How eliminating sheep burps and cow pee could slow global warming

Thursday, 29 November 2018

A respiratory chamber, designed for scientists to measure cow burps.

Drones, pee-detecting machines, burp chambers and secret code words.

New Zealand's fight to tackle greenhouse gas emissions from farming is a hi-tech battle, being fought in labs around the country. And it's costing about $12 million a year.

The mission began 15 years ago when the agriculture sector and the government formed a partnership: the Pastoral Greenhouse Gas Research Consortium (PGGRC).

In the same year, National MP Shane Ardern gunned an elderly tractor named Myrtle up the steps of Parliament, heading a farmers' protest against a proposed 'fart tax'.

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So, how far have we come since then – and just how close are our boffins to making a dent in New Zealand's emissions?

THE PROBLEM

Agriculture is responsible for almost half of the country's emissions, mostly methane and nitrous oxide.

Methane is burped out when sheep, cattle and deer 'chew the cud' – or softened food. A small amount comes from manure.

Nitrous oxide is released from urine patches in paddocks, dung produced during grazing, manure spread on pasture and from nitrogen fertiliser.

Methane emissions have gone up by about 10 per cent since 1990, but there has been a 28 per cent rise in nitrous-oxide emissions.

Generally, that's because farmers are producing more. Dairy cow numbers are rising in New Zealand, up 2.7 per cent from the 2016-17 year to almost five million.

Both gases are much more aggressive than carbon in warming the atmosphere.

Carbon dioxide and methane are both about 45 per cent of New Zealand's total emissions. Nitrous oxide is around 10 per cent.

Trials have shown that diets based on 100 per cent forage rape can reduce methane emissions from sheep by as much as 30 per cent

Agriculture also emits carbon dioxide through land clearance, loss of soil carbon, feed crop production and energy use.

New Zealand has committed to reducing emissions to 30 per cent below the 1990 level. The Government also has a target of becoming carbon-neutral by 2050.

But how can that be done without hobbling our largest export industry?

New Zealand scientists have identified five key solutions.

EXTRA MUSTARD

Forage brassicas come from the mustard plant family, a sort of cousin of cabbage, kale or broccoli, and are grown for feeding livestock.

Field trials have shown that a diet of forage rape - one of these brassicas - can reduce methane emissions in sheep by as much as 25-35 per cent.

But, the animals would have to be fed the plant 100 per cent of the time, and in current New Zealand farming systems, that isn't practical.

Livestock here is predominantly grass-fed, although other feeds are used in the winter months to make up for slower pasture growth.

Using forage rape for about six weeks of the year would reduce emissions by only about one per cent.

And growing more forage rape is difficult. Of New Zealand's 10 million hectares of pasture land, about 2.5m ha is flat. A large chunk of that is taken up by dairy.

There is another potential downside. 'We are looking at the soil carbon and the nitrous oxide effects [of forage rape]. You have to till and fertilise so there are potential offsets of methane but we don't know what we do to those other gases,' Peter Janssen of AgResearch says.

There are other alternative feeds but they also come with complications. Oregano, seaweed, coconut oil, spent beer from beer brewing and even tea have all been tried and ruled out.

Dr Peter Janssen pictured with the 'burp' chambers at AgResearch in Palmerston North.

Grain is expensive and not that popular in New Zealand. Fodder beet has also attracted a lot of interest and is becoming popular in the South Island.

'With fodder beet, over 50-75 per cent of the diet has to be that at any one time for you to see an impact,' Janssen says. 'Once you go high, there are also animal health and welfare issues. It is a difficult one to use; managing [to feed it] all the time might be tricky.'

AgResearch scientists also studied plantain planted at a dairy farm in Waikato in 2016-17, and found nitrous oxide emissions were 39 to 74 per cent less than other crops. But more research is needed.

So, while changing livestock diets is promising, it is unlikely that alone will dramatically reduce emissions.

'Farmers may be able to get some credit for these practices but they are unlikely to rush over to increasing these things to be large parts of the feed base,' Janssen says.

GOOD BREEDING

It sounds like a Viz comic strip, but Kiwi scientists are breeding sheep that belch less.

The work started in a burp – or respiratory – chamber. That's an open-sided, perspex crate where computers continuously monitor the air entering and leaving the chambers, to measure the amount of methane released by a single sheep.

More than 1300 animals have been screened by AgResearch scientists, who discovered that it's an inherited trait.

Dairy cows on a South Taranaki farm. Around 96 per cent of the methane emitted by cows comes from belching.

They've now created a 100-strong flock of low-burpers – who produce about six per cent less methane than other flock-mates. The team is now working with breeders to see if the trait can be propagated more widely.

So far, it looks like the low-emitting animals are no less productive. But farmers select rams for their wool quality, meat production and survival. Success in selective breeding depends on how much weight farmers will place on environmental footprint.

'Agriculture is all about getting the highly desirable traits that people want in their products, be it A2 milk or whatever,' says PGGRC chairman Rick Pridmore.

'Every time you want to put in a new trait, it has got to fit in with all the traits that are highly desirable. If it hurts a trait that is highly desirable, no-one is going to use it.

'It takes a long time because every breeder has to want to put it into their animals and eventually get the whole national herd or flock to use it. So, it would probably take about 15 to 20 years.'

The 'genetic' solution has so far been confined to sheep. Only early work has begun into cattle – and AgResearch has just four cow-sized burp-chambers, compared with 24 for sheep.

BLOCKERS

Cows and sheep have four-chambered stomachs, the first of which is known as the rumen.

Our human stomachs use acid to break down food. 'Ruminant' animals depend on specialised bacteria, known as methanogens, to ferment the food in the rumen.

But the by-product is methane, about 96 per cent of which is silently burped into the atmosphere.

Methanogens are not essential to the animal, so scientists are working on a way to chemically block the creation of methane in the gut.

Pridmore calls work on these inhibitors 'the good-news story'. AgResearch scientists have narrowed 40 chemical compounds down to one 'lead'. The work is secretive and it's known only as PG1200.

Dairy cows grazing on fodder beet, which has soared in popularity in the South Island.

They are now rigorously testing it.

Janssen explains: 'It is not allowed to have any negative impact on animal health or human health, or product quality, and also [leave] no residues in any of the products.

'It is an enormous task and success is fragile. It could fall over at any time because if it fails any of those criteria it is essentially no good. That is why it is taking such a long time.'

Once the tests are complete, the scientists must find a commercial partner. Then they must work out how to deliver a product suitable for New Zealand's grazing system, like a slow-release capsule or drench.

A Dutch company is readying an inhibitor for market next year, but it is suitable only for feedlot farming systems, where farmers have twice-daily contact with their animals.

'It takes five to seven years to take something you have just discovered to get it commercialised,' Pridmore says. 'We have something – but these are real, rigorous bells-and-whistles tests. Every new drug that comes on the market takes this long.

'It is animal safety, people safety – you don't want residues. So even if you had all the money in the world, you couldn't speed the process up.'

AN ANTI-BURP VACCINE

A rumen vaccine, injected into the saliva through the animal's snout, is 'Nobel-prize winning stuff', Pridmore reckons.

The nitrous oxide problem occurs as cow pee hits the earth.

Work on this 'holy grail' of gas-shrinking technology started a decade ago – and it is being done only in New Zealand labs.

In theory, the vaccine would thwart methanogens by developing antibodies in the animals' saliva, that are then swallowed into the rumen. It's estimated it could reduce emissions by as much as 20-30 per cent.

'It is our No 1 target that we are trying to achieve as an industry. Once you do that you could inject every animal with a rumen in the world and get a mass reduction.'

But the scientists have hit a stumbling block, and time is running out because their funding ends next August.

'Right now, all the parts work but when you put them together they don't work yet. We haven't been able to make it work in the animals' gut.

'It's like saying we know the engine works, the gears work, the tyres work, but we can't start the car. It is frustrating: we are so close but we haven't cracked it.'

Pridmore is working on getting the funding renewed, while laboratory work continues. Trials will even run over Christmas.

'We have a code word that they will use when they ring me up and tell me they have cracked it – but I won't tell you what it is. I live in anticipation that one day, in the next couple of months, I am going to get this call and we are going to nail it.'

LAUGHING GAS

Most of the nitrous oxide emitted here comes when animal pee – already full of nitrogen from the grass they've munched – hits the ground. Urea fertilisers are a more minor source, about 17 per cent.

The urine patch contains too much concentrated nitrogen for the soil to absorb.

It either becomes nitrate and forms the run-off and water pollution commonly associated with 'dirty dairying'. Or it becomes nitrous oxide or N2O (commonly known as the dentist's friend: laughing gas).

It is much more potent in planet-warming than carbon dioxide: one tonne of nitrous oxide is equivalent to 298 tonnes of carbon dioxide.

And it hangs around in the atmosphere a lot longer than methane.

Landcare Research principal scientist Surinder Saggar has been involved in the development of technology to 'treat' the patches.

The sensor machine is towed behind, or mounted on, a tractor and detects fresh cow pee on grazed paddocks. It can then treat them with an inhibitor spray, blocking the troublesome urease enzyme within the pee.

But the machines are pricey – each one costs between $80,000 and $100,000. 'It can scan about 10-15 hectares per day, so initially it was built on the basis that a group of farmers can buy it and then use it on their farms,' Saggar says.

'But now, with this mycoplasma bovis problem, farmers are less willing to share with another farmer.'

Saggar says they have also developed a smaller, research model, to see how the urine flows into the soil. He is also in discussions with the European Union, Ireland, Chile and Britain about further research.

Rick Pridmore, chair of the Pastoral Greenhouse Gas Research Consortium.

Drones can also be flown over pastures to detect the patches, which appear much greener after about 10 days.

Saggar says progress has been remarkable. 'About 15-20 years ago we were struggling even to measure gases.'

DCD, an inhibitor sprayed on crop or pasture soils, was in widespread use in New Zealand from 2007 until 2012, when traces were found in milk powder.

Urease inhibitors are already added to about 20 per cent of all nitrogen fertiliser sold in New Zealand. If that was rolled out to all fertiliser, the total nitrous oxide from agriculture could be reduced by up to three per cent.

But because of the DCD scare, the risk of leaving any chemical residues in meat or milk will meet both consumer and farmer resistance.

Dave Frame, director and Professor of Climate Change at Victoria University.

Another option is to keep livestock off pasture in autumn and winter. Grass grows more slowly during these seasons, and the soil is waterlogged, making the urine more damaging to the environment.

Experiments in Waikato and Southland have seen cattle placed in dairy barns or on stand-off pads, where excrement can be collected, during these times. The annual reduction in nitrous oxide from the trial farms was between seven and 11 per cent.

However, the slurry produced has to be carefully managed as it can also be a significant source of biological emissions.

THE BOTTOM LINE

The ideal solution can't slow productivity, because farmers won't buy it.

'We could reduce our emissions today – we just reduce the size of the industry. No-one is really putting up their hand up to do that,' says PGGRC general manager Mark Aspin.

Pridmore, a former Niwa chief executive before working for a decade with Dairy NZ, says farmers have come a long way since the 'fart tax' protests.

'Will farmers play if we find a solution? My experience is that every time we have found something that works, they pick it up.

'I've never had anybody give me the two-finger salute when I talked to them about fixing things on the farm. The vast majority of farmers out there are out there to help.'

CARBON VS METHANE

Professor Dave Frame, director of the Victoria University-based New Zealand Climate Change Research Institute, worries New Zealand is placing too much emphasis on methane, a pollutant that sticks around for only a decade or so. Carbon dioxide and nitrous oxide are long-lived pollutants.

The purpose of the Paris Agreement is to keep the global average temperature well below 2 degrees Celsius above pre-industrial levels, and pursue efforts to limit increase to 1.5 degree Celsius.

'Our Paris obligations are mainly about stopping the warming. To stop the warming we need to get long-lived climate pollutants to net zero emissions, and we need to stabilise or slightly reduce methane emissions,' Frame says.

'Going after methane instead of CO₂ will lead to a warmer world. So we should focus on carbon dioxide and nitrous oxide and ensure methane emissions don't grow. If we can bring them down at low cost, through efficiency gains, or on the back of nitrous oxide policy, then great. But the main action is the long-lived climate pollutants.'

Frame says his argument is not giving agriculture a free pass.

'I'd rather put it that we are doing nowhere near enough on carbon dioxide. I am in favour of methane reductions as long as they are not crowding out CO₂ reductions.

'They [agriculture] can't avoid doing something about nitrous oxide, that is a long-lived climate pollutant. It also doesn't give a free pass on methane because it says that you can't grow methane.

'But New Zealand deserves to have a decent conversation about some of these big policy issues.'

That conversation involves better public transport policies, and tackling the country's ageing car fleet, both vital to tackle carbon dioxide pollution.

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