Holy grail or hype

In the case of Asparagopsis, scientists have worked out that bromoform – a chemical found in many seaweeds – inhibits the methanogens, reducing methane release.

The first thorny fact is that bromoform is a known animal carcinogen. While it occurs in low levels in chlorinated water, the United States’ Environmental Protection Agency has classified it as a probable human cancer-causer. It also depletes the ozone layer.

Proponents argue that, in seaweed, bromoform is locked away in a complex cellular structure. But scientists and farming industry bodies are wary.

Andy Reisinger, the New Zealand Agricultural Greenhouse Gas Research

Centre deputy director, who raised the bromoform problem back in 2016, says his concerns remain unanswered.

‘‘I don’t think it’s a bad idea. I think it’s an idea where claims have run ahead of the evidence and people haven’t addressed core problems, or have tried to ignore them or make them go away by continuing to be terribly excited about it.’’

Pastoral Greenhouse Gas Research Consortium (PGGRC) general manager Mark Aspin says the farming industry remains nervous about the risk to its reputation of bromoform residue turning up in meat or milk. The memory is still raw of the fears sparked by the discovery of a trace of chemical DCD – which was not considered a food-safety risk – in milk.

‘‘I think there’s still quite a bit of work to do. It’s not trivial to think about no residues, no food safety issues, no challenges like that. DCD – the nitrification inhibitor that was released was found in milk – it wasn’t meant to be there, end of story.’’

CH4 Global co-founder – cleantech entrepreneur Nick Gerritsen – is promising big things. As well as harvesting wild Asparagopsis on Rakiura, CH4 Global is undertaking tank trials to grow the seaweed from cuttings and has experimental growing ropes in the ocean – like mussel lines – in Rakiura and South Australia.

The South Australia project is researching both taxiformis and armata, while the New Zealand efforts are limited to armata.

In New Zealand they’ve produced more than a tonne of the algae, but that’s almost all wild harvest. They’re also investigating using existing freeze-drying operations in Invercargill to process the seaweed to a dried powder.

Their first target market is California, where lawmakers have decreed the state must reduce emissions by 40 per cent by 2030, which requires methane cuts in its 1.7 million dairy cows and 650,000 beef cattle.

Gerritsen estimates 1000ha of Asparagopsis farm would be enough to provide 10 per cent of that market, and that should be doable by 2022.

The business could create more than 3000 new jobs, CH4’S website says. Gerritsen has also predicted CH4 would be the first commercial-scale producer and leading global supplier into Australasia, California and other farming areas.

The rhetoric is similar to that surrounding a previous venture Gerritsen founded in 2005 with renewable energy champion Barrie Leay and former Christchurch mayor Vicki Buck.

Called Aquaflow Bionomic, the company planned to produce biofuel from algae harvested from Blenheim poo ponds. Despite continuous promises that the company was on the verge of commercial production, its pilot plant only ever produced a tiny amount of green crude. Former staff say the media hype bore no resemblance to the reality on the ground.

Gerritsen does not accept he over-hyped Aquaflow and says it’s unfair to compare the two.

Rhetoric aside, growing enough seaweed to reduce emissions in the world’s cows presents a mammoth logistical challenge. Dairy cows eat about 16kg of dry feed a day, so at 1 per cent that’s 160g of seaweed per cow per day during milking season. That would mean 1000 tonnes a day just to feed the New Zealand dairy herd.

That’s dry weight. But seaweed is 70-90 per cent water, so the drying costs could be astronomical. For one research study, the seaweed was blastfrozen for six hours then freezedried for another 30 hours. Gerritsen says the economics of processing need more work, but at this stage it looks viable.

Asked how easy it is to grow algae, Niwa seaweed specialist Wendy Nelson laughs.

‘‘That’s like asking how easy it is to have an orchard and grow fruit. It’s very species-specific, it depends on seasonality, kinds of growth, and, for example, how