Frequently Asked Questions
1. What are the advantages and disadvantages of algae fuels?
Algae biofuels have a number of advantages over crop-grown biofuels. Algae biofuels also have their own challenges and bottlenecks.
The advantages associated with algae fuel include the following:
- Algae can be grown in non- arable land.
- Oil yield is higher than traditional oil seeds
- There is no need for fresh water to cultivate algae. It can be grown using either marine water or waste water.
- Biofuels from algae solve the food versus fuel problem
- It also offers a wide variety of products apart from fuel.
The drawbacks of algae fuel are
- Fuel from algae is quite expensive
- Harvesting of algae is difficult
- Since algae biofuel production is a relatively new technology, more research is required to develop standardized protocols for cultivation and biofuel production.
2. Which are the algal strains that have high oil content?
Some algal strains have high oil content and can be potentially used for biodiesel production.
Provided is a list of algae with their oil content (% by weight)
|Schizochytrium sp||50-77 %|
|Botryococcus braunii||25-75 %|
|Nitzschia sp.||45-47 %|
|Neochloris oleoabundans||35-54 %|
|Nannochloropsis sp.||31-68 %|
|Chlorella sp||28-32 %|
3. How does a raceway pond work?
A raceway pond is a shallow artificial pond used in the cultivation of algae. In these ponds, the algae, water & nutrients circulate around a racetrack. Paddlewheels provide the flow and the algae are kept suspended in the water. The algae are then circulated back to the surface at regular frequencies.
The ponds can be operated in a continuous manner by feeding the ponds constantly with CO2 and nutrients and also removing the algae-containing water constantly on the other end. The NREL’s (National laboratory of the U.S. Department of Energy) Aquatic Species Program ( http://www.nrel.gov/docs/legosti/fy98/24190.pdf ) experimented with raceway ponds for the cultivation of algae.
4. How are photobioreactors (PBR) used in algae cultivation?
A photobioreactor (PBR) is a closed environment which incorporates natural sunlight or artificial illumination to provide a suitable environment for algae growth. There are several types of PBR, namely bubble column, airlift column, stirred-tank, helical and tubular. Among these, Tubular PBR is most commonly used for mass cultivation of algae.
Tubular photobioreactors are made up of transparent and semitransparent tubes which allow sunlight to pass through. In these tubes, algae are circulated along with water and nutrients. The mixing is enhanced by centrifugal or diaphragm pumps. The algae grow inside these closed systems and are harvested once the maximum density is reached.
5. Are algae photobioreactors economically feasible?
As of 2009, algal photobioreactors are not economically feasible to cultivate algae for biofuels. Photobioreactors are highly expensive to construct as well as to operate. Though they are more efficient than open ponds, the capital costs range between $60-$100/m2.
6. Compare open pond algae cultivation systems with photobioreactors
The following table provides a comparative analysis of algae cultivation in open ponds and photobioreactors.
|Water & CO2 losses||High||Low|
|Process control||Complicated||Less complicated|
|Dissolved oxygen concentration||Low||High|
7. How do we harvest algae?
Harvesting is done differently for microalgae and macroalgae.
For macroalgae, harvesting is a fairly simple process that uses a combination of rakes and haulers to harvest and gather the algae.
In the case of microalgae, harvesting is an expensive process. There are several methods used to harvest microalgae. Choosing a particular method of harvesting depends on a variety of factors, such as the size of algae, the environment and more. Filtration is the most common method used for algae cultivation. The other methods include sedimentation, flotation, centrifugation and flocculation.
To know more about each of these methods please refer the below pages:
8. What is the composition of algae oil?
The composition of oil varies with the species of algae. As a sample, provided below is the composition of oil from Dunaliella cells.
|Neutral lipids||58.5% of the lipid mass|
|Phospholipids||22.9% of the lipid mass|
|Galactolipids||10.9% of the lipid mass|
|Isoprenoid hydrocarbons (including β-carotene)||7.0% of the lipid mass|
|Aliphatic hydrocarbons (straight chain and methyl-branched C17 and C19 hydrocarbons)||5.2% of the lipid mass|
Reference: NREL, ASP
9. How do we extract oil from algae?
The extraction methods used to derive oil from algae can be classified as mechanical and chemical methods. Mechanical methods use physical pressure to break open the algal cells and release the oil, while chemical methods use chemicals to dissolve the oil for separation.
Examples for each of the main extraction methods:
- Mechanical methods - Expeller/Press
- Chemical methods - Hexane Solvent Oil Extraction and Supercritical Fluid Extraction
To know more about each of these methods please refer the below pages:
- Algae Oil Extraction
- Extraction of algal oil by Mechanical Methods
- Extraction of algal oil by Chemical Methods
10. What is the density and BTU value of algae oil?
The density of algae oil is similar to that of soybean oil and is approximately 918 Kg/m3 (Weyer et al., 2009). A typical algal mass has a heating value (heat produced by combustion) of 8,000-10,000 BTU/lb, but the heating value of algal oil and lipids is 16,000 BTU/lb. (SERI Research, 1985)
11. What are the possible uses of algae paste that are left after oil extraction?
The lipid or the oil represents only about 25-30% of the algae. After oil extraction, the remaining 70% of the algae are rich in proteins and carbohydrates. Algae cake can be used for a variety of purposes such as animal feed, aquaculture feed, poultry feed, and organic fertilizer. The algae cake can also be processed to produce ethanol, methane and electricity.
12. Why is algae oil is not commercialized yet?
Although there are significant benefits that result from the use of algae as a biofuel feedstock, it has not reached a commercial scale to date. One of the major problems is the cost of algae fuel.
Today, producing micro-algae oil or biomass is highly expensive. According to experts, algae-to-biodiesel projects face problems of high costs due to various factors such as land costs, expensive bioreactors and costs involved in cultivation and harvesting. A highly focused research to reduce the cost of the algal biomass produced could help in the commercialization of this technology.
13. How is biodiesel produced from algae?
Biodiesel is produced by transesterification of the oil extracted from algae. Glycerol is produced as a by-product of this reaction.
To know more about transesterification, please refer the link - Transesterification
14. How is ethanol produced from algae?
Ethanol is produced by the microbial fermentation of algal carbohydrates. The deoiled algae cake can also be used as feedstock for ethanol production.
Fermentation process to produce ethanol includes the following stages.
- The algal cells are disintegrated to release carbohydrates
- The algal carbohydrates are fermented using yeast
- Ethanol produced is separated by distillation
Among algae, macroalgae (also known as seaweeds) are more widely researched than microalgae for ethanol production because of their high carbohydrate content.
15. Is it possible to obtain gasoline from algae?
Yes. Biogasoline can be produced from algal biomass by catalytic cracking of triglycerides. The algal biomass containing high amount of triglycerides will undergo hydrolysis to produce FFAs (Free Fatty Acids). These free fatty acids are further deoxygenated and converted to biogasoline (91-octane gasoline) through decarboxylation.
16. What are the benefits of using algae fuel over conventional fuel?
Fuels from algae have several advantages over fossil fuels as well as over the first and second generation biofuels.
1. Compared to other biofuels most of them made from crops, algae grows much faster and contains much more energy per unit of weight.
2. Algae produces 30-100 times more oil per acre than corn and soybeans
3. Algae biofuel contains no sulfur and hence is non-toxic
4. Microalgae biofuel is highly biodegradable
5. Algae solves the food vs. fuel crisis.
6. Algae fuel is carbon neutral.
17. Name some companies which are involved in algae fuel production?
Provided below are some of the top companies in algae fuel industry
- A2BE Carbon Capture
- Aurora BioFuels, Inc.
- Aquaflow bionomics corporation
- Blue Marble Energy
- Community Fuels
- International Energy
- OilFox Argentina
- Organic Fuels
- PetroSun Biofuls
- Sapphire Energy
- Solix Biofuels
18. What is the level of investments made so far in algae fuel development?
To develop algae biofuel as a viable commercial fuel, a large investment of starting capital and several years of research and development will be required.
In 2006, about $15 million were invested in this industry by venture capital companies (Source: Oilgae estimates). In 2007, investment rose to $32 million. In 2008, until end of Oct, about $180 million in venture capital money has been raised for algae research. (Source: Cleantech)
In July 2009, Exxon Mobil signed a $600 million dollar multi-year partnership with a biotechnology company, Synthetic Genomes, which is the largest and most serious investment that has been made thus far in the development of commercial algae biofuel.
19. What are the dos and don’ts for investing in the algae fuel industry?
- Have a technical expertise and scientific research team before entering the industry.
- A SWOT Analysis is necessary to understanding your opportunities and threats.
- A niche focus could prove quite useful
- Do not get in without being updated about the industry
- Never skip the pilot phase
- Do not fail to assess the project’s risk profile
20. Name some algal strains that are used for wastewater treatment?
Following is the list of algal strains that are employed to treat wastewater.
- Chlorella minutissima
- B. braunii
- Dunaliella salina
- Microactinium sp
- Pediastrum sp
- Scenedesmus sp
- Ankistrodesmus sp
21. How are algae used for wastewater treatment?
Microalgae enhance the removal of nutrients (like N and P), organic contaminants, heavy metals, and pathogens from domestic as well as from industrial wastewater. Microalgae supplies oxygen for the bacteria to biodegrade the pollutants.
Apart from this, algae are widely used for specific purposes like pH reduction, heavy metal removal and decolourization of effluents.
22. Which are the industries that are using wastewater for algae cultivation?
In the last few years, many companies have shown accelerated interest in algae-based wastewater treatment. The following are some of the companies using wastewater for algae cultivation.
- Aquaflow Bionomic Corporation (ABC)
- Blue Marble Energy
- PetroSun Biofuels
- Sunrise Ridge Algae, Inc.
- Kent Bioenergy Corporation
23. How are algae used for capturing CO2?
Algae need CO2 for their growth. For capturing CO2, algae are fed with industrial emissions after the removal of sulphur dioxide. Algae utilize the CO2 which are dissolved in the water (bicarbonates) as a source of carbon and grows. To grow 1 T of algae about 1.8 T of CO2 is required. (Becker, 1994)