Future actions

The table below summarises the main technologies being researched, their timeframe and potential for reducing greenhouse gas emissions ('maximum efficacy'). 

Some of the mitigation options that could have the largest potential impact on agricultural greenhouse gas emissions are not yet commercially available in New Zealand, e.g. methane inhibitors. Others are not yet available anywhere e.g. methane vaccine.

These options are being actively researched but have uncertain end outcomes in some cases and will require time to bring them to market suitable for New Zealand's pastoral farming systems. Challenges lie not only in the development of the technologies themselves, but also the required regulatory settings and domestic as well as international market responses. Ongoing investment in science and commercialisation pathways is essential, as is work to ensure that the technologies are acceptable in New Zealand's markets. 

Timeframe and efficacy of new/novel mitigation technologies

A methane inhibitor is a chemical compound that suppresses the activity of methanogens in the rumen. Inhibitors could be delivered as a feed additive or as a bolus (a small capsule containing the active compound inserted into the rumen). For more on the science of methane see the Reduce methane goal page.

Experiments have already shown that it's physiologically possible to raise lambs completely free of methanogens, and that long-term inhibition of methane production by 30-50% still allows the rumen to continue functioning.

Sheep spend less than an hour in the respiration chambers having their methane levels measured. Credit: AgResearch Limited.

However, compounds that show promise as methane inhibitors must be rigorously tested to ensure that they are safe from both an animal and human perspective.

Usually an inhibitor must be fed daily, which makes it unsuitable for many of New Zealand's grazing-based systems. Development of slow-release formulations could change this.

Recently, a compound developed by the Dutch company DSM (known as ‘Bovaer') has been extensively trialled around the world with promising results—achieving methane reductions of 22-35%. However, the current formulation must be fed in every mouthful of feed to obtain full efficacy so isn't ideal for New Zealand's grazing systems. New slow-release formulations are being developed and tested. DSM is in the process of registering Bovaer for use in New Zealand. It is highly likely that this methane inhibitor will be on the market in the near future.

For more information, see:

• This presentation on methane inhibitors to the 2023 NZAGRC conference
• This presentation on Bovaer to the 2023 NZAGRC conference
• This factsheet from NZAGRC and PGgRc
• This research summary by DSM
• The inhibitors page on the NZAGRC website
• Page 18 of this report by NZAGRC to the Biological Emissions Reference Group (BERG)

Nitrification inhibitors are chemical compounds that inhibit the formulation of nitrate in the soil, and thus the potential for nitrous oxide production. These compounds can be added to fertiliser or deposited directly onto grazed pasture.

Scientist measures nitrous oxide emissions from a pasture trial. Credit: AgResearch Limited.

For more on the science of nitrous oxide see the Reduce nitrous oxide goal page.

Researchers in New Zealand are seeking new nitrification inhibitors that have wide applicability, are low cost, and have a low risk of residues. A number of promising compounds have been identified and testing has begun to deliver proof of concept in the field. Researchers are also investigating ways in which these inhibitors can be practically delivered. 

For more information, see:

• The nitrous oxide page of the NZAGRC website
• Page 34 of this report by NZAGRC to the Biological Emissions Reference Group (BERG).

A successful methane vaccine would trigger an animal's immune system to generate antibodies in saliva that suppress the growth of methanogens in the rumen in a similar way to an inhibitor. Vaccination against rumen methanogens is expected to have broad applicability globally and could be practical and cost-effective even in extensive systems.  

Research into a methane vaccine remains in the development phase and has not yet been demonstrated in live animals. However, all major components of a vaccine chain have been demonstrated: genome sequencing of methanogens has identified targets that stimulate antibody production, antibodies can be created by host animals and detected in saliva and the rumen, and those antibodies have been shown to suppress pure methanogen cultures in vitro (in lab experiments). The in vivo (in animal) efficacy of a vaccine is necessarily speculative but a reduction of 30% is considered plausible given the efficacy of methane inhibitors. 

Commercial availability of a vaccine is estimated to take 7-10 years after demonstration of a prototype.  

For more information, see:

• The vaccine page on the NZAGRC website
• This vaccine presentation by Dr Peter Janssen (AgResearch) to the 2023 NZAGRC conference
• Page 22 of this report by NZAGRC to the Biological Emissions Reference Group (BERG).

Seaweed

Asparagopsis have been shown to reduce ruminant methane emissions by 20-98%, although the persistence of this effect over multiple seasons remains unclear.

The role of bromoform and bromochloromethane as active ingredients in Asparagopsis raises challenges from a regulatory and market acceptability perspective, given that both substances are confirmed animal carcinogens and probable/possible human carcinogens. Animal trials have detected residues in urine and milk, but no detrimental effects on meat quality. There are also open questions regarding palatability to livestock, animal health and the ability to produce and supply seaweed at large scale, especially to extensively grazed livestock. 

For more, see this presentation on seaweed from CH4 Global to the 2023 NZAGRC conference.

Genetically modified ryegrass

Researchers have developed a genetically modified ryegrass that has a higher lipid content. In vitro testing and modelling suggest that a genetically modified ryegrass with a higher lipid content could potentially lead to a reduction in greenhouse gas emissions. Work is ongoing to confirm efficacy. 

Direct-fed microbials (DFMs)

DFMs refer to any type of live microbe-based feed additive. The term 'DFM' and 'probiotic' are often used interchangeably in animal nutrition. On-farm DFMs are typically used as a feed supplement to promote growth and improve health of young animals and improve the health and performance of ruminants. 

Literature on the use of DFMs to reduce methane production in ruminants is limited. However, research is ongoing.

'Kowbucha' is a DFM product being developed by Fonterra. Early work suggests that calves emit up to 20% less methane when they receive Kowbucha. The Kowbucha powder is blended into a milk-like drink, which is then fed to the calves. Trials are ongoing to confirm its efficacy. For more, see this presentation on Kowbucha to the 2023 NZAGRC conference.

Industry is developing wearable devices for livestock that reduce methane production at an individual animal level. Devices are intended to be fitted over the animal's snout, capturing exhaled methane and using a special catalytic converter to turn it into a combination of carbon dioxide and water vapour. Work is currently focused on pilot trials to demonstrate proof of concept and practicality. 

Sheep vary naturally in the amount of methane they produce per kg of dry matter consumed. Scientists have confirmed that this trait is heritable, so is passed onto the next generation.

A low-methane sheep breeding programme has been underway in New Zealand since 2007. This research found that emissions differ by approximately 20% between the lowest and highest emitting animals, with the selected low-emitting flock approximately 10% better than an 'average' flock. This has been confirmed through three generations with no adverse effects on major production traits and some indications of positive correlations. 

The research breeding values for low methane emissions are now available to selected ram breeders through Beef + Lamb Genetics. This is a major step forward, with researchers predicting that a 1% decrease in methane emissions per year is achievable.

Breeders can now measure methane in their own sheep and rank them to keep the low emitters for breeding. This initiative is a world first and the result of many years of government and industry investment into research tools developed to measure sheep on the farm in their own environment. Many leading breeders have already booked in to get this information for their sheep.

Genomic breeding values are being estimated by Beef & Lamb New Zealand for the low-emission trait and it's likely they'll be incorporated into selection indices during the early 2020s.

International studies indicate that cattle show a similar natural variation in their methane emissions per unit of dry matter intake, and this was confirmed in New Zealand in 2020. A low-methane dairy cattle breeding programme is now underway. It is hoped that selection for low-emission cattle could be possible in New Zealand by about 2025.

Research to date indicates that selecting for low-emitting traits has no negative effects on an animal's health, growth and fertility, or its ability to produce meat, wool or milk. It has also been shown that the microbes in the gut responsible for methane production are partly controlled by the sheep's genetics and we can predict methane by sampling the gut microbiome. This means sheep can potentially be bred with a more environmentally friendly microbiome. Methane has been the target to date, but it may also be possible to breed animals that excrete less nitrogen.

For more information, see:

• The breeding page on the NZAGRC website.
• This Farmers Weekly article published on 17 November 2022.
• This Stuff article published on 30 June 2022. 
• Page 25 of this report by NZAGRC to the Biological Emissions Reference Group (BERG).

Asparagopsis armata is a native red seaweed that grows in New Zealand waters. It contains the chemical compound bromoform, which belongs to a group of chemicals known as halogens, which are well documented methane inhibitors. An initial animal trial with Asparagopsis armata suggests that when included at 1% of the diet reductions in methane emissions per unit of dry matter intake of around 40% are possible. However, dry matter intake was also reduced by close to 40%.

Very large quantities of seaweed (hundreds of thousands of tonnes) would be needed for meaningful mitigation at the national scale. There are also concerns around animal health and palatability that need to be addressed, along with any impact on milk composition and the greenhouse gas emissions associated with harvesting, drying and processing the seaweed and transporting it to farms. Bromoform is a suspected animal and human carcinogen and is an ozone depleting substance. Research is underway to explore these issues and establish whether seaweed has potential as a mitigation option for New Zealand farmers in the future.

AgResearch scientists have been working for a number of years to develop genetically modified ryegrass cultivars with improved animal performance characteristics via manipulation of the lipid content. High lipid diets have also been shown to reduce methane emissions in some circumstances. Modelling studies suggest that high lipid ryegrasses would result in reduced methane emissions. High lipid cultivars may also have reduced nitrogen concentrations and hence could also have a positive impact on nitrous oxide emissions. Work is still in its early stages, but scientists have been able to substantially increase the lipid content in experimental material. Laboratory testing for the impact on methane emissions is underway.