Cited by 141Advanced Aircraft Design and TechnologiesAdvanced Combustion Engine TechnologiesBiofuel production and bioconversion

The DOI matches its Crossref record; 130 of the 131 references it cites were found in a registry or an index; 1 of the 182 sources its claims cite were checked for support.

Investigation of Biofuel as a Potential Renewable Energy Source

Open access

Abstract

An accelerating global energy demand, paired with the harmful environmental effects of fossil fuels, has triggered the search for alternative, renewable energy sources. Biofuels are arguably a potential renewable energy source in the transportation industry as they can be used within current infrastructures and require less technological advances than other renewable alternatives, such as electric vehicles and nuclear power. The literature suggests biofuels can negatively impact food security and production; however, this is dependent on the type of feedstock used in biofuel production. Advanced biofuels, derived from inedible biomass, are heavily favoured but require further research and development to reach their full commercial potential. Replacing fossil fuels by biofuels can substantially reduce particulate matter (PM), carbon monoxide (CO) emissions, but simultaneously increase emissions of nitrogen oxides (NOx), acetaldehyde (CH3CHO) and peroxyacetyl nitrate (PAN), resulting in debates concerning the way biofuels should be implemented. The potential biofuel blends (FT-SPK, HEFA-SPK, ATJ-SPK and HFS-SIP) and their use as an alternative to kerosene-type fuels in the aviation industry have also been assessed. Although these fuels are currently more costly than conventional aviation fuels, possible reduction in production costs has been reported as a potential solution. A preliminary study shows that i-butanol emissions (1.8 Tg/year) as a biofuel can increase ozone levels by up to 6% in the upper troposphere, highlighting a potential climate impact. However, a larger number of studies will be needed to assess the practicalities and associated cost of using the biofuel in existing vehicles, particularly in terms of identifying any modifications to existing engine infrastructure, the impact of biofuel emissions, and their chemistry on the climate and human health, to fully determine their suitability as a potential renewable energy source.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This review assesses biofuels as a renewable transport energy source, weighing their emission trade-offs, feedstock generations, and aviation-fuel pathways against food-security, land-use, and atmospheric-chemistry concerns. It concludes that biofuels can help decarbonise transport but that a shift to advanced (non-edible) feedstocks and further research on air quality and climate impacts are needed.

Key findings

  • Replacing fossil fuels with biofuels reduces particulate matter (PM), CO and unburned VOC emissions (attributed to higher oxygen content and more complete combustion), but generally increases NOx, acetaldehyde (CH3CHO) and peroxyacetyl nitrate (PAN) emissions — a trade-off the paper states explicitly.
  • Biofuel production and consumption grew ~3% and ~6% respectively in 2019; the US was the largest consumer, followed by Brazil, Indonesia, China and France. Ethanol accounts for ~80% of all liquid biofuel production, with global production predicted to exceed 135 billion L by 2024 (USA 42%, Brazil 31%).
  • EROEI for US bioethanol and biodiesel is "slightly higher than 1," whereas Brazilian sugarcane ethanol is 5–10, indicating regional variability in energy balance.
  • A modelling study (STOCHEM-CRI) found that adding 1.8 Tg/year of i-butanol emissions as biofuel increased upper-tropospheric ozone and PAN by up to 6% and 4.5%, respectively; a separate study found ~11.5 Tg/year ethanol emission flux raised acetaldehyde by up to 30% and PAN by up to 3%.
  • Aviation biofuels (FT-SPK, HEFA-SPK, ATJ-SPK, HFS-SIP) are currently more costly than conventional aviation fuel and must be blended with kerosene (e.g., FT-SPK and HEFA-SPK at 50:50; HFS-SIP at 10 vol%; ATJ-SPK ~15 vol%).

Methods

  • Narrative literature review; no new data were created or analysed (stated in the Data Availability section).
  • Synthesises prior studies on biofuel generations (first to fourth), production/consumption statistics (BP, USEIA data), emission and air-quality literature, and aviation-fuel conversion chemistry.
  • Includes discussion of global 3-D chemistry transport modelling results (STOCHEM-CRI with the CRI mechanism) drawn from the authors' and others' prior work, plus reaction schemes for ethanol/acetaldehyde and i-butanol degradation.

Limitations

  • Stated: research on biofuels is "inconclusive and contradictory," partly due to differing biofuel generations and geographic regions studied; most studies focus on first-generation biofuels and on single countries without global comparison; transport of biofuel emission products was not analysed; few studies examine impacts on O3 and SOA formation; projections of advanced-biofuel environmental impact are difficult due to limited industrial application.
  • Evident from the text: this is a review without primary data or new modelling, so its quantitative claims rest on cited studies; the i-butanol and ethanol ozone/PAN figures come from model simulations rather than measurements, and the paper itself notes a larger number of studies is needed to assess practicalities and costs of using biofuels in existing vehicles.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3390/atmos12101289

Cites

130 of 131 references verified0 citation errors · 1 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

146 Not checked yet · 33 No basis given · 29 Own interpretation · 1 Partly supported · 1 Own result · accuracy not yet measured

Verify all 181 references — free account

Show all 95 claims

  • It may state two separate claims as one. 71
  • Probably not a substantial claim. 63
115 of 115
  • The paper relies on this without support.

    Biofuels can be used within current infrastructures.

    “Biofuels are arguably a potential renewable energy source in the transportation industry as they can be used within current infrastructures and require less technological advances than other renewable alternatives, such as electric vehicles and nuclear power.”
    “In addition, biofuels can be used within current infrastructures and require less technological advances compared with other energy sources.”
  • The paper relies on this without support.

    Biofuels require less technological advances compared with other energy sources.

    “Biofuels are arguably a potential renewable energy source in the transportation industry as they can be used within current infrastructures and require less technological advances than other renewable alternatives, such as electric vehicles and nuclear power.”
    “In addition, biofuels can be used within current infrastructures and require less technological advances compared with other energy sources.”
  • The paper relies on this without support.

    Global demand for biofuels is projected to increase.

    “As global demand for biofuels is projected to increase, it is essential to understand the consequences of using these fuels.”
  • The paper relies on this without support.

    There is a strong agreement amongst scholars that a shift towards advanced biofuels is needed.

    “However, as there is a strong agreement amongst scholars that a shift towards advanced biofuels is needed, it seems necessary to compare the emission properties and air quality impact of these different biofuel generations.”
  • The paper relies on this without support.

    The first flight to use a biofuel blend was in 2008 and since then over 150,000 flights using biofuels have taken place.

    “The first flight to use a biofuel blend was in 2008 and since then over 150,000 flights using biofuels, have taken place.”
  • The paper relies on this without support.

    Both FT-SPK and HEFA-SPK have already been implemented in 50:50 blends with kerosene-type fuels and used commercially in aircraft.

    “Both FT-SPK and HEFA-SPK, have already been implemented in 50:50 blends with kerosene-type fuels and used commercially in aircraft.”
  • The paper relies on this without support.

    The use of non-edible jatropha oil coupled with Ni catalysts at high temperatures led to a production of 8% aromatic content.

    “The use of non-edible jatropha oil coupled with Ni catalysts at high temperatures led to a production of 8% aromatic content.”
  • The paper relies on this without support.

    The method of extracting sugars initially provides some difficulty.

    “However, the method of extracting sugars initially provides some difficulty.”
  • The paper relies on this without support.

    With edible feedstocks, sugar cane and corn, extraction of sugar is relatively simple and requires only hot water treatment.

    “With edible feedstocks, sugar cane and corn, extraction of sugar is relatively simple and requires only hot water treatment.”
  • The paper relies on this without support.

    Ethanol cannot be used directly in aircraft engines due to its high volatility, high water absorption and a [cut off].

    “Ethanol, in particular, cannot be used directly in aircraft engines due to its high volatility, high water absorption and a”
  • The paper relies on this without support.

    Butanol's energy density and chemical structure are much closer to gasoline than ethanol, overcoming miscibility issues associated with bioethanol.

    “The energy density and chemical structure of butanol is much closer to gasoline, thus overcoming miscibility issues associated with bioethanol.”
  • The paper relies on this without support.

    i-Butanol burns more cleanly (contains around 22% oxygen) and is far less corrosive than ethanol, allowing shipment through existing infrastructure.

    “It also burns more cleanly (containing around 22% oxygen) and is far less corrosive than ethanol, meaning that it can be shipped and distributed through existing infrastructure.”
  • The paper relies on this without support.

    PAN enables long-range transport of NOx away from primary sources and thermally decomposes to release NOx into the remote troposphere.

    “PAN enables the long-range transport of NO x , away from primary sources and then thermally decomposes to release NO x into the remote troposphere.”
  • The paper relies on this without support.

    There is a significant price difference between BAF and CAF.

    “First, there is still a significant price difference between BAF and CAF.”
  • The paper relies on this without support.

    Many biofuel processes require catalysts, and designing and selecting catalysts to improve cost-effectiveness is costly.

    “Many processes discussed also require catalysts, the design and selection of catalysts to improve cost-effectiveness is in itself a costly process.”
  • The paper relies on this without support.

    Algae growth requires stringent temperature conditions, which presents a problem.

    “Additionally, stringent temperature requirements are needed for algae growth which presents a problem.”
  • The paper relies on this without support.

    Fuel efficiencies of alternative fuels are still largely undefined.

    “Furthermore, fuel efficiencies of alternative fuels are still largely undefined”
  • The paper relies on this without support.

    BAF must be compatible with CAF because they are currently blended in aircraft.

    “Finally, BAF must be compatible with CAF as they are currently blended when used in aircraft.”
  • The paper relies on this without support.

    First-generation biofuels raise issues of food security and production that can increase poverty levels and harm the economy, particularly in developing countries.

    “This is particularly important in developing countries as first-generation biofuels raise issues of food security and production which can increase poverty levels and harm the economy.”
  • The paper relies on this without support.

    Commercialisation of advanced biofuels faces challenges because production costs are very high and conversion technologies need improvement.

    “However, there are current challenges with commercialisation of advanced biofuels as their production costs are very high and conversion technologies need improvement.”
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Citations

Cites

Research works printed but not linked: 5

  1. BP (2020). Statistical Review of World Energy, BP p.l.c.. [69th ed.]. Available online: https://www.bp.com/en/global/corporate/energy-economics/statistical-review-of-world-energy.html.
  2. Locke, A., and Henley, G. (2014). A Review of the Literature on Biofuels and Food Security at a Local Level: Assessing the State of the Evidence, Overseas Development Institute.
  3. Varol, 2014, Comparison of methanol, ethanol, or n-butanol blending with unleaded gasoline on exhaust emissions of an SI engine. Energy Sources, Part A: Recovery, Util. Environ. Eff., 36, 938
  4. Ehhalt, D., Prather, M., Dentener, F., Derwent, R., Dlugokencky, E.J., Holland, E., Isaksen, I., Katima, J., Kirchhoff, V., and Matson, P. (2001). Atmospheric Chemistry and Greenhouse Gases, in Climate Change 2001: The Scientific Basis, Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press.
  5. Chuck, C. (2016). Biofuels for Aviation: Feedbacks, Technology and Implementation, Academic Press.

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Metadata

Authors
Khan, M. A. H., Bonifacio, S., Clowes, J., Foulds, A., Holland, R., Matthews, J. C., Percival, C. J., & Shallcross, D. E.
Affiliations
  • University of Bristol (GB)
  • University of Manchester (GB)
  • Jet Propulsion Laboratory (US)
Corresponding author
Shallcross, Dudley E.
Venue
Atmosphere
Publisher
MDPI AG
Published
2021-10-03
Volume
12
Issue
10
Pages
1289
ISSN
2073-4433 (ISSN-L)
OpenAlex
W3204882063
Cited by
140
References
130
Citations by year
2026: 29 · 2025: 32 · 2024: 42 · 2023: 25 · 2022: 11 · 2021: 1
FWCI
8.09
Type
journal article
Language
en
Open access
Locations
  • Atmosphere (publishedVersion, cc-by)
  • Explore Bristol Research (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • UWC Research Repository (University of the Western Cape) (submittedVersion)
Funders
Natural Environment Research Council (NE/K004905/1)
Topics
  • Physical Sciences › Engineering › Aerospace Engineering › Advanced Aircraft Design and Technologies
  • Physical Sciences › Chemical Engineering › Fluid Flow and Transfer Processes › Advanced Combustion Engine Technologies
  • Physical Sciences › Engineering › Biomedical Engineering › Biofuel production and bioconversion
Keywords
biofuels, renewable energy, transportation fuels, aviation biofuels, advanced biofuels, biofuel emissions, nitrogen oxides, particulate matter, food security, biofuel feedstock, ozone, climate change impacts, kerosene replacement, fuel blends, production costs

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