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Human growth and development can be linked to the harnessing of energy sources. As technology advances and greater, more efficient energy sources are utilised, quantum leaps in industry, economic growth and human development follow.
Today we find ourselves on the edge of the New Energy revolution. Unlike previous energy revolutions this one will need to consider whole supply chains, macro-economic conditions and environmental sustainability instead of independent energy generation solutions. The potential game changer? Microalgae.
Microalgae are tiny, single-celled organisms that are capable of photosynthesis, responsible for producing 75% of the oxygen in the atmosphere. Unlike other sources of energy, microalgae are well-suited for closing the energy and waste supply chains loop and being tailored for sustainable economic solutions. They have the potential to revolutionise food and farming, combating climate change and even support developments in space exploration.
Why? They have immense potential in waste treatment and production of co-products, along with the ability to provide a renewable, carbon-neutral form of energy generation.
Microalgae take part in the Calvin cycle, where they convert CO2, nutrients and water into oxygen, hydrocarbons, lipids and proteins, and even hydrogen.
Because microalgae produce oily lipids, they are a source for liquid renewable biofuels, such as biodiesel.
Figure 1 – Process
Biodiesel is traditionally developed from oil crops, is compatible with existing infrastructure and can supply numerous co-products. CO2 emissions from biodiesel are also significantly less than fossil fuels, particularly when derived from palm oil - the most energy-dense oil crop.
Figure 2 - CO2 emission of fuels from UK government data
However, an over-reliance on traditional oil crops to produce biodiesel can lead to excessive deforestation. These crops require temperate, arable lands and plenty of fresh water which puts resources for oil crops in competition with food production. Also, the low energy density of oil crops means impractical amounts of land would be required if they were to replace fossil fuels.
Figure 3 - Oil yields of terrestrial crop
Microalgae could be a suitable alternative to produce biodiesel instead of oil crops. It can grow just as easily in saline water as fresh water and as they grow in water suspensions they don’t require arable land. This means coastlines or offshore production of microalgae could be viable. Further, the energy density of microalgae is 10-20 times greater than traditional oil crops.
Using microalgae to replace the annual global production of 1.1bn tons of conventional diesel would require a surface area of approximately 60 million hectares - equivalent to the size of France. This could easily be accommodated on coastlines and/or offshore. On the other hand, using palm oil to create biodiesel would require a much larger (and arable) landmass of approximately 200 million hectares. This is equivalent to the historic arable lands of the US, or the entire landmass of Mexico.
Microalgae strains have been cultivated with oil contents as high as 70%, however, these have not translated into large-scale production yet. The below graph demonstrates the range of microalgae yield from a conservative 10% -20% oil content, with a calorific value of 4.7-5.2 Kcal/g.
Figure 4 - Yield comparison: palm oil to microalgae
An additional benefit of microalgae is its faster growth rates, doubling in size over 24hrs with the ability to grow all year round.
Some products of microalgae are of particularly high value, such as nutritional supplements, vegetarian omega-3 and proteins. Microalgae dry biomass can also be a nutrient rich animal feed.
Fertiliser from microalgae biomass can also revolutionise farming. Recent trials in rural India, supported by the Indian Agricultural Institute, have shown blue-green algae bio-fertiliser can improve paddy crop yields by 30%.
Carbon capture and storage has been developed as a means of storing CO2 emissions produced through coal burning energy generation. This process requires adequate and valuable high-pressure storage sites, typically salt caverns or suitable oil and gas reservoirs that have been depleted, which would compete for natural gas energy storage sites.
An alternative solution is the utilisation of microalgae for carbon capture sequestration. This allows for storage in several ways that would not compete with natural gas storage sites and would not require high-pressure conditions. Microalgae in this way could facilitate CO2 removal by utilising the cultivated microalgae (which has captured CO2) for production of co-products such as lipstick, food products or animal feed.
Microalgae’s ability to remove CO2 from the atmosphere has found its way to vehicle exhaust systems, with the development of scrubbers such as ‘CO2ube Filters’.
Given microalgae can grow in wastewater, it can also be combined with wastewater treatment plants to produce drinking water; supplying two of the raw materials it requires for growth from existing waste streams.
Research conducted by the National Renewable Energy Laboratory (NREL) found that microalgae, when deprived of sulphur and oxygen, will produce hydrogen. It can also produce green hydrogen via pyrolysis of the algae biomass after extraction of algae oil.
Microalgae’s combination of benefits (oxygen, food, fuel, waste treatment etc.) can be applied for space exploration.
Recently the German Aerospace Centre, DLR successfully demonstrated that algae can survive exposure to outer space after being exposed for nearly 2 years attached to the outside of the International Space Station. This provides a further step in their continued research in algae to support space habitation and exploration.
With the atmosphere of Mars approximately 95% CO2, NASA has also initiated several research projects to study microalgae for future Mars explorations. It is possible to seed the Martian landscape with microalgae so that over the long term it could produce enough oxygen to create a breathable atmosphere. While terraforming Mars may be a long way off, these studies will yield technological advancements that will facilitate utilisation on Earth.
The biggest challenge to commercialising microalgae is its processing cost. Harvesting and processing is approximately 2.5 times as energy intensive than that of diesel production. Typically, cultivation occurs in open ponds or in Photo-Bio-Reactors (PHBs), with open ponds more economical but with lower production rates and vulnerable to contamination. To reduce costs, a combined bio-refinery approach is often taken, where other benefits and value-products of microalgae are also produced.
Current microalgae biodiesel prices of approximately $2.64/litre ($10/gallon) for oil content strains of less than 30%, have been achieved, though this is still expensive when compared to conventional diesel at approximately $0.80/litre ($3/gallon). Also, higher yielding strains in laboratories have not successfully scaled up due to survivability and macro-environment limitations.
Further system optimisation is possible. In 2012 NASA pioneered ‘The Offshore Membrane Enclosures for Growing Algae’ (OMEGA) project. OMEGA’s aim is to develop innovative methods of growing algae, cleaning wastewater, capturing carbon dioxide and ultimately producing biofuel, without competing with agriculture for water, fertiliser or land.
Technology is still in the nascent state, with governments and companies around the world investing into research and development. Japan has initiated a program to fly commercial jets powered by microalgae biofuel in time for the 2020 Tokyo Olympics, and numerous Japanese companies have cultivated various strains with commercialisation targets within the next 20 years.
The MINERVA EU-Japan Fellowship supports EU and Japanese companies in the research and development of microalgae products. ExxonMobil is also investing in research of super strains that will translate to large-scale production.
The U.S. Department of Energy projects further technology and efficiency improvements will reduce costs of open ponds and PHB microalgae production by as much as 60%. This is before even considering the valuable co-product stream. As with electric vehicles, solar power, or even the shale-oil revolution, technological advancements and industry experience will eventually drive costs down.
With its inherent advantages, the future of almost every industry is set to undergo a microalgae paradigm shift.
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