What kind of algae for biofuel

Sunlight is the most readily available and inexpensive source of energy on earth. The efficiency of microalgae in converting captured solar energy into biomass exceeds the potential of terrestrial plants. Microalgae do not compete with terrestrial plants for land or water supply as they can be grown in wastewater, leading to their remediation coupled with biomass production. The acumen of microalgae to inhabit diverse habitats could be exploited to allow for the production of compounds near the site of use, which could reduce the transportation costs [ 3 ].

Microalgae are one of the most promising candidates for plethora of biofuels owing to their easy, inexpensive and simple cultivation system. They grow easily with basic nutritional requirements like air, water and mineral salts with light as the only energy source.

They grow on liquid media, so diverse wastewater can also be utilized, which can be efficiently remediated by algae coupled with biofuel production. The optimal use of light energy through photosynthesis is very efficiently executed by microalgae. They possess higher photosynthetic levels and growth rates and can be used for the production of desired biofuels. They can contain considerable amounts of lipids that are mainly present in the thylakoid membranes.

Their biofuels are nontoxic and highly biodegradable. They are essentially free-living chloroplasts and are the pinnacle of minimizing structural component. They have high carbon dioxide sequestering efficacy thereby, reducing GHG emissions. They reduce nutrient load in wastewater as they can utilize nitrogen and phosphorous present in agricultural, industrial and municipal wastewater owing to their phycoremediation acumen.

They can be cultivated in areas like seashore, desert, and so on, which is not suitable for agricultural plants and not competing with cultivable land. Their cultivation is independent of seasons as they can be cultivated round the year and have minimal environmental impact.

The cultures can be facilitated to produce high yields through technological interventions of genetic engineering, synthetic biology, metabolic engineering, and so on as algal systems are readily adaptable.

The biofuels from algae are diverse in nature. Carbohydrate component of biomass is used for bioethanol production, while algal oil for biodiesel and the residual biomass can be utilized for methane, fuel gas or fuel oil production. The biomass after biofuel production can further be used as source of many value-added products like eicosapentaenoic acid EPA , docosahexaenoic acid DHA , nutraceuticals, protein supplements, therapeutics, biocontrol agents, fertilizers, animal feed and aquaculture.

A plethora of biofuels are derived from microalgae by virtue of their unique potential Figure 2. The biofuels include alcohols, which are produced through fermentation, processing of algal biomass through dual approach of hydrolysis and fermentation, traditional method of transesterification, gasification of biomass or Fischer-Tropsch synthesis [ 4 ].

Biofuels derived from microalgae. Biodiesel has comparable engine performance to petroleum diesel fuel, while reducing sulfur and particulate matter emissions [ 5 , 6 ]. Biodiesel is a biodegradable alternative fuel derived from renewable sources and is nontoxic in nature [ 7 ]. During the manufacturing process, triacylglycerols TAGs are transesterified with an acid or alkali catalyst to produce biodiesel and glycerol [ 8 ].

The algal biodiesel production processes fatty acid methyl esters FAME. The chemical composition of biodiesel is generally produced by transesterification of algal oil in the presence of acid or alkali as a catalyst [ 5 ]. The biodiesel from algae can be derived directly from transesterification of algal biomass [ 9 ].

Alternately, it can also be produced by two-step process wherein the lipids are initially extracted and later on transesterified, though either of the processes involves lipid extraction through solvents and alcohols like methanol, isopropanol and petroleum ether [ 8 , 10 ].

The process of direct transesterification is fast and cost-effective technology. Biodiesel generated from microalgae can be an excellent alternative to current diesel crisis, but in order to efficiently produce biodiesel from microalgae, strains with a high growth rate and oil content have to be selected [ 11 ]. The anaerobic digestion of organic matter leads to formation of fuel called biogas or biomethane. There are four stages of anaerobic digestion [ 12 ], which are described as follows: Biopolymer hydrolysis to monosaccharaides mediated by hydrolytic bacteria.

Microalgae has been reported to produce biogas as source of fuel, although the yield of biogas formation is quite low because of the sensitivity of algal cells to bacterial degradation and low carbon and nitrogen C:N ratio, which leads to the formation of inhibitor ammonia. In Scenedesmus spp. The microalga species are capable of producing hydrocarbons, which can further be converted to diesel, kerosene and gasoline. The microalga, Botryococcus braunii, has been reported to produce hydrocarbons with excellent oil yield [ 14 ].

The habitat of B. While algae comprise less than 2 percent of global plant carbon, they absorb and fix up to 50 percent of atmospheric carbon dioxide 30 billion to 50 billion metric tons per year , converting it to organic carbon. Through photosynthesis, they produce up to 50 percent of global oxygen. The Environmental Protection Agency estimates that algae-based biodiesel produced through fatty acid methyl transesterification the only type of algae biofuel modeled to date can reduce greenhouse gas emissions by more than 60 percent compared to petroleum diesel.

Biofuel companies are currently seeking to scale commercial production of algae and are pursuing several engineering approaches to the design of an economical system for growing algae. Companies are investigating use of closed systems and open pond systems. In closed systems, engineers can precisely regulate algae growth conditions. Closed systems include both photobioreactors for photosynthetic algae strains and traditional bioreactors enclosed tanks such as those used in other microbial growth for those, such as cyanobacteria, that do not require sunlight.

After 16 years of research, DOE concluded that the algal biofuel production was still too expensive to be commercialized in the near future. Three major factors limiting commercial algal production exist: the difficulty of maintaining desirable species in the culture system, the low yield of algal oil, and the high cost of harvesting the algal biomass.

DOE concluded that there was a significant amount of land, water, and CO 2 to support the algal biofuel technology. In recent years, algal biofuel production has gained renewed interest. Both university research groups and start-up businesses are researching and developing new methods to improve the algal process efficiency with a final goal of commercial algal biofuel production.

The research and development efforts can be categorized into several areas:. One way to achieve these goals is to genetically and metabolically alter algal species. The other is to develop new or improve existing growth technologies so that the same goals listed above are met. However, it should be noted that this new wave of interest has yet to result in a significant breakthrough.

The production cost of the algal oil depends on many factors such as the yield of biomass from the culture system, the oil content, the scale of production systems, and the cost of recovering oil from algal biomass. Currently, algal oil production is still far more expensive than petroleum diesel fuels. For example, Chisti estimated the production cost of algae oil from a photobioreactor with an annual production capacity of 10, tons per year.

This estimation did not include the costs of converting algal oil to biodiesel, or the distribution and marketing cost for biodiesel and taxes. Whether algal oil can be an economic source for biofuel in the future is still highly dependent on the petroleum oil price. This equation assumes that algal oil has roughly 80 percent of the caloric energy value of crude petroleum. In addition to producing biofuel, algae can also be explored for a variety of other uses, such as fertilizer and pollution control.

Certain species of algae can be land-applied for use as an organic fertilizer, either in its raw or semi-decomposed form Thomas, Algae can be grown in ponds to collect fertilizer runoff from farms; the nutrient-rich algae can then be collected and reapplied as fertilizer, potentially reducing crop-production costs.

In wastewater-treatment facilities, microalgae can be used to reduce the amount of chemicals needed to clean and purify water. In addition, algae can also be used for reducing the emissions of CO 2 from power plants.

Coal is, by far, the largest fossil energy resource available in the world. Consumption of coal will continue to grow over the coming decades, both in the United States and the world. Through photosynthetic metabolism, microalgae absorb CO 2 and release oxygen. If an algae farm is built close to a power plant, CO 2 produced by the power plant could be utilized as a carbon source for algal growth, and the carbon emissions would be reduced by recycling waste CO 2 from power plants into clean-burning biodiesel.

Microalgae are an ideal biodiesel feedstock, which eventually could replace petroleum-based fuel due to several advantages, such as high oil content, high rates of production, less land, etc. Currently, algal biodiesel production is still too expensive to be commercialized. Due to the static costs associated with oil extraction and biodiesel processing and the variability of algal biomass production, cost-saving efforts for algal oil production should focus on the production method of the oil-rich algae itself.

This needs to be approached through enhancing both algal biology in terms of biomass yield and oil content and culture-system engineering. In addition, using all aspects of the microalgae for producing various value-added products besides the algal fuel, via an integrated biorefinery, is an appealing way to lower the cost of algal biofuel production. Indeed, microalgae contain a large percentage of oil, with the remaining parts consisting of large quantities of proteins, carbohydrates, and other nutrients Spolaore et al.

This makes the post-oil extraction residue attractive for use as animal feed or in other value-added products. Skip to content Research is examining microalgae, 20 to 80 percent oil by dry weight biomass, as a biofuel energy crop.

They are classified into three broad groups based on their pigmentation: brown seaweed Phaeophyceae , red seaweed Rhodophyceae and green seaweed Chlorophyceae. Microalgae are unicellular photosynthetic microorganisms, living in saline or fresh water environments that convert sunlight, water and carbon dioxide to algal biomass.

Among the eukaryotic, green microalgae of the class Chlorophyceae , those most widely utilized belong to the genera Chlamydomonas , Chlorella , Haematococcus , and Dunaliella. As aquatic relatives of plants, microalgae flourish in aerated, liquid cultures where the cells have sufficient access to light, carbon dioxide, and other nutrients.

Algae are primarily grown photoautotrophically; still, some species are able to survive heterotrophically by degrading organic substances like sugars. Unlike terrestrial plants, microalgae do not require fertile land or irrigation. Because algae consume carbon dioxide, large-scale cultivation can be used to remediate the combustion exhaust of power plants Rosenberg et al. Algae biomass can play an important role in solving the problem between the production of food and that of biofuels in the near future.

Microalgae appear to be the only source of renewable biodiesel that is capable of meeting the global demand for transport fuels. Reducing the use of fossil fuels would significantly reduce the amount of carbon dioxide and other pollutants produced. This can be achieved by either using less energy altogether or by replacing fossil fuel by renewable fuels. Renewable energy is a promising alternative solution because it fixes CO 2 in the atmosphere through photosynthesis.

They also produce lower or negligible levels of greenhouse gases and other pollutants when compared with the fossil energy sources they replace. Algae, like corn, soybeans, sugar cane, wood, and other plants, use photosynthesis to convert solar energy into chemical energy.

They store this energy in the form of oils, carbohydrates, and proteins. The plant oil can be converted to biodiesel, which is why biodiesel is a form of solar energy. The more efficient a particular plant is at converting that solar energy into chemical energy, the better it is from a biodiesel perspective, and algae are among the most photosynthetically efficient plants on earth. The annual productivity and oil content of algae is far greater than seed crops.

Soybean can only produce about l of oil per hectare. Canola can produce l per hectare, and palm can produce l. Microalgae contain lipids and fatty acids as membrane components, storage products, metabolites and sources of energy. Algae can grow anywhere there is enough sunshine and some can grow in saline water. All algae contain proteins, carbohydrates, lipids and nucleic acids in varying proportions. Microalgae can complete an entire growth cycle every few days. The algae used in biodiesel production are usually aquatic unicellular green algae Chlorophyceae.

This type of algae is a photosynthetic eukaryote characterized by high growth rates and high population densities. Under good conditions, green algae can double its biomass in less than 24 hours. Chlorella is a single-celled green algae belonging to the class of Chlorophyceae. It is a primary algae because it grows autotrophically. Chlorella has green photosynthetic pigments, chlorophyll-a and chlorophyll-b, in its chloroplast.

Using photosynthesis, it multiplies rapidly requiring only carbon dioxide, water, sunlight, and a small amount of minerals to reproduce. Manipulation of metabolic pathways can redirect cellular function toward the synthesis of preferred products and even increase the processing capabilities of microalgae Figure 1.