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Biofuel from Algae

Biofuel is fuel in liquid or gas form derived from biomass. Biofuel is considered as a promising source of energy to help reduce greenhouse gas emissions and increase energy security by providing an alternative to fossil fuels. Currently, the main biofuel products include biodiesel and ethanol. Biofuel can be produced from any carbon source that can be replenished rapidly e.g. plants.

Generally, corn, soybean, canola, jatropha, coconut, oil palm, animal fat are used as feedstock for biofuel production. However, these products are consumed by mankind and the competition between the biofuel production and food consumption can potentially cause the increase of oil price. In addition, even if all these oil products are used for biofuel production, they cannot realistically satisfy the biofuel consumption rate. Thus, the new sources for biofuel production are increasingly in demand. Researchers conducted studies on algae as one such source of biofuel

Content Table

Background information on algae1,2

Algae are Eukaryota although conventionally they have been regarded as simple plants within the study of botany. Algae do not represent a single evolutionary direction or line but a level of organization that may have developed several times in the early history of life on Earth. Algae range from single-cell organisms to multi-cellular organisms, some with fairly complex differentiated form. All of them lack leaves, roots, flowers, seeds and other organ structures that characterize higher plants (vascular plants). They are distinguished from protozoa in that they are photoautotrophic.

Algae are usually found in damp places or bodies of water and thus are common in terrestrial as well as aquatic environments. 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. It is estimated that algae produce about 73 to 87 percent of the net global production of oxygen- which is available to humans and other animals for respiration3.

The existing large-scale natural sources are of algae are: bogs, marshes and swamps - salt marshes and salt lakes. Micro-algae contain lipids and fatty acids as membrane components, storage products, metabolites and sources of energy. Algae contain anything between 2% and 40% of lipids/oils by weight.

Algae culture for Biofuel production

The difficulties in efficient biofuel production from algae lie not in the extraction of the oil or production of ethanol, but in finding an algal strain with a high lipid content and fast growth rate that is not too difficult to harvest, and a cost-effective cultivation system (i.e. type of photo-bioreactor) that is best suited to that strain.

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).

The production of algae 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 the projected high yield, algae culture - unlike crop-based biofuels - does not entail a decrease in food production, since neither farmland nor fresh water is required. Many companies are pursuing the development of algae bioreactors for various purposes– including biodiesel production and CO2 capturing.

Algae biomass production4

Producing algae biomass is generally more expensive than growing crops. Photosynthetic growth requires light, carbon dioxide, water and inorganic salts. Temperature must remain generally within 20 to 30 °C. To minimize costs, algae biomass production must rely on freely available sunlight, despite daily and seasonal variations in light levels.

Large-scale production of algae biomass generally uses continuous culture during daylight.  And the practical methods of large-scale production of microalgae are raceway ponds and tubular photobioreactors.

 A raceway pond is made of a closed loop recirculation channel that is typically about 0.3 m deep (Fig. 1).  Raceway ponds for mass culture of microalgae have been used since the 1950s.  In raceway ponds, temperature fluctuates within a diurnal cycle and seasonally. Evaporative water loss can be significant. Because of significant losses of water to atmosphere, raceways use carbon dioxide much less efficiently than photobioreactors. Productivity is affected by contamination with unwanted algae and microorganisms that feed on algae. The biomass concentration remains low because raceways are poorly mixed and cannot sustain an optically dark zone. Raceways are perceived to be less expensive than photobioreactors, because they cost less to build and operate. Although raceways are low-cost, they have a low biomass productivity compared with photobioreactors.

Biofuel1.jpg

Fig 1. Raceway ponds

A tubular photobioreactor consists of an array of straight transparent tubes that are usually made of plastic or glass. This tubular array, or the solar collector, is where the sunlight is captured (Fig. 2). Unlike open raceways, photobioreactors permit essentially single-species culture of microalgae for prolonged durations. Photobioreactors have been successfully used for producing large quantities of algae biomass. Photobioreactors require cooling during daylight hours. Furthermore, temperature control at night is also useful. Outdoor tubular photobioreactors are effectively and inexpensively cooled using heat exchangers. Large tubular photobioreactors have been placed within temperature controlled greenhouses, but it is quite expensive for biofuel production. Photobioreactors provide much greater oil yield per hectare compared with raceway ponds (Table 3). This is because the volumetric biomass productivity of photobioreactors is more than 13-fold greater in comparison with raceway ponds.

Biofuel2.jpg

Fig 2. A tubular photobioreactor with parallel run horizontal tubes

Advantages of Biodfuel from Algae oil

Producing biofuel from algae is considered as one of the most efficient ways of generating biofuels. The main advantages of deriving biodiesel from algae oil include:

• Rapid growth rates,

• A high per-acre yield (7 to 31 times greater than the next best crop – palm oil),

• Certain species of algae can be harvested daily,

• Algae biofuel contains no sulphur,

• Algae biofuel is non-toxic,

• Algae biofuel is highly bio-degradable,  

• 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.

Patents in the Algae oil sector

At present, the photo-bioreactor and algae pond layouts to cultivate algae as well as optimization processes have been patented, but the procedure of production biodiesel from Algae oil is fairly simple. Most companies in the sector are early stage start-ups and involved in R&D rather than commercialisation. To date, none has launched full commercialisation/industrialization of biodiesel from Algae oil on a large scale.

Main obstacles to realize biofuel production from algae

The obstacles to the realization of Algae oil projects lies as follows:

1. The oil-rich algae are difficult to protect from consumption or displacement by invading organisms as they were grown in ponds open to the environment.

2. Algae best produce oil within a narrow temperature band, thus night sky radiation and low temperature and high temperature days and excessive solar IR radiation interfere with pond experiments by wildly varying the cultivation temperature.

A list of companies developing processes for the production of biofuel from algae5.

  • Enhanced Biofuels & Technologies (www.ebtplc.com): The EBT algae process combines a bioreactor with an open pond, both using waste CO2 from coal-fired power plant flue gases as a fertilizer for the algae. The biodiesel and ethanol produced can be sold, or used as an alternative fuel. Emissions are reduced by up to 82%. EBT’s headquarters are in London, UK and the company has a biofuel R&D centre in India.
  • GreenFuel Technologies (www.greenfuelonline.com) - Emissions-to-Biofuels™ process harnesses photosynthesis to grow algae, capture CO2 and produce high-energy biomass. Retrofitting fossil-fired power plants and other anthropogenic sources of carbon dioxide, the algae can be economically converted to solid fuel, methane, or liquid transportation fuels such as biodiesel and ethanol.
  • GreenShift (www.greenshift.com/news.php?id=97) has a license agreement with Ohio University for its patented bioreactor process based on a newly discovered iron-loving cyanobacterium (blue-greenalgae), through their subsidiary Veridium (www.veridium.com), for the purpose of air pollution control of exhaust gas streams from electrical utility fossil-fuelled power generation facilities. Once the algae grow to maturity, they fall to the bottom of the bioreactor and are harvested for fuel or fertilizer.http://www.greenshift.com/news.php?id=97%29%20hashttp://www.veridium.com. GreenShift’s shares are traded on the OTC-BB in NewYork. The company owns majority stakes in the following subsidiary companies-GS Clean Tech  Corporation, GS AgriFuels Corporation, GS Enviro Services, GS Carbon Corporation and GS Energy Corporation.
  • Solazyme (www.solazyme.com) is devoted to harnessing the energy-harvesting machinery of various species of algae to produce valuable products. The company utilizes proprietary genetic engineering methods to develop and optimize commercially relevant biochemical pathways for production of hydrocarbons (for energy and specialty chemicals) & bioactive compounds.
  • LiveFuels A national alliance of labs and scientists dedicated to transforming algae into biocrude by the year 2010. Working on breeding various strains of algae, driving down the costs of harvesting algae and extracting fats and oils from the algae.
  • Valcent Products (www.valcent.net/news_detail.sstg?id=36) has developed a high density vertical bio-reactor for the mass production of oil bearing algae while removing large quantities of CO2 from the atmosphere. This new bio-reactor is tailored to grow a species of algae that yields a large volume of high grade vegetable oil, which is very suitable for blending with diesel to create a bio-diesel fuel.
  • Aquaflow Bionomics Corporation (aquaflowgroupcom.axiion.com), New Zealand-based, has set itself the objective to be the first company in the world to economically produce biofuel from wild algae harvested from open-air environments and to market it.
  • Infinifuel Biodiesel (www.infinifuel.com)-Wabuska Nevada is home to a unique biodiesel project under development and is being touted as the world’s first geothermal-powered and heated biodiesel plant. The existing geothermal power plant features two production wells and seven power production units creating more than 5 MW of electricity, according to Infinifuel. The power plant will provide 2 MW of electricity and 104°C (220°F) steam to the biodiesel facility, which is nearing completion. The company has over 300 acres to grow oil-seed and develop algae ponds on site.
  • Solix Biofuels (www.solixbiofuels.com) is a developer of massively scallable photo-bioreactors for the production of biodiesel and other valuable bio-commodities from algae oil. Solix’ closed photo-bioreactors allow fossil-fuel power plant exhaust to be captured through the growing system. The algae growth rates increase in the presence of the carbon dioxide that would otherwise be emitted into the atmosphere.

Economics of biodiesel production

The cost of biomass production is an important part of the cost of biofuel produced by algae.  Based on the two kinds of reactors to produce biofuel, the cost of microalgae biomass was estimated as follows:

Table 1 The cost estimation of biofuel production

photobioreactors

Raceways ponds

Annual biomass production (t)

100

10,000

100

10,000

The cost to produce 1 kg algae biomass 1 ($)

2.95

0.47

3.8

0.6

Cost of 1 liter oil 2 ($)

1.40

1.8

1 assume that carbon dioxide is available at no cost

2assuming that the biomass contains 30% oil by weight

The estimated cost of producing a kilogram of algae biomass is $2.95 and $3.80 for photobioreactors and raceways, respectively.  The cost of production per kilogram reduces to roughly $0.47 and $0.60 for photobioreactors and raceways respectively, if the annual biomass production capacity is increased to 10,000 t. The cost of biomass for providing a liter of oil would be about $1.40 and $1.81 for photobioreactors and raceways, respectively. Assuming that the biomass contains 30% oil by weight, the cost of biomass for providing a liter of oil would be about $1.40 and $1.81 for photobioreactors and raceways, respectively. Oil recovered from the lower-cost biomass produced in photobioreactors is estimated to cost $2.80/L. This assumes that the recovery process contributes 50% to the cost of the final recovered oil.

In comparison with this, during 2006, crude palm oil, that is probably the cheapest vegetable oil, sold for an average price of $465/t, or about $0.52/L. In the United States during 2006, the on-highway petrodiesel price ranged between $0.66 and $0.79/L. This price included taxes (20%), cost of crude oil (52%), refining expenses (19%), distribution and marketing (9%). If taxes and distribution are excluded, the average price of petrodiesel in 2006 was $0.49/L with a 73% contribution from crude oil and 27% contribution from refining. Thus, a reasonable target price for algae oil is $0.48/L for algal diesel to be cost competitive with petrodiesel. Elimination of dependence on petroleum diesel and environmental sustainability require reducing the cost of production of algal oil from about $2.80/L to $0.48/L. This is a strategic objective.

In conclusion, the biofuel production from algae is feasible based on the technology. However, it will take some time to realize commercialization as an alternative energy

References

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