ĐẠI HỌC QUỐC GIA THÀNH PHỐ HỒ CHÍ MINH
TRƯỜNG ĐẠI HỌC BÁCH KHOA

KHOA MÔI TRƯỜNG VÀ TÀI NGUYÊN
BỘ MÔN KỸ THUẬT MÔI TRƯỜNG

BÀI TIỂU LUẬN

ĐÁNH GIÁ TÁC ĐỘNG CỦA VI TẢO
ĐẾN BIẾN ĐỔI KHÍ HẬU

HỌ VÀ TÊN: ĐINH CHÍ ĐẠT
MSSV: 1811848

GVHD: PGS.TS VÕ LÊ PHÚ

TP. HỒ CHÍ MINH, THÁNG 04, NĂM 2023

Table of contents

I. Introduction .........................................................................................................................................3
1.1. Background..................................................................................................................................3
1.2. Characteristics of microalgae.....................................................................................................3
1.3. Bioplastic ......................................................................................................................................4
1.4. Biofuel...........................................................................................................................................4

II. Application of microalgae...............................................................................................................5
2.1. Bioplastic products form microalgae.........................................................................................5
2.2. Microalgae as a source of biofuel ...............................................................................................5
2.3. Microalgae in wastewater treatment .........................................................................................6
2.4. Bioproducts from microalgae.....................................................................................................7

III. Conclusion........................................................................................................................................8

I. Introduction

1.1. Background

The last two decades' attempts to slow global warming have had positive outcomes, with
greenhouse gas emissions rising at a slower rate during 2010 - 2019 than they performed
during 2000 – 2009 [1]. Each individual should participate in become environmental citizens
which require basic scientific knowledge and insights into social, political, and economics
systems that impact on our environment. Science is a powerful tool for finding answers to
environmental issues. Known for its extensive application possibilities in the renewable
energy, biopharmaceutical, and nutraceutical industries, microalgae have recently gained
significant interest on a global scale. Biofuels, bioactive pharmaceuticals, and food products
can all be produced from microalgae in an environmentally friendly, economically feasible
approach. A number of microalgae species have been looked into for their potential to become
high-value products with remarkable pharmacological and biological properties. They are an
ideal biofuel alternative to liquid fossil fuels in terms of price, renewability, and sustainability
issues [2].

Since that microalgae have numerous applications, ranging from food to medical, they can
also be seen as a solution for future sustainable development. [3]. The primary goal of this
essay is to describe how microalgae can be used to reduce greenhouse gas emissions.

1.2. Characteristics of microalgae

Microscopic algae, often known as microphytes, are not observable with the naked eye. These
are phytoplankton that typically inhabit the water column and sediment in freshwater and
marine environments. These are single-celled species that can be found alone, in chains, or in

groups. Their diameters can range from a few micrometers (μm) to a few hundred micrometers
(μm), depending on the species. Microalgae don't have roots, stems, or leaves like higher
plants do. They have been specifically designed for a setting where viscous forces dominant
[4].

The chemical composition of microalgae changes widely in response to an array of parameters,
including the species and the growth conditions. It is not a characteristic constant element. By
changing their chemical composition in response to environmental variability, some
microalgae are able to adapt to changes in environmental conditions. Their capacity to switch

out phospholipids with non-phosphorus membrane lipids in phosphorus-depleted conditions
is a particularly great example. By simply changing environmental elements including
temperature, illumination, pH, CO2 supply, salt, and nutrients, microalgae can accumulate the
necessary products to a particular level [5].

1.3. Bioplastic

A polymer that is created into a commercial product from a natural source or renewable
resource is known as a bioplastic [7]. A biodegradable plastic consists of material that breaks
down as a result of the action of living things like fungi and microorganisms, bioplastic
material has the ability to biodegrade in nature, but a biodegradable plastic cannot be referred
to bioplastic because the components differ in some cases. A bioplastic is comparable to a
traditional plastic, such as polypropylene, since it can be applied to manufacture commercial
products. The extraction and modification of natural polymers from biomass; polymerization
of bio-based monomers; and extraction of polymers generated in microorganisms are three
generic approaches for generating plastics from natural sources. Bioplastics can be made from
natural organic components such as polysaccharides, proteins, and lipids, as well as plentiful
starch. Some researchers have succeeded in developing starch-based biodegradable bioplastics
[8][9]. Because of its natural composition and inexpensive cost, starch is a natural polymer
derived from plants that can be utilized to manufacture biodegradable polymers.


1.4. Biofuel

Biofuel is a fuel derived directly or indirectly from biomass, such as fuelwood, charcoal,
bioethanol, biodiesel, biogas (methane), or biohydrogen. However, most people associate
biofuel with liquid biofuels (bioethanol, biodiesel, and straight vegetable oil). The term
"biofuels" refers to liquid biofuels used in transportation defined in [10]. Biofuels are
classified into three types. First one is solid biofuels refer to solid organic, non-fossil
biological material (also known as biomass) that can be used as a fuel for heat generation or
electricity generation. Solid biofuels are a product aggregate in energy statistics that includes
charcoal, fuelwood, wood residues and byproducts, black liquor, bagasse, animal waste,
other vegetal materials and residuals, and the renewable fraction of industrial waste. Second
one is biogas, a gas primarily composed of methane and carbon dioxide that is produced by
anaerobic digestion of biomass or thermal processes from biomass, including waste biomass.
In energy statistics, biogas is a product aggregate consisting of landfill gas, sewage sludge
gas, other anaerobic digestion biogases, and thermal process biogases. The last is liquid
biofuels include all liquid fuels of natural origin (e.g., biomass and/or the biodegradable
fraction of waste) that can be blended with or replaced by liquid fuels of fossil origin. Liquid

biofuels is a product aggregate in energy statistics that includes biogasoline, biodiesels,
biojet kerosene, and other liquid biofuels.

II. Application of microalgae

2.1. Bioplastic products form microalgae

Lipids (7%-23%), carbohydrates (5%-23%), and proteins (6%-52%) are the main components
of microalgae. Microalgae also contains calcium (0.1%-3.0%), magnesium (0.3%-0.7%),
phosphorous (0.7%-1.5%), potassium (0.7%-2.4%), sodium (0.8%-2.7%), sulfur (0.4%-1.4%),
copper (18-102 mg.kg-1), iron (1395-11,101 mg.kg-1), manganese (45-454 mg.kg-1), selenium

(0-0.5 mg.kg-1), and zinc (28-64 mg.kg-1) [11]. Chlorella is a genus of green algae found in
freshwater commonly used for bioplastic studies which contains approximately 58% (by
weight) protein. It has higher crack resistance and thermal stability than Spirulina due to its
dense cell walls [12]. This species is frequently found in biomass-polymer blends. After
comparing bioplastic production from 100% microalgae biomass and blends containing
additives and polymers, [12] discovered that blending is required for commercial applications.
In current market mass production of bioplastic synthesis for microalgae biomass still a
challenge as the technical requirement of outcome products haven’t meet.

2.2. Microalgae as a source of biofuel

Because of their high photosynthetic efficiency to produce biomass and their higher growth
rates and productivity when compared to conventional crops, microalgae have emerged as one
of the most promising alternative sources of lipid for use in biodiesel production. They are
easier to cultivate than many other types of plants and can produce a higher yield of oil for
biodiesel production in addition to their rapid reproduction. Microalgae with high oil content
have the potential to produce oil yields up to 25 times greater than traditional biodiesel crops
like oil palm. Microalgae require only 0.1 m2 year per kg biodiesel of land to produce 121,104
kg of biodiesel per year, with an oil production of at least 70% oil by weight of dry biomass
[14].

When compared to other biomass materials such as trees and crops, the costs of harvesting
and transporting microalgae are relatively low. Furthermore, they have no direct impact on the
human food supply chain and environment. In comparison to other plant sources, microalgae
cultivation does not require a large amount of land. Microalgae can be grown in a variety of
environments that would be unsuitable for other crops, such as fresh, brackish, or salt water,

or non-arable lands [15] that would be unsuitable for conventional agriculture. Also mass
culturing of microalgae reduce the greenhouse gas as microalgae can fix carbon dioxide in the
atmosphere, allowing for a reduction in atmospheric carbon dioxide levels. Furthermore, the

production of microalgae biomass can influence the biofixation of waste carbon dioxide,
lowering emissions of a major greenhouse gas. (1 kg dry algal biomass requires approximately
1.8 kg CO2).

2.3. Microalgae in wastewater treatment

Organic and inorganic pollutants are caused by organic and inorganic substances released into
the environment as a result of domestic, agricultural, and industrial water activities. The
classic primary and secondary treatment processes for these wastewaters have been
implemented in an increasing number of locations in order to eliminate easily settled materials
and oxidize the organic material present in wastewater. The end result is a clear, seemingly
clean effluent that is discharged into natural bodies of water. However this secondary effluent
is loaded with inorganic nitrogen and phosphorus, causing eutrophication and other long-term
problems. Microalgae culture is an intriguing step for wastewater treatment because it
provides tertiary biotreatment while also producing potentially valuable biomass that can be
used for a variety of purposes. Because microalgae can use inorganic nitrogen and phosphorus
for growth, they provide an elegant solution to tertiary and quandary treatments.

One of the most promising technologies for advanced wastewater treatment and nutrient
recovery in recent years has been the microalgae wastewater treatment process. Many
researchers have demonstrated the feasibility of using microalgae in wastewater treatment as
a supplement for tertiary wastewater treatment due to its high efficiencies on nutrient removal
in the advanced treatment of municipal, agricultural, and industrial wastewaters [16][17]. It
has been demonstrated that microalgae can efficiently utilize nutrients and grow well in
wastewaters because their growth requires a high amount of nitrogen and phosphorous as well
as solar energy and CO 2 or organic matters as carbon sources for protein, nucleic acid, and
phospholipid synthesis [18]. From the standpoint of design and configuration, it can be divided
into three categories: traditional open systems, enclosed photo-bioreactors (PBRs), and newly
designed multi-technology hybrid systems.


Fig 2.1 Types of photobioreactors (PBR) systems located at the AlgaePARC at Wageningen
University and Research. [21]

These system often aiming for light distribution efficiency as not only use for wastewater
treatment but also for biomass cultivation for other purpose such as bioplastic and biodiesel
mentioned before that.

2.4. Bioproducts from microalgae

Biomass of cultivated microalgae could also utilize for various product development such as
food, healthcare and cosmetic products, biofertilizer. Japan has a well-established market for
edible algae products (algae soup) [19] and according to [20], China and Japan produce and
consume the most dry algae globally. There is use as whole cell (e.g., nori) and extracts,
which can be used as an ingredient.

Fig 2.2 A small bow of algae soup of Philippines

Food, agar, alginates, astaxanthin, beta-carotene, omega-3 fatty acids, phycocyanin,
phycoerythrin, and fucoxanthin are examples of potential high-value products (HVPs) from
microalgae. These are primarily used in pharmaceuticals, nutraceuticals, cosmeceuticals, and
industrial sectors. High-value products derived from microalgae improve the economics of a
biorefinery approach while expanding market scope and opportunities [22].

III. Conclusion

The application of microalgae in wastewater treatment optimize to mass produce biomass
form microalgae as material for various purpose such as bioplastic, biofuels and many
bioproducts. The meaning of reuse microalgae biomass from wastewater nutrients is to form
a cycle for material circulation, as we use discharge materials turn it into other product
ingredients. This prevent large amount of greenhouse gas emission from sludge incineration

such as China in 2019 produce 48.8 × 108 kg CO2 from only sludge incineration and
drying. The microalgae mass production and application also reduce GHG by fixation of
CO2 through process of photosynthesis up to 2.5 g.L-1 per day according to [25], many
photobioreactor system recently been designed and studied to enhance the CO2 fixation rate
of microalgae. Therefor microalgae applications can have huge impact on the climate
changes in many ways.

From self opinions I suggest that more of microalgae research should be focus only as
develop microalgae to become much more accessible for community in form of bioproducts
and apply more microalgae wastewater treating system as not only reduce CO2 in

atmosphere but also prevent later on emission from sludge drying and incineration. Study
more about biofertilizer from microalgae as an alternative for tradition fertilize which cause
salinity accumulation in soil.

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