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Encouraging prospects for creating renewable energy fuel from microalgae

WRITTEN BY ANDREW MOURANT. The race to create renewable energy fuel from microalgae – of potential huge significance – is leading research teams around the world in diverse directions. The science is becoming better understood, but no one can yet say what will be the best model for commercial production.

It’s possible, even, that the best potential source for alga-derived fuel has yet to be discovered.  Scientists working with algae predict that within a decade, some will make significant contributions to the global mix of renewable energy.

Professor Pat Harvey, a UK academic and head of Bioenergy Research at the University of Greenwich, is leading a 13-strong team of universities, institutes, and specialist companies from across Europe to examine the energy potential of the microalga dunaliella. It’s a 10 million euro, four-year project funded by the European Union.

“The potential is massive,” Prof. Harvey states. “We’ve been cultivating plants forever, but not algae. The field of molecular biology is vast – we need to delve into those cells and understand them much better. There are several thousand algae we don’t know anything about.”

This close study of dunaliella is a departure from other research projects around the world focusing on algae species with a high concentration of lipids – organic compounds with a fatty acid content that can convert to fuel. For the Greeenwich-led team, the great interest in dunaliella lies in its ability to flourish in harsh, saline conditions — and its high yield of glycerol.

The salt water habitat makes it sustainable — few other organisms can survive in such an environment. No freshwater or agricultural land is needed, and there’s no competition with any other element of the food chain.

Dunaliella remains – for the moment – too expensive to cultivate for fuel alone, Prof. Harvey noted. In fact, the possibility of extracting glycerol was investigated by Israeli scientists as long ago as the 1970s, though the imperative of pursuing technology that would enable conversion to fuel receded as the oil price dropped. 
 
But they also discovered dunaliella’s potential for producing beta carotene. And that’s what the Greenwich-led team’s work is all about – exploiting dunaliella in every possible way, with commercial backing. “It produces a range of compounds of great interest in pharmaceutical, cosmetic and other applications,” Prof. Harvey explains. “If we can make algae bio-refineries commercially viable, we’ll have developed a new industry. Pharma and cosmetics companies are showing interest in investing but it’s early days, though we are doing some collaborative work.”
 
Dunaliella can cope with extreme conditions, from salt caves in the Antarctic to tropical salt pans. The Greenwich-led project intends creating ‘the largest commercial cultivation of the single-cell organisms.’ “Dunaliella produces 30% glycerol without the need for photobioreactors that add on quite a big cost,” Prof. Harvey notes.
 
Cultivating algae with the focus purely on lipid content is expensive and complex.  “You’re taking lipid out and, as a cost, adding sodium hydroxide and methanol(to convert it into fuel),” Harvey explains. “It’s an energy-intensive process.”
 
Déjà vu
The University of Greenwich had previously examined the possibility of exploiting the glycerol content of oilseed rape, working alongside a local company, Kent-based Aquafuel. Writing in Chemical Engineer Magazine andexamining the potential for glycerol-based fuel to power engines, Aquafuel project leaders stressed the environmental benefits — that it could be shipped in bulk, and that the consequences of any ocean fuel spill would be minimal.  
Before refinement, glycerol appeared to have little in its favour as engine fuel: it is barely combustible, too viscous, and emits toxic acrolein through the exhaust. Aquafuel, however, has patented a process that it claims can fire a standard 40KWh Deutz engine using glycerine. The company has also stated that glycerol formed within dunaliella requires no further refinement or chemical modification before use.
Another advantage, Aquafuel says, is the near impossibility of igniting glycerine under normal conditions; that it’s safe to handle. Moreover, viscosity drops dramatically with temperature. Its calorific value is little more than a third that of diesel, but when its far high density is factored in, the calorific value is then nearer to 60%.  
 
According to Aquafuel, the use of catalyst abatement has a dramatic effect in cutting glycerol emissions when compared with those from diesel — carbon monoxide (CO) and acrolein to zero; nitrogen oxide by almost 95%. As glycerine is a single compound and not a complex blend, like diesel, its combustion chemistry is much simpler. Being partly oxidised accounts for the low calorific value, but there’s an upside: oxidation is responsible for low emission levels as combustion proceeds at a much higher temperature than that of the normal diesel cycle.
 
Aquafuel says it has yet to take hold on the (energy) market because pharmaceutical-grade glycerine is too expensive and ‘way over spec’ for combustion needs. Moreover, glycerine-distillation capacities are limited. But things could be very different in 10 years (Prof. Harvey says that several countries offer potential algae cultivation.)
 
A pilot plant is expected to be established either in 2017 or 2018, with a small demonstration project to be working within 18 months, according to Harvey. One partner company has been charged with identifying ‘ideal sites… looking at land values’; and then pushing things forward to a point where further investment becomes attractive.  
 
What will a pilot cost? “I don’t think I can tell you that at this stage,” Prof. Harvey stated.
 
Look for Andrew Mourant’s forthcoming piece on “Biofuel from Algae” in August.

Posted 09/07/2014 by Reg Tucker

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