- Programme Title: Methane emissions by grazing ruminants.
- Programme Title:Climate change and greenhouse gas emissions from agriculture
8.2 Atmosphere
New Zealand has signed the UN Framework Convention on Climate Change (FCCC). This convention contains obligations to formulate and implement measures to mitigate climate change by addressing anthropogenic emissions (the results of human activity) by sources and sinks of all greenhouse gases. The aim is to return emissions of carbon dioxide (CO2) and other greenhouse gases including methane (CH4) and nitrous oxide (N2O) to 1990 levels by 2000. In addition, there is an obligation to develop, update and publish national inventories of emissions by sources, and removal by sinks, of all greenhouse gases.
Approximately 50% of New Zealand’s greenhouse gas emissions come from agriculture, making it New Zealand’s largest source. Information on sources and sinks of the gases relevant to agriculture, particularly nitrous oxide, is incomplete. International data in this area is often difficult to import because it is rarely based on extensive pastoral systems as in New Zealand. It is important that New Zealand obtain better inventory information in order to fulfil its international obligations and provide input into the policy development process.
8.2.1
Programme Title: Methane emissions by grazing ruminants.Research Leader: Dr M Ulyatt Institution:AgResearch |
Summary
This research aimed to measure the variation in methane emissions between grazing cows. Methane emissions from a group of dairy cows were determined by analysing samples of each animal’s breath, collected while grazing. These emissions were related to the cows’ feed intakes. A large variation was found between animals in methane emission per unit of feed intake. Tentative conclusions, based on this experiment and a similar experiment on sheep, were that methane emissions could be reduced by selecting animals or rumen microorganisms for this characteristic.
Description
To measure the variation in methane emission between grazing ruminants in New Zealand by:
- developing and testing a new method for measuring methane emissions from grazing animals using the marker SF6; and
- measuring methane emissions and feed intakes of at least 10 dairy cows under standard conditions.
Approach & Outcomes
Daily methane emissions were determined over 5 successive days from each of 10 dairy cows, by analysing samples of each animal’s breath collected while grazing. The marker technique of Johnson et al. (1994) was used, whereby a calibrated source of the tracer gas SF6. (QSF6) was placed in the rumen and breath was collected near the nose into an evacuated yoke. Methane emission rate (QCH4) was calculated as:
QCH4=Q SF6 x [CH4]/[SF6]
where [CH4] and [SF6] are the yoke concentrations in excess of background.
A total of 40 cow days of methane samples were collected from the cows and given that one cow was removed after one day because of an abscess, this represents an 87% success rate. Emissions ranged from 229-313 g CH4/cow/day with a herd mean of 262.8±9.6. Variation between cows (87%) was the main source of variation. It was intended to estimate feed intake by measuring faecal output using a slow-release Cr205 device (Captec) and in vitro digestibility. The animals were dosed with the Captec device 6 days prior to methane measurement commencing, but Cr concentrations in collected faeces were too variable to be useful. Intake was therefore calculated from liveweight, liveweight gain and milk production using a model of animal requirements. Feed DM intake was calculated to be 1285±0.24 kg/day and methane emission per kg feed DM intake was 20.5. This corresponded to 6.2% gross feed energy loss as methane.
In a concurrent experiment (FRST Contract C10526) methane emission was measured from 50 cryptorchid lambs aged eight months, using the same technique. Mean methane emission was 20.4±2.1 g/day and the main source of variation was between sheep (94%). This figure corresponds to 16.2 g CH4 emitted/kg DM intake or 4.9% of gross feed energy. Four high and four low emitters were identified which differed in methane emission by almost 100% (16.8 vs 30.3 g/d) at the same feed intake (1401 g DM/day).
In conclusion, the large variation found between animals in methane emission per unit of feed intake raises for the first time the prospect of selecting animals or rumen microorganisms for this characteristic and by this means reducing ruminant methane emission. Caution must at this stage be exercised because the results so far are only from one group of cows and one of sheep, each at one site, grazing one pasture type, at a particular time of the year.
8.2.2
Programme Title: Climate change and greenhouse gas emissions from agricultureResearch Leader: Dr R Sherlock Institution:Lincoln Soil Quality Research Centre |
Summary
New Zealand has international obligations to reduce greenhouse gas emissions to 1990 levels by 2000. A literature review to assess the influence of the factors responsible for greenhouse gas emissions from agriculture was undertaken. Particular attention was paid to information on nitrous oxide and methane emissions. Also a new estimate was made of the nitrous oxide emissions from New Zealand agriculture, based on methodology recommended by the Intergovernmental Panel on Climate Change was made. The results show nitrous oxide emissions levels may be approximately the same as net CO2 emissions. In addition, researchers developed amechanistic N2O emissions model, executable within a Geographic Information Systems (GIS) environment and examined its efficacy.
Description
To improve understanding and knowledge of the factors affecting the rate of greenhouse gas emissions from New Zealand agriculture, and to enable sound policy advice to be given on potential mitigation strategies, by:
- conducting a critical review of the latest international literature to assess the influence of the factors responsible for greenhouse gas emissions from New Zealand agriculture;·1340
- revising and up-dating the nitrous oxide inventory for emissions occurring from New Zealand agriculture;·1340
- if sufficient data is available, developing initial estimates of other greenhouse gas source and sink activity in soil; and·1340
- developing interim guidelines for potential mitigation methods to reduce nitrous oxide emissions from New Zealand agriculture (with particular focus on pastoral systems).·1340
Approach & Outcomes
A literature review to assess the influence of the factors responsible for greenhouse gas emissions from agriculture was undertaken. This research concentrated on the role of agriculture as both a source and sink of the two other principal "greenhouse" gases, nitrous oxide (N2O) and methane (CH4).
As a signatory of the United Nations Framework Convention on Climate Change, New Zealand aims to reduce its greenhouse gas emissions to the levels occurring in 1990. To facilitate the reporting of progress towards this goal for the year 2000, the Intergovernmental Panel on Climate Change (IPCC) has developed draft guidelines to calculate national greenhouse gas inventories.
Using the IPCC methodology, New Zealand’s emmissions of N20 have been revised upwards in the greenhouse gas inventory.
A mechanistic N20 emission model, executable within a GIS environment was developed and its efficacy examined within a ‘pilot’ implementation for a 10 km x 10 km area centred on Lincoln University.
The study also examined mitigation methods to reduce nitrous oxide emissions from New Zealand agriculture and found that some options are available but are unsuitable for New Zealand pastoral systems.
Contact for Enquiries
Farm Monitoring Programme Manager
Monitoring and Evaluation
MAF Policy
PO Box 2526
Wellington
NEW ZEALAND
Phone: +64 4 894 0623
Fax: +64 4 894 0741
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