Down in the sewer

This column was published in the Waikato Times on 2 June

algaeWhile our government flounders around still somewhat directionless when it comes to a sustainable economy, others are getting on with the job ahead. Blenheim company Aquaflow is one such. It’s actually Marlborough sewage water that is flowing, but the company extracts renewable energy from it in the form of “green crude” oil. The secret lies in the tiny algae that colonise the settling ponds. They may be individually miscroscopic, but in mass they add up to tonnes per day harvested. And they contain oil, stored as they convert the sun’s energy into chemical energy, something they are very efficient at, given access to CO2 and dissolved nutrients in the water in which they are suspended.

Aquaflow harvests algae from the water at the point of discharge from the oxidation ponds.  From this biomass comes the oil which has so far been successfully processed to produce a biodiesel used in an unmodified car and more recently a jetfuel which meets specifications making it suitable for blending with petroleum-based kerosene to power commercial aircraft. It is expected to be able to be refined to produce, like fossil oil, a range of chemical uses as well as fuel.

Algae has been recognised as a feedstock for biofuel for some years. Indeed from 1978 to 1996 the U.S. Department of Energy’s Office of Fuels Development funded a programme to develop renewable transportation fuels from algae, which saw tremendous advances made in the science of manipulating the metabolism of algae and the engineering of production systems.  The programme was brought to a close for economic reasons, but renewed interest in recent years has resulted in several companies, particularly in the US, working on selecting or modifying algae to enhance their oil production and growing them in controlled environments. Bill Gates and the Rockefeller family have produced big capital to fund one of them, Sapphire Energy in California.  The formidable Craig Venter of human genome fame has also entered the field.

Aquaflow has taken a different route. Rather than select or modify algae and provide them with an engineered environment, they work with the wild algae occurring naturally in the sewage ponds.  The oil yield from such algae at 5% to 10% of the biomass is considerably lower than that expected from the higher tech operations, but Director Nick Gerritson explains that there are offsetting advantages in terms of the simplicity of the process. Harvesting at the point of discharge from the ponds is straightforward. There are no measures necessary to guard against contamination or predation of the algae. Nutrient is provided from the waste-water. Capital intensive structures to house the algae are not needed.  Which is not to say there can’t be steps to enhance the process; the company is assembling data to detect where they might usefully be taken, but meanwhile working from a do-nothing baseline is proving viable.

All the more is this so because of a most valuable by-product of the operation. After the algae is removed the discharged water meets the standard set by the WHO for use in irrigation. In other words the same system is producing both fuel and also water which can be re-used, a feature of widespread interest in a world increasingly in need of good quality water.

Aquaflow is working at scale and is through to the stage of a business model.  Six patents have been filed in the US. They are now seeking opportunities for the commercialisation of their technology in the wide field of renewable energy.  There are no guarantees of success, but companies like this give us all reason to cheer. They are an indication of the human inventiveness, knowledge and enterprise which is ready, given half a chance, to steer us to a future no longer reliant on fossil fuel.

4 thoughts on “Down in the sewer”

  1. That’s a very good question George. In that the waste is the feedstock for the algae, it’s creating a fuel from carbon that’s already in the biosphere – in circulation, as it were – so nothing is sequestered. It reduces the amount of fossil carbon being burned though… I would suspect that the process would also reduce the emissions from rotting waste, but that’s not something I’ve read anything about. Perhaps Aquaflow might chip in…?

Leave a Reply