From cement stacks to fish ponds – algae carbon capture

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An update on the algae bioreactor project at Votorantim's St Marys cement plant in Canada this week provides a good opportunity to review this particular aspect of carbon sequestration. The project, run with Pond Biofuels, went live in 2009. It has now reached its third generation bioreactor at the site.

Little or no performance data has been released generally so we have no way at present of knowing how viable the process is commercially. Cement backers, Brazilian firm Votorantim, are certainly excited by the project even if only for the sustainability kudos it gives them. Director Edvaldo Araújo Rabello presented the project as one of the company's highlights at a keynote presentation at the 6°CBC Congresso do Cimento held in São Paulo, Brazil in May 2014.

One hurdle for the St Marys pilot is the relative lack of light, a required input for algae photosynthesis, even in Canada's most southerly state. Pond Biofuels have reportedly dodged this by using continuously flashing LEDs to simulate artificially short days that encourage growth. On paper or powerpoint a process that could potentially cut even a proportion of CO2 emissions from a cement plant sounds enticing. Yet if it creates more CO2 than it saves, through electricity requirements for example, than it isn't worth using.

This is probably what shelved Lafarge's Carbon Capture and Transformation project. It ran a pilot project at its Val d'Azergues plant in France in 2009 with Salata GmbH. The pilot worked but the researchers decided that new advances in processes and biotechnology were required to make the economic and environmental results better. Other companies have also had problems. Holcim started its Aurantia – GreenFuel project in late 2007 at its Jerez cement plant in Spain, backing it with an investment US$92m. This project stalled when GreenFuel shut in 2009 citing lack of funding as the recession hit.

ACC in India also reportedly started its own algae project in 2007, mentioning it in its sustainability report, but nothing more has been reported since. Since this burst of interest InterCement has invested US$2.5m towards algae research in 2013 working with the Federal University of São Carlos, the Federal University of Santa Maria and Algae Biotecnologia.

Algae-based carbon projects for cement plants may remain stuck in the research stage but the market for biofuels continues to grow. For example, this week we report that Ohorongo Cement in Namibia plans to increase its use of blackthorn as a biofuel to use as an alternative fuel in co-processing. The prospects of turning waste CO2 into a valuable commodity remains uncertain, but the rewards are great. Let's wait and see what St Marys can do.

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