Simple algal organisms develop biomass that can be harvested and then transformed to make fuels and other products. In a recent post, Aramco revealed that they had produced the 1st batch of biocrude from algae. They along with other researchers and companies are exploring ways to produce and use low-carbon fuels from wastewater and seawater microalgae.
Creating Low-Carbon Fuels from Wastewater and Seawater Microalgae: Aim of the Study
To find out more about alternative liquid fuels that can be used to manufacture eco-friendly and sustainable energy. Also, to determine microalgae’s requirement for producing energy and types of biofuel.
- According to the study by Kleinova et al., biodiesel originated from oleaginous microbes. They are being used as a significant renewable alternative for producing diesel and petroleum.
- Another study by Demirbas suggests that only microalgae hold the potential of renewable biodiesel which can meet the global transportation demands.
What are Microalgae?
They are the world’s tiniest rootless and leafless plants that can produce more than half of the oxygen we breathe. Also, they are a host to bioactive compounds.
Characteristics of Microalgae
- Generally, algae are classified into 2 groups namely eukaryotic and prokaryotic. Microalgae are the oldest living species.
- They have photosynthesis mechanisms similar to those of other plants made of chlorophyll.
- Microalgae are cultivated as aqueous suspension and have more access to water, nutrients, and carbon dioxide.
- Factors defining their classification are their pigment types, chemical composition, cell wall constituents, and morphological features.
- They have the potential to fix CO2 for many sources like soluble carbonate salts, atmosphere, and factory waste gases.
Types of Microalgae
- They can be heterotrophic if they use organic compounds for development.
- Autotrophic, if they are obtaining carbon from inorganic compounds.
- They are characterized as photoautotrophic when they use light as an energy source.
- Similarly, mixotrophic microalgae are photosynthetic ones as they incorporate autotrophy and heterotrophy over photosynthesis.
Challenges of Using Microalgae for Biofuel Generation
Even though using algae for biofuel production is advantageous but has high processing costs. Also, it has low competitiveness which is a critical barrier to its widespread commercialization.
- Establishing biofuel production industries through algae and ensuring cost competitiveness is a major challenge.
- As per the Jones & Mayfield study, by 2030, around 6% of the total energy demand will be fulfilled by biofuels.
- As per some researchers, microalgae for biofuel production includes high amounts of lipids from microalgae. The following tables show the said data.
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Step Involved in Biofuel Production Microalgae
This includes 2 major steps which include various sub-step procedures.
Cultivation of Algae
Algae growth can last from 1 to 10 days, and it allows several harvests. These microorganisms can develop even on dry and arid land. Moreover, some type of algae can grow 20 to 30 times higher than food crops. This study discusses open pond cultivation as it is the most commonly applied method.
Open pond for Cultivation
It is critical to choose the correct technology for cultivating and harvesting algal biomass. Due to economic issues, industrial-scale open ponds are the only option now as they have a straightforward design. Generally, they are developed in the shape of a pond or racetrack and through diffusion CO2 is collected from the atmosphere. The system is further categorized into 3 types: circular pond, raceway pond, and unstirred open system.
Limitations
This method leads to water losses due to evaporation and has low biomass output. Moreover, certain vulnerable algae species are unable to thrive in this environment. The open pond cultivation method is only ideal for places with lots of sunlight and easy access of water, particularly along the coast.
Closed Cultivation System
Since the open system has resource restrictions, closed-system PBRs were developed. There are no direct interactions between the environment and cultural media. It results in relatively more consistent and reliable surroundings for algae cultivation and harvesting.
The closed system produces valuable products and fine chemicals that are used in a number of applications. Biopharmaceuticals, cosmetics, biofuels, and human health supplements are made from them. Flat-panel, vertical tube, horizontal tube, and stirred tank are types of closed cultivation methods.
Limitations
This system is a bit costly as it includes a process parameter approach, air tightness, and mass transfer. Lightning systems require a significant amount of energy making this system inefficient. Its commercialization has become challenging due to its limitations.
Nano-Additives Approach for Speedy Microalgae Culture
Some researchers recently applied nano additives at different stages of microalgae culture. Their focus was to enhance the efficiency of biomass and by-product development.
- Nanomaterials like nanotubes and nanofibers coated with enzymes can be used for immobilization. Certain carbon structures like carbon nanotubes and graphene oxide have the potential to provide stability and activity for enzymes.
- Moreover, nanoparticles have also been used for increasing biofuel and biomass production.
- According to the researchers, it is possible to enhance microalgae biomass by 20-30% with nanoparticle application.
- Gallium aluminum arsenide-based LEDs have been used to scale up the algal culture, thus achieving higher biomass production.
- Optical fibers are also used during algal culture for improving growth efficiency and it also saves lighting costs.
Biofuels in the Transport Sector
Biofuel is important here because it helps in meeting the growing demands of fuel. They are better alternatives than fossil fuels and for the environment as they produce less carbon dioxide emissions. This in turn reduces GHG emissions and makes fighting against climate change a bit easier. Petrol from old algae deposits is a limited source and is becoming more expensive and is possibly running out.
A study states that microalgae are valuable biofuel sources. Microalgae accumulate and synthesize a considerable amount of neutral lipids, which is advantageous. Moreover, microalgae offer all year-round production and ensure efficient oil yield for each cultivated area in comparison to oilseed crops.
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Importance of Algae in Biofuel Production: Aspects from Various Studies
There have been numerous studies testifying to the advantages of microalgae in comparison to other terrestrial plants.
Study #1
Jones & Mayfield study suggested that microalgae can be used to produce different forms of biofuels. For example, methane production by aerobic digestion from microalgal oil from biohydrogen.
Study #2
The Pienkos & Darzins survey states that they observed microalgae, single-celled organisms, can be duplicated with high-speed techniques and create rapidly changing strains. The study showed eco-friendliness and easy growing possibilities of microalgae. Moreover, the cultivation process of microalgae can reduce waste streams.
Study #3
As per the Pittman et al. study, microalgae can provide the highest biomass yield per unit area and length. This is the reason it has received significant attention for renewable energy generation. It has high oil and starch content and does not require specific agricultural land for cultivation or freshwater to survive. It can easily be grown with carbon dioxide and wastewater.
Study #4
According to the Patil et al. study, microalgae are favored over macroalgae as the latter is less flexible and provides only one processing method. Whereas microalgae use CO2 and sunlight for the process to produce biofuels, feeds, and high-value bioactivities. It is notable that microalgae account for more than 40% of global C-fixation, with marine microalgae that accounts for most productivity.
Study #5
Another study by Singh & Olsen, there is around 50% carbon by dry weight in microalgal biomass. Algae can produce large amounts of biomass in a short period of time. This is because no cellulose is needed for their branches, leaves, or roots. Moreover, to make biodiesel from microalgae, collection, extraction, and conversion into nano catalyst is easily done resulting in efficient biodiesel production. Whereas macroalgae have various lipids, hydrocarbons and complex oils which makes the process complex.
Here is a simplified and explained version of Global Energy Outlook 2024-2050.
Conclusion
Microalgae have a better growth rate than other terrestrial crops, have high lipid content, and breed fast. It is evident that no single strategy is capable of providing an effective solution. Thus, a combination of processes is required to ensure dependence on biofuels for energy production. It is important to ensure algal effectiveness in biofuel processing and oil extraction. With this, it becomes clearer that low-carbon fuels from wastewater and seawater microalgae can be the next best sustainable solution.
