By Fiona Hodge

Unicellular algae, although invisible to the naked eye, are the brave new hope in the challenge to find fossil fuel alternatives that won’t wreck the world. Small single celled algae contain oils, often in large amounts. Oil can be up to 86 percent of the dry weight of one high yielding species of algae (Botryococcus braunii).

High yields are just one of the many characters that make algae ideal for biofuel. Algae are remarkably diverse, allowing a variety of production styles. They can be grown in high-tech photo-bio-reactors in a lab, or they can be grown in raceway style ponds in farms. They can happily grow in salty, fresh, and even waste water.

One of the cleverest algal biofuel set ups is right here in New Zealand, where some of Christchurch’s finest sewage is being converted into biofuel by scientists at NIWA. The scientists have built large shallow ponds that are mechanically mixed (think water wheels). The algae drift about the ponds converting carbon dioxide and the nutrients from the effluent, with the help of sunlight, into biomass. This algal biomass is then harvested and fed into their splendidly-named Super Critical Water Reactor which, with the help of heat (300ºC) and pressure (20MPa) results in bio-crude oil. This process replicates the conditions which converted ancient algae into the fossil fuels we have today.

Investment in algal biofuels is coming thick and fast around the world. Boeing heads a massive research team, as does the fuel companies, and many independent algal fuel companies. As well as this government and not-for-profits are becoming involved. In the USA the National Science Foundation is aiming for annual biofuel production target of 35 billion gallons by 2017 with algal biofuels expected to be a significant component. Last week in the UK Carbon Trust announced £8 million funding and a target of 70 billion litres annual algal biofuel production by 2030.

With these ambitious algal biofuel targets there will need to be some serious research. Algae are an extremely diverse group of organisms. They vary in almost every imaginable way, with the only commonality being photosynthesis. Research will need to focus on isolating algae that have high oil content, grow rapidly and can reproduce in the ponds or photo-bio-reactors. The design and shape of engineering systems also needs to be researched. How much light optimises growth? What level of aeration, nutrients, temperature, etc is best for algal growth. How do the different strains reproduce? Do they have different oil contents at different stages of their lives (consider oily teenagers compared to the elderly)? The list goes on.

There is a lot to look forward to in the world of algal biofuels... but in the meantime we should be considering how we’re using our fossil fuels today. One of the most obvious low hanging fruits is fuel economy standards on our vehicle fleet: the development of which was cancelled by National Transport Minister Steven Joyce in 2009.

Fishermen row a boat in the algae-filled Chaohu Lake in Hefei (Reuters)

P.S. It should be noted that these algae absorb carbon dioxide (good for climate change) but release the carbon dioxide upon combustion of biofuels in engines (bad for climate change). So the net result is, when you have extremely efficient biofuel production techniques, a carbon neutral fuel…

Check out this video for a nice introduction into algal biofuels.