biodiesel is about 55, which is at par with premium and synthetic diesel.
A higher cetane rating diesel fuel will not benefit your vehicle much, but using fuel with a lower rating than the manufacturer’s recommendation could lead to severe engine damage over time.
6. Flash Point
Flashpoint is the lowest temperature at which a fuel vaporizes and causes ignition.
It is a measure of fuel safety that is important for transportation and storage.
The average value of flashpoint for biodiesel fuel is 150°C whereas petrodiesel ranges from 55°C to 66°C making biodiesel fuel safer to transport and store.
Regular diesel fuel has a low flashpoint, as they are composed of low molecular weight molecules
7. Low-Temperature applications
Operating various types of diesel fuels in low-temperature environments is a major concern where cloud point and pour of fuel is the main decisive factor.
The cloud point is the lowest temperature at which the liquid fuel started to crystallize whereas the pourpoint is the temperature below which a liquid fuel flow ceases.
These two factors are very important to consider while using a specific type of fuel as they cause many problems such as filter plugging.
It is desirable to have a considerable difference between the cloud and the pour point of various diesel fuels.
Petroleum diesel has a difference of around 20-degrees but biodiesel has a difference of only a few degrees.
The presence of higher amounts of long chains saturated fatty esters in biodiesel fuel cause cold flow problems.
Blending biodiesel with fossil diesel can reduce filter-plugging problems during cold weather.
8. Biodegradability
Biodegradability refers to the natural decay of organic materials by living organisms not posing any threat to the environment.
A report from DOI states that biodiesel fuel degrades 80.4% to 91.2% in 30 days whereas only 24.5% biodegradation occurs for regular diesel.
Biodiesel fuel decomposes more readily when exposed to relevant environmental conditions due to the presence of fatty acid methyl ester components.
9. Energy Content & Fuel Consumption
Bio-diesel has lower energy content (2-8% less) than regular diesel.
It has about 12% less heating value than petro-diesel fuel causing a power loss.
Increasing the fuel amount during the injection process compensates for this power loss thus fuel consumption is more.
10. Economics of Byproducts
Glycerol is a byproduct obtained during bio-diesel production that requires no further processing except purification.
Increased biodiesel production leads to a surplus supply of glycerol in the markets that negatively affect the economics of existing glycerol plants.
Currently, glycerol found its use in many industries such as personal care products (soaps, cosmetics, hair care, and toothpaste), pharmaceuticals, sweeteners, etc.
In order to compensate for additional glycerol due to increased biodiesel production new applications to be explored.
Markets are already set for crude byproducts and petro-diesel production causes little or no impact.
Conclusion
In The Battle of biodiesel vs diesel, there are many advantages & disadvantages in terms of fuel properties, energy content, and environmental issues.
Bio-diesel and its blends are becoming an inexpensive option as compared to regular diesel due to the swelling prices of petroleum-based products.
There are certain limitations using bio-diesel fuel but with upcoming advanced technologies they will diminish in future
Considering energy efficiency, price, and environmental impact what are your thoughts on the ideal fuel for our future.
Please let us know your opinion in the comments.
References
- Demirbaş (2008) Biodegradability of Biodiesel and Petrodiesel Fuels, Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 31:2, 169-174, DOI: 10.1080/15567030701521809
- Demshemino, Innocent & Sylvester, Donnell & Yahaya, Muhammad & Isiomanwadike, Linus & Okoro, Linus. (2013). COMPARATIVE ANALYSIS OF BIODIESEL AND PETROLEUM DIESEL. 1.
- Knothe, Gerhard. (2010). Biodiesel and renewable diesel: A comparison. Progress in Energy and Combustion Science. 36. 364-373. 10.1016/j.pecs.2009.11.004.
- A Comparative Analysis of Biodiesel and Diesel Emissions, WORCESTER POLYTECHNIC INSTITUTE, by Joshua Wayne Curto, Matthew David Giambrone, Alexander Scott MacGrogan & George Hutchinson Williamson IV
- Knothe G, Sharp CA, Ryan III TW. Exhaust emissions of biodiesel, petrodiesel, neat methyl esters, and alkanes in a new technology engine. Energy Fuels 2006;20:403–8
Biofuel is trending concern & the need of an hour. We are fortunate to have it as an alternative for fossil fuels. Lets be more mindful towards environment & our choices for future. Aris Bioenergy is one of the company that aids biofuel infrastructure. More companies are entering into the sector to build sustainable sources of fuel. Biofuel causes lesser emissions still needs to be treated properly.
Ford says use only B20 ultra low sulphur fuel, which is getting difficult to find. Diesel #2 is still everywhere when on the road. California is pushing renewable diesel everywhere. So I have the 6.7 diesel and I love it!
Lubricity seems to be the most important issue. We need to protect the fuel pump. So renewables, biofuels, diesel #2 with additives? It’s all confusing! Any information today has to be questioned. Political bents every where.