‘Algae Biodiesel’ – Tremendous potential for next-generation Green Energy:
1. Introduction – Biodiesel is a clean burning fuel, produced from renewable resources. It contains no petroleum, but can be blended at any level with petroleum diesel to create a biodiesel blend. Biodiesel is biodegradable, nontoxic, and essentially free of sulfur and aromatics. One of the biggest advantages of biodiesel compared to many other alternative transportation fuels is that it can be used in existing diesel engines, which relieves manufacturers of having to make costly engine modifications. Biodiesel can also be mixed, at any ratio, with conventional petroleum diesel. As a result, the alternative fuel can be used in the current distribution infrastructure, replacing petroleum diesel either wholly, or as a diesel fuel blend with minimal integration costs.
As per the most scientists, biofuels including biodiesel will play an increasingly important role in diversifying energy supplies to meet the world’s growing energy needs. Algae oil is an interesting sustainable feedstock for biofuel / biodiesel manufacturing. It is an alternative to popular feedstocks, like soybean, canola and palm.
Algae are considered a promising potential feedstock for next-generation biofuels, as certain species of algae contain high amounts of oil. This oil from algae can be extracted, processed and refined for various uses. This biodiesel can also be used as transportation fuels using currently available technology. Other benefits of algae as a potential feedstock are their availabilities. They are found in abundance and their growth rates are fast as well. The major technical challenges for algae based biodiesel include identifying the proper strains with the highest oil content with higher growth rates. Developing cost-effective growing and harvesting methods is the key to success for algae based biodiesel. Algae have some redeeming values such as:
(i) Cultivated and harvested as a source of energy,
(ii) Used to remove carbon dioxide, phosphorus and nitrogen from wastewater,
(iii) Used as a carbon offset to meet anticipated greenhouse gas emission requirements.
2. What are algae – Algae are a large group of primitive, mostly aquatic, chlorophyll-bearing plants, lacking specialize tissues and organs namely roots, stems, leaves, flowers etc. Algae are usually found in damp places or bodies of water and thus are common in terrestrial as well as aquatic environments. Form of algae ranges from giant seaweeds to single-celled diatoms and pond scums. Algae are simple plants. Like plants, algae require primarily three components to grow: sunlight, carbon-dioxide and water. Photosynthesis is an important bio-chemical process in which plants, algae, and some bacteria convert the energy of sunlight to chemical energy. Different types of algae grow in different environments. They have different nutritional requirements as well.
3. Harvesting algae – The photo-bioreactor is the main equipment used to harvest algae. Photo-bioreactors can be set up to be continually harvested, or by harvesting a batch at a time. A batch photo-bioreactor is set up with nutrients and algal seed, and allowed to grow until the batch is harvested. A continuous photo-bioreactor is harvested, either continually, as daily, or more frequently.
Some of the factors effecting algae harvest are listed below:
(a) Sunlight – too much direct sunlight can kill them,
(b) Temperature must be held steady,
(c) Overcrowding of algae inhibit their growth,
(d) The waste oxygen produced by them should be continually removed from the water for healthy growth,
(e) Open algal ponds are subject to evaporation and rainfall – causes salinity and pH imbalances,
(f) Some time, local species of algae overgrow the desired strain.
4. Oil from algae – The process of extracting oil from algae is basically the same as other biofuel technology. However, algae do not require prime agricultural land and has a potential yield that far exceeds other renewable sources. Algae consume carbon dioxide to grow. Through photosynthesis, algae pull carbon dioxide from the air, replacing it with oxygen. For this reason, algae based biofuel manufacturers are building biofuel units close to energy manufacturing plants that produce lots of carbon dioxide. In other words, algae based biofuel recycling carbon dioxide, which reduces pollution.
To be more elaborate, algae based biodiesel requires large amounts of CO2 – for the algae to be able to photosynthesize. Coal-fired power plants are the effective source of CO2 as algae growth enhancer. Typical coal-fired power plants emit flue gas up to 13% CO2. This high concentration of CO2 enhances transfer and uptake of CO2 in the ponds. Therefore, the concept of coupling a coal-fired power plant with an algae farm provides an elegant approach to recycle of the CO2 from coal combustion into a useable liquid fuel.
The idea of oil extraction from algae is quite simple. Extract the algae from its growth medium (using an appropriate separation process), and use the wet algae to extract the oil (Note: The algae need not be dried before oil extraction). There are three well known methods to extract the oil from oilseeds, and these methods should apply equally well for algae too:
(ii) Hexane solvent oil extraction
(iii) Supercritical Fluid extraction
5. Advantages of algae based biofuel –
(a) Algae are naturally comprised of up to 60 percent oil.
(b) Algae can be grown in fresh or brackish water (saltier water algae are oilier)
(c) Algae can even be fed on liquid human sewage and on streams polluted by fertilizer run off reducing pollution. Thus, algae farms can be used to clean up our waste streams such as sewage or streams of animal farms (Refer note on “Treatment of sewage using microorganisms” below).
(d) Agricultural produce such as corn generates 100 gallons per acre per year whereas with algae biofuel can be produced 4,000 gallons per acre per year. Studies have shown that, algae are capable of yielding 30 times more oil per acre than the crops currently used in biofuel / biodiesel production. As per some of the experts algae offer per acre yields that is 250 times that of soybeans.
(e) The land used for algae farms is likely to be desert and unused land.
(f) Algae are the fastest growing plants found in nature. Corn or other agricultural crop takes a year to grow; an algae crop can be grown in a couple of days.
(g) Algae can also be economically converted into solid fuels, methane gas or bio-ethanol.
(h) 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.
(i) Algae biofuel contains no sulfur; it is non-toxic and highly bio-degradable.
(j) After the initial building of algae farms it may cost about 1/3 of what we spend every year for importing oil from other nations.
(k) The investment on algae fuel is for ever, actually help to stimulate our nation’s economy.
6. Summary and Conclusion – It is widely believed that, petroleum had its origins in kerogen, which was converted to an oily substance under conditions of high pressure and temperature. Kerogen is formed from algae, biodegraded organic compounds of plankton, bacteria and plant materials. Several studies have been conducted to simulate petroleum formation by pyrolysis. On the basis of these findings, it can be inferred that algae grown in carbon dioxide rich air can be converted to oily substances. Such an approach can contribute to solving two major problems: (a) air pollution resulting from carbon dioxide evolution, (b) future crises due to a shortage of energy sources.
Therefore, it is believed that, algae are one of the most promising feedstocks for future bio-diesel production. The advantegeous points about algae are their widespread availability, higher oil yields and pressure on cultivated land for production of bio-diesel is reduced.
Thus, algae will be the future of fuel. Algae as a fuel source are incredible. Some types of algae are made up of 50% oil, which can be made into biofuel more economically. Theoretically, algae can yield between 1,000 to 20,000 gallons of oil per acre, depending on the specific strain. That is enormous productivity as compared with agricultural based biofuels. In fact, the factors that most influence cost are biological, and not engineering-related.
Process of algae based oil into biodiesel is as simple as oil derived from land-based crops. The difficulties in efficient biodiesel production from algae lie not in the extraction of the oil, but in finding an algal strain with a high lipid content and fast growth rate that isn’t too difficult to harvest, and a cost-effective cultivation system, that is best suited to that strain. Micro-algae have much faster growth-rates than terrestrial crops.
The production of algae to harvest oil for biodiesel has not yet been undertaken on a commercial scale, but feasibility studies have been conducted to arrive at the above yield estimate. In addition to its projected high yield, algae culture – unlike crop-based biofuels – does not entail a decrease in food production, since it requires neither farmland nor fresh water. Many companies are pursuing the development of algae bioreactors for various purposes – including biodiesel production and CO2 capturing.
7. Note: Treatment of sewage using microorganisms – The sewage is defined as the waste water resulting from the various human activities, agriculture and industries and mainly contains organic and inorganic compounds, toxic substances, heavy metals and pathogenic organisms. The sewage is treated to get rid of these undesirable substances by subjecting the organic matter to biodegradation by microorganisms. The biodegradation involves the degradation of organic matter to smaller molecules (CO2, NH3, PO4 etc.) and requires constant supply of oxygen. The process of supplying oxygen is expensive, tedious, and requires a lot of expertise and manpower. These problems are overcome by growing microalgae in the ponds and tanks where sewage treatment is carried out. The algae release the O2 while carrying out the photosynthesis which ensures a continuous supply of oxygen for biodegradation.
The algae are also capable of adsorbing certain heavy toxic metals due to the negative charges on the algal cell surface which can take up the positively charged metals. The algal treatment of sewage also supports fish growth as algae are a good source of food for fishes. The algae used for sewage treatment are Chlorella, Euglene, Chlamydomnas, Scenedesmus, Ulothrix, Thribonima etc.
8. New developments:
* Extracting algae oil on a continuous basis:
OriginOil Inc. has succeeded in extracting algae oil on a continuous basis without cell sacrifice. This new “milking” process will join the company’s Cascading Production technique to create a combined cycle promising new efficiencies. [Refer http://www.indusbusinessjournal.com/ME2/Audiences/Default.asp?AudID=0AD64D9611024CD8A69EAA84C4AF124A ]