A range of sectors contribute to emissions in any country including transport, energy, industrial businesses, households, and agriculture.
All these sectors have continued to increase the level of greenhouse gases in the atmosphere causing the earth to heat up at an unprecedented rate.
New Zealand's Dairy Carbon Footprint
All New Zealand’s emissions are reported through the Government’s National Inventory which uses the emissions information for national and international reporting requirements.
The Agricultural industry makes up 48% of New Zealand’s overall emissions.
Dairy contributes just under half of New Zealand’s agricultural livestock emissions.
However, on the international stage, Kiwi dairy farmers have the world’s lowest carbon footprint.
AgResearch analysis commissioned by DairyNZ, shows New Zealand’s dairy industry produces less than half (48%) of the average emissions of international producers studied.
Why do Kiwi dairy farmers need to change?
Despite Kiwi dairy farmers being world leaders in the production of sustainable, low carbon milk, it is important to continue improving if we want to remain internationally competitive. New Zealand’s international brand, and the value of our products in international markets, is built on our environmental credentials.
The importance of sustainability is growing among our consumers here and overseas.
A report done by Fonterra’s NZMP brand in 2020 showed 63% of consumers are concerned about the state of the environment, and 45% of consumers have then changed their diet in the last 2 years to lead a more environmentally friendly lifestyle.
Farmers are also amongst the first to feel the effects of a changing climate; an increase in the frequency and intensity of extreme weather events including rain events and droughts. It is important that action is taken now to sustain the future for not only our consumer and communities, but also the environment and future generations.
Where do agriculture emissions come from?
Many gases created by human activities act as greenhouse gases (GHGs). The three most important from a New Zealand agricultural perspective are outlined below in priority order.
All agriculture GHGs are part of a natural cycle, however because there are larger concentrations of them accumulating in the atmosphere, which are unable to be controlled through the natural cycle, they contribute to Climate Change.
Methane (CH4), Sometimes called biogenic methane, is generated by ruminants as a by-product of digestion. Less than 5% comes from dung and effluent systems.
The total feed eaten by livestock on your farm (per kilogram of dry matter intake) is the driver of CH4 emissions.
How methane is produced
Methane which is mostly emitted when cows burp, is produced in the rumen of the cows by microbes. These microbes are naturally present in all ruminant animals.
The average dairy cow produces about 98kg of CH4 per year, 95% of that occurs from digestion. New Zealand studies have shown that about 21-22 grams of methane are produced per kg of dry matter eaten.
Why is methane recognised differently?
Methane is a short-lived gas, which does not accumulate in the atmosphere in the same way as long-lived gases, Carbon Dioxide CO2 and Nitrous Oxide N2O. However, methane is much more effective at trapping heat than carbon dioxide.
The Zero Carbon Act is unique in that it uses a spilt gas approach, and therefore recognises that biogenic methane needs to reduce, not net zero in the same way long-lived gases do
Shortlived gases are biogenic methane from animals and plants and these gases have a relativley short lifetime. Despite this short lived gases maintain warming if being 'sustained' however if they were to increase they add to warming. If they decrease they have a cooling effect.
Long-lived gases are carbon dioxide CO2 and nitrous oxide N2O. If carbon dioxide emissions are not net zero they are adding to the warming.
Nitrous oxide (N2O) is the gas released into the atmosphere from dung and urine patches, and nitrogen (N) fertilisers.
The amount of nitrogen applied in a dairy system as well as the % of N in feed are the main drivers of N2O emissions, temperature and soil moisture can also play a role.
How is nitrous oxide (N2O) produced?
When animals graze nitrogen-rich pastures only a fraction of the nitrogen consumed supports the production of milk or meat. Most of it ends up excreted in urine and dung.
The loading rate of N in a urine patch can be up to 1000 kg N per ha
N2O is released from the soil when urine, faeces and fertilisers are broken down by naturally occurring microbes in the soil.
Haynes, R.J., Williams, P.H., 1993. Nutrient cycling and soil fertility in the grazed pasture ecosystem. Advances in Agronomy 46, 119-199.
The main driver of carbon dioxide (CO2) emissions is the area of woody vegetation. Woody vegetation captures CO2, and releases it when cleared. To a lesser extent the application of lime and urea nitrogen (N) fertilisers can also contribute to farm CO2 emissions. Carbon capture (and release) through soil can also occur, this is under investigation so it can be better quantified.
Energy use is the other driver of farm CO2 emissions. It is already accounted for under the New Zealand Emissions Trading Scheme so it will not be included in the farm greenhouse gas emissions you will report.
How are emissions measured?
Agricultural emissions are recorded with a New Zealand specifically approved method, using production data from processors and Stats NZ Agricultural Production Survey.
Internationally the current metric for measuring emissions is GWP100. This metric creates one single figure for a country’s emissions to measure all greenhouse gases in a 'carbon dioxide equivalent' over 100 years.
GWP100 works well for carbon dioxide emissions as CO2 stays in the atmosphere for thousands of years. However, it over-states the warming impact of methane CH4 emissions by three to four times, when emissions are stable.
It is particularly important biogenic methane CH4 is measured and treated accurately in New Zealand because agriculture is a much larger proportion of our economy than other countries.
DairyNZ is advocating for an alternative metrics to measure and report on emissions, such as GWP*, which better reflect the warming impact of methane over time.
He Waka eke Noa
Learn about how DairyNZ alongside other primary sector bodies are working together to get the best agricultural pricing mechanism for the dairy industry.
Find out more about climate change
DairyNZ helps fund and contributes to the content in AgMatters. This is a one-stop-shop to help farmers and growers understand climate change.
Know your Numbers
By now you should of received an emissions report from your dairy processor or consultant with your farm's emissions numbers. It is important that you know and understand where your farm sits.