What are Biofuel?
- Biofuels are renewable fuels made from organic matter (biomass), which can be used in place of fossil fuels.
- ”first-generation” biofuels are derived from land crops, including sugar cane, maize and vegetable oil.
- Some first-generation biofuels have come under criticism for competing with food production for land and water resources, motivating the search for alternatives.
- “second generation” biofuels from wood, wastes, grasses and agricultural residues, and biofuels from algae.
What are Algae?
- Algae range from small, single-celled organisms(Micro algae) to multi-cellular organisms(Macro algae).
- Research into algae for the mass-production of oil is mainly focused on micro-algae. The preference towards micro-algae is due largely to its less complex structure, fast growth rate, and high oil content.
- The existing large-scale natural sources are of algae are: bogs, marshes and swamps - salt marshes and salt lakes.
- The existing microalgae industry (strongest in the USA, Australia and Israel) produces around 10,000 tonnes of dry algae per year,5 mainly for dyes, fish feed and dietary supplements. With an oil yield of 25%.
- Fuels from Algae
The types of fuel that can be derived from algae depend on the species of algae and the part of it that is used:-
- Biodiesel is produced from the oil (lipid) content of microalgae by chemical processing to give biodiesel (fatty acid methyl ester; FAME) and glycerol, used in chemical manufacturing.
- Bioethanol is used as a substitute for petrol, and is produced by fermentation of the carbohydrate content of algae by microbes or yeasts. Most cars can use fuel containing up to 10% ethanol, while flexible-fuel vehicles can use blends with up to 85% ethanol.
- Biobutanol is produced by fermentation of the carbohydrates in either micro- or macroalgae. It contains more energy per molecule than ethanol and is less corrosive to internal combustion engines.
- Hydrocarbons can be produced by treating unprocessed algae with high pressures and temperatures or by chemical conversion of microalgal oil. Some species of algae produce hydrocarbons directly. Hydrocarbons are used as aviation fuel.
- Biogas is produced from microalgae and macroalgae by bacteria, in a process known as anaerobic digestion. It can be burned directly for heat and electricity generation, or purified to give biomethane, which is used as an alternative to natural gas in electricity generation, heating or transport. Biogas can be produced from unprocessed algae, or from residues left after other products have been extracted.
- Hydrogen is produced from water by some species of algae and bacteria in the absence of oxygen.
the fuels of most interest for transport are biodiesel and bioethanol.
- Biodiesel is produced from the oil (lipid) content of microalgae by chemical processing to give biodiesel (fatty acid methyl ester; FAME) and glycerol, used in chemical manufacturing.
- Bioethanol is used as a substitute for petrol, and is produced by fermentation of the carbohydrate content of algae by microbes or yeasts. Most cars can use fuel containing up to 10% ethanol, while flexible-fuel vehicles can use blends with up to 85% ethanol.
- Biobutanol is produced by fermentation of the carbohydrates in either micro- or macroalgae. It contains more energy per molecule than ethanol and is less corrosive to internal combustion engines.
- Hydrocarbons can be produced by treating unprocessed algae with high pressures and temperatures or by chemical conversion of microalgal oil. Some species of algae produce hydrocarbons directly. Hydrocarbons are used as aviation fuel.
- Biogas is produced from microalgae and macroalgae by bacteria, in a process known as anaerobic digestion. It can be burned directly for heat and electricity generation, or purified to give biomethane, which is used as an alternative to natural gas in electricity generation, heating or transport. Biogas can be produced from unprocessed algae, or from residues left after other products have been extracted.
- Hydrogen is produced from water by some species of algae and bacteria in the absence of oxygen.
How to harvest Algae?
The photo-bioreactor is the main equipment used to harvest algae.
Advantages of Biodiesel from Algae oil :-
Producing
biodiesel from algae has been touted as the most efficient way to make
biodiesel fuel.
1. Micro-algae have
much faster growth-rates than terrestrial crops. The per unit area yield of oil from algae is estimated to be
from between 5,000 to 20,000 gallons (18,927 to 75,708 litres) per acre, per
year; this is 7 to 31 times greater than the next best crop, palm oil (635
gallons or 2,404 litres). a high per-acre yield (7 to 31 times
greater than the next best crop – palm oil).
o certain
species of algae can be harvested daily.
o Microalgae, can potentially produce 100
times more oil per acre than soybeans—or any other terrestrial oil-producing
crop.
o
Some algal strains are capable of
doubling their mass several times per day.
o In some cases, more than half of
that mass consists of lipids or triacylglycerides—the same material found in
vegetable oils.
2.
algae
biofuel contains no sulphur,
non-toxic, highly bio-degradable.
3.
Unlike
land plants microalgae produce only one cell type and don’t divert resources
into multicellular structures such as flowers, roots or vasculature, and so
they grow much more quickly than land plants. Microalgae can be grown in large
bioreactors and continually harvested unlike crops or macroalgae.
4.
Flexible on Water Quality: Many species of algae thrive
in seawater, water from saline aquifers, or even wastewater from treatment
plants.
5. produce lower
levels of air pollution than fossil fuels.
6. Some commercial
interests into large scale algal-cultivation systems are looking to tie in to
existing infrastructures, such as coal-fired power plants or sewage treatment
facilities. This approach not only provides the raw materials for the system,
such as CO2 and nutrients; but also it changes those wastes into resources. Because:-
o
algae consume carbon dioxide as they grow, so they could
be used to capture CO2 from power stations and other industrial plant that
would otherwise go into the atmosphere.
o Algae can grow in very nutrient rich
environments that are toxic to other plants so they could be used for treating
‘waste waters’, from a range of industrial sources.
7. Mitigation of CO: During
photosynthesis, algae use solar energy to fix carbon dioxide (CO) into biomass,
so the water used to
cultivate algae must be enriched with CO. This requirement offers an opportunity
to make productive use of the CO from power plants, biofuel facilities, and
other sources.
8.The
ability of microalgae to be cultivated on non-agricultural land or in the sea
reducing their competition with food crops for land, makes them an attractive
proposition both economically and sustainably.
o In
addition to its prunlike crop-based biofuels — does not entail a decrease in
food production, since it requires neither farmland nor fresh water.
Challenges in Algaculture
- too much direct sunlight can kill them so temperature must be held steady.
- overcrowding will inhibit their growth.
- the waste oxygen they produce must be continually removed from the water.
- open algal ponds are subject to evaporation and rainfall, which cause salinity and pH imbalances, and local species of algae often overgrow the desired strain.
- finding an algal strain with a high lipid content and fast growth rate that isn't too difficult to harvest.
Challenges to Commercialization
- Algal biofuels are not economical to produce using the technology available today.
- $8 per gallon (in contrast to $4 per gallon for soybean oil today).
- a cost of more than US$6 per litre of biodiesel, more than ten times higher than petroleum.With currently available technology, the production cost is around US$3 per litre.7
- The net cost of fuel production could also be decreased by growing algae for biofuel as part of a waste water treatment process. Waste water may contain nitrate and phosphate, which are essential nutrients for algae. Using biofuel-producing algae to absorb these nutrients could decrease the cost of algae cultivation, as well as providing revenue from the water treatment process.
- Algae can contain other substances with a higher market value than fuel. If these can be extracted along with fuel, and markets for the co-products exist, the income generated can reduce the net cost of biofuel production.
Examples of these co-products include:
- animal and fish feed:-produced from algal residues left after oil extraction.
- food and food additives:-including carrageenan (a thickener) and Omega-3 oil, used to fortify foods or as a dietary supplement.
- chemical feedstocks, such as dyes and ‘building block’ chemicals for manufacturing including hydrocarbons, alcohols and sugars.
- health and beauty products, including cosmetics and sunscreens.
- pharmaceuticals. Substances in algae are being screened for medical applications and include antibiotics and antiviral or antifungal extracts.
- A ‘biorefinery’, where oil and other useful products are extracted, the remaining biomass converted to bioethanol or biogas, and nutrients and water recycled.
