In today’s world, the applications of nanotechnology and nanomaterials are attracting interest in a wide variety of study domains because of their appealing qualities. The use of nanotechnology and nanomaterials in biodiesel processing and manufacturing is a focus of research globally. For accelerating the progress and development of biodiesel production, more focus is being given to the application of advanced nanotechnology for maximum yield in low cost. Hence, this paper will discuss the utilization of numerous nanomaterials/nanocatalysts for biodiesel synthesis from multiple feedstocks. This study will also focus on nanomaterials’ applications in algae cultivation and lipid extraction. Furthermore, the current study will comprehensively overview the nanoadditives blended biodiesel in diesel engines and the significant challenges and future opportunities. Moreover, this paper will also focus on human and environmental safety concerns of nanotechnology-based large-scale biodiesel production. Hence, this review will provide perception for future manufacturers, researchers, and academicians into the extent of research in nanotechnology and nanomaterials assisted biodiesel production and its efficiency enhancement.

1. Review Article
Utilization of Nanotechnology and Nanomaterials in Biodiesel
Production and Property Enhancement
Adib Bin Rashid
Department of Industrial and Production Engineering, Military Institute of Science and Technology, Dhaka, Bangladesh
Correspondence should be addressed to Adib Bin Rashid; adib8809@gmail.com
Received 25 October 2022; Revised 10 January 2023; Accepted 23 January 2023; Published 13 February 2023
Academic Editor: Yasuhiko Hayashi
Copyright © 2023 Adib Bin Rashid. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
In today’s world, the applications of nanotechnology and nanomaterials are attracting interest in a wide variety of study domains
because of their appealing qualities. The use of nanotechnology and nanomaterials in biodiesel processing and manufacturing is a
focus of research globally. For accelerating the progress and development of biodiesel production, more focus is being given to the
application of advanced nanotechnology for maximum yield in low cost. Hence, this paper will discuss the utilization of numerous
nanomaterials/nanocatalysts for biodiesel synthesis from multiple feedstocks. This study will also focus on nanomaterials’ applica-
tions in algae cultivation and lipid extraction. Furthermore, the current study will comprehensively overview the nanoadditives
blended biodiesel in diesel engines and the significant challenges and future opportunities. Moreover, this paper will also focus on
human and environmental safety concerns of nanotechnology-based large-scale biodiesel production. Hence, this review will
provide perception for future manufacturers, researchers, and academicians into the extent of research in nanotechnology and
nanomaterials assisted biodiesel production and its efficiency enhancement.
1. Introduction
Developing molecular-scale machines and devices that are a
few nanometers (10−9
m) wide, much smaller than a cell, can
be broadly characterized as the field of nanotechnology. The
effect of nanoparticles on the creation and manufacturing of
biofuels/biodiesels is currently estimated using a variety of
nanomaterials, including nanofibers, nanotubes, and nano-
metals [1].
The use of nanotechnology and nanomaterials in biodie-
sel research has emerged as a viable instrument for delivering
efficient methods to raise production quality at a reasonable
cost. Due to their tiny size, particular characteristics, and
traits, including a high surface area to volume ratio, consid-
erable crystallinity, catalytic activity, adsorption capacity,
and stability, nanoparticles (NPs) have several benefits over
biodiesel production [2]. With additional features that sup-
port high potential recovery, carbon nanotubes, and metal
oxide nanoparticles are often utilized as nanocatalysts to
manufacture biofuel and biodiesel [3, 4]. The use of nano-
technology in the manufacture and improvement of biodiesel
is critically examined in this paper, along with the main
obstacles and promising future developments.
Microalgae are a promising feedstock for the manufacture
of biodiesel. Diverse nanoparticles may quickly enhance the
effectiveness of the microalgae harvesting process. Addition-
ally, the reuse of nanomaterials and the incorporation of cell
harvesting, disruption, and extraction also help to lower costs.
Additionally, a variety of nanocatalysts have the potential to
improve biodiesel conversion efficiency [5].
However, increasing combustion efficiency and lowering
harmful emissions have become popular research areas in the
engineindustryandrelatedfields.Accordingtovariousresearch,
nanoadditivestodiesel–biodieselfuelblendshaveshownnotable
outcomes. Numerous investigations and research findings on
nanoparticles have shown the critical function that nanoaddi-
tives play in enhancing the efficiency of internal combustion
engines and lowering the emission of hazardous pollutants [6].
Many researchers have extensively investigated the appli-
cations of nanotechnology and nanomaterials assisted bio-
diesel production and its efficiency enhancement which will
be summarized in this review paper [7–9]. Hence, this review
examines the use of nanotechnology in several biodiesel
Hindawi
Journal of Nanomaterials
Volume 2023,Article ID 7054045, 14 pages
https://doi.org/10.1155/2023/7054045

2. manufacturing process phases, including microbial culture,
lipid extraction, hydrocarbon purification from oil, and
transesterification. The use of nanoparticles as fuel additives
for diesel–biodiesel fuel blends will also be covered in this
paper. This review also discusses the benefits and drawbacks
of using nanotechnology at different process stages.
2. Overview of Nanotechnology
The core components of the burgeoning nanotechnology
research industry are known as nanoparticles. They come
in various forms, including cylindrical, spherical, flat, coni-
cal, and tubular, and varying diameters between 1 and
100 nm. Nanoparticles may be amorphous or crystalline,
packed tightly or loosely, and comprised of single or many
crystal solids. They can also exist in all four dimensions as
zero, one, two, and three dimensions [10].
Various classifications of nanoparticles based on surface,
material, size, and structure are shown in Figure 1. Based on
where they come from and the fundamental chemical ele-
ments that make up their structure, nanoparticles may be
categorized as carbon-based, organic, inorganic, or compos-
ite based. Long chains of carbon atoms joined together in
unique configurations, such as spherical in fullerenes, hon-
eycomb lattice in carbon nanotubes, or conical in carbon
nanofibers, make up the whole of carbon-based nanoparti-
cles. On the other hand, organic nanoparticles are biodegrad-
able, nontoxic, and mostly used in the medical industry as a
drug delivery system, antioxidant, etc. [11].
The researchers have discovered the potential of nanopar-
ticles as an addition because of the significant impact nano-
particles have on the base fuel’s ignition and combustion
characteristics. Concerning the field of CI engines, metal
and metal oxide nanoparticles, which fall under the category
of inorganic nanoparticles, have far more advantageous prop-
erties to offer, such as their capacity to boost reactivity, speed
up evaporation rates by serving as an oxygen buffer, and
enhance the calorific values, thermal conductivity, and viscos-
ity of the base fuel. Because they may improve the thermo-
physical characteristics of the fuel, nanoparticles are used
as an additive for CI engines. Nanoparticles have a more
excellent surface-to-volume ratio due to their nanostructure,
a desired feature for mixes used in CI engines as they give
a bigger reactive surface for the chemical reaction and com-
bustion [12].
2.1. Methods of Nanomaterial Synthesis. A nanofluid is a
fluid created by evenly scattering nanoparticles in a liquid
fluid. The synthesis and characterization of nanofluids are
crucial because different nanomaterials significantly impact
the dispersion and stability of these fluids. The use of nano-
particles has been the subject of many studies in recent years.
They have progressed in manipulating nanoparticle size,
shape, and porosity and their physical and chemical charac-
teristics. Therefore, choosing an appropriate preparation
technique is crucial for nanofluids. Nanofluids are typically
synthesized in one or two steps, while newer procedures have
also been developed. Numerous physical, chemical, biologi-
cal, and hybrid strategies may be used to create nanoparticles
(Figure 2) [13, 14].
2.1.1. One-Step Preparation Method. Nanoparticles and the
base solution are mixed in the one-step process. Compared to
other approaches, the one-step method’s key benefits include:
Sphere
100 nm
Cube Cylinder
Plate Star
1 nm
Size
Nanoparticles
Surface
Shape
Material
Dendrimer
Carbon
nanotube
Liposome
Metal oxide
nanoparticles
Graphene
Hydrogel
Polymer
nanoparticle
Micelle
Surface charge (–/+, +/–)
Surface functional group
(e.g., –COOH, –SH)
Targeting ligand
(e.g., antamer, peptide, antibody)
Trioglucose, PEGylation, or other coatings
✓
✓
✓
✓
✓
FIGURE 1: Classification of nanoparticles based on physical attributes [12].
2 Journal of Nanomaterials

3. (1) lower production costs due to the method’s simplicity and
lack of need for drying, storage, or dispersion, (2) due to the
minimal aggregation of nanoparticles, the nanofluid created
by the one-step technique may remain stable for an extended
period. Laser ablation, direct evaporation, vapor deposition,
and submerged arc welding nanoparticle synthesis technolo-
gies are now the principal approaches for the one-step syn-
thesis of nanofluids.
Vacuum evaporation was initially used by Akoh et al. [15]
to produce 0.25 nm ferromagnetic metal superparticles in the
one-step approach. According to Tran and Soong [16], nano-
particles with a diameter of 9–21 nm were created by laser
ablation without dispersants or surface chemicals. Using the
gas coalescence concept, Lo et al. [17] constructed a sub-
merged arc nanosynthesis system where copper aerosols rap-
idly amalgamated into nanoparticles in the presence of
dielectric liquid. As a result, metallic nanofluids were formed
from the nanoparticles. This process is typically utilized to
manufacture copper, copper oxide, cuprous oxide, and copper
phase nanoparticles to create a metal nanofluid.
2.1.2. Two-Step Preparation Method. First, nanoparticles are
made and then blended with the base fluid in a two-step
procedure. In terms of dispersion efficiency and stability,
two-step nanofluids are the most often employed approach.
Bottom-up and top-down nanomaterials synthesis methods
are now the most widely used [10].
The bottom-up approach involves accumulating compo-
nents, such as atoms, aggregates, and nanoparticles. Chemical
vapor deposition, sol–gel, pyrolysis, and biosynthesis are the
most often utilized techniques. Researchers currently choose
the sol–gel approach because of its straightforward synthesis,
scalability, and controllability. An environmentally friendly
process called biosynthesis uses bacteria, plant extracts, fun-
gus, and precursors to create nontoxic, biodegradable nano-
particles [16].
Reducing the bigger size of materials to nanoscale parti-
cles is the top-down method. Laser ablation, nanolithography,
mechanical grinding, and thermal breakdown are frequently
employed techniques. Mechanical grinding is a physical tech-
nique for producing nanoparticles, which involves plastically
deforming bulk materials into particle forms. Using improved
photolithography, nanolithography can shrink massive mate-
rials from microns to <10 nm. Nanolithography may be done
using various techniques, including electron beam, optical,
nanoimprinting, multiphoton, and scanning probe lithogra-
phy. Laser solution ablation is a trustworthy top-down tech-
nique, typically more dependable than traditional chemical
reduction techniques for synthesizing precious metal nano-
particles [19].
2.2. Factors Affecting the Synthesis of Nanoparticles. The pro-
duction, characterization, and use of nanoparticles are all
affected by various circumstances. According to several stud-
ies, produced nanoparticles may alter in nature depending on
the adsorbate and catalyst activity utilized in the synthesis
process. In some instances, the dynamic character of the
produced nanoparticles has been described, with distinct
Nanoparticle synthesis
Top-down approach Bottom-up approach
•
•
•
•
•
•
•
Physical method
Arc discharge method
Electron beam lithography
Ion implantation
Inert gas condensation
Mechanical
grinding/milling
Spray pyrolysis
Vapor-phase synthesis
Chemical method
• Coprecipitation method
• Chemical reduction of
metal salts
• Electrochemical
method (electrolysis)
• Pyrolysis
• Photochemical
(irradiation) method
• Sol–gel method
• Solvothermal synthesis
•
•
•
•
•
Biological method
Using plant and their
extract
Using microorganisms
(bacteria, fungai and
actinomycetes)
Using algae (microseaweeds)
Using enzymes and
biomolecules
Using industrial and
agricultural waste
Nanoparticle
Bulk material
Powder
Atoms
Clusters
FIGURE 2: Different approaches and methods for synthesizing nanoparticles [18].
Journal of Nanomaterials 3

4. kinds of symptoms and consequences changing with time
and the environment. Furthermore, several other critical
variables might impact how nanoparticles are synthesized.
These include pH levels, temperatures, concentrations of
extracts, concentrations of raw materials, sizes, and processes.
Some dominant factors that affect nanoparticle synthesis are
described in the following sections [18].
2.2.1. Particular Method or Technique. Chemical or biological
processes, including a variety of organic or inorganic com-
pounds and living organisms, as well as physical approaches
employing mechanical operations, may all be used to synthe-
size nanoparticles. The advantages and disadvantages of each
technique are unique. Nanoparticles may be made using bio-
logical processes, which employ nontoxic and ecologically
benign ingredients in combination with green technology,
making them more environmentally friendly and acceptable
than previous methods [19].
2.2.2. pH of the Solution. The production of nanoparticles is
influenced by the pH of the solution. The pH of the solution
medium affects the size and texture of produced nanoparti-
cles. Thus, the pH of the solution medium may be altered to
adjust the size of nanoparticles [19].
2.2.3. Synthesis Temperature and Pressure. For nanoparticle
production, temperature and pressure are crucial. The nature
(size and form) of the nanoparticle produced depends on the
temperature of the medium in which the reaction takes place.
Nanoparticles may be synthesized at different temperatures
using any of the three processes. Temperatures >350°C are
required for the physical approach, whereas temperatures
<350°C are required for the chemical method. In most situa-
tions, temperatures as low as 100°C or ambient temperature
are required to produce nanoparticles [20].
2.2.4. Synthesis Time. The amount of time of the reaction
medium is incubated significantly impacts the kind and qual-
ity of nanoparticle that is generated. The synthesis procedure,
exposure to light, storage conditions, and other factors sig-
nificantly impacted how the generated nanoparticles’ features
changed over time. Particles may aggregate as a result of long-
term storage, contract or expand over that time, have a shelf
life, and so on, all of which impact their potential [20].
2.2.5. Particle Shape and Size. The characteristics of nanopar-
ticles are significantly influenced by particle size. For instance,
it has been shown that the melting point of nanoparticles
drops as they approach the nanoscale range. Because nanopar-
ticles in various configurations contain equivalent amounts of
energy, changing their shape is simple. The nanoparticle’s
form changes due to the typical energy type utilized during
nanoparticle analysis. The chemical characteristics of produced
nanoparticles are significantly influenced by their dynamic
nature and form [20].
2.2.6. Pore Size. The porosity of the produced nanoparticles
significantly impacts their quality and use. To boost their
usage in the drug delivery and medicinal fields, biomolecules
have been successfully immobilized onto nanoparticles [20].
3. Various Nanoparticles Used for
Production of Biodiesel
Biodiesel is produced by the transesterification process in
which the triglyceride is reacted with alcohol in presence of
a catalyst to produce biodiesel and glycerol. Various nano-
materials and nano-sized particles can be used as biodiesel
production catalysts [21].
3.1. Magnetic Nanoparticles. In general, magnetic nanoparti-
cles (MNPs) are categorized as a subclass of nanoparticles
that may be manipulated or controlled by magnetic fields.
This particular form of nanomaterial often consists of two
parts: a chemical component with functionality and a mag-
netic component (typically Fe, Ni, or Co).
Due to their tiny size, high surface-to-volume ratio, and
exceptional quantum characteristics, MNPs are of tremen-
dous interest to scientists and researchers. Magnetic nanos-
tructure materials of various types are now being researched
for use as effective catalysts. Typically, these materials consist
of Fe, Co, Ni, platinum alloys, and other metal oxides.
3.2. Carbon Nanotubes (CNTs). CNTs are a kind of nanoma-
terial that stands out above others in terms of their mechanical,
thermal, structural, and biocompatible qualities. They are widely
employed in biodiesel applications. When employed correctly,
multiwalled carbon nanotubes (MWCNT) nanomaterial
improves both the diesel engine’s efficiency and the blending
efficiency of biodiesel–diesel.
3.3. Graphene and Graphene-Derived Nanomaterial. Graphene
oxide (GO), graphene, and reduced graphene oxide (RGO) are
all used as catalysts in biodiesel production. Although gra-
phene and materials based on it are effective catalysts for
manufacturing biodiesel, researchers have always had diffi-
culty developing high-quality graphene and its derivatives.
3.4. Other Nanoparticles Applied in Heterogeneous Catalysis.
Because of the significant characteristics, such as tiny pore size,
specific surface area, acidic quantity, and acidic strength, inor-
ganic nanoparticles are sometimes utilized as heterogeneous
catalysts in a variety of applications. Biodiesel may be made
using a variety of nanomaterials, including H-form zeolites,
cation-exchange resins, transition-metal oxides, solid acids,
heteropoly compounds, and solid carbonaceous acids [21].
4. Role of Nanomaterials in
Biodiesel Production
4.1. Transesterification of Oil into Biodiesel in the Presence of
Nanocatalysts. Transesterification process is the most promis-
ing process which is a reversible reaction as shown in Figure 3.
It is carried out by reacting fatty acids (oils) with alcohol in the
presence of a suitable catalyst to obtain FAMEs (biodiesel) and
glycerol. A strong base like sodium hydroxide, sodium meth-
oxide, and potassium hydroxide or a strong acid such as
hydrochloric acid and sulfuric acid can be used as a catalyst
[22]. The catalyst is usually used to start the reaction and acts
as an alcohol solubilizer; it is essentially required because alco-
hol is sparingly soluble in the oil phase, and noncatalyzed
4 Journal of Nanomaterials

5. reactions are extremely slow. The catalyst helps in alcohol
solubility and ultimately facilitates the reaction to proceed at
a reasonable rate [23]. The separation of catalyst from the
reaction mixture is the most difficult. After the completion
of reaction, the catalyst needs to be neutralized or removed
with a large amount of hot water, which generates a large
amount of industrial wastewater and makes the process expen-
sive [24]. Figure 4 shows the schematic overview of the process
of biodiesel production.
The catalyst’s specific surface area is one of the most
essential variables in the generation of biodiesel. A more
excellent surface/volume ratio in a nanocatalyst improves
the catalyst’s performance because there are more active sites
for reactions to take place on the catalyst’s surfaces. The high
specific surface area of nanocatalysts creates favorable cir-
cumstances for the transesterification reaction. Calcium oxide
is a common nanocatalyst for biodiesel production due to its
inexpensive cost and strong catalytic activity. CaO can thus be
utilized either alone or in conjunction with other materials to
produce biodiesel. MgO, SrO, and ZnO are other nanocata-
lysts utilized in the transesterification procedure. Again,
Fe3O4, CuFe2O4, activated carbon, and other materials can
be used to enhance these catalysts’ characteristics [24–31].
The ideal biodiesel production feedstock includes edible
oil sources such as palm, sunflower, soybean, olive, maize,
rapeseed, safflower, peanut, and coconut oil [26]. Table 1 pro-
vides an overview of the use of nanocatalysts for manufacturing
biodiesel from vegetable oil, waste cooking oil (WCO)
extracted from animal fat, and algal oil for different operation
conditions. Table 1 displays that nanocatalysts can significantly
increase biodiesel yields, most of the biodiesel yield from these
nanocatalysts is above 90%.
The reusability and recovery of nanocatalysts in the bio-
diesel manufacturing process are the most significant advan-
tages of heterogeneous nanocatalysts. In these procedures,
the nanocatalyst is collected and used again after each cycle
in the manufacture of biodiesel. Nanocatalyst recovery is
frequently accomplished using chemical means. The main
product and byproduct from the reaction mixture can be
recovered from the reaction mixture quickly and easily
with the use of heterogeneous catalysts. There is no need
for a washing step with this kind of catalyst. Nanocatalysts
proposed numerous benefits for the esterification process,
including faster reaction times, reduced reaction time, and
quick and easy separation from the reaction mixture. Accord-
ing to previous studies, the catalyst can be easily recovered
utilizing an external magnetic field and recovered multiple
times without significantly losing its catalytic activity and
biodiesel yield [32–38].
4.2. Biodiesel Production using Nanoimmobilized Lipase. In
recent years, various nanomaterials have garnered much inter-
est as potential carriers for immobilizing enzymes [44–46].
Compared to other materials for enzyme immobilization,
nanomaterials have much larger surface areas, one of the
numerous benefits they provide as immobilization carriers.
Utilizing nanoimmobilized enzyme systems may help increase
enzymes’ activity, stability, and reusability, leading to a consid-
erable reduction in the costs associated with their usage
[47–49]. Several researchers have immobilized lipases on func-
tional nanomaterials, and there is reason to be optimistic about
their potential uses (Table 2).
5. Nanotechnology for Algal Biodiesel
Microalgae are a promising feedstock for the manufacture of
biodiesel (Figure 5). Nanomaterials were added to an algal
culture system to promote microalgal growth and induce
lipid buildup. Furthermore, the efficiency of lipid extraction
may be improved by using nanomaterials. The following
sections discuss the current and noteworthy nanotechnology
uses in algal biodiesel generation. Nanotechnology’s applica-
bility in algal culture, lipid buildup, extraction, and transes-
terification has been critically appraised in the following
sections [55–57].
5.1. Algal Cultivation and Lipid Induction. Illumination is
one of the prerequisites for growing algae. Low sunlight expo-
sure, inappropriate for growth, may occur in high-density
microalgae cultures. Thus, the issue of soft light illumination
has been solved by using metallic NPs with localized surface
plasmon resonances (LSPR) technology [58]. The coupled
oscillations of free electrons at a metallic dielectric contact
are the foundation of LSPR technology [59]. Light at a certain
Feedstock oil
Methanol
Catalyst
Water
Washer
Wash
water
Separator
Glycerol
Glycerin
Methanol
Reactor
Methyl
ester/
raw
biodiesel
Fuel-grade
biodiesel
Drier
FIGURE 4: Schematic overview of the process of biodiesel production
[25].
+ +
+
+
CH2 COOR1
CH
Triglyceride Alcohol Esters Glycerol
Catalyst
COOR2 3ROH
CH2 COOR3
CH2 OH
CH OH
CH2 OH
R1COOR
R2COOR
R3COOR
FIGURE 3: Transesterification reaction.
Journal of Nanomaterials 5

6. TABLE 1: Biodiesel production from vegetable oil using different nanocatalysts.
Feedstock Nanocatalyst (wt%)
Operating parameters
Yield (%) Ref.
MOR T (°C) Time (hr)
Vegetable oil
Palm oil
CaO–Al2O3 (6) 12 : 1 65 5 98.64 [27]
CaO–CeO2 (5) 20 : 1 85 3 95 [28]
Rapeseed oil Li/Fe3O4 (0.8) 12 : 1 35 0.58 99.8 [29]
Soybean oil MgAlCe (5) 9 : 1 67 3 >90 [30]
Sunflower oil MgO/MgFe2O4 (4) 12 : 1 110 4 91.2 [31]
Jatropha oil MgO–ZnO (3) 25 : 1 120 3 83 [32]
Neem oil Copper-doped zinc oxide (10) 10 : 1 55 1 97.18 [33]
Animal fat
Chicken oil CaO/CuFe2O4 (3) 15 : 1 70 4 94.52 [34]
Goat fat MgO (1) 12 : 1 70 3 93.12 [35]
Mutton fat Lithium ions-supported MgO (5) 12 : 1 – 40 min 99 [36]
Waste cooking oil (WCO)
Copper/zinc oxide (12) 8 : 1 55 0.833 97.71 [37]
CaO (1) 8 : 1 50 1.5 96 [38]
CaO–ZrO2 (10) 30 : 1 65 2 92.1 [39]
MgO (2) 24 : 1 65 1 93.3 [40]
TiO2–MgO (5) 30 : 1 5 150 6 >85 [41]
Microalgae oil
Waste-based calcium oxide (2) 11 : 1 60 3 92 [42]
Nano-Ca(OCH3)2 (calcium methoxide)
(3)
30 : 1 80 3 99 [43]
MOR, methanol-to-oil ratio.
TABLE 2: Nanomaterial-bound enzymes used for biodiesel production.
Enzyme (lipase) Nanomaterial Type of bonding Oil–alcohol Yield (%) Ref.
P. cepacia Fe3O4 nanoparticle Covalent Soyabean oil + methanol 88 [50]
Burkholderia sp. Magnetic nanoparticle Adsorption Olive oil + methanol 90 [51]
Rhizopus miehei Silica nanoparticle Encapsulation Triolein + methanol 89 [52]
Thermomyces lanuginosus Fe3O4 nanoparticle Covalent Waste grease + methanol 80–89 [53]
P. cepacia Polyacryonitrile fibere Adsorption Rapeseed oil + n-butanol 94 [54]
Drying
Microalgae powder
Harvesting
Microalgae paste
Microalgae biomass
Crude lipid Transesterification
Biodiesel
Transesterification
Ex situ transesterification
Wet in situ transesterification
FIGURE 5: Transesterification of microalgae biomass to biodiesel [57].
6 Journal of Nanomaterials

7. wavelength is selectively absorbed and scattered to resonant
interactions between photons and surface plasmons. Strong
blue light backscattering from a solution of silver nanoparti-
cles was used in an experiment with Chlamydomonas rein-
hardtii and Cyanothece 51142 in PBR to measure a 30%
increase in cell growth [59]. In a different research, spheroidal
silver nanoparticles and gold nanorods were used to boost
the chlorophyll and carotenoid pigment accumulation in
Chlorella vulgaris [60].
To promote microalgae growth and lipid accumulation,
nanomaterials are also employed as nutritional supplements
for photosynthetic microalgae cells in a culture medium. It is
said that although microalgae’s typical growing medium
contains specific nutrients and minerals, it is insufficient
for the optimum level of development. The absence of essen-
tial nutrients may be supplemented by metallic nanoparticles
found in particular wastewater. It is conceivable to add nano-
particles to microalgae growing medium to positively impact
lipid accumulation since these nanomaterials may increase
microbial activity [61].
The hybrid nanoparticles’ functionalized groups can accel-
erate the uptake and absorption of the CO2 present in the
culture medium. They provide the microalgae’s photosynthetic
system with a sufficient supply of CO2. In contrast to the
suppression of carbon nanotubes (CNTs), nano-Fe2O3, and
nano-MgO, He et al. [62] demonstrated that only nano-Fe2O3
increased cell growth. Intriguingly, the NPs mentioned above-
improved lipid production and total lipid content by raising
their concentrations. MgSO4 NPs may cause microalgae to floc-
culate, reducing their access to light and, as a result, increasing
their chlorophyll content to stabilize their photosynthetic activ-
ity. This is likely a defensive mechanism reaction. In a report,
Metzler et al. [63] made similar claims. San et al. [64] also noted
that Chlorella vulgaris, green microalgae, grew more quickly
when cultured with silica nanoparticles ranging in size from
38 to 190 nm.
5.2. Microalgae Harvesting. More than a quarter of the total
production costs of the process from culture to the manufac-
ture of biofuels are incurred during the algal biomass harvest-
ing from the aqueous phase. One of the most practical and
affordable technologies for collecting algae is flocculation,
which is used in conjunction with other processes, including
centrifugation, magnetophoretic separation, membrane-based
filtering, and electrolysis [65].
Additionally, apart from flocculation, collecting smaller
algal cells in size range of 2–4 µm is challenging and con-
tinues to be a significant obstacle for effective harvesting
technology [66]. One of the most effective methods for col-
lecting microalgae recently has been magnetic flocculation.
Magnetic nanoparticle harvesting is a rapid, low-cost, and
energy-efficient procedure. Target cells are coated with mag-
netic nanoparticles during this process, which is influenced
by an external magnetic field. Separation occurs, and the
microalgal biomass is detached from the magnetic nanofloc-
culant for recycling. Fishponds and freshwater bodies are
using magnetic iron oxide nanoparticles to remove algae.
The algal harvesting process in Figure 6 uses Fe3O4 nano-
particles, and the magnetic flocculant with the maximum
flocculation was created using iron oxide and 0.1 mg/mL cat-
ionic polyacrylamide (CPAM). Chlorella sp. was incubated
with CTAB-decorated Fe3O4 nanoparticles to evaluate the
harvesting effectiveness; as a result, 96.6% of the microalgae
were harvested at a dosage of 0.46 g particle/g cell [67].
5.3. Lipid Extraction. The lipid extraction process is one of the
primary contributors to the overall cost of producing biodiesel
from microalgae. Because algae’s cell walls are made of com-
plex polysaccharides and glycoproteins, they have a broad
spectrum of chemical resistance and high mechanical strength
[58]. Using various solvents to extract lipids from algae is the
most used method (chloroform, methanol, hexane, etc.).
They are used in various ratios, either alone or in combi-
nation. With the use of different solvent combinations, it has
Superparamagnetism Superparamagnetism
Algal
broth
Flocculation
Absorbed by magnet
Fe3O4
CPAM–Fe3O4
CPAM
Magnet
FIGURE 6: Algal harvesting using Fe3O4 nanoparticles [67].
Journal of Nanomaterials 7

8. been shown that the lipid production of algae dramatically
changes. The extraction conditions may also impact the total
lipid yield, including homogenization, ultrasonication, and
irradiation. All of these elements should be considered to
create an optimum extraction methodology with a greater
lipid yield, which may increase the total cost of downstream
processing for biodiesel manufacturing [68].
Recent advances in nanotechnology have provided trust-
worthy, secure, and economical alternatives. Nanomaterials,
unlike solvents, provide nontoxic methods of lipid extraction
in addition to their greater percentage of oil extraction effec-
tiveness. Additionally, the time-consuming and expensive
solvent-lipid separation phase in the standard extraction
procedure may be removed by using nanomaterials [68].
5.4. Transesterification of Algal Oil using Nanocatalysts. The
utilization of nanomaterials has several advantages, one of
which is their high surface-to-volume ratio, which provides a
large surface area for the immobilization of lipase. In addi-
tion, the tiny pore size of nanomaterials allows for a high
reactant diffusion rate to be supplied at the active regions of
the lipase enzyme. Because they are so simple to recover from
reaction mixtures and have improved thermostability, mag-
netic nanoparticles can provide an excellent alternative that
is both convenient and economical [53]. In research, the
covalent attachment of T. lanuginosus lipase to aminofunc-
tionalized magnetic nanoparticles resulted in a conversion
efficiency of 90% for biodiesel [54]. This was done by using
magnetic nanoparticles. Using P. cepacia lipase (PCL) immo-
bilized on Fe3O4 magnetic nanoparticles, Huang et al. [55]
reported a 100% success rate in converting oil into biodiesel.
6. Reusability and Recovery of Nanocatalysts
The reusability and recovery of nanocatalysts in the biodiesel
manufacturing process are the most significant advantages
of using heterogeneous nanocatalysts. The nanocatalyst is
employed in these procedures in multiple cycles to produce
biodiesel, and it is recovered and reused at each stage. Nano-
catalyst recovery is frequently accomplished using chemical
means. The main product and byproduct from the reaction
mixture can be recovered from the reaction mixture quickly
and easily with the use of heterogeneous catalysts. There is
no need for a washing step with this kind of catalyst. Numer-
ous benefits were proposed for the esterification process
using nanocatalysts, including quick and easy separation
from the reaction mixture and faster mixing of the reactants
with the catalyst.
An external magnetic field allows for easy catalyst recov-
ery, and previous studies have shown that it may be recov-
ered multiple times without a noticeable decrease in catalytic
activity or biodiesel yield. Table 3 summarizes the various
nanocatalysts utilized in the manufacture of biodiesel, as
reported by Esmaeili et al. [69]. Also included the data on
nanocatalysts’ reusability and the number of cycles at which
they were employed. These results reveal that the nanocata-
lysts used in this study can be reused multiple times without
suffering a noticeable drop in biodiesel output.
7. Nanoadditives-Blended Biodiesel in
Diesel Engines
Biodiesel has several drawbacks in CI engines, including a
10% drop in fuel efficiency on an energy basis, slightly
greater density, poor fuel atomization, piston ring sticking,
lower cloud and pour points, cold starting issues, and signif-
icant NOx emissions. These drawbacks may be solved by
using a few relatively recent techniques, such as adding gas-
oline additives and utilizing hybrid fuel, which improve
engine performance and reduce exhaust emissions.
Nanoparticles have emerged as a unique and potential
addition to current additives used in biodiesel and diesel
fuels, resulting in lower emissions and improved engine per-
formance. Many researchers have concentrated on nanoad-
ditives fuel modification approaches to increase combustion
efficiency. The pollutants emitted by CI engines are subject
to severe emission regulations worldwide. Gasoline additives
may change a variety of fuel qualities, including density,
volatility, and sulfur content, all of which impact emis-
sions [70].
Incorporating the nanoparticle into liquid fuels as an
additional energy carrier has enhanced combustion proper-
ties. Thus, the researchers investigated whether these modi-
fied fuels might be used in diesel engines. Metal oxides of Fe,
Al, B, Pt, Ce, Cu, Ti, and Co have long been utilized as addi-
tives in biodiesel and diesel fuel mixtures. Carbon nanotubes
(CNTs), graphene, and graphene oxide (GO) nanoparticles
have recently become popular as additions in biodiesel–diesel
blends [71–73].
7.1. Fuel Properties Enhancement. Nanoparticles offer unique
features (such as a greater surface area/volume ratio, a higher
combustion rate, and so on) that make them ideal for various
TABLE 3: Reusability conversion yield (%) of different nanocatalysts to produce biodiesel [69].
Nanocatalyst Oil source Biodiesel yield (%) Number of cycles Reusability conversion yield (%)
MgO/MgFe2O4 Sunflower oil 91.2 5 82.4
KF/CaO–Fe3O4 Stillingia oil 95 14 >90
SiO2/ZrO2 Soybean oil 96.2 1.4 6 84.1
CaO Crude jatropha oil 98.54 6 95.8
Fe–Mn–SO4/ZrO2 Tannery waste 96.6 4 90
Ni0.5Zn0.5Fe2O4 Soybean oil 99.54 3 98.45
CaO_Au Sunflower 97 10 89
8 Journal of Nanomaterials

9. engineering purposes. In addition, nanometric materials may
achieve the necessary chemical and thermal properties stan-
dard. Combining different nanoparticles with biodiesel has
been used in several studies to increase engine performance
and reduce pollution. Figure 7 shows the microexplosion
process of the diesel–metal additive. It has been found that
mixing NPs in BD improves atomization [74, 75].
The physical and thermal parameters (such as radiative
heat transfer, thermal conductivity, and mass diffusivity) of
diesel fuel were greatly enhanced by adding nanoparticles
to it. Adding nanoadditives to biodiesel also increases the
thermochemical parameters (calorific value, density, viscos-
ity, flashes point, and fire point).
7.2. Engine Performance and Emission Characteristics. Adding
nanoparticles to diesel–biodiesel fuel blends can improve
their radiation, heat, and mass transfer performance to obtain
fuller combustion and higher thermal efficiency. Diesel engine
performance parameters, in particular brake-specific fuel con-
sumption (BSFC) and brake thermal efficiency (BTE), could
be improved significantly due to nanofluid additives. The
BSFC is the ratio of the engine’s fuel consumption ratio to
its power output over a specified period. Because the engine
needs more gasoline to run at a similar level, a lower BSFC
number is anticipated. The comparison with engine load is
crucial because BSFC typically declines as load increases. The
viscosity, density, volumetric fuel injection, and calorific value
are the performance factors that control the BSFC. On the
other hand, brake thermal efficiency refers to the ratio
between the engine’s actual brake power and the energy trans-
mitted to the engine. BTE can be used to explore how different
fuels and fuel blends affect an engine’s performance. Due to
superior radiative and heat mass transfer capabilities, the
inclusion of nanoparticles to diesel–biodiesel fuel emulsions
promotes rapid and thorough combustion, which signifi-
cantly increases combustion efficiency [76].
Many researchers have found that when engines run on
biodiesel–diesel, the high amount of oxygen in the biodiesel’s
structure leads to complete combustion, resulting in lower
HC and CO emissions [66–70]. The nanoparticles would
improve the oxidation process during combustion, leading
to increased NOx emissions and lower HC and CO emis-
sions. In addition, some researchers found that nanoaddi-
tives could reduce NOx emissions [72, 73].
Table 4 displays the impact of different nanofluid addi-
tive dosage levels on performance metrics under full load.
It is observed that nanoadditives could significantly improve
BTE and reduce BSFC and noxious emissions.
8. Human and Environmental Safety
Concerns of Nanotechnology-Based
Large-Scale Production
The impacts of nanoparticle exposure on people and the
environment are anticipated to increase their widespread
use in several areas substantially. In light of this, a new
area called nanotoxicity has developed recently, with a pri-
mary emphasis on the risks that nanoparticles pose to
human health and the environment.
Because nanoparticle surfaces may operate as nanocata-
lysts and are tiny enough to reach human cells, these reactions
can have various harmful consequences on human tissues.
In addition, most nanoparticles are made of metals, which
are already well-known to be highly hazardous to particular
organs and readily bioaccumulated by humans [85].
Humans are most exposed to nanoparticles by ingestion,
absorption, or cutaneous contact. Through any of the meth-
ods mentioned above, nanoparticles may enter the circulation
and go to any organ in the body, which can have harmful
effects that are greatly influenced by the organ’s activity level,
size, and concentration. The kidney, lungs, and liver have high
Water containing
nanoparticles
Fuel droplet
containing
encapsulated
nanoparticles
into water
Rapid turning
into vapor of
the droplets
Fuel–air mixing in
the cylinder
increased by rapid
evaporation of
smaller fuel
droplets
Microexplosion
accrued at high
temperature
Emulsification
process
Injection emulsion
into the cylinder by
injector
Nano-
particles
Water
Secondary
atomization
FIGURE 7: The process of microexplosion in the diesel–metal additive [74].
Journal of Nanomaterials 9

10. metabolic rates, which puts them at a greater risk of interact-
ing with any substance the body takes in, including nanopar-
ticles [86].
Therefore, research on the potentially harmful effects of
nanoparticles on these organs in animal models is essential.
Multiwall carbon nanotubes, for example, have been shown
to induce inflammatory and fibrotic responses in the lungs of
Sprague–Dawley rats when injected intratracheally at doses
of 0.5, 2, or 5 mg [87]. Furthermore, according to scientists,
CNTs might aggregate into the tissues of the lungs and the
surrounding areas to create collagen-rich granulomas that
protrude into the bronchial lumen and cause alveolitis.
Wistar rats were exposed to subacute and intraperitoneal
doses of TiO2 nanoparticles, which led to pathological altera-
tions in the liver, increased platelet count, and moderate
inflammation. Additionally, it was shown that rats exposed
to titanium had bioaccumulated titanium in their liver, lungs,
and brain, adversely affecting the animals’ neurobehavioral
development and their organs [88]. Kwon et al. [89] described
the exposure of a freshwater invertebrate to these particles,
TABLE 4: Effects of nanoadditives in diesel/biodiesel mixed fuel.
Nanoparticle Diesel blend with
Main effects increase(s) (↑) and decrease(s) (↓)
Ref.
BTE (%) BSFC (%) HC (%) CO (%) NOx (%)
ZnO Soyabean biodiesel ↑23.2 ↓26.66 ↓32.24 ↓28.21 ↓21.66 [77]
Al2O3 Jatropha biodiesel ↑7.8 ↓4.93 ↓5.69 ↓11.24 ↓9.39 [78]
Graphene oxide Dairy scum oil ↑11.56 ↓8.34 ↓21.68 ↓38.62 ↓5.62 [79]
GNPs Palm oil ↑22.80 ↓5.05 ↓25 ↓4.41 ↑3.65 [80]
NiO Neem oil ↑2.9 ↓1.8 – – ↓6.2 [81]
CNTs Cooking oil ↑8.12 ↓7.12 ↓ ↓ ↑ [82]
CeO2–MWCNT Waste cooking oil – 4.50 ↓71.40 ↓38.8 ↓18.90 [83]
CuO Pongamia ↑4.01 ↓1.0 – – ↓9.8 [84]
Organ damages
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Decreased
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reproduction
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NMs
size, shape
coating
Soil
Organisms, pH, water content,
texture, ionic strength,
organic matter
FIGURE 8: Environmental impact of NMs [90].
10 Journal of Nanomaterials

11. demonstrating their ability to permeate into its digestive sys-
tem, concerning environmental concerns over TiO2 nanopar-
ticles. These particles sometimes significantly damaged the gut
epithelial cells and microvilli, which changed the test subject’s
shape. Although the environmental toxicity of nanoparticles is
not well known, natural populations of aquatic, terrestrial, and
atmospheric creatures may experience some long-term conse-
quences, as shown in Figure 8.
The primary issue stems from the fact that these particles
are tiny enough to interact with biomolecules including pro-
teins, lipids, and DNA, which may readily be collected by
creatures in the food chain and result in significant physiolog-
ical damage [90]. Further research on the ecotoxicity of nano-
particles in animal models is required to understand better the
specific harm these particles may inflict and the genuine haz-
ard of particle buildup. These researches will be crucial in
stopping or lessening the hazardous effects of the nanoparticles
on both exposed persons and the environment as a whole.
When using these incredibly beneficial particles in large-
scale operations like biodiesel manufacturing, there should
be worries about their positive and negative consequences.
Understanding these negative impacts will aid researchers in
developing innovative solutions to lessen them, preserving a
balance between their use and the security of any environ-
ments that could be exposed to these nanoparticles.
9. Future Prospects
In order to implement the reaction process on a broad scale,
technological development is required to reduce mass-transfer
resistance, reduce energy consumption, and maximize the use
of byproducts. The scope for preserving optimum reaction con-
ditions grows, allowing for more biodiesel to be produced using
nanotechnology. High-quality biodiesel, discounted labor and
energy costs, and decreased water and chemical usage have all
contributed to the rising popularity of the data-driven machine
learning (ML) technique in the biodiesel systems [91]. Hence,
the optimum concentration and size of nanocatalysts could be
optimized efficiently using the ML approach.
In addition, there has only been a limited amount of
research done on employing NPs as fuel additives to this
point, and new methods are needed to address issues such
nanoparticle aggregation, erosion, and settling. Trapping the
unburned nanoparticles in the exhaust has become more dif-
ficult due to the addition of nanoadditions to biodiesel. As a
result, efforts are being made to develop a filter that can
remove unburned nanoadditives from the exhaust of diesel
vehicles. It is important to study what happens to the air
quality after the nanoparticle additives are burned in the
engine. Several methods have been used to investigate the
toxicity of nanoparticles, the majority of which involve in
vitro examination of nanotoxicity [92]. However, in vivo
interaction should be explored in detail, with a special empha-
sis on nanoparticles utilized in biodiesel.
10. Conclusion
The scientific community is paying close attention to biodie-
sel since it has several advantages over fossil fuels. This type
of renewable bioenergy has the potential to revolutionize the
transportation industry and offer a suitable replacement for
traditional diesel. The creation of nanocatalysts using various
nanomaterials, which can overcome most of the drawbacks
associated with conventional homogeneous and heteroge-
neous catalysts, has been discovered to play a crucial role
in the biodiesel industries. Due to their exceptional and dis-
tinctive qualities, such as high reactivity, improved catalytic
performance, selectivity, economic feasibility, and ecofriend-
liness, nanocatalysts are becoming more and more critical in
manufacturing biodiesel. Therefore, various nanocatalysts,
including those based on metals, carbon, magnetic materials,
nanoferrites, nanoclays, etc., can be employed to increase
biodiesel production from a variety of feedstocks.
This review has broached interests in the progress and
recent applications of the utilization of nanotechnology and
nanomaterials in biodiesel production and property enhance-
ment. When enzymes are immobilized, their activity and
stability are increased, which increase biodiesel output. Nano-
catalysts are essential for biodiesel generation because they aid
in the transesterification process. Heterotrophic algae cultiva-
tion might benefit from nanotechnology-enabled lipid accu-
mulation. Disruption of cells and extraction of lipids from
algae are two further applications for nanotechnology.
To enhance the efficiency of diesel engines, nanofluids
may be added to diesel–biodiesel blends to increase evapora-
tion, minimize ignition delay, increase flame temperatures,
and maintain flames for extended periods. Nanoadditive
mixed combinations of biodiesel may be used to address other
issues, such as carbon monoxide emissions, hydrocarbon
emissions, NOx emissions, combustion, and evaporation.
However, research in the use of NPs as fuel-additives and
the in vivo toxicity of NPs remains sparse, leaving a number
of technical gaps in the field of nanotechnology-based bio-
diesel synthesis. Last but not least, life cycle analysis (LCA), a
cost–benefit analysis (CBA), and a safety assessment (SA) of
using nanomaterials in biodiesel production are all crucial
for illuminating current issues and outlining potential ave-
nues for future study.
Conflicts of Interest
The author declares that there is no conflicts of interest.
Acknowledgments
The author would like to thank the respective organizations
for supporting this work.
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