Is Biodiesel Really Cleaner than Diesel?

By Abdul Ahad NazakatReviewed by Laura ThomsonApr 30 2025

Traditional petroleum diesel is a significant source of global greenhouse gas emissions. As climate change remains a growing concern, biodiesel is frequently presented as a potential alternative. This article takes a closer look at the environmental impacts of both fuels to evaluate whether biodiesel offers a cleaner solution. It examines key factors such as emissions, resource use, and production methods to better understand the benefits and limitations of biodiesel as an alternative fuel.

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Production Fundamentals of Diesel and Biodiesel

Diesel

Conventional diesel is a petroleum-based fuel produced through the fractional distillation of crude oil. This process involves heating the crude oil to separate its hydrocarbon components according to their boiling points.

Diesel typically contains hydrocarbons with 8 to 21 carbon atoms per molecule and is refined to meet specific standards for combustion and emissions. Despite its widespread use, diesel relies entirely on non-renewable fossil resources, contributing to resource depletion and environmental harm.

Biodiesel

In contrast, biodiesel is a renewable fuel made from feedstocks such as vegetable oils, animal fats, and used cooking grease. The most common production method is transesterification, where oils or fats react with an alcohol, typically methanol, in the presence of a catalyst to produce fatty acid methyl esters (FAME), the primary components of biodiesel, along with glycerin as a byproduct.¹

Other production approaches include pyrolysis (the thermal breakdown of biomass), microemulsion (which stabilizes oil-alcohol mixtures using surfactants), and enzymatic transesterification, which employs environmentally friendly enzymes as catalysts.

Emissions Comparison of Diesel vs. Biodiesel

Due to its chemical properties, diesel combustion tends to produce higher emissions levels, particularly soot and organic carbon. Biodiesel, on the other hand, offers a notable reduction in particulate matter (PM) emissions. For instance, third-generation biodiesels derived from microalgae have been shown to reduce PM emissions by approximately 15.82% to 27.09% compared to conventional petroleum diesel.²

Biodiesel leads to lower carbon monoxide (CO) emissions due to more complete combustion. Biodiesel blends also emit fewer hydrocarbons (HC) and contain almost no sulfur, eliminating sulfur dioxide (SO₂) emissions.³

Nitrogen oxide (NOₓ) emissions, once a major concern for biodiesel, are now better managed. A 2023 study reported NOₓ reductions with optimized blends. Waste fry oil biodiesel has also shown improved NOₓ and CO emissions. Algae-based biodiesels have shown 11.03–15.55% NOₓ reductions, indicating that emissions depend significantly on feedstock and processing.^2,4,5

Life Cycle Analysis of Biodiesel and Diesel

A life cycle analysis (LCA) evaluates emissions from resource extraction to fuel combustion. Diesel’s life cycle includes high greenhouse gas emissions from fossil fuel extraction and refining.

In contrast, biodiesel, particularly when derived from waste cooking oil (WCO), offers emission reductions and promotes waste recycling to support a circular economy.⁶

Studies indicate that biodiesel from mixed vegetable oil waste has a global warming potential of only 1.36 × 10⁻⁴ kg CO₂ equivalent per ton, far lower than petroleum diesel.

Microalgae biodiesel also performs well, particularly with low-energy production methods. Combining microalgae and WCO improves environmental outcomes. Heterogeneous catalysts also enhance efficiency and reduce emissions.^6,7,8,9

Carbon Neutrality

Diesel emits ancient, geologically stored carbon, while biodiesel feedstocks absorb atmospheric CO₂ during growth. Microalgae can sequester CO₂, reducing net emissions. Combined algae systems have reduced carbon emissions by 21.16–24.08%.¹⁰

However, complete carbon neutrality is complex. Waste- and algae-based biodiesels approach it, but crop-based options involve emissions from fertilizer use, land-use change, and processing. Net carbon savings depend heavily on the feedstock and production system.

Resource Competition

Diesel relies on finite fossil reserves. Crop-based biodiesel can raise concerns over food security and land use. In contrast, microalgae offer non-food, high-yield alternatives.^{2, 7}

WCO conversion into biodiesel diverts waste from landfills and reduces demand for virgin oils. While crop cultivation and refining require water, algae-based wastewater methods minimize freshwater use and enhance resource efficiency.¹¹

Technological Advances in Biodiesel

Conventional diesel technology is highly developed, with most recent innovations centered around improving emissions control rather than altering the core fuel itself. In contrast, biodiesel research is rapidly evolving. For example, 30% microalgae biodiesel blends have improved brake thermal efficiency and reduced emissions. Optimized blends combining microalgae and WCO have yielded superior fuel quality.^3,8

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Technologies such as hydrotreated vegetable oil (HVO), enzymatic methods, and heterogeneous catalysts are advancing biodiesel’s sustainability.

Companies like Neste (Finland) and researchers at institutions such as the University of São Paulo are making progress in commercializing adaptable biodiesel technologies.^9,12

Engine Performance Comparison

Recent studies suggest that biodiesel’s performance gap with diesel is closing. Microalgae-based biodiesels have shown favorable results in energy and sustainability metrics. Blends of HVO, used cooking oil, and diesel have improved performance and emissions in compression ignition engines.^2,12

Although diesel still performs better in energy density and cold weather, biodiesel blends work increasingly well with existing engines. Advances continue to address durability and temperature-related concerns.

Is Biodiesel Truly a Cleaner Alternative?

Biodiesel contributes to lower emissions of particulate matter (PM), carbon monoxide (CO), and sulfur dioxide (SO₂). Under certain conditions, the correct blend ratios and feedstock selection can also reduce nitrogen oxides (NOₓ).

It generally has a lower life cycle carbon footprint and supports waste utilization. Biodiesel also helps reduce reliance on non-renewable fossil fuels and is becoming increasingly compatible with modern diesel engines. However, it does come with challenges. Some biodiesel blends can increase nitrogen oxide (NOₓ) emissions, and using edible crops as feedstock raises concerns about food security.

Certain feedstocks also require significant water resources and may contribute to land-use changes, potentially impacting ecosystems and agriculture.

High energy inputs in some methods can also offset environmental gains.

The Future of Biodiesel as Diesel Replacement

Whether biodiesel can fully replace conventional diesel goes beyond emissions—it also involves considerations of sustainability, technological maturity, and resource efficiency. Biodiesel lowers emissions and supports circular economy principles by repurposing waste materials and renewable resources.

However, challenges remain. Land use concerns, water demands, and variability in nitrogen oxide (NOₓ) emissions depending on feedstock and processing methods must be addressed. High-energy processes also require improvement.

Continued innovation is essential to improve the sustainability of biodiesel. Advancements in feedstock diversification, efficient cultivation practices, energy-efficient production methods, and better control of NOₓ emissions will play a key role in shaping biodiesel’s future as a cleaner fuel alternative.

References and Further Reading

1. Randive, A. B., Khadake, S. B., & Mallad, H. M. (2024). Biodiesel: A Renewable Source of Fuel. International Journal of Advanced Research in Science, Communication and Technology, 225–240. https://doi.org/10.48175/ijarsct-22836
2. Rajpoot, A. S., Choudhary, T., Chelladurai, H., Shukla, A. K., & Sinha, A. A. (2024). Comparative analysis of energy, exergy, emission, and sustainability aspects of third generation microalgae biodiesels in a diesel engine. Process Safety and Environmental Protection, 188, 1026-1036. https://doi.org/10.1016/j.psep.2024.05.142
3. Liu, J., Devi, P. B., Chinnathambi, A., & Alharbi, S. A. (2024). Mitigating fossil fuel deficiency and environmental impacts: performance analysis of Scenedesmus obliquus microalgae biodiesel in a diesel engine. Fuel, 364, 131033. https://doi.org/10.1016/j.fuel.2024.131033
4. Kheiralipour, K., Khoobbakht, M., & Karimi, M. (2024). Effect of biodiesel on environmental impacts of diesel mechanical power generation by life cycle assessment. Energy, 289, 129948. https://doi.org/10.1016/j.energy.2023.129948
5. Dhanumjaya, M. V., Kocherla, A., Krishna, J. R., Sethu, M., Singh, T., & Mandal, A. (2024, May). Comparative Analysis by Machine Learning of Waste Biodiesels in CI Engine. In 2024 IEEE Recent Advances in Intelligent Computational Systems (RAICS) (pp. 1-5). IEEE. https://doi.org/10.1109/raics61201.2024.10689952
6. Musharavati, F., Sajid, K., Anwer, I., Nizami, A. S., Javed, M. H., Ahmad, A., & Naqvi, M. (2023). Advancing biodiesel production system from mixed vegetable oil waste: a life cycle assessment of environmental and economic outcomes. Sustainability, 15(24), 16550. https://doi.org/10.3390/su152416550
7. Bradley, T., Rajaeifar, M. A., Kenny, A., Hainsworth, C., del Pino, V., del Valle Inclán, Y., ... & Heidrich, O. (2023). Life cycle assessment of microalgae-derived biodiesel. The International Journal of Life Cycle Assessment, 28(5), 590-609. https://doi.org/10.1007/s11367-023-02140-6
8. Beyene, D., Bekele, D., & Abera, B. (2024). Biodiesel from blended microalgae and waste cooking oils: Optimization, characterization, and fuel quality studies. Aims Energy, 12(2). https://doi.org/10.3934/energy.2024019
9. Gaide, I., Grigas, A., Makareviciene, V., & Sendzikiene, E. (2024). Life cycle assessment and biodegradability of biodiesel produced using different alcohols and heterogeneous catalysts. Green Chemistry Letters and Reviews, 17(1), 2394503. https://doi.org/10.1080/17518253.2024.2394503
10. Zhao, Q., Han, F., You, Z., Huang, Y., She, X., Shi, X., & Han, P. (2024). Evaluation of microalgae biodiesel for carbon neutrality based on the waste treatment by the autotrophic and heterotrophic combination. Energy, 291, 130314. https://doi.org/10.1016/j.energy.2024.130314
11. Ogundele, O. D., Jayeola, J. O., Oyegoke, D. A., & Oyeniran, T. P. (2023). Sustainable biodiesel production from waste cooking oil: A green path from grease to fuel. J. Sustain. Energy, 2(2), 68-75. https://doi.org/10.56578/jse020203
12. Sonthalia, A., & Kumar, N. (2023). Performance Improvement and Emission Reduction Potential of Blends of Hydrotreated Used Cooking Oil, Biodiesel and Diesel in a Compression Ignition Engine. Energies, 16(21), 7431. https://doi.org/10.3390/en16217431

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