Algae fuel, algal biofuel, or algae oil is an alternative to liquid fuel that uses algae as its source of energy.Algae fuels are an alternative to common known bio-fuel sources, such as corn and sugarcane. Several companies and government agencies are funding efforts to reduce capital and operating costs to make algae oil production commercially viable.
Just like fossil fuel, algaeoil has many characteristic properties.Some of them are listed below :
Releases CO2 when burnt, but unlike fossil fuel, algae oil and other bio-fuels only release CO2 recently removed from the atmosphere via photosynthesis during the algae’s growth.
The energy crisis and the world food crisis have ignited interest in alga-culture (farming algae) for making bio-diesel and other bio-fuels using land unsuitable for agriculture.
Among algal fuels’ attractive characteristics are that they can be grown with minimal impact on fresh water resources, can be produced using saline and wastewater .
have a high flash point, and are biodegradables and relatively harmless to the environment if spilled.
Algae cost more per unit mass than other second-generation biofuel crops due to high capital and operating costs, but are claimed to yield between 10 and 100 times more fuel per unit area.
History of Algae Oil
In 1942 Harder and Von Witsch were the first to propose that micro-algae could be grown as a source of lipids for food or fuel(algae oil).
Following World War II, research began in the US, Germany,Japan,England, and Israel on culturing techniques and engineering systems for growing microalgae on larger scales, particularly species in the genus cholerra .Since the need for alternative transportation fuel had subsided after World War II, research at this time focused on culturing algae as a food source or, in some cases, for wastewater treatment.
Other contributions to algal biofuels research have come indirectly from projects focusing on different applications of algal cultures. For example, in the 1990s Japan’s Research Institute of Innovative Technology for the Earth (RITE) implemented a research program with the goal of developing systems to fix CO2 using microalgae.
Algae can be converted into various types of fuels, depending on the technique and the part of the cells used. The lipid , or oily part of the algae biomass can be extracted and converted into bio-diesel through a process similar to that used for any other vegetable oil, or converted in a refinery into “drop-in” replacements for petroleum-based fuels.
Algae growing on smokestack pollution and sunlight, producing oil
Alternatively or following lipid extraction, the carbohydates content of algae can be fermented into bioethanol or butanol fuel .
Biodiesel is a diesel fuel derived from animal or plant lipids (oils and fats). Studies have shown that some species of algae can produce 60% or more of their dry weight in the form of oil. Since their cells grow in aqueous suspension, where they have more
efficient access to water, CO2 and dissolved nutrients, micro-algae are capable of producing large amounts of biomass and usable oil in either high rate algal ponds or photo-bioreactor.This oil can then be turned into biodiesel which could be used in automobiles. Regional production of microalgae and processing into biofuels will provide economic benefits to rural communities.As they do not have to produce structural compounds such as cellulose for leaves, stems, or roots, and since they can be grown floating in a rich nutritional medium,microalgae have faster growth rates than terrestrial crops. They can convert a much higher fraction of their biomass to oil than conventional
Butanol can be made from algae or diatoms using only a solar powered bio-refinry. This fuel has an energy density 10% less than gasoline, and greater than that of either ethanol or methanol. In most gasoline engines, butanol can be used in place of gasoline with no modifications. In several tests, butanol consumption is similar to that of gasoline, and when blended with gasoline, provides better performance and corrosion resistance than that of ethanol or E85.
The green waste left over from the algae oil extraction can be used to produce butanol. In addition, it has been shown that macroalgae (seaweeds) can be fermented by Clostradia genus bacteria to butanol and other solvents.
Methane, the main constituent of natural gas can be produced from algae in various methods, namely gasification, pyrolysis and anaerobic digestion. In gasification and pyrolysis methods methane is extracted from algae under high temperature and pressure.
Anaerobic digestion is a straightforward method involved in decomposition of algae into simpler components then transforming it into fatty acids using microbes like acidogenic bacteria followed by removing any solid particles and finally adding methanogenic bacteria to release a gas mixture containing methane.
A number of studies have successfully shown that biomass from microalgae can be converted into biogas via anaerobic digestion.
Therefore, in order to improve the overall energy balance of microalgae cultivation operations, it has been proposed to recover the energy contained in waste biomass via anaerobic digestion to methane for generating electricity.
This process is one of the more costly processes which can determine the sustainability of algae-based biodiesel.You have to Harvest the algae from its growth medium (using an appropriate separation process), and extract the oil out of it. Extraction can be broadly categorized into two methods:
The mechanical methods are further classified into:
The chemical methods are further classified into:
- Hexane Solvent Method
- Soxhlet extraction
- Supercritical fluid Extraction
Each of these methods has drawbacks:
- The mechanical press generally requires drying the algae, which is energy intensive
- The use of chemical solvents cause safety and health issues
- Supercritical extraction requires high pressure equipment that is both expensive and energy intensive.
Since enzymes are rather flexible structures, the active site is continually reshaped by interactions with the substrate.
Many manufacturers of algae oil use a combination of mechanical pressing and chemical solvents in extracting oil.Apart from these, there are some other methods which are not well-known. Some of them are:
Enzymatic extraction – Enzymatic extraction uses enzymes to degrade the cell walls with water acting as the solvent, this makes fractionation of the oil much easier. The costs of this extraction process are estimated to be much greater than hexane extraction.
Osmotic shock – Osmotic Shock is a sudden reduction in osmotic pressure, this can cause cells in a solution to rupture. Osmotic shock is sometimes used to release cellular components, such as oil.
Challenges faced in Algae Oil Extraction
Microscopic algae suspended in water are virtually indestructible
Algae Cell wall has a high elasticity modulus
Even when free water has been removed, wet biomass retains sufficient interstitial water to act as lubricant
Rupture of cell wall through mechanical friction and steam explosion is only possible when dry
Breakthroughs in Algal Oil Extraction
The OriginOil’s algae Single-Step oil extraction process is simpler and more efficient than current systems, which does not require any chemicals or significant capital expenditure for heavy machinery.
The Single Step Process has 2 parts:
- It harvests, concentrates and extracts oil from algae
- It also separates oil, water and biomass in same step.
The process does not use chemicals or heavy machinery and no initial de-watering is required.It separates oil, water and biomass in less than an hour. The company’s Quantum Fracturing technology uses electromagnetic pulses and pH modifications to break down cell walls and release oil from the algae cells.
Continuous Algal Oil Extraction System
Cavitation Technologies Inc. (CTI) has developed a technology that is able to extract oil from algae on a continuous basis utilizing cavitation based extraction. CTI’s Nano reactor is used to create cavitation bubbles in a solvent material.When these bubbles collapse near the cell walls they create shock waves and liquid jets that causes these cells walls to break and release their contents into the solvent. The company plans to license the technology to algal fuel developer
[ YOU MAY ALSO BE INTERESTED IN : Miseries and Happiness ]
Extraction using nanotechnology
In Catilin and Iowa State University – Center for Catalysis (ISU-CCAT), members of the National Alliance for Advanced Biofuels and Bioproducts (NAABB), will build their own pioneering algal oil extraction technology using mesoporous nanoparticles to selectively extract and sequester, targeted fuel-relevant and high value compounds within the algal lipid mixture. The remaining algal oil, which contains free fatty acids (FFA) and triglycerides, will be converted to biodiesel using Catilin’s commercially available T300 catalyst. This technology is efficient and a solid catalyst provides a cost effective conversion route.