ENVIRONMENT
FEWER BUT BETTER SHEEP NEEDED Phil Journeaux examines the work done to help farmers reduce GHG emissions.
T
he response to climate change has seen New Zealand sign up to the Paris Agreement, to reduce our greenhouse gas (GHG) emissions by 30% below 2005 levels. The advent of the Zero-Carbon Act has set a target of a 10% reduction in methane levels, relative to 2017, by 2030. That’s a 24-47% reduction in methane levels by 2050, and net zero emissions in carbon dioxide and nitrous oxide by 2050. A key component of any GHG reductions will involve the agricultural sector, which emits 48% of NZ’s GHGs. As a result, a range of work is being undertaken to understand what farmers can do to reduce or offset GHG emissions. On the research front, there is a range of work being undertaken to develop new technologies farmers can use:
Genetics Lower methane-producing rams (by 10%) have been bred, with animals likely to be commercially available in the next two to three years. Similarly, LIC and CRV-AmBreed are working to identify low-methane bulls in the dairy industry, with these likely to be used in the AB system in about five years.
Vaccine A methane vaccine is being developed, which could significantly reduce methane emissions by 30%. This is complex work, and a vaccine is not expected for another 10 years.
Methane inhibitors These are additives which when fed to ruminants again reduces methane production (by ~30%). A range of these
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are being investigated, with one likely to be registered in Europe over the next year, and possibly in NZ over the next ~2-3 years.
Nitrogen inhibitors These are compounds which when applied to the ground inhibit the production of nitrous oxide. Several possible compounds have been identified, but there is still several years of work ahead to prove they work effectively.
Forages A number of forages also reduce methane or nitrous oxide emissions, e.g. forage rape, fodder beet, cereal grain, plantain, but to be effective generally they need to be make up at least 30% of the diet, which then poses some farm system challenges. At the farm level, there are three key drivers of GHG emissions: • Amount of drymatter eaten. There is a direct correlation between DM eaten and methane production (21g methane/kg DM) and a strong correlation with nitrous oxide production. • Amount of protein in the diet. This is a strong driver of nitrous oxide emissions; unneeded protein is expelled as nitrogen (urea) in the urine, some of which is turned into nitrous oxide within the soil. • Amount of nitrogen fertiliser applied. The main driver of applying nitrogen fertiliser in the pastoral sector is to grow more drymatter – go back to ‘drymatter eaten’ above, plus there is some direct carbon dioxide and nitrous oxide emissions from the fertiliser. These constitute the toolbox
Country-Wide
October 2021
