Conservation comment: Methane-eating filter floated

Methane from dairy farms, emitted from cows as they burp and belch while digesting grass, makes up a significant part of our country's greenhouse gas emissions.

At the New Zealand Climate Change Conference in June 2013, Dr Kevin Tate, a research associate at Landcare Research, presented his latest work. He had been placing bacteria with an insatiable appetite for methane above effluent ponds, from which 10 per cent of dairy farm methane comes.

In a Radio New Zealand interview at that time he said: "We've managed to develop a very active population that consume masses of methane. They're also self-regulating in the sense that, as they consume methane they produce water, so they never dry out.

"Some of them can also fix nitrogen and they also seem to be able to catch ammonia and reduce odour from the ponds, which is a very useful additional property. So they seem to do a lot of things very, very well."

Dr Tate said they were testing a floating biofilter and trying to develop a cheap technology that would be attractive for farmers to use.

He said the technology could be on dairy farms within a few years.

"We could do it fairly soon, but we need to demonstrate that the floating biofilter technology works as well as the original prototype that we tested on the Massey University farm. We're doing that at the moment.

"I would say in another three years we should be in a position to say, 'This is how much it would cost you.' We can show how they can be managed well on a farm by a farmer to make it as simple as possible. So far, experience shows us they're virtually maintenance-free, they look after themselves, essentially."

That was 2013. What happened next?

Funding for this research came from Landcare Research and MAF (now MPI). In 2014, a NZ Agricultural Greenhouse Gas Research Centre (NZAGRC) review deemed floating biofilters too costly to be used by farmers and funding stopped. There was interest from the UK and Spain but the research team were unable to secure funding to collaborate. Recently, delegations from Africa, Brazil and Uruguay have visited Massey to view the biofilter at work.

This work has not been patented because Dr Tate views the atmosphere as a global commons and is happy for the technology to be used wherever it can help to reduce methane emissions. Maybe someone else will pick up the ball.

As for the researchers?

They went back to work and came up with another elegant idea. The NZAGRC is funding a small project to test it.

This one takes an even simpler and lower-tech approach. Some areas of New Zealand soil are rich in methanotrophs (methane-eating bacteria). Methane from housed animals could possibly be consumed if extracted from barns and filtered through methanotroph-rich soil adjacent to the building. It's early days for this work ... stay tuned. It will be interesting to see if the recent cuts to AgResearch mean that this work is also abandoned.

-Information for this column came from Radio New Zealand and the generous help of Dr Tate.

-Lorna Sutherland has lived in many different places and observes the changes in the natural environment.