Two in one: protecting streams and the climate

Two in one: protecting streams and the climate

Thursday, March 21, 2019

Deer farmers wanting to ‘do their bit’ to reduce the impact of climate change can reduce their net emissions from their farms.

“While at present there are no major changes they can make – short of reducing production – to reduce their greenhouse gas emissions, on many farms it is possible to offset emissions through tree planting,” says Deer Industry NZ environmental stewardship manager Lindsay Fung. 

“Many farmers are already looking at fencing off wetlands, erosion-prone faces and riparian areas in order to improve water quality. These areas can capture carbon in trees as they grow.” 

Fung says the Pastoral Greenhouse Gas Research Consortium (PGGRC), which is funded by pastoral farmers and government, has been very successful in building understanding of livestock emissions and what influences them. Its 16 years of research has shown that some promising technologies for reducing emissions on extensive drystock farms could be several years away.

Commercial firms are also looking for answers. Dutch nutrition company DSM has developed a proprietary feed additive, 3NOP, that may be offered to dairy farmers later this year. The company claims it can cut a cow's methane emissions by up to 30 per cent when fed as part of a total mixed ration. Pasture-fed cows could be offered a 3NOP supplement during milking. Because this would make up only a small proportion of the diet, it would likely provide only a 5-6 per cent reduction in methane.

Methane, from the rumen of grazing animals, and nitrous oxide, generated by soil bacteria, are the two main greenhouse gases generated on deer farms.

“Methane is generated in direct proportion to the quantity of pasture consumed, with little variation for pasture species, feed quality and animal type. The amount of nitrous oxide produced is largely proportional to the amount of feed consumed, but is influenced by soil type, topography, soil moisture levels, weather and season,” Fung says.

The only ways at present to significantly reduce methane output are to reduce the amount of feed eaten, either by reducing the area of land in pasture, the amount of feed grown on each hectare or by reducing the amount of supplementary feed brought into the farm.

“Grain feeding results in the production of less methane than pasture feeding, but it is associated with other indirect emissions, and is not compatible with our pasture-based deer farming systems. Some non-pasture forage crops produce less methane per kg of dry matter than pasture, but they also produce more nitrous oxide and nutrient loss.”  

He says alternative forages, like plantain and fodder beet, can reduce nitrogen excretion in urine (meaning less nitrogen is converted to nitrous oxide) if they make up enough of the diet. However there are practical limitations on their use.

Also, nitrification inhibitors can be used to reduce the loss of nitrous oxide from the soil, so long as they can jump all regulatory hurdles and are approved by trading partners. A previous inhibitor based on dicyandiamide (DCD) and marketed as Eco-N for 10 years, had to be withdrawn from sale in 2013 when traces were found in dairy products for export. There are still no internationally accepted residue limits for DCD in food.

Fung says the best long-term possibilities for reducing methane emissions are probably methane inhibitors and the development of a methane vaccine. Low-nitrogen forage crops and genetic selection are proven to have a benefit, but their impact is likely to be small.

A methane inhibitor could be delivered through feed or in a slow release capsule. The PGGRC has discovered a promising compound that reduced methane by 30 per cent in limited animal trials, but still needs further research. If this promise is confirmed, it will then need to jump over some significant regulatory hurdles, with delivery of a PGGRC product at least seven years away.

DSM is developing a “slow release pellet” formulation of 3NOP better suited to drystock farming systems, which they hope to release earlier than this. But it too will need to jump the hurdles.

Using the animal’s immune system via a vaccine to target methane-producing microbes in the rumen has potential for all species but is proving to be technically very challenging. The PGGRC believes this is achievable, but the concept still needs to be proved in practice and once that has been achieved, delivery will be at least five years away.  

So far the PGGRC has done all its genetics research with sheep because they are easier to work with in a research setting than deer or cattle. It has found that a low-methane genetic trait exists in sheep but its heritability is low, which means it might be possible to reduce per head emissions by about 1 per cent a year with intensive selection.

“If the same genetic markers exists in deer, it would be theoretically possible to record and select for   low-methane deer. But to do this would require methane emission rates to be measured in thousands of individual deer in breeding herds, so it can probably be probably ruled out as a practical option,” says Fung.

Because all these potential solutions lie in the future, Fung encourages deer farmers to think carbon offsetting before fencing and planting for water quality reasons.

“On many properties, trees – depending on the species – may offer additional income streams from carbon credits, honey and plantation timber. In some cases, the shelter provided by trees may well increase deer welfare and productivity without significantly sacrificing any deer income,” he says.

“But take advice. It is important to have the right trees in the right place. There are forestry consultants operating in most districts and some Farm Forestry Association members are very happy to share their knowledge.

“Also it may pay to wait until the end of the year, to see the shape of the government’s new climate change policy, before making a major investment in trees and fencing. There may well be incentives for trees that are planted after the policy has been announced. Also the eligibility rules for earning carbon credits from tree plantings on farms may change.”

Fung says agricultural methane and nitrous oxide are not as yet part of the Emissions Trading Scheme (NZETS), though the inclusion of agriculture in the scheme – with a free allocation of 95% of emissions – is included in the coalition agreement between Labour and NZ First.

Nitrous oxide is a very powerful long-lived greenhouse gas. Methane is short-lived, but has a high impact in the short-term. How it should be accounted for is the subject of debate.  

How these gases will be included in the NZETS is one of the major topics being considered by policymakers as the government attempts to develop a climate change policy that is supported by all major political parties (see separate news item).

For those with an interest in climate change and farming, the NZ Agricultural Climate Change Conference 2019 is being held in Palmerston North on April 8-9. It is being organised by the NZ Agricultural Greenhouse Gas Research Centre (NZAGRC), the Ministry for Primary Industries (MPI) and the PGGRC. For more information or to register:

A young stag in a methane measurement trial at Massey University deer farm in 2003