A decade ago, the green technology space was alight with the energy potential of algae. Fuel derived from algae, dubbed the ‘third-generation biofuel’, holds several key advantages over earlier feedstocks based on plant crops such as sugar cane and corn (the first generation of biofuel production) and vegetable or animal waste streams (the second).
These algal advantages include higher biofuel yields compared to previous systems, a diverse list of possible fuel types including biodiesel, butanol, ethanol and even jet fuel, as well as the fact that large-scale algae cultivation – whether in open ponds or more advanced closed-loop systems – can be done on land unsuitable for food crops, removing a key concern that biofuel feedstock crops would compete with food producers.
Algae biofuel: hype and disappointment
For more than five years from around 2005, algae-based biofuel companies, including the likes of Algenol, Sapphire Energy and Solazyme, raised hundreds of millions of dollars in private sector investment on the promise that chemically engineering algae could scale up to produce tens of millions of gallons of fuel in a matter of years, at prices competitive with fossil fuels. Fuel conversion from algae is broadly based on the feedstock’s high concentrations of lipids: fatty, oil-containing acid molecules that can be extracted to create biofuels.
Nearly 15 years later, the green tech world has fallen out of love with algal biofuel. Despite the large sums spent on developing the conversion process, the industry’s ambitious production goals – not to mention cost-competitiveness with fossil fuels – remain a distant dream. In terms of cost, major oil price declines in 2008 and 2014 certainly didn’t help biofuel competitiveness, but technical issues have also proven a major sticking point. Intractable problems have been encountered in terms of the energy balance of lipid extraction, maintaining suitable growing conditions in open ponds, and the immense volumes of water, CO₂ and fertiliser required to allow the algae to photosynthesise fast enough at large scales.
“Simulations of microalgal biofuel production show that to approach the 10% of EU transport fuels expected to be supplied by biofuels, ponds three times the area of Belgium would be needed,” wrote Swansea University marine biologist Professor Kevin Flynn in 2017. “And for the algae in these ponds to produce biofuel, it would require fertiliser equivalent to 50% of the current total annual EU crop plant needs.”
As a result, most of the companies touting algal biofuel in 2005-2012 have been driven out of business or shifted their business models to algal production of higher-value products such as dietary supplements, food additives, animal feed and cosmetics.
But while the prospect of algal biofuel lies dormant and the venture capital funding of 2005 has long since moved on, the technology’s long-term potential remains and advances in recent years are keeping the algal ball rolling. The road ahead might be long, but these recent ideas and discoveries could all represent significant steps.
Solving the energy balance issue
One of the main points of friction in the lipid extraction component of algal biofuel production is the need to remove all moisture from the algae in advance, leaving a dry powder from which the lipids can be separated. This is part of the reason that it often requires more energy to power the process than the resulting fuel provides at the other end of the equation.
However, a new method invented by researchers at the University of Utah may have a solution to the energy parity conundrum. A team of chemical engineers have developed a new jet mixer technology that precludes the need for energy-intensive drying processes. The new mixing reactor shoots jets of solvent into jets of algae in liquid suspension, creating the turbulence needed to prompt the lipids to transfer into the solvent stream. Not only does this process require much less energy, the researchers say it is also faster, with lipids extracted in mere seconds.
“There have been many laudable research efforts to advance algal biofuel, but nothing has yet produced a price point capable of attracting commercial development,” said University of Utah chemical engineering assistant professor Swomitra Mohanty, who co-authored the team’s results, which were published in the journal Chemical Engineering Science X. “Our designs may change that equation and put algal biofuel back in play.”
Optimising the production process
Further thoughts on how to optimise the algal biofuel process have been offered by the US National Renewable Energy Laboratory’s (NREL) National Bioenergy Center. In a June 2018 article published by R&D, National Bioenergy Center strategic project lead Philip Pienkos laid out NREL’s research into the economics and practicality of producing algal biomass in large open ponds.
According to the team’s techno-economic analyses, once certain economies of scale are reached and improvements are made in strain characteristics and cultivation methods, it would be possible in the future to produce algal biomass at a cost of $300 per dry ton. This would still not be enough to compete with crude oil, however.
In response, NREL has been investigating the viability of a ‘combined algal processing’ (CAP) concept, which involves a plant capable of simultaneously producing algal biofuels along with a number of useful co-products, including surfactants, polyurethanes and plastic composites.
Scaling up with ExxonMobil and Synthetic Genomics
Synthetic Genomics is one of the few companies founded during the ‘gold rush’ period of algal biofuel development that still has a focus on fuel, having partnered with ExxonMobil to work towards producing biofuel from algae at an unprecedented scale. After years of biological research into optimising algae oil production, the partners are now progressing on an outdoor field study growing naturally-occurring algae in several contained ponds in California.
Synthetic Genomics and Exxon believe that with the progress so far – and expectations of further advances to come – they will be able to produce 10,000 barrels of algae biofuel a day by 2025. Major breakthroughs thus far include the partners’ announcement in the summer of 2017 that the genetic modification of the microalgae strain Nannochloropsis gaditina has resulted in the doubling of lipid content in the algae from 20% to more than 40%, a major increase in the energy yield of the feedstock.
The current outdoor study will use wild algae rather than the gene-edited version; as Swansea University’s Kevin Flynn noted in 2017, there is a wider debate to be had on the ecological implications of genetic modification that could “risk generating unstoppable harmful algal species that could destroy fisheries and damage drinking water supplies”.