Algae represent the third generation feedstock for biodiesel, with much higher yields than second generation crops. Algae yields could reach a high of 50 T of biodiesel per hectare year against 2 T for competing feedstock such as Jatropha.
While biodiesel is the fuel end product that is pursued most, algae can be processed to yield other energy products such as ethanol, diesel, gasoline, aviation fuel, hydrogen and other hydrocarbons. Some companies have started exploring production of these products as well.
Upstream processes such as strain selection, cultivation and harvesting present challenges that are unique to the algae industry and hence deserve closer attention.
Microalgae, owing to their relatively high oil content can be a feedstock for biodiesel while macroalgae is a potential feedstock for ethanol.
From over 30,000 strains of algae available, selecting the most suitable strain needs evaluation of parameters such as desired end products, oil/energy yields, performance in mass culture, complexity of structure, culturing media/environment and more.
In harsh environments such as deserts, photobioreactors might be the most suitable method to grow algae, owing to the control they offer on the external elements.
Costs of setting up and operating a photobioreactor for algae cultivation would be much higher than open ponds, but photobioreactors provide higher efficiency and oil yields. While open ponds costs about $100,000 per hectare in capital costs, photobioreactors cost about $1-$1.5 million per hectare – ten times as much as open pond! On the other hand, photobioreactors provide much higher control for algal monocultures and provide yields that are 3-5X those for open ponds.
Currently, photobioreactor costs range between $70-150/m2. Some of the most important research efforts currently being undertaken are for reducing the capital and operational costs for photobioreactors.
Ensuring high yield, providing optimal light penetration and cost effective aeration are some of the key challenges in microalgae cultivation.
In order to benefit from the advantages of photobioreactors and open ponds, some companies are exploring a hybrid cultivation system that uses both open ponds and PBRs.
Key challenges for cultivating microalgae in wastewater include the availability of large amounts of wastewater, prevention of contamination of desired strains, and cost-effective harvesting.
Photobioreactors might be the most suitable system to grow algae in deserts, owing to control they offer on the harsh environment present in the region.
Algae are already being cultivated in oceans for non-fuel end products such as cosmetics, medicines and food additives.
Using freshwater for algae cultivation is likely to be more expensive than using wastewater or salt water, as large quantities of freshwater might not so easily accessible, and nutrient credits might not be applicable for cultivation in fresh water.
While algae-based CO2 capture at power plants has excellent innate potential, such an activity is not expected to become commercialized until 2015.
Key challenges to this include large land requirements next to power plants, inefficiencies in the actual CO2 capture process and high costs of cultivation should photobioreactors be used.
Oilgae estimates that the current production costs for algae based biodiesel is about $18 per gallon if photobioreactors were used.
Companies that have come up with unique concepts for algae biofuels include Algenol, AlgoDyne, Blue Marble Energy, Inventure, Sapphire Energy and Solazyme.
As of Mar 2010, there are about 100 companies worldwide that have a focus on algae fuels.
While there are no dominant designs in the industry, there are entry barriers in the form of large financing requirements and the need for high end scientific expertise.
There could be some challenges faced while converting algae oil into biodiesel using the transesterification process, owing to the high Free Fatty Acid (FFA) content of algae oil.
Prominent methods currently used for harvesting microalgae are filtration, centrifugation, and flocculation.
Centrifugation and flocculation are expensive harvesting methods, but these are expected to have the most potential in future for harvesting microalgae.
The operational cost of centrifugation for algae harvesting varies from $100 to $500 per ton of algae biomass.
Companies are trying to overcome the challenges faced by the open pond system such as contamination, light penetration and water evaporation by using a hybrid algae product system – cross between open and closed system. For instance, the company GreenStar has introduced a hybrid of open-air and closed bioreactor system that combines the controlled environment of a closed photobioreactor with the inexpensive construction of an open pond system.
Algae in Bioremediation – Significant efforts are being undertaken for the use of algae in waste water treatment, and as a source of carbon capture from power plants, cement factories etc.
Research is going on with regard to harvesting microalgae growing in sewage and industrial wastewater. Dissolved air flotation and filtration have shown promise in the research done so far.
For power plants and other entities that are large scale emitters of CO2, sequestering CO2 using algae provides the opportunity of monetization through carbon credits while at the same time producing biofuels.
About 100 companies are pursuing the production of fuels from algae. Pilot projects undertaken by some of these companies suggest that algae could provide over 10,000 gallons of biodiesel per hectare per year.
Algae – both microalgae and macroalgae – have non-fuel applications that cover diverse industries. The food, health products and nutraceutical markets are the largest among these.
Prominent industries that have synergetic benefits from producing algae fuels are industries that either produce waste water or deal with treatment, power plants and cement plants that are large emitters of CO2, companies in the agriculture industry, poultry & cattle industry, and existing producers of non-fuel algae products such as nutraceuticals or animal feed.
The global biodiesel industry is projected to grow and touch around 14.4 billion gallons by 2015, from 5 billion gallons in 2009.
Venture capitalists are fully aware that algae energy is a high risk- high return domain, and that only companies that are willing to take big efforts to solve the problem have a chance of winning. Hence, they look for companies and teams that are trying to solve the problem by thinking big.
CCRES ALGAE project of CROATIAN CENTER of RENEWABLE ENERGY SOURCES (CCRES)