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​​Algal Bioenergy:
Over the past decade the biofuel industry has seen massive growth globally, more than
doubling in production every 2 years. It is thought however, that the biofuel industry is currently operating far below its capacity due to the lack of a suitable feedstock. International experts and policy makers have tipped microalgal systems as playing a crucial role in a clean and environmentally sustainable future.
So what are microalgae? And why have they been chosen as a superior alternative to terrestrial biofuels?
This section gives an overview of what algal bioenergy is and their benefits as a biofuel feedstock.
Understanding Algae
Algae are a very large and diverse group of simple plants that live in bodies of water or damp conditions. They are capable of growing by harnessing the sun's energy during photosynthesis. Algae, like humans, are eukaryotic organisms due to the defining feaure of tiny organelles within the cells that are encased by a protective membrane layer. This feature distinguishes eukaryotes from bacteria species, also known as prokaryotes.
Although not strictly an algae, cyanobacteria, also reffered to as blue-green algae, are also a particular area of interest in biofuel production. These organisms evolved billions of years ago in the oceans, long before plants colonised the land. They were responsible for shaping the atmosphere today through the production of large volumes of oxygen. Unlike microalgae, they do not produce lipids naturally, however, they do have a rapid growth rate, producing large amounts of biomass (biological material) in specific conditions. As well as this, cyanobacteria species have a relatively simple and well understood genetic make-up. This has allowed scientists, through genetic modification (GM) of cyanobacteria species, to introduce new and desireable traits, not normally found in the species, such as lipid production or enhanced growth.
The lipids produced and overall biomass gained from the cultivation of algal species have been an area of interest as a potential feedstock in the bioenergy world since initial research funded by the US Government in the 70s.
Biofuel production from these species prevents one huge difference between the production of other high-value products. A huge increase in oil yield must be obtained to sell vast quantities of lower value per unit products. In order to achieve this, cultivation and harvesting systems must be significantly upscaled and manipulated to lower overall production costs. If achieved algae could have enormous benefits as a biofuel feedstock.
Oil produced from single celled microalgae
(Photo courtesy of IBEB Fr.)
Algae can be classified into large seaweeds (macroalgae) or microscopic, single celled, microalgal species. The group microalgae account for an estimated 200,000-800,000 different types of species with thousands of genetic variants (or strains) among each species.
Different species of microalgae are capable of producing unique products such as carotenoids, antioxidants, enzymes, polymers, peptides and toxins. As a result, microalgae have been produced commercially for several decades, most commonly as nutritional supplements and natural pigments. One important feature that has drawn recent attention to their use as a biofuel feedstock, is their natural ability to produce fatty acids. These fatty acids, also known as lipids, are made up of long chains of hydrocarbons with a carboxyl group (-CHO) on their end. These are the primary components of oil which can be further processed to produce fuels.
The Advantages:
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Rapid growth rate and excellent yields
One of the main advantages of microalgae is their high productivity. They are the fastest growing photosynthesising, single celled organism and complete an entire growing cycle every few days. Certain species have been shown to produce up to ten times the amount of biofuel per area of land than the best plant sources. Current research involving GM techniques have suggested even higher yields per acre.
For more information about increasing productivity through GM algae, please follow this link:
Land areas unsuitable for agriculture
Unlike plant biofuels, the cultivation of algae is not dependent upon agricultural land. They are some of the most robust organsims in the world and can be grown in open ponds and closed photobioreactors in a variety of different conditions. Current systems have been used in the desert (as seen in the image below), integrated into sewage and wastewater systems as well as marine environments. These areas that have no functional use, pose no adverse effects on global food markets and open new economic opportunities for arid, drought or salinity-affected regions.
In the barren desert of New Mexico USA, Sapphire Energy are in the process of building the first commercial open-pond algae system for energy
Versatility: ability to produce several different types of biofuels
An important feature of algae as a potential biofuel feedstock is their ability to produce various types of biofuels. Through a series of different processing techniques, the oil and biomass recieved as a result of large scale cultivation can be converted to biodiesel, bioethanol, biogas and biohydrogen. The left over biomass can also create energy from direct combustion. First generation crop biofuels, on the other hand, are specific to the species grown. Corn and sugar cane are used in the production of ethanol whilst soybeans are used to produce biodiesel.
To learn more about how different biofuels are produced from algae species, please visit the next page:
Integrated Systems
It has been proposed that large scale cultivation of algae could be incorporated with other uses. One such integrated system is with the treatment of wastewater. Many of the important nutrients needed in algal growth can be found in wastewater. Algae grown in wastewater would receive sufficient and cost effective nutrients to grow with the additional benefits of cheaper nutrient removal involved in the treatment of wastewater.
For further information on this innovative form of cultivation, follow the text link:
The fundamental factor underpinning the success of any biofuel is its economical feasibility. For a biofuel to be produced on a large scale and used as a replacement to fossil fuels it must be competitive in price.
While algae biofuels have shown enormous environmental benefits, doubts remain over the economics and carbon mitigation of current production techniques. To learn more about how biofuels can be made from algae and how developing technology can improve current systems, please follow this link: