Biofuel is a fuel formed from biomass. It is developed from organic materials like plant or algae material or animal waste. We also get biofuels from forestry, agricultural or fishery products, or municipal wastes and agro-industry, or from special energy crops, food industry, and food service by-products and wastes. Biofuels can be solid, gaseous, or liquid.
Classification of Biofuels
- First-generation biofuels
- Second-generation biofuels
- Third-generation biofuels
First-generation biofuels are the fuel that requires food crops grown on arable land i.e., eatable feedstock such as corn, maize, or soybean. The crop’s sugar, starch, or oil content gets to transform into biodiesel or ethanol, using transesterification, or yeast fermentation. 1G biofuels perform even worse than petroleum-based fuels, due to land-use change, fertilizer usage, and process yields. Bioethanol produced from – Wheat, barley, corn – Potato, sugarcane, beet – Oilseeds (soybeans coconut, sunflower rapeseed), Animal fat, used cooking oil.
Second-generation biofuels are fuels made from lignocellulosic or woody biomass, or agricultural residues/waste. The feedstock used to make the fuels either grow on arable land but are byproducts of the main crop or grown on marginal land. Second-generation feedstocks include straw, bagasse, perennial grasses, jatropha, waste vegetable oil, municipal solid waste, and so forth. Bioethanol & Biodiesel produced from – Cassava, jatropha miscanthus – Straw, grass, wood. Due to the stability of these biopolymers, cost-effective 2G biofuels are now only on the verge of commercialization. Processes to break up the biomass into fuels are thermochemical and biochemical, using enzymes.
In third-generation biofuel, microorganisms utilization takes place. Microalgae are microscopic algae present in freshwater as well as marine systems i.e., in ponds, tanks, or sea.
Microalgae provide several different types of renewable biofuels. This includes biodiesel, methane, and bio-hydrogen. Biohydrogen is produced photobiological, and further processed for bio-oil, and syngas is produced through liquefaction and gasification.
Biodiesel produced from – Microalgae – Microbes
Algae are considered a source for biofuel production which is overcoming the disadvantages of first- and second-generation biofuels. They are biodegradable and less harmful to the environment. Algae are perfect 3G biofuel because of their short harvesting cycle and high growth rate, greenhouse gas fixation ability (net-zero emission balance), and high production capacity of lipids (fat). They also do not compete with food or feed crops and can be grown on non-arable land and saline water.
Microalgae are usually more efficient converters of solar energy comparing to higher plants because the cells grow in aqueous suspension, they have more efficient access to water, CO2, and other nutrients in culture medium.
Numerous species of microalgae can have oil contents up to 80% of their dry body weight. Some microalgae double their biomasses within 24 hours and the shortest doubling time during their growth is around 3.5 hours which makes microalgae an ideal renewable source for biofuel production. It can form up to 200 times more biomass per area than terrestrial biomass.
Production of biofuel from microalgae
Production of biofuel from microalgae requires large amounts of energy and fertilizer. The produced fuel degrades faster than other biofuels, and it does not flow well in cold temperatures which causes minimal impact if spilled. Producing microalgal biomass is more expensive and technologically challenging than growing crops.
Photosynthetic growth of algae requires light, CO2, water, and inorganic salts under controlled temperature and pH conditions. For most microalgae growth, the temperature generally remains within 20°C to 30°C. The growth medium must provide the inorganic elements that constitute the algal cell. Essential elements include nitrogen (N), phosphorus (P), iron (Fe), and in some cases silicon (Si).
To minimize expense, biofuel production must rely on freely available sunlight, despite daily and seasonal variations in natural light intensities. So, Seawater or open ponds are supplemented with commercial nitrate and phosphate fertilizers and a few other micronutrients are commonly used for growing marine algae.
The biofuels produced from microalgae are generally carbon neutral. HOW? The burning process of biofuel produces CO2 which is in turn consumed by the algae in biomass production. Hence the process is carbon neutral and is a viable alternative to fossil fuels.
Advantages of algal biomass for biofuels production:
Algae has major potential for third-generation biofuel due to the given reasons.
(a) ability to grow throughout the year, therefore, algal oil productivity is higher in comparison to the conventional oilseed crops;
(b) the consumption rate of water is very less in algae cultivation;
(c) higher tolerance to high carbon dioxide content;
(d) no requirement of herbicides or pesticides in algae cultivation;
(e) the growth potential of algae species is very high in comparison to others;
(f) different sources of wastewater containing nutrients like nitrogen and phosphorus can be utilized for algal cultivation apart from providing any additional nutrient; and
(g) the ability to grow under harsh conditions like saline, brackish water, and coastal seawater does not affect any conventional agriculture.
You can go through the link given below to find about How biofuel from algae can be produced in detail.
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