Use of Models and Facility-Level Data in Greenhouse Gas Inventories

Use of Models and Facility-Level Data in Greenhouse Gas Inventories
monthly animal populations. These monthly populations are viewable for every year that the Inventory is calculated.
Although predicted animal monthly populations can not be validated against actual statistical data, due to the
transparency of these populations they can be easily reviewed to determine if they match expert opinion in this area.
Recently such a review was carried out not only to check current model assumptions but to determine any changes in
the industry since the model was developed. Although there has been some small movement within the industries for
such things as birth date and slaughter dates, because the model uses actual activity data for the start and end
populations in a year, these movements have had little over all affect on the monthly populations, highlighting the
robustness of the current assumptions within the model.
As new research and improvements are incorporated into the model data management, transparency and
documentation are improved. Initially inventory model input and output data was contained within excel spreadsheets.
But as further years of emission are calculated, the move to regionalisation of dairy and improvements in the science,
the amount of data needing to be managed is increasing. Therefore recently there has been substantial effort invested
into developing an automated data management system which can easily and transparently store all required data. The
ease of recalling data and checking data will be improved, and quality control checks will be automatically documented.
This model will continue to use existing input and output data spreadsheets but these will automatically be populated
from the data base. Outputs from the model will automatically be stored in the database. By keeping the spreadsheet
and allowing them to be manually viewable the transparency of the calculations will not be compromised.
Integration with IPCC guideline methods
Both methane and nitrous oxide for the four main livestock species are derived from the tier 3 Inventory model. Implied
methane emissions factors and nitrogen excretion rates for these species are calculated from these model results so that
they can be integrated into IPCC default equations for comparison purposes. This information, along with tier 1
equations for other categories and minor livestock species are contained within tables in one final workbook for the final
agricultural inventory compilation.
Along with improvements to data management for the inventory model, improvements to the final compilation process
are also planned. Currently the compilation work book is a mixture of manual data input and automatic data input from
the inventory model output worksheets. Once the data management system is finalised model outputs and data required
for tier 1 calculations will automatically be retrieved from the database. Again access to tables and workbooks which
carry out final calculations will still be achievable to ensure transparency of the process.
New Zealand’s Emissions Trading Scheme
In September 2008, New Zealand introduced an emissions trading scheme (ETS). The aim of the ETS is to spread the
cost of emissions to New Zealand under its Kyoto Obligations to the polluter, The agricultural sector will be able to
voluntarily report their emissions from 1 January 2011 and will be required to report from 1 January 2012. Because the
ETS has been implemented to help New Zealand meeting its Kyoto obligations, it is important that the methodology used
to estimate the cost to the industry aligns with the methodology used to calculate the National Inventory. The
methodology for the ETS emission factor development is still currently in progress. However, a broad overview of the
current draft methodology is detailed below.
Using the Inventory model
Inventory model outputs for livestock categories are annual emissions. These annual emissions for each livestock
category were used to estimate lifetime emissions for animals captured by the ETS. For example the life time emissions
for a slaughter bull of 2 years old were made up of the annual emissions from a slaughter bull 0 – 1 year, and emissions
from a slaughter bull 1 – 2 yrs. Because of the extensive range of livestock categories modelled by the Inventory model,
developing lifetime emission factors for all production animals was achievable. By changing the various production
inputs into the Inventory model, lifetime emissions for animals with different production levels could also be determined.
In order to develop factors that could easily be used by the industry in the ETS, emission factors were developed based
on information currently collected by the industry. For example, the industry already collects data on slaughter weight
and slaughter animal number by stock class such as lamb. Therefore, a relationship between the slaughter weight and
the lifetime emissions of slaughter animals was determined, a best fit linear trend line fitted and as this passed through
IPCC Expert Meeting Report 51 TFI