Algae could turn pig waste into an asset

Researchers at Murdoch University’s Algae R&D Centre are investigating whether the effluent from piggeries can be treated with micro- and macroalgae so that species of the organism can be fed back to pigs. The Cooperative Research Centre for High Integrity Australian Pork (Pork CRC) has invested $300,000 with the centre to investigate the proposal, which would cut costs, recover energy from waste and reduce the potential for groundwater contamination at piggeries.

Anaerobic digestion in lagoons or ponds on farms is currently the most common method used to process piggery waste. R&D Centre Director Dr Navid Moheimani and his team from Murdoch’s School of Veterinary and Life Sciences have discovered three different types of microalgae that can grow on untreated piggery anaerobic digestate effluent, which typically contains extremely high levels of ammonium.

The team has found that microalgae remove ammonia and other nutrients, and potentially reduce the pathogen load in the effluent, meaning that the treated wastewater can be re-used. The algal biomass produced is potentially a protein-rich food source for pigs and other animals.

“We have high hopes that this method of treating effluent will ensure the algal biomass produced can be fed back to the pigs, which will make Australian piggeries much less wasteful and more cost competitive,” Dr Moheimani said.

“Pig slurry could well be viewed by the industry as a resource rather than a waste management issue.”

Dr Moheimani and his colleagues are now looking at methods to optimise the growth of the microalgae on the effluent and are bioprospecting for suitable species of macroalgae to grow on piggery effluent. Macroalgae are larger and easier to harvest than microalgae.

If the micro- and macroalgae grown on the effluent is found to be unfit for consumption by pigs, Dr Moheimani said his team will investigate how algae can help to maximise biogas production from piggery effluent. Consisting mostly of methane and carbon dioxide, biogas is a renewable energy source that is currently produced as a by-product of anaerobic digestion and can be used to generate electricity on farms.

“Australian pork producers are a resourceful group, as demonstrated by the successful uptake of energy replacement by the capture and use of biogas on-farm,” said Pork CRC Program Four Leader Dr Rob Wilson. “This work complements the environmental credentials of pork producers while exploring the possibility of producing a food source or a co-digestion product for bioenergy output.”

Image caption: Dr Rob Wilson and Dr Navid Moheimani at Murdoch University’s Algae R&D Centre.

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