Pilot plant turns wastewater into protein for feed and fuels

An industrial plant that turns wastewater into protein for animal feed and biofuels is due to open in Gloucestershire next month.

The pilot facility, run by UK company Aragreen and Bath University, will use sewage provided by Welsh Water to grow algae, which will then be processed using food manufacturing technology into a saleable product.

The company hopes that by treating water for utility companies in the process of producing the algae, as well as using waste CO2, low-energy lighting and other technology, it will lower the costs enough to make the process commercially viable.

Finding a cost-effective way of growing algae on a large scale could help fuel companies develop low-carbon biofuels that do not impact food production.

Algae-derived protein could also be used as an alternative to soy-based animal feedstock, which is often imported from South American countries and grown on land that could be used for cereals or where rainforest has been cleared.

As well as trialling an upscaled version of techniques used in the lab, the plant will test different types of algae to find ones that efficiently remove nitrates and phosphates from water while producing sufficient amounts of protein.

‘The key challenge is producing algae at a cost that makes it viable to sell,’ Aragreen’s founder Jerome Vaughan told The Engineer.

‘Underlying that, the main cost centres are electricity in terms of the lighting required to substitute sunlight, the nutrients required to feed the algae and the CO2.’

‘Water companies treating wastewater and returning it to the environment often don’t treat it for phosphate and nitrate removal because it’s very expensive to do that. We’re proposing the algae process can be used to remove those nitrates.’

The pilot plant is due to open on 12 August in Stowfield, Gloucestershire. It will take wastewater from a nearby facility and feed it into photo-bioreactors with capacity for 4m3 of liquid, where pulsing LED lights will encourage algal growth.

Using lights of a specific wavelength that rapidly turn on and off — faster than can be seen by the human eye — is more efficient because the algae cannot convert all the light provided by regular bulbs into chemical energy.

The algae will then be concentrated using equipment developed through a joint venture with a company in the US that usually produces manufacturing technology for the food industry.

‘An algal culture may typically have 10g per litre of algae — if you’re lucky — so you somehow have to harvest it from the water at a reasonable cost,’ said Rod Scott, Bath University’s professor of plant molecular biology and academic lead on the project.

The algae are first concentrated by a factor of four or five using a filtering system that copies the way some marine animals feed in coral reefs.

Then a series of belts are passed through the liquid. The algae stick to the fibres of the belts and are extracted from the culture, ready to be dried out. This process is more typically used to concentrate products such as tomato purée.

Vaughan said he hoped the plant would enter commercial production by the end of 2012 once the amount of protein it can produce is determined.

Welsh Water will provide the sewage without charge for the trial but part of defining the business model will involve working out how much it is worth as a resource.

Future operations may also use waste CO2 from manufacturing or wastewater facilities, which could help bring costs down further.

The project was funded by around £400,000 from the university’s EPSRC Knowledge Transfer Account, matched by a similar amount from Aragreen, which is also building the plant for an additional cost.

Bath University is also involved in a project to source algae species from the hot springs of the city’s Roman baths. As these algae can survive at higher temperatures, they could cut the cost of cooling the biofuel production process.