Most methane is emitted when cattle burp. Nitrous Oxide (N2O) is emitted from soil when urine, faeces and fertilisers are broken down by microbes in the soil.
How are the different greenhouse gases are compared?
To compare agricultural emissions with other sectors, the methane and nitrous oxide gases are converted into CO2 equivalents as these two gases have a different life span and effect in the atmosphere.
The standard units used for carbon accounting are CO2 equivalents and the standard ratios are based on Global Warming Potential (GWP) over 100 years.
The methane ratio is 25 - i.e. one tonne of methane will cause the same amount of warming as 25 tonnes of CO2. Methane is shorter lived than CO2 (~12 years for methane and 100s of years for CO2) and creates a strong burst of warming, but over a shorter period.
The nitrous oxide ratio is 298 – it is a much longer lived molecule.
The National Inventory
Each year the Government produces a National Inventory Report summarising New Zealand’s annual greenhouse gas emissions, which are categorised into five sectors (agriculture, energy, industrial processes, waste, and land use change and forestry). The inventory covers the emissions of carbon dioxide, methane, nitrous oxide and fluorinated gases, and reports these emissions as units of carbon dioxide equivalent (CO2-e) in order to account for the different global warming potency of these gases.
The information for the agriculture section of the inventory is gathered from a variety of sources including:
- Agricultural Production Survey and Census
- LIC/DairyNZ Dairy Statistics
- Beef & Lamb NZ
- Deer Industry NZ
- Slaughter statistics
- Fertiliser Association
- Assure Quality
- Potatoes NZ
- Ministry for the Environment.
Following methodology agreed by the IPCC (Intergovernmental Panel for Climate Change), the Government calculates the emissions for all the major activities on farms, producing tables and graphs in different categories which form part of the National Inventory Report.
The 1990-2015 National Inventory Report and a brief snapshot can be downloaded from Ministry for the Environment’s website.
New Zealand greenhouse gas emissions
New Zealand has a unique GHG profile compared to other developed countries around the world because our agricultural sector is a significant part of our economy. Also, a large proportion of our energy comes from renewable sources. Agricultural emissions make up almost half of New Zealand emissions, while in other developed countries, agriculture makes up around 11 percent on average.
New Zealand’s greenhouse gas inventory for the year 2013. Emissions from forestry are not included in the estimate of total emissions. Percentages may not add up to 100 due to rounding.
Source: Ministry for the Environment, New Zealand’s Climate Change Target (2015).
Dairy industry greenhouse gas emissions
Source: Ministry for the Environment, New Zealand’s Climate Change Target (2015).
Frequently asked questions
Why is DairyNZ involved in addressing greenhouse gas emissions?
- Greenhouse gases have a big impact globally on climate change, and therefore global action is required. This is the basis of the international climate change agreements like the Paris Agreement. New Zealand has signed up to these agreements as a responsible global citizen.
- New Zealand’s GHG reduction targets are economy wide and include all the GHGs. This includes agriculture and on-farm nitrous oxide and methane emissions.
- Half on New Zealand’s emissions come from agriculture and a quarter come from the dairy industry.
- To meet New Zealand’s GHG targets action is required across New Zealand’s economy, this includes the dairy industry.
- There are currently limited mitigation options available to reduce dairy farm methane and nitrous oxide emissions.
What is DairyNZ doing?
- Partnering with the Government and iwi to deliver our commitments under He waka eke noa.
- Partnering with Fonterra, with the support of the Ministry for the Environment and the Ministry for Primary Industries, via the Dairy Action for Climate Change.
- Building the climate change capability of rural professionals through professional training courses.
- Raising awareness with farmers of the actions they can take now.
- Undertaking dairy farm greenhouse gas pilot case studies to determine the potential reduction in greenhouse gas emissions which could be possible across different farm systems and to quantify the effect on the farms profitability and productivity.
- Investing and undertaking research and development to identify and commercialise breakthrough technologies and mitigation options to lower emissions.
Why do we need to reduce (methane) emissions?
Dairy biological emissions make up 22.5 percent of New Zealand’s emissions and nearly half of agriculture's emissions. Although methane only remains in the atmosphere for a relatively short period of time, it is 25 times more potent at warming the planet than carbon dioxide.
It's estimated that international emissions from livestock are currently responsible for about 20% of the total global warming. This is why the agricultural sector has a role to play in managing our climate change contribution.
Is there any real solution to methane production by cows on the horizon or is it an impossible problem to solve?
Both the Government and the agricultural sector, including dairy farmers via the milk solids levy, are investing in technological solutions like methane inhibitors and vaccines to address methane emissions. We are seeing such solutions on the horizon internationally, and we are hopeful that a solution will be found that fits the needs of a New Zealand farmer.
New Zealand’s emissions are so small compared to other countries, any reductions we make won’t prevent climate change. Why bother?
While New Zealand's share of greenhouse gas emissions globally is just 0.16%, small emitters like us make up 24% of the worlds emissions. Together we can make a big difference. It would be a huge reputational and trade risk for New Zealand if we didn’t make an effort to reduce our emissions profile. We need to live up to our brand image and show we are ‘doing our bit’ for the environment.
Does 'net carbon emissions' include the carbon that is captured in the soil?
Soils store significantly more carbon than trees and plants together. However it’s difficult to monitor and measure. It also takes a long time to build up soil carbon but is lost very quickly through poor land management practices, wind erosion and droughts.
While at a national scale New Zealand soils have higher soil carbon levels than the world average, there appears to be little change in overall levels over time. This suggests there is limited potential for significant carbon sequestration from New Zealand’s soils.
For these reasons soil is not accounted for in New Zealand’s Greenhouse Gas Inventory or the international greenhouse gas reporting framework and is not considered a viable offsetting option at this point in time. New Zealand’s inventory does, however, assume the carbon content of soil changes when the land use changes.
Does ‘net carbon emissions’ include the carbon that is captured in growing grass?
No, carbon dioxide (C02) is absorbed from the atmosphere by grass in the process of photosynthesis. Carbon dioxide leaves the system again through respiration and decaying grass.
Is methane carbon neutral?
Methane is released when animals like cows and sheep burp, and it’s known as a short-lived gas because it remains in the atmosphere for a relatively short period of time – just over a decade. However, despite this, it’s 25 times more potent at warming the planet than carbon dioxide.
To keep the earth’s warming within a 1.5-degree threshold, science shows both nitrous oxide and carbon dioxide need to reduce to net zero. Methane however can be treated differently. Methane should be reduced as much as possible to limit warming in the short-term, but can then be stabilised at that reduced level.
Is there any chance all planting can be included in mitigation and be recognised by the Government?
Simple changes to the National Greenhouse Gas Inventory requirements could significantly increase the uptake of different types of on-farm planting by New Zealand dairy farmers. Many dairy farmers are small forestry block owners, but many more are already plant for shelter, fodder, and to improve water quality or to retire land. We would like to see a wider range of planting recognized and are working to achieve this through He waka eke noa.
Should environmental issues of water quality and GHGs be treated as separate issues?
No, the two are very much linked. Much of the work farmers have underway to improve water quality also has the co-benefits of improving their greenhouse gas emissions profile and biodiversity. We know that increased on-farm planting has positive effects for soil, air, and water quality – therefore these environmental issues all need to be treated together.
What is the difference between short and long-lived gases and how are they accounted?
Not all greenhouse gases have the same warming effect or stay in the atmosphere for the same amount of time.
Methane has a short life (around 12 years) in the atmosphere and an initial high level of warming that occurs within 50 years after it is emitted, however some warming lingers beyond 100 years. Carbon dioxide and nitrous oxide have less of an immediate impact, but because they are both long lived gases the warming they cause continues for hundreds or thousands of years.
The science shows both nitrous oxide and carbon dioxide must be reduced to net zero if we are to keep global warming within the 2-degree warming threshold. However methane doesn’t need to reduce to net zero, it can be reduced and then stabilised at a certain point. This is because if methane is stabilised at a certain level the concentration in the atmosphere will rapidly level off as new emissions to the atmosphere are balanced by the breakdown in the atmosphere of previous emissions. However this will take some time.
What is DairyNZ’s position on methane accounting?
DairyNZ, just like many other commentators, is interested in other options for accounting (or not accounting) methane emissions. But the decision of whether methane contributes to global warming is not up for debate.
Right now New Zealand must follow the same rules that every other country has to follow when calculating and accounting what our greenhouse gas emissions are – and this includes the way we account for our methane emissions. In New Zealand this means that 48 percent of our greenhouse gas emissions are from agriculture (the responsible gases being biological methane and nitrous oxide).
The Climate Change Response (Zero Carbon) Amendment Act has set our biogenic methane reduction targets at 10% by 2030 and 24-47% by 2050.
DairyNZ accepts the 2030 target of a 10% methane reduction and will be supporting our farmers to achieve this. We do not support the 2050 target of a 24-47% reduction but are confident that when this target is reviewed farmers will get a fair deal that is firmly grounded in science.
What is DairyNZ's position on climate change?
DairyNZ has long been supportive of the dairy sector playing its part in helping New Zealand meet its international climate change obligations. New Zealand is already one of the lowest emissions producers of dairy nutrition in the world, but is responsible for 22.5 percent of all New Zealand’s emissions. We are well aware of the challenges and opportunities this emissions profile presents.
This is the premise of our 2017 Dairy Action for Climate Change. We are focusing on what mitigation options our farmers can adopt right now to start making a difference, while supporting continued scientific investment to find a long-term solution.
We see climate change mitigation and adaptation as an opportunity to show the world it is possible to produce milk in an emissions-conscious way. This is our chance to set a global standard as a climate resilient agricultural nation.
Many of New Zealand’s dairy farmers across the country are already refining and adapting their farm systems to improve the environmental, social, and economic sustainability of their businesses. In part, this is because some of the work underway to improve water quality also has the co-benefits of reducing greenhouse gas emissions.
DairyNZ is supportive of the Zero Carbon Act and engaged positively with the Government through the consultation period. We want to see all sectors aligned and accountable towards a common goal which will see New Zealand transition towards a low emissions economy. We support and welcome the Government’s commitment to planning early and avoiding sudden change. This will allow all sectors to transition over time.
DairyNZ supports the new 2050 target which will see New Zealand reduce long-lived gases (like carbon dioxide and nitrous oxide) to net zero,.
DairyNZ believes there is a need to reduce and stabilise methane, in accordance with scientific evidence. Current science shows that methane doesn’t need to be reduced to zero because it is a short-lived gas, and we are committed to working with the Climate Change Commission and the sector to determine just at what level methane should be stabilised.
New Zealand’s transition to a low emissions economy will also require significant uptake in forestry planting. Many dairy farmers have the ability to plant on farm, but in more spaced out or smaller lot sizes, with a wider variety of species.
We want to see farmers recognized for planting species that currently fall outside of the Greenhouse Gas Inventory definition and yet provides similar benefits to the environment as the planting of traditional trees.
There needs to be continued support from both industry and Government for emerging emissions mitigation technologies if New Zealand is to transition to a low emissions economy. Until long-term technological solutions to significant methane reduction are found, DairyNZ will be looking at options to increase on-farm planting as well as continuing to encourage farmers to reduce on-farm emissions where possible.