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NEW Zealand minister of energy Gerry Brownlee has officially opened a CO₂-enhanced wastewater-algae-to-biocrude demonstration project at a Christchurch sewage treatment plant.

“No one in the world has done anything on this scale,” says Rupert Craggs from the NZ National Institute of Water & Atmospheric Research, which leads the project with partner company Solray.

Part of a 230-hectare facility, the project is trialing 5 hectares of high rate algal ponds in which CO₂ is injected into a deep pit against a current.“Adding CO₂ into the ponds enhances wastewater treatment and doubles algal production,” says Craggs. “Our trial aims to show that this complete process can be cost effective and efficient.”

Algae will be harvested from the bottom of the shallow ponds and pumped to Solray’s reactors to produce bio-crude. The goal is to harvest 300 t/y of algae to yield up to 500 bbl of biocrude.  

The shallow, mechanically-mixed ponds are also more efficient at wastewater treatment than conventional oxidation ponds as maximised light supply drives photosynthesis rates, pushing nutrients into the algal biomass. High light levels and continuous mixing also accelerate pathogen destruction. The Foundation for Research Science and Technology is providing NZ$2.5m ($1.8m) to the three-year trial, matched in-kind by Solray.