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Chapter 6: Agriculture

6.1 Sector overview

In 2008, the agriculture sector contributed 34,826.3 Gg of carbon dioxide equivalent (Gg CO2-e) (46.6 per cent) of New Zealand’s total greenhouse gas emissions. Emissions in this sector have increased by 2,960.9 Gg CO2-e (9.3 per cent) from the 1990 level of 31,865.4 Gg CO2-e (Figure 6.1.1). The increase since 1990 is primarily due to an 820.3 Gg CO2-e (3.8 per cent) increase in methane (CH4) emissions from the enteric fermentation category and a 1,993.3 Gg CO2-e (21.3 per cent) increase in nitrous oxide (N2O) emissions from the agricultural soils category.

Figure 6.1.1 New Zealand agricultural sector emissions from 1990 to 2008

  Gg CO2 equivalent
1990 31865.4
1991 32026.0
1992 31404.5
1993 31746.2
1994 32741.6
1995 33191.8
1996 33496.6
1997 34172.7
1998 33455.8
1999 33882.6
2000 35076.3
2001 35677.9
2002 35810.7
2003 36425.0
2004 36462.7
2005 36782.5
2006 36745.9
2007 35563.4
2008 34826.3

In 2008, CH4 emissions from enteric fermentation were 65.1 per cent (22,657.5 Gg CO2‑e) of agricultural emissions and 30.3 per cent of New Zealand’s total emissions. Nitrous oxide emissions from the agricultural soils category were 32.7 per cent (11,372.3 Gg CO2-e) of agricultural emissions and 15.2 per cent of total emissions.

Agriculture is a major component of the New Zealand economy, and agricultural products comprise 56 per cent of total merchandise exports (Ministry of Agriculture and Forestry, 2009). This is facilitated by the favourable temperate climate, the abundance of agricultural land and the unique farming practices used in New Zealand. These practices include the use of year-round extensive grazing systems and a reliance on nitrogen fixation by legumes rather than nitrogen fertiliser.

Figure 6.1.2 Change in New Zealand’s emissions from the agricultural sector from 1990 to 2008


Figure 6.1.2 Change in New Zealand’s emissions from the agricultural sector from 1990 to 2008

 

1990 Gg CO2 equivalent 2008 Gg CO2 equivalent
Enteric fermentation 21,837.2 22,657.5
Manure management 617.2 776.3
Rice cultivation NO NO
Agricultural soils 9,379.0 11,372.3
Prescribed burning of savannas 3.2 1.0
Field burning of agricultural residues 28.7 19.1

Note: Rice cultivation does not occur (NO) in New Zealand.

Since 1990, there have been changes in the proportions of the main livestock species farmed in New Zealand. Due to the higher profitability of dairy in recent years, there has been an increase in dairy production. The extra land required to accommodate the extra dairy production has mainly come out of sheep farming due to the reduction in profitability of sheep products since 1990. Over the long term, beef numbers have remained relatively static although in recent years there has been a fall in numbers due to drought (Ministry of Agriculture and Forestry, 2009).

There was a gradual increase in the implied emission factors for dairy cattle and beef cattle from 1990 to 2007 that reflects the increased levels of productivity achieved by New Zealand farmers since 1990. Increases in animal liveweight and productivity (milk yield and liveweight gain per animal) require an increased feed intake by the animal to meet higher energy demands. Increased feed intake results in increased CH4 emissions per animal. The drop in implied emission factors in 2008 is due to a small reduction in productivity as a consequence of the nationwide drought in 2008.

The land area used for horticulture also increased by 50 per cent since 1990 and the types of produce grown have changed (Ministry of Agriculture and Forestry, 2009). There is now less cultivated land area for barley, wheat and fruit but more for grapes (for wine production) and vegetables than in 1990. There has also been a net increase in land planted in forestry, reducing the land available for agricultural production.

Changes in emissions between 2007 and 2008

Total agricultural emissions in 2008 were 737.1 Gg CO2-e (2.1 per cent) lower than the 2007 level. This was largely due to a decrease in the population of sheep (4,372,613 or 11.4 per cent), deer (172,699 or 12.4 per cent) and non-dairy cattle (256,745 or 5.8 per cent). The drought that affected most of New Zealand throughout 2008 was the main cause for these decreases in animal numbers (Ministry of Agriculture and Forestry, 2009). This was the second year in a row that some regions of New Zealand experienced drought.

6.1.1 Methodological issues for the agriculture sector

New Zealand uses a June year for all animal statistics as this reflects the natural biological cycle for animals in the southern hemisphere. The models developed to estimate agricultural emissions work on a monthly time step, beginning on 1 July of one year and ending on 30 June of the next year. To calculate emissions for a single calendar year (January–December), emission data from the last six months of a July–June year are combined with the first six months’ emissions of the next July–June year.

To ensure consistency, a single livestock population characterisation and feed-intake estimate is used to estimate CH4 emissions from the enteric fermentation category, CH4 and N2O emissions from the manure management category, and N2O emissions from the pasture, range and paddock manure subcategory.

Information on livestock population census and survey procedures is included in Annex 3.1.

New Zealand has formed an independent Agricultural Inventory Advisory Panel. This panel is made up of representatives from the Ministry of Agriculture and Forestry, the Ministry for the Environment, and science representatives from the Royal Society of New Zealand, New Zealand Methanet and New Zealand NzOnet expert advisory groups. New Zealand Methanet and NzOnet are two groups of New Zealand experts in the areas of agricultural inventory methane and inventory nitrous oxide emissions respectively. The panel is independent and has been formed to advise if changes to New Zealand’s agricultural section of the national inventory are scientifically robust. Reports and papers on proposed changes must have been peer reviewed before they are presented to the panel. The panel then assesses if the proposed changes have been rigorously tested and if there is enough scientific evidence to support the change. The panel advises the Ministry of Agriculture and Forestry of its recommendations. The inaugural meeting of the panel was held on 27 November 2009 where three adjustments were presented. These were (1) calculating dairy emissions using regional data rather than national averages (2) changing how the uncertainty for enteric fermentation is calculated and (3) adopting a country-specific value of 0.1 for FracGASM and FracGASF. All changes were approved and are detailed in the relevant sections of this report.

6.2 Enteric fermentation (CRF 4A)

6.2.1 Description

Methane is a by-product of digestion in ruminants, for example, cattle, and some non-ruminant animals, such as swine and horses. Within the agriculture sector, ruminants are the largest source of CH4 as they are able to digest cellulose. The amount of CH4 released depends on the type, age and weight of the animal, the quality and quantity of feed, and the energy expenditure of the animal.

In 2008, CH4 emissions from the enteric fermentation category were identified as the largest key category for New Zealand in the level assessment (excluding land use, land-use change and forestry (LULUCF)). In accordance with Intergovernmental Panel on Climate Change (IPCC) good practice guidance (IPCC, 2000), the methodology for estimating CH4 emissions from enteric fermentation in domestic livestock is a Tier 2 modelling approach.

In 2008, enteric fermentation contributed 22,657.5 Gg CO2-e. This represented 30.3 per cent of New Zealand’s total CO2-e emissions and 65.1 per cent of agricultural emissions. Cattle contributed 13,947.7 Gg CO2-e (61.6 per cent) of emissions from the enteric fermentation category, and sheep contributed 8,079.9 Gg CO2-e (35.7 per cent) of emissions from this category. Emissions from the enteric fermentation category in 2008 were 820.3 Gg CO2-e (3.8 per cent) above the 1990 level of 21,837.2 Gg CO2-e. Since 1990, there were changes in the source of emissions within the enteric fermentation category. The largest increase came from emissions from dairy cattle. In 2008, dairy cattle were responsible for 9,028.9 Gg CO2-e, an increase of 3,999.6 Gg CO2-e (79.5 per cent) from the 1990 level of 5,029.3 Gg CO2-e. Meanwhile, there have been decreases in emissions from sheep and minor livestock populations, such as goats, horses and swine. In 2008, emissions from sheep were 8,079.9 Gg CO2-e, a decrease of 3,200.1 Gg CO2-e (28.4 per cent) from the 1990 level of 11,280.0 Gg CO2-e.

6.2.2 Methodological issues

Emissions from cattle, sheep and deer

New Zealand’s Tier 2 method (Clark et al, 2003) uses a detailed livestock population characterisation and livestock productivity data to calculate feed intake for the four largest categories in the New Zealand ruminant population (dairy cattle, beef cattle, sheep and deer). The amount of CH4 emitted per animal is calculated using CH4 emissions per unit of feed intake (Figure 6.2.1).

Livestock population data

The New Zealand ruminant population is separated into four main categories: dairy cattle, beef cattle, sheep and deer. Each livestock category is further subdivided by population models (Clark et al, 2003; Clark, 2008b). The populations within a year are adjusted on a monthly basis to account for births, deaths and transfers between age groups. This is necessary because the numbers present at one point in time may not accurately reflect the numbers present at other times of the year. For example, the majority of lambs are born and slaughtered between August and May and, therefore, do not appear in the June census or survey data.

Livestock numbers are provided by Statistics New Zealand from census and survey data conducted in June each year. For all livestock other than dairy, national population numbers are used. However, dairy livestock numbers are calculated on a regional basis and therefore regional dairy population numbers are used.

Statistics New Zealand collects population data on a territorial authority basis. Territorial authorities are the lowest local political division in New Zealand. These territorial authorities are then aggregated up to regional council boundaries by Statistics New Zealand. In 1993, these regional council boundaries changed. Therefore dairy population data for 1990–1993 was collected from Statistics New Zealand at a territorial authority level and then aggregated up to the regional council boundaries currently used. From 1993, Statistics New Zealand supplied livestock population data at the required regional council aggregation and therefore no manipulation of data was required.

Figure 6.2.1 Schematic diagram of how New Zealand’s emissions from enteric fermentation are calculated


Figure 6.2.1 Schematic diagram of how New Zealand’s emissions from enteric fermentation are calculated

The schematic illustrates an overview of the enteric fermentation model. All of the details in the figure are contained within the text of this chapter (Agriculture).

Note: GEI is the gross energy intake and DMI is the dry-matter intake.

Livestock productivity data

Productivity data comes from Statistics New Zealand and industry statistics. To ensure consistency, the same data sources are used each year. This ensures the data provides a time series that reflects changing farming practices, even if there is uncertainty surrounding the absolute values.

Obtaining data on the productivity of ruminant livestock in New Zealand, and how it has changed over time, is a difficult task. Some of the information collected is complete and collected regularly. For example, the slaughter weights of all livestock exported from New Zealand are collected by the Ministry of Agriculture and Forestry from all slaughter plants in New Zealand. This information is used as a surrogate for changes in animal liveweight over time. Other information, such as liveweight of dairy cattle and breeding bulls, is collected at irregular intervals from small survey populations, or is not available at all.

Livestock productivity and performance data are summarised in the time-series tables in the MS Excel worksheets available for download with this report from the Ministry for the Environment’s website (www.mfe.govt.nz/publications/climate/). The data includes average estimated liveweights, milk yields and milk composition of dairy cows, average liveweights of beef cattle (beef cows, heifers, bulls and steers), average liveweights of sheep (ewes and lambs), and average estimated liveweights of deer (breeding and growing hinds and stags).

Dairy cattle: Data on milk production is provided by the Livestock Improvement Corporation, a dairy-farmer-owned company providing services to the dairy, beef and deer industries (2009). This data includes the amount of milk processed through New Zealand dairy factories and milk for the domestic market.

Productivity data (milk yield and composition) is collected from the Livestock Improvement Corporation at the same territorial authority level as the population data is collected by Statistics New Zealand. Ministry of Agriculture and Forestry officials then aggregated this data up into the regional council boundaries used for the population data. Prior to 2004, not all productivity data required could be collected from the Livestock Improvement Corporation at a territorial authority level. Therefore some manipulation of data was required to obtain the required values. For example, from 1993–2003 milk per cow was determined by the following equation.

Litres milk per cow = Average kg milk fact per cow*100/ per cent milk fat

From 2004, annual milk yields per animal are obtained by dividing the total milk produced by the total number of milking dairy cows and heifers. For all years, lactation length is assumed to be 280 days. In 1992, no productivity data was available at a territorial authority level and therefore trends were fitted to data from 1990–2008 to estimate data.

Average liveweight data for dairy cows is obtained by taking into account the proportion of each breed in the national herd and its age structure based on data from the Livestock Improvement Corporation. Dairy cow liveweights are only available from the Livestock Improvement Corporation from 1996 onwards for six large livestock-improvement regions each comprising several regional councils. As there are 16 regional council regions, some regions use the same liveweight data as other regions. For years in the time series prior to 1996, liveweights were estimated using the trend in liveweights from 1996 to 2008, together with data on the breed composition of the national herd.

Dairy replacement animals (calves) at birth are assumed to be 9 per cent of the weight of the average cow and 90 per cent of the weight of the average adult cow at calving. Growth between birth and calving (at two years of age) is divided into two periods: birth to weaning, and weaning to calving. Higher growth rates are applied between births and weaning, when animals receive milk as part of their diet. Within each period, the same daily growth rate is applied for the entire length of the period.

No data is available on the liveweights and performance of breeding bulls. An assumption is made that their average weight is 500 kg and that they are growing at 0.5 kg per day. This is based on expert opinion, taking into account industry data. For example, dairy bulls range from small Jerseys through to larger-framed European beef breeds. The assumed weight of 500 kg and growth rate of 0.5 kg per day provides an average weight (at the mid-point of the year) of 592 kg. This is almost 25 per cent higher than the average weight of a breeding dairy cow but it is realistic given that some of the bulls will be of a heavier breed (eg, Friesian and some beef breeds). Total emissions are not highly sensitive to these assumed values, as breeding bulls only make a small contribution to total emissions, for example, breeding dairy bulls contribute less than 0.1 per cent of emissions from the dairy sector.

Beef cattle: The principal source of information for estimating productivity for beef cattle is livestock slaughter statistics provided by the Ministry of Agriculture and Forestry. All growing beef animals are assumed to be slaughtered at two years of age, and the average weight at slaughter for the three subcategories (heifers, steers and bulls) is estimated from the carcass weight at slaughter. Liveweights at birth are assumed to be 9 per cent of an adult cow weight for heifers, and 10 per cent of an adult cow weight for steers and bulls. As with dairy cattle, growth rates of all growing animals are divided into two periods: birth to weaning, and weaning to slaughter. Higher growth rates are applied before weaning when animals receive milk as part of their diet. Within each period, the same daily growth rate is applied for the entire length of the period.

The carcass weights obtained from the Ministry of Agriculture and Forestry slaughter statistics do not separate carcass weights of adult dairy cows and adult beef cows. Therefore, a number of assumptions 4 are made in order to estimate the liveweights of beef breeding cows. A total milk yield of 800 litres per breeding beef cow is assumed.

Sheep: Livestock slaughter statistics from the Ministry of Agriculture and Forestry are used to estimate the liveweights of adult sheep and lambs, assuming killing-out 5 percentages of 43 per cent for ewes and 45 per cent for lambs. Lamb liveweights at birth are assumed to be 9 per cent of the adult ewe weight, with all lambs assumed to be born on 1 September. Growing breeding and non-breeding ewe hoggets are assumed to reach full adult size at the time of mating when aged 20 months. Adult wethers are assumed to be the same weight as adult breeding females. No within-year pattern of liveweight change is assumed for either adult wethers or adult ewes. All ewes rearing a lamb are assumed to have a total milk yield of 100 litres. Breeding rams are assumed to weigh 40 per cent more than adult ewes. Wool growth (greasy fleece growth) is assumed to be 5 kg per annum in mature sheep (ewes, rams and wethers) and 2.5 kg per annum in growing sheep and lambs.

Deer: Liveweights of growing hinds and stags are estimated from Ministry of Agriculture and Forestry slaughter statistics, assuming a killing-out percentage of 55 per cent. A fawn birth weight of 9 per cent of the adult female weight and a common birth date of mid-December are assumed. Liveweights of breeding stags and hinds are based on published data that has liveweights changing every year by the same percentage change recorded in the slaughter statistics for growing hinds and stags above the 1990 base. It is assumed there is no pattern of liveweight change with any given year. The total milk yield of lactating hinds is assumed to be 240 litres (Kay, 1995).

Dry-matter intake calculation

Dry-matter intake (DMI) for the major livestock classes (dairy cattle, beef cattle, sheep and deer) and sub-classes of animals (breeding and growing) is estimated by calculating the energy required to meet the levels of animal performance and dividing this by the energy concentration of the diet consumed. For dairy cattle, beef cattle and sheep, energy requirements are calculated using algorithms developed in Australia (CSIRO, 1990). These algorithms are chosen as they specifically include methods to estimate the energy requirements of grazing animals. This method estimates a maintenance requirement (a function of liveweight, the amount of energy expended on the grazing process), and a production energy requirement influenced by the level of productivity (eg, milk yield and liveweight gain), physiological state (eg, pregnant or lactating) and the stage of maturity of the animal. All calculations are performed on a monthly basis.

For deer, an approach similar to that used for cattle is adopted using algorithms derived from New Zealand studies on red deer. The algorithms take into account animal liveweight and production requirements based on the rate of liveweight gain, sex, milk yield and physiological state.

Monthly energy concentrations

A single data-set of monthly energy concentrations of the diets consumed by beef cattle, dairy cattle, sheep and deer is used for all years in the time series. This is because there is no comprehensive published data available that allow the estimation of a time series dating back to 1990. The data used is derived from farm surveys on commercial cattle and sheep farms.

Methane emissions per unit of feed intake

There are a number of published algorithms and models 6 of ruminant digestion for estimating CH4 emissions per unit of feed intake. The data requirements of the digestion models make them difficult to use in generalised national inventories and none of the methods have high predictive power when compared against experimental data. Additionally, the relationships in the models have been derived from animals fed indoors on diets unlike those consumed by New Zealand’s grazing ruminants.

Since 1996, New Zealand scientists have been measuring CH4 emissions from grazing cattle and sheep using the SF6 tracer technique (Lassey et al, 1997; Ulyatt et al, 1999). New Zealand now has one of the largest data-sets in the world of CH4 emissions determined using the SF6 technique on grazing ruminants. To obtain New Zealand-specific values, published and unpublished data on CH4 emissions from New Zealand were collated and average values for CH4 emissions from different categories of livestock were obtained. Sufficient data was available to obtain values for adult dairy cattle, sheep more than one year old and growing sheep (less than one year old). This data is presented in Table 6.2.1 together with the IPCC default values for per cent gross energy used to produce CH4 (IPCC, 2000). The New Zealand values fall within the IPCC range and are applied in this submission. Table 6.2.2 shows a time series of CH4 implied emission factors for dairy cattle, beef cattle, sheep and deer. Measurements using open-circuit respiration chamber techniques that provided complete gas balances were conducted to further confirm the SF6 tracer technique.

The adult dairy cattle value is assumed to apply to all dairy and beef cattle, irrespective of age, and the adult ewe value is applied to all sheep greater than one year old. An average of the adult cow and adult ewe value (21.25g CH4/kg DMI) is assumed to apply to all deer. In very young animals receiving a milk diet, no CH4 is assumed to arise from the milk proportion of the diet. Not all classes of livestock are covered in the New Zealand data-set and assumptions are made for these additional classes.

Table 6.2.1 Methane emissions from New Zealand measurements and IPCC default values
  Adult dairy cattle Adult sheep Adult sheep <1 year
New Zealand data (g CH4/kg DMI) 21.6 20.9 16.8
New Zealand data (% GE) 6.5 6.3 5.1
IPCC (2000) default values (% GE) 6 ± 0.5 6 ±0.5 5 ± 0.5

Note: GE is gross energy.

Table 6.2.2 New Zealand’s implied emission factors for enteric fermentation from 1990 to 2008
Year Dairy cattle
(kg CH4 per animal per annum)
Beef cattle
(kg CH4 per animal per annum)
Sheep
(kg CH4 per animal per annum)
Deer
(kg CH4 per animal per annum)
1990 69.6 50.7 9.3 18.8
1991 73.2 51.9 9.4 19.3
1992 73.1 52.4 9.4 20.2
1993 74.6 53.5 9.5 20.4
1994 72.8 54.2 9.6 19.7
1995 72.8 53.3 9.4 20.6
1996 75.1 54.6 9.8 20.9
1997 75.5 55.1 10.2 21.0
1998 73.0 55.1 10.2 21.2
1999 75.3 54.1 10.2 21.3
2000 76.9 56.1 10.7 21.8
2001 77.7 57.0 10.7 21.7
2002 77.1 56.6 10.7 21.6
2003 80.0 56.1 10.7 21.6
2004 78.2 57.0 11.0 21.7
2005 79.2 57.7 11.1 22.2
2006 78.9 58.6 10.9 22.2
2007 77.6 57.3 10.7 22.3
2008 77.1 56.6 11.3 22.4

Emissions from other farmed species

A Tier 1 approach is adopted for minor livestock, such as goats, horses, alpaca and swine, using either IPCC default emission factors (horses, alpaca and swine) or New Zealand-derived values (goats). These minor species comprised 0.2 per cent of total enteric CH4 emissions in 2008.

Livestock population data

The populations of goats, horses and pigs are reported using the animal census (or survey) data from Statistics New Zealand.

The population of alpacas are reported using the animal census (or survey) data from Statistics New Zealand in years where it is available. For other years, an equation derived from a fitted polynomial trend was used.

Livestock emissions data

Horses and swine: Enteric CH4 from these classes of livestock were not a key category in 2008 and, in the absence of data to develop New Zealand emissions’ factors, IPCC default values were used.

Goats: Enteric CH4 from goats was not a key category in 2008. There is no published data available to attempt a detailed categorisation of the performance characteristics, as has been done for the major livestock categories. New Zealand uses a country-specific value of 9 kg CH4/head/year. This was calculated by assuming a default CH4 emission value from goats for all years that is equal to the per-head value of the average sheep in 1990 (ie, total sheep emissions/total sheep population). The goat emission factor is not indexed to sheep over time because there is no data to support the kind of productivity increases that have been seen in sheep.

Alpacas: Enteric CH4 from alpaca was not a key category in 2008. The IPCC default value from the IPCC 2006 guidelines (IPCC, 2006b) is based on a study carried out in New Zealand. In the absence of further work carried out on alpacas in New Zealand this value has been used but is yet to be taken on as a country-specific value.

6.2.3 Uncertainties and time-series consistency

Livestock numbers

Many of the calculations in this sector require livestock numbers. Both census and survey data are used. Surveys occur each year between each census. Detailed information from Statistics New Zealand on the census and survey methods is included in Annex 3.1.

Methane emissions from enteric fermentation

In the 2003 inventory submission, the CH4 emissions data from domestic livestock in 1990 and 2001 were subjected to Monte Carlo analysis using the software package @RISK to determine the uncertainty of the annual estimate (Clark et al, 2003). In subsequent submissions, the uncertainty in the annual estimate was calculated using the 95 per cent confidence interval determined from the Monte Carlo simulation as a percentage of the mean value.

In 2009, the Ministry of Agriculture and Forestry commissioned a report on recalculating the uncertainty of the enteric fermentation methane emissions for sheep and cattle (Kelliher et al, 2009). Since the Monte Carlo analysis carried out in 2003, there has been extensive research in the area of measuring enteric methane emissions from sheep and cattle. The initial analysis expressed the coefficient of variation according to the standard deviation of the methane yield. The recent report investigated calculating the uncertainty by expressing the coefficient of variation according to the standard error of the methane yield. Since further research has been carried out since 2003, the number of studies this uncertainty analysis is based on is larger. The current analysis was restricted to one diet, grass, the predominant diet of sheep and cattle in New Zealand. The new overall uncertainty of the enteric methane emissions inventory, expressed as a 95 per cent confidence interval, is ±16 per cent (Kelliher et al, 2009).

Table 6.2.3 New Zealand’s uncertainty in the annual estimate of enteric fermentation emissions for 1990 and 2008, estimated using the 95 per cent confidence interval of ±16 per cent
Year Enteric CH4 emissions (Gg/annum) 95% confidence interval minimum (Gg/annum) 95% confidence interval maximum (Gg/annum)
1990 1,039.7 873.3 1,206.1
2008 1,078.9 906.3 1,251.5

Note: The CH4 emissions used in the Monte Carlo analysis exclude those from swine and horses.

Uncertainty in the annual estimate is dominated by variance in the measurements of the “CH4 per unit of intake” factor. For the measurements used to determine this factor, the coefficient of variation (standard error as a percent of the mean) is equal to 0.03. This uncertainty is predominantly due to natural variation from one animal to the next. Uncertainties in the estimates of energy requirements, herbage quality and population data are much smaller (0.005–0.05).

6.2.4 Source-specific QA/QC and verification

In 2008, CH4 from enteric fermentation was identified as a key category (level and trend assessment). In preparation for this inventory submission, the data for this category underwent Tier 1 quality checks.

Methane emission rates measured for 20 dairy cows and scaled up to a herd have been corroborated using micrometeorological techniques. Laubach and Kelliher (2004) used the integrated horizontal flux technique and the flux gradient technique to measure CH4 flux above a dairy herd. Both techniques are comparable, within estimated errors, to scaled-up animal emissions. The emissions from the cows measured by integrated horizontal flux and averaged over three campaigns are 329 (±153) g CH4/day/cow compared with 365 (±61) g CH4/day/cow for the scaled-up measurements reported by Waghorn et al (2002; 2003). Methane emissions from lactating dairy cows have also been measured using the New Zealand SF6 tracer method and open-circuit respiration chamber techniques (Grainger et al, 2007). Total CH4 emissions were similar, 322 and 331 g CH4/day, when measured using chambers or the SF6 tracer technique respectively.

Table 6.2.4 shows a comparison of the New Zealand-specific 2008 implied emission factor for enteric fermentation with the IPCC Oceania default and the Australian and United Kingdom implied emission factors for dairy, beef cattle and sheep (UNFCCC, 2009). New Zealand has a slightly higher implied emission factor than the IPCC Oceania default due to the higher productivity of the livestock compared with the Oceania average. The converse is true for the lower implied emission factor for dairy in comparison with Australia and the United Kingdom. Also, New Zealand livestock have a predominant diet of pasture with a higher digestibility than the value reported in Table A-1 of the revised 1996 IPCC guidelines (IPCC, 1996). New Zealand’s emissions factor for sheep is higher than the Australian and United Kingdom emission factor as New Zealand takes into account lambs when determining actual methane emissions but not when estimating the implied emission factor, hence, a higher implied emission factor than when the lamb population is taken into account. Other countries report an implied emission factor including lambs.

IPCC default values and values from some countries for methane emissions from cattle are also determined from relationships based on analyses of the higher-quality feeds typically found in the United States temperate agriculture system (IPCC, 1996). New Zealand methane emissions from cattle have been based on algorithms related to a pastoral diet and will therefore produce different values for emissions.

Table 6.2.4 Comparison of IPCC default emission factors and country-specific implied emission factors for CH4 from enteric fermentation for dairy cattle, beef cattle and sheep
  Dairy cattle
(kg CH4 /head/year)
Beef cattle
(kg CH 4 /head/year)
Sheep 7
(kg CH4/head/year)
IPCC (2006b) Oceania default value 68 53 8
Australian-specific IEF 2008 value 113 72 6.9
United Kingdom-specific IEF 2008 value 105 43 4.7
New Zealand-specific 2008 value 77 57 10.9

Note: IEF is implied emission factor.

6.2.5 Source-specific recalculations

Previously, emissions from dairy animals were calculated using national averages of populations and productivity data. This data was used in the Tier 2 method. A report was commissioned by the Ministry of Agriculture and Forestry to determine if it was feasible to calculate dairy emissions at a regional level before being aggregated up into a national figure. By changing to this method of calculation, differences in animal performance and subsequent emissions efficiencies across the regions could be identified. The report found that data was available for this to occur and for recalculations back to 1990 (Clark 2008a). Data required for the Tier 2 method is now gathered at the regional level rather than using national averages. Details of how the activity data is sourced are outlined in section 6.2.2. This methodological change affects the enteric fermentation, manure management and agricultural soils sections and recalculations have been carried out for each section. The impact of the change is reported in chapter 10.

Alpacas have a very small population in New Zealand but are increasing in number and have therefore been included in the current submission. Although population estimations were required in order to calculate emissions back to 1990, the New Zealand Alpaca Association has begun to collate this data and therefore future population estimates will improve. The impact of this change to the inventory is reported in chapter 10.

All activity data was updated with the latest available data (Statistics New Zealand table builder and Infoshare database (2009), Meat and Wool statistics (2009), Livestock Improvement Corporation statistics (2009)).

6.2.6 Source-specific planned improvements

New Zealand scientists are investigating improvements to the population models and live animal weights used in the Tier 2 method. Research is also under way to determine if satellite imagery can obtain more accurate spatial and temporal values of the metabolisable energy concentration, digestibility and nitrogen content of the diets consumed by New Zealand’s grazing ruminants.

A national inter-institutional ruminant CH4 expert group has been running for eight years. The group was formed to identify the key strategic directions of research into the CH4 inventory and mitigation, and to develop a collaborative approach to improve the certainty of CH4 emission data. This expert group is supported through the Ministry of Agriculture and Forestry. The improved uncertainty analysis and the implementation of the Tier 2 approach for CH4 emissions from enteric fermentation and manure management are a consequence of the research identified and conducted by the expert group.

The Pastoral Greenhouse Gas Research Consortium has been established to carry out research, primarily into mitigation technologies and management practices but also on improving on-farm inventories. The consortium is funded from both public and private sector sources.

6.3 Manure management (CRF 4B)

6.3.1 Description

In 2008, emissions from the manure management category comprised 776.3 Gg CO2-e (2.2 per cent) of emissions from the agriculture sector. Emissions from manure management had increased by 159.1 Gg CO2-e (25.8 per cent) from the 1990 level of 617.2 Gg CO2-e.

Livestock manure is composed principally of organic material. When the manure decomposes in the absence of oxygen, methanogenic bacteria produce CH4. The amount of CH4 emissions is related to the amount of manure produced and the amount that decomposes anaerobically. Methane from manure management was identified as a key category (level assessment) for 2008.

The manure management category also includes N2O emissions related to manure handling before the manure is added to the soil. The amount of N2O emissions depends on the system of waste management and the duration of storage. With New Zealand’s extensive use of all-year-round grazing systems, this category contributed a relatively small amount of N2O of 56.9 Gg CO2-e in 2008. In comparison, N2O emissions from the agricultural soils category totalled 11,372.3 Gg CO2-e in 2008.

In New Zealand, dairy cows only have a fraction (5 per cent) of their excreta stored in anaerobic lagoon waste systems. The remaining 95 per cent of excreta from dairy cattle is deposited directly onto pasture. These fractions relate to the proportion of time dairy cattle spend on pasture compared with the time they spend in the milking shed. All other ruminant species (sheep, beef cattle, goats, deer, alpaca and horses) graze outdoors all year round and deposit all of their faecal material (dung and urine) directly onto pastures. This distribution is consistent with the revised 1996 IPCC guidelines (IPCC, 1996) for the Oceania region. New Zealand scientists and Ministry of Agriculture and Forestry officials consider the default distributions are applicable to New Zealand farming practices for the ruminant animals listed. Further work is being carried out to confirm proportions of different waste management systems for swine and poultry in the manure management systems. Table 6.3.1 shows the current distribution of livestock in animal waste management systems in New Zealand.

Table 6.3.1 Distribution of livestock across animal waste management systems in New Zealand
  Proportion of animals in each animal waste management system (%)
Livestock Anaerobic lagoon Pasture, range and paddock Solid storage and dry-lot Other
Non-dairy cattle 100
Dairy cattle 5 95
Poultry 3 97
Sheep 100
Swine 55 17 28
Goats 100
Deer 100
Horses 100
Alpaca 100

6.3.2 Methodological issues

Methane from manure management

The IPCC Tier 2 approach is used to calculate CH4 emissions from ruminant animal wastes in New Zealand. The Tier 2 approach is based on the methods recommended by Saggar et al (2003) in a review commissioned by the Ministry of Agriculture and Forestry.

The approach relies on (1) an estimation of the total quantity of faecal material produced; (2) the partitioning of this faecal material between that deposited directly onto pastures and that stored in anaerobic lagoons; and (3) the development of New Zealand-specific emission factors for the quantity of CH4 produced per unit of faecal dry-matter deposited directly onto pastures, and that stored in anaerobic lagoons. Table 6.3.2 summarises the key variables in the calculation of CH4 from manure management.

Table 6.3.2 Derivation of CH4 emissions from manure management in New Zealand
Livestock Proportion of faecal material deposited on pasture (%) CH4 from animal waste on pastures (g CH4/kg faecal dry-matter) Proportion of faecal material stored in anaerobic lagoons (%) Water dilution rate (litres water/kg faecal dry-matter) Average depth of a lagoon (metres) CH4 from anaerobic lagoon
(g CH4/m2/
year)
Dairy cattle 0.95 0.98 0.05 90 4.6 3.27
Beef cattle 1.0 0.98 0.0
Sheep 1.0 0.69 0.0
Deer 1.0 0.92 0.0
Dairy cattle

Faecal material deposited directly onto pastures: The quantity of faecal dry-matter produced is obtained by multiplying the quantity of feed eaten by the dry-matter digestibility of the feed, minus the feed retained in product. These feed intake and dry-matter digestibility estimates are used in the enteric CH4 and N2O Tier 2 model calculations. Consistent with the N2O inventory, 95 per cent of faecal material arising from dairy cows is assumed to be deposited directly onto pastures (Ledgard and Brier, 2004). The quantity of CH4 produced per unit of faecal dry-matter is 0.98 g CH4/kg. This value is obtained from New Zealand studies on dairy cows (Saggar et al, 2003; Sherlock et al, 2003).

Faecal material stored in anaerobic lagoons: Five per cent of faecal material arising from dairy cows is assumed to be stored in anaerobic lagoons. The current method assumes that all faeces deposited in lagoons are diluted with 90 litres of water per kilogram of dung dry-matter (Heatley, 2001). This gives the total volume of effluent stored. Annual CH4 emissions are estimated using the data of McGrath and Mason (2002). McGrath and Mason (2002) calculated specific emissions values of 0.33–6.21 kg CH4/m2/year from anaerobic lagoons in New Zealand. The mean value of 3.27 CH4/m2/year of this range is assumed in the New Zealand Tier 2 calculations.

Beef cattle, sheep and deer

The quantity of faecal dry-matter produced is obtained by multiplying the quantity of feed eaten by the dry-matter digestibility of the feed, minus the feed retained in product. These feed intake and dry-matter digestibility estimates are used in the enteric CH4 and N2O Tier 2 model calculations.

Beef cattle, sheep and deer are not housed in New Zealand and all faecal material is deposited directly onto pastures.

No specific studies have been conducted in New Zealand on CH4 emissions from beef cattle faeces and values obtained from dairy cattle studies (0.98 g CH4/kg) are used (Saggar et al, 2003; Sherlock et al, 2003).

The quantity of CH4 produced per unit of sheep faecal dry-matter is 0.69 g CH4/kg. This value is obtained from New Zealand studies on sheep (Carran et al, 2003).

There are no New Zealand studies on CH4 emissions from deer manure, and values obtained from sheep and cattle are used. The quantity of CH4 produced per unit of faecal dry-matter is assumed to be 0.92 g CH4/kg. This value is the average value obtained from all New Zealand studies on sheep (Carran et al, 2003) and dairy cattle (Saggar et al, 2003; Sherlock et al, 2003).

Other minor livestock categories

New Zealand-specific emission factors are not available for CH4 emissions from manure management for goats, swine, horses and poultry. These are minor livestock categories in New Zealand and IPCC default emission factors are used to calculate emissions.

There is no IPCC default value available for CH4 emissions from manure management for alpacas. Therefore this was calculated by assuming a default CH4 emission from manure management value for alpacas for all years that is equal to the per head value of the average sheep in 1990 (ie, total sheep emissions/total sheep population). The alpaca emission factor is not indexed to sheep over time because there is no data to support the kind of productivity increases that have been seen in sheep.

Nitrous oxide from manure management

This subcategory reports N2O emissions from the anaerobic lagoon, solid storage and dry-lot, and other animal waste management systems. Emissions from the pasture range and paddock animal waste management system are reported in the agricultural soils category.

The calculations for the quantity of nitrogen in each animal waste management system are based on the nitrogen excreted (Nex) per head per year multiplied by the livestock population, the allocation of animals to animal waste management systems (Table 6.3.1), and an N2O emission factor for each animal waste management system.

The Nex values are calculated from the nitrogen intake less the nitrogen in animal products. Nitrogen intake is determined from feed intake and the nitrogen content of the feed. Feed intake and animal productivity values are the same as used in the Tier 2 model for determining CH4 emissions (Clark et al, 2003). The nitrogen content of feed is estimated from a review of over 6000 pasture samples of dairy, sheep and beef systems (Ledgard et al, 2003).

The nitrogen content of product is derived from industry data. For lactating cattle, the nitrogen content of milk is derived from the protein content of milk (nitrogen = protein/6.25) published annually by the Livestock Improvement Corporation. The nitrogen content of sheep meat, wool and beef, and the nitrogen retained in deer velvet, are taken from New Zealand-based research.

Table 6.3.3 (overleaf) shows Nex values increasing over time reflecting the increases in animal productivity in New Zealand since 1990.

Table 6.3.3 Nex values for New Zealand’s main livestock classes from 1990 to 2008
Year Sheep N (kg/head/year) Non-dairy cattle N (kg/head/year) Dairy cattle N (kg/head/year) Deer N (kg/head/year)
1990 12.61 65.51 104.22 24.88
1991 12.83 66.98 109.06 25.64
1992 12.80 67.78 109.09 26.83
1993 12.93 69.26 110.81 27.06
1994 12.96 70.15 108.13 26.20
1995 12.81 68.95 108.05 27.42
1996 13.32 70.82 110.91 27.76
1997 13.89 71.48 111.29 27.84
1998 14.01 71.48 108.23 28.06
1999 13.97 70.00 111.23 28.24
2000 14.58 72.60 112.89 28.91
2001 14.72 73.71 113.79 28.85
2002 14.68 73.14 113.13 28.74
2003 14.66 72.38 117.48 28.67
2004 15.07 73.61 115.21 28.88
2005 15.19 74.60 116.45 29.47
2006 15.01 75.81 115.64 29.58
2007 14.75 73.91 113.95 29.69
2008 15.57 72.99 112.86 29.79

New Zealand-specific Nex values are not available for swine, horses and poultry. These are minor livestock categories in New Zealand and IPCC default emission factors are used to calculate emissions.

There is no IPCC default value available for Nex for alpacas. Therefore this was calculated by assuming a default Nex value for alpacas for all years that is equal to the per head value of the average sheep in 1990 (ie, total sheep emissions/total sheep population). The alpaca emission factor is not indexed to sheep over time because there is no data to support the kind of productivity increases that have been seen in sheep. Sheep were used rather than the IPCC default value for “other animals” as literature indicates that alpacas have an N intake close to that of sheep, and no significant difference in the partitioning of N (Pinares-Patino et al, 2003). Therefore using the much higher default value for ‘other animals’ would be greatly overestimating the true Nex value for alpacas.

6.3.3 Uncertainties and time-series consistency

The main factors causing uncertainty in N2O emissions from manure management are the emission factors from manure and manure management systems, the livestock population, nitrogen excretion rates, and the use of the various manure management systems (IPCC, 2000).

New Zealand uses the IPCC default values for EF3 (direct emissions from waste) for all animal waste systems except for EF3(PR&P) (manure deposited on pasture, range and paddock). The New Zealand-specific emission factor for EF3(PR&P) is 0.01 kg N2O-N/kg N (further details in section 6.5.2). The IPCC default values have uncertainties of –50 per cent to +100 per cent (IPCC, 2000).

6.3.4 Source-specific QA/QC and verification

Methane from manure management was identified as a key category (level assessment) in 2008. In preparation for this inventory submission, the data for this category underwent Tier 1 quality checks.

Table 6.3.4 shows a comparison of the New Zealand-specific 2008 implied emission factor for methane from manure management with the IPCC Oceania default and the Australian and United Kingdom implied emission factor for dairy, beef cattle and sheep. New Zealand has a lower implied emission factor for methane from manure management than the IPCC Oceania default and the United Kingdom. This is due to the much higher proportion of animals in New Zealand that are grazed on pastures and not housed, resulting in less manure being stored in a management system. This is also reflected in the Australian implied emission factor as Australia also has significant pasture-grazed livestock.

Differences between the implied emission factors and the IPCC default factors are also due to the reasons outlined in the enteric fermentation section, that is, productivity of the animals and the use of different algorithms to determine energy intake as well as values used for nitrogen content of feed and digestibility.

Table 6.3.4 Comparison of IPCC default emission factors and country-specific implied emission factors for CH4 from manure management for dairy cattle, beef cattle and sheep
  Dairy cattle
(kg CH4/head/year)
Beef cattle
(kg CH4/head/year
Sheep
(kg CH4/head/year
IPCC (1996) developed temperate climate/Oceania default value 32 6 0.28
Australian-specific IEF 2008 value 0.89 0.04 0.00
United Kingdom-specific IEF 2008 value 25.79 4.18 0.11
New Zealand-specific 2008 value 3.31 0.7 0.11

Note: IEF is implied emission factor.

6.3.5 Source-specific recalculations

Due to improvements in how dairy emissions are calculated (ie, using regional data rather than a national average), Nex and methane emissions from manure management have been recalculated for all years. Details of how activity data is sourced can be found in section 6.2.2. The impact of the change to the inventory is reported in chapter 10.

Estimates of emissions from alpacas have been incorporated into this submission and emissions have been recalculated back to 1990. See section 6.2 for further details. The impact of the change to the inventory is reported in chapter 10.

All activity data was updated with the latest available data (Statistics New Zealand table builder and Infoshare database (2009), Meat and Wool statistics (2009), Livestock Improvement Corporation statistics (2009)).

6.3.6 Source-specific planned improvements

Both the Poultry Industry Association New Zealand and New Zealand Pork are currently working to improve knowledge on the distribution of each industry’s manure into each of the manure management categories. This work will be assessed once completed.

6.4 Rice cultivation (CRF 4C)

6.4.1 Description

Although it is possible to grow rice in New Zealand it is uneconomical to do so. Therefore currently no rice cultivation is being carried out in New Zealand. This has been confirmed with experts from Plant and Food Research, Lincoln, New Zealand. The “NO” notation is reported in the common reporting format tables.

6.5 Agricultural soils (CRF 4D)

6.5.1 Description

In 2008, the agricultural soils category contributed 11,372.3 Gg CO2-e (15.2 per cent) to New Zealand’s total emissions and 95.5 per cent to total N2O emissions. Emissions were 1,993.3 Gg CO2-e (21.3 per cent) above the 1990 level of 9,379.0 Gg CO2-e. This category comprises three subcategories. Each of these subcategories has been identified as a key category. The trend for each subcategory is provided below.

  • Direct N2O emissions from agricultural soils as a result of adding nitrogen in the form of synthetic fertilisers, animal waste, biological fixation in crops, inputs from crop residues and cultivation of organic soils. Direct N2O soil emissions contributed 1,777.7 Gg CO2-e (15.6 per cent) to emissions from the agricultural soils category in 2008. This was an increase of 1,262.5 Gg CO2-e (245.1 per cent) from the 1990 level of 515.2 Gg CO2-e. Direct N2O emissions from agricultural soils were identified as a key category (level and trend assessment).
  • Indirect N2O from nitrogen lost from the field as NO3, NH3 or NOx. In 2008, indirect N2O emissions from nitrogen used in agriculture contributed 2,468.8 Gg CO2-e (21.7 per cent) to emissions from the agricultural soils category. This was an increase of 463.7 Gg CO2-e (23.1 per cent) from the 1990 level of 2,005.1 Gg CO2‑e. Indirect N2O emissions from agricultural soils were identified as a key category (level assessment).
  • Direct N2O emissions from animal production (the pasture, range and paddock animal waste management system). Nitrous oxide emissions from animal production contributed 7,125.9 Gg CO2-e (62.7 per cent) to emissions from the agricultural soils category. This is an increase of 267.1 Gg CO2-e (3.9 per cent) from the 1990 level of 6,858.7 Gg CO2-e. Direct N2O emissions from animal production were identified as a key category (trend and level assessment).

Carbon dioxide emissions from limed soils are reported in the LULUCF sector (chapter 7).

6.5.2 Methodological issues

The two main inputs of nitrogen to the soil are excreta deposited during animal grazing and the application of nitrogen fertilisers. Emission factors and the fraction of nitrogen deposited on the soils are used to calculate N2O emissions.

Five New Zealand-specific emission factors and parameters are used in the inventory: EF1, EF3(PR&P), FracLEACH, FracGASM and FracGASF. The use of a country-specific emission factor for EF1 (direct emissions from nitrogen input to soil) of 1 per cent, is based on work by Kelliher and de Klein (2006). The country-specific EF3(PR&P) emission factor of 1 per cent and FracLEACH of 0.07 are based on extensively reviewed literature and field studies (Carran et al, 1995; de Klein et al, 2003; Muller et al, 1995; Thomas et al, 2005). A new value of 0.1 has been adopted for the emission factor FracGASM after an extensive review of scientific literature (Sherlock et al, 2009). Conversely, the 1996 IPCC default value of 0.1 for FracGASF has been verified as appropriate to New Zealand after an extensive review of the scientific literature (Sherlock et al, 2009) and has therefore been adopted as a country-specific emission factor. Details of recalculations can be found in section 6.5.5 and chapter 10.

The emission factors and other parameters used in this category are documented in Annex 3.1. The calculations are included in the MS Excel worksheets available for download with this report from the Ministry for the Environment’s website (www.mfe.govt.nz/publications/climate/greenhouse-gas-inventory-2010/index.html).

Animal production (N2O)

Direct soil emissions from animal production refers to the N2O produced from the pasture, range and paddock animal waste management system. This system is the predominant regime for animal waste in New Zealand as 95 per cent of dairy cattle excreta and 100 per cent of sheep, deer and non-dairy cattle excreta are allocated to it (Table 6.3.1).

The emissions calculation is based on the livestock population multiplied by nitrogen excretion (Nex) values and the percentage of the population on the pasture, range and paddock animal waste management system. The Nex values and allocation to animal waste management systems are discussed in section 6.3. The Nex values have been calculated based on the same animal intake and animal productivity values used for calculating CH4 emissions for the different animal classes and species in the Tier 2 model. This ensures the same base values are used for both the CH4 and N2O emission calculations.

New Zealand uses a country-specific emission factor for EF3(PR&P) of 0.01 (Carran et al, 1995; Muller et al, 1995; de Klein et al, 2003; Kelliher et al, 2003). Considerable research effort has gone into establishing a New Zealand-specific emission factor for EF3(PR&P). Field studies have been performed as part of a collaborative research effort called NzOnet. The EF3(PR&P) parameter has been measured by NzOnet researchers in the Waikato (Hamilton), Canterbury (Lincoln) and Otago (Invermay) regions for pastoral soils of different drainage classes (de Klein et al, 2003). These regional data are comparable because the same measurement methods were used at the three locations. The percentage of applied nitrogen (in urine or dung) emitted as N2O, and relevant environmental variables, were measured in four separate trials that began in autumn 2000, summer 2002, spring 2002 and winter 2003. Measurements were carried out for up to 250 days at each trial site or until urine-treated pasture measurements dropped back to background emission levels.

Kelliher et al (2003, 2005), assessed all available EF3(PR&P) data and its distribution to pastoral soil drainage class, to determine an appropriate national annual mean value. The complete EF3(PR&P) data set of NzOnet was synthesised using the national assessment of pastoral soil drainage classes. These studies recognise that:

  • environmental (climate) data is not used to estimate N2O emissions using the methodology in the revised 1996 IPCC guidelines (IPCC, 1996)
  • the N2O emission rate can be strongly governed by soil water content
  • soil water content depends on drainage that can moderate the effects of rainfall and drought
  • drainage classes of pastoral soils, as a surrogate for soil water content, can be assessed nationally using a geographic information system.
  • drainage classes of pastoral soils, as a surrogate for soil water content, can be assessed nationally using a geographic information system.

An earlier analysis in New Zealand showed that the distribution of drainage classes for pasture land is highly skewed, with 74 per cent well-drained, 17 per cent imperfectly drained and 9 per cent poorly drained (Sherlock et al, 2001).

The research and analysis to date indicates that, if excreta is separated into urine and dung components, EF3 for urine and dung could be set to 0.007 and 0.003 respectively. However, it is recognised the dung EF3 data is limited. By combining urine and dung EF3 values, the dairy cattle total excreta EF3 is 0.006. By conservatively rounding the total excreta, an EF3 of 0.006 provides a New Zealand-specific value of 0.01 for EF3(PR&P). The IPCC default value of EF3(PR&P) is 0.02 (IPCC, 1996).

Incorporation of the mitigation technology DCD into the agriculture inventory

A methodology to incorporate a N2O mitigation technology, the nitrification inhibitor dicyandiamide (DCD), into the agriculture sector of the inventory has been developed. A detailed description of the methodology can be found in Clough et al (2008). The N2O emissions reported in the agricultural soils category for 2008 take into account the use of nitrification inhibitors on dairy farms using the methodology described in Clough et al (2008). For the 2008 calendar year, DCD mitigated 40.8 Gg CO2-e, a 0.1 per cent decrease in total agricultural N2O emissions.

Dicyandiamide is a well researched and environmentally safe nitrification inhibitor that has been demonstrated to reduce N2O emissions and nitrate leaching in pastoral grassland systems grazed by ruminant animals. There have been 28 peer-reviewed, published New Zealand studies on the use and effects of DCD.

The method to incorporate DCD mitigation of N2O emissions into New Zealand’s agricultural inventory is by an amendment to the existing IPCC methodology. Activity data on livestock numbers is drawn from Statistics New Zealand’s annual agricultural survey. This survey has recently included questions on the area that DCD is applied to on grazed pastures.

The DCD product is applied to pastures based on research that has identified good management practice to maximise N2O emission reductions. This is at a rate of 10 kg per hectare of DCD applied twice per year in autumn and early spring within seven days of the application of excreta or fertiliser nitrogen. “Good practice” application methods are by slurry or granule.

Changes to the emission factors EF3PR&P, EF1 and parameter FracLEACH were established for use with DCD application. These emission factors and parameters were modified based on comprehensive field-based research that showed significant reductions in N2O emissions and nitrate leaching where DCD was applied.

The peer-reviewed literature on DCD use in grazed pasture systems was critically reviewed and it was determined that, on a national basis, reductions in EF1, EF3PR&P and FracLEACH of 67 per cent, 67 per cent and 53 per cent could be made respectively (Clough et al, 2008). However, due to the limited amount of data available on nitrogen fertiliser use in New Zealand, it is currently not possible to apply these reductions to EF1 in the inventory calculations.

The reductions in the emission factors and parameters are used along with the fraction of dairy land treated with DCD to calculate DCD weighting factors.

DCD weighting factor = (1-% reduction in EFx /100 X DCD treated area/ Effective dairy area)

The appropriate weighting factor is then used as an additional multiplier in the current methodology for calculating indirect and direct emissions of N2O from grazed pastures. The calculations use a modified EF3PR&P of 0.0094 and FracLEACH of 0.0658 for a dairy grazing area in the months that DCD is applied (May to September). The modified emission factors are based on information from the agricultural survey that 5.1 per cent of the effective dairying area in New Zealand received DCD in 2008.

Table 6.5.1 Emission factors and parameters for New Zealand’s DCD calculations
  New Zealand emission factor or parameter value for untreated area
(kg N2O-N/kg N)
Reduction from DCD treatment (%) Proportion land treated with DCD (%) Final modified emission factor or parameter
(kg N2O-N/kg N)
EF3PR&P 0.01 67 5.1 0.0094
FracLEACH 0.07 53 5.1 0.0658

All other emission factors and parameters relating to animal excreta and fertiliser use (FracGASM, FracGASF, EF4 and EF5) remain unchanged when DCD is used as an N2O mitigation technology. Based on the physico-chemical reaction of DCD in the soil, DCD should have no effect on ammonia volatilisation during May to September when DCD is applied. This is supported by the results of field studies (Clough et al, 2008; Sherlock et al, 2009).

The derivations of the modified emission factors and the resulting calculations are included in the MS Excel worksheets available for download with this report from the Ministry for the Environment’s website (www.mfe.govt.nz/publications/climate/greenhouse-gas-inventory-2010/index.html).

The method will be refined over time to reflect any updated information that may arise from ongoing research in this area.

Indirect N2O from nitrogen used in agriculture

Nitrous oxide is emitted indirectly from nitrogen lost from agricultural soils through leaching and run-off. This nitrogen enters water systems and eventually reaches the sea, with N2O being emitted along the way. The amount of nitrogen that leaches is a fraction (FracLEACH) of that deposited or spread on land.

Research studies and a literature review in New Zealand have shown lower rates of nitrogen leaching than are suggested in the revised 1996 IPCC guidelines (IPCC, 1996). A New Zealand parameter for FracLEACH of 0.15 was used in inventories submitted before 2003. However, using a FracLEACH of 0.15, IPCC-based estimates for different farm systems were found on average to be 50 per cent higher than those estimated using the OVERSEER® nutrient-budgeting model (Wheeler et al, 2003). The OVERSEER® model provides average estimates of the fate of nitrogen for a range of pastoral, arable and horticultural systems. In pastoral systems, nitrogen leaching is determined by the amount of nitrogen applied in fertiliser, in dairy-farm effluent and that excreted in urine and dung by grazing animals. The latter is calculated from the difference between nitrogen intake by grazing animals and nitrogen output in animal products, based on user inputs of stocking rate or production and an internal database with information on the nitrogen content of pasture and animal products.

The IPCC estimates were closer for farms using high rates of nitrogen fertiliser, indicating that the IPCC-based estimates for nitrogen leaching associated with animal excreta were too high for New Zealand. When the IPCC method was applied to field sites where nitrogen leaching was measured (four large-scale, multi-year animal grazing trials), it resulted in values that were double the measured values. This indicated that a value of 0.07 for FracLEACH more closely followed actual field leaching in New Zealand (Thomas et al, 2005). The 0.07 value has been adopted and is used for all years as it best reflects New Zealand’s national circumstances.

Some of the nitrogen contained in animal excreta and fertiliser deposited or spread on land is emitted into the atmosphere as ammonia (NH3) and nitrogen oxides (NOx) through volatilisation. A fraction of this returns to the ground during rainfall and is then re-emitted as N2O. This is calculated as an indirect emission of N2O. The fraction of nitrogen that is deposited or spread on land that then indirectly becomes nitrous oxide through this process is calculated using the fractions FracGASM from animal excreta and FracGASF from nitrogen fertiliser.

International and New Zealand-based scientific research and a literature review of this work have shown that the current 1996 IPCC default value for FracGASM is too high for New Zealand conditions. In most European countries, ammonia emitted from pasture soils following grazing is just one of several sources contributing to reported FracGASM inventory values, whereas, in New Zealand, 97 per cent of all livestock urine and dung is deposited directly on soils during grazing. Excluding studies on nitrification inhibitors, eight international papers covering 45 individual measurements and nine national papers covering 19 individual measurements were reported on. The report determined a value of 0.1 for FracGASM was more appropriate for New Zealand conditions (Sherlock et al, 2009). The 0.1 value has been adopted and is used for all years as it best reflects New Zealand’s national circumstances.

Seventeen peer-reviewed papers covering 79 individual measurements have also been reviewed for FracGASF. Taking into account that approximately 80 per cent of nitrogen fertiliser used in New Zealand is urea with the remaining being diammonium phosphate (DAP), a value of 0.096 for FracGASF was determined (Sherlock et al, 2009). As this is almost identical to the IPCC default value of 0.1 currently used, 0.1 has been adopted as a country-specific value for FracGASF.

New Zealand uses the IPCC default EF4 emission factor for indirect emissions from volatilisation of nitrogen in the form of NH3 and oxides of NOx.

Direct N2O emissions from agricultural soils

The N2O emissions from the direct soils emissions subcategory arise from synthetic fertiliser use, spreading animal waste as fertiliser, nitrogen fixing in soils by crops, and decomposition of crop residues left on fields. All of the nitrogen inputs are summed together and a New Zealand-specific emission factor of 0.01 kg N2O-N/kg N (Kelliher and de Klein, 2006) is applied to calculate total direct emissions from non-organic soils.

Data on nitrogen fertiliser use is provided by the New Zealand Fertiliser Manufacturers’ Research Association from sales records for 1990 to 2008. There has been a five-fold increase in the amount of synthetic fertiliser nitrogen applied to soils over the time series, from 59,265 tonnes in 1990 to 328,157 tonnes in 2008. These figures differ by 10 per cent from those reported in the common reporting format tables. This is because the values reported in the common format reporting tables are adjusted to account for the amount that volatises as NH3 and NOx (IPCC, 2000).

The calculation for animal waste includes all manure that is spread on agricultural soils, irrespective of the animal waste management system it was initially stored in. This includes all agricultural waste in New Zealand except for emissions from the pasture range and paddock animal waste management system. New Zealand uses a country-specific value for EF1 of 0.01 kg N2O-N/kg N (Kelliher and de Klein, 2006).

Direct N2O emissions from organic soils are calculated by multiplying the area of cultivated organic soils by an emission factor (EF2). Analysis identified 202,181 hectares of organic soils under agricultural pasture in New Zealand (Kelliher et al, 2002). Kelliher et al (2002) estimated 5 per cent (ie, 10,109 hectares) of organic soils under agricultural pasture are cultivated on an annual basis. New Zealand uses the IPCC default emissions factor (EF2 equal to 8 kg N2O-N/kg N) for all years of the time series.

6.5.3 Uncertainties and time-series consistency

Uncertainties in N2O emissions from agricultural soils were assessed for the 1990 and 2002 inventory using a Monte Carlo simulation of 5000 scenarios with the @RISK software (Kelliher et al, 2003) (Table 6.5.2). The emissions’ distributions are strongly skewed, reflecting pastoral soil drainage whereby 74 per cent of soils are classified as well drained and 9 per cent are classified as poorly drained. For the 2008 data, the uncertainty in the annual estimate was calculated using the 95 per cent confidence interval determined from the Monte Carlo simulation as a percentage of the mean value (ie, in 2002, the uncertainty in annual emissions was +74 per cent and –42 per cent).

Table 6.5.2 New Zealand’s uncertainties in N2O emissions from agricultural soils for 1990, 2002 and 2008 estimated using Monte Carlo simulation (1990, 2002) and the 95 per cent confidence interval (2008)
Year N2O emissions from agricultural soils (Gg/annum) 95% confidence interval minimum (Gg/annum) 95% confidence interval maximum (Gg/annum)
1990 30.3 17.5 52.5
2002 37.3 21.6 64.9
2008 35.8 20.8 62.3

The overall inventory uncertainty analysis shown in Annex 7 demonstrates that the uncertainty in annual emissions from agricultural soils is a major contributor to uncertainty in the total estimate and to the uncertainty in the trend from 1990. The uncertainty between years was assumed to be correlated. Therefore, the uncertainty is mostly in the emission factors and the uncertainty in the trend is much lower than uncertainty for an annual estimate.

The Monte Carlo numerical assessment is also used to determine the effects of variability in the nine most influential parameters on uncertainty of the calculated N2O emissions in 1990 and 2002. These parameters are shown in Table 6.5.3, together with their percentage contributions to the uncertainty. There was no recalculation of the influence of parameters for the 2008 data. The Monte Carlo analysis confirmed that uncertainty in parameter EF3(PR&P) has the most influence on total uncertainty, accounting for 91 per cent of the uncertainty in total N2O emissions in 1990. This broad uncertainty reflects natural variance in EF3, determined largely by the vagaries of the weather and soil type.

Table 6.5.3 Proportion contribution of the nine most influential parameters on the uncertainty of New Zealand’s total N2O emissions for 1990 and 2002
  1990 2002
Parameter Contribution to uncertainty (%) Contribution to uncertainty (%)
EF3(PR&P) 90.8 88.0
EF4 2.9 3.3
Sheep Nex 2.5 1.8
EF5 2.2 2.8
Dairy Nex 0.5 0.7
FracGASM 0.5 0.5
EF1 0.3 2.4
Beef Nex 0.2 0.3
FracLEACH 0.1 0.2

6.5.4 Source-specific QA/QC and verification

In 2008, N2O emissions from the direct soil emissions and pasture range and paddock manure subcategories were key categories (level and trend assessment), and N2O from the indirect emissions category was also a key category (level assessment). In preparation for this inventory submission, the data for these categories underwent Tier 1 quality checks.

In 2008, the Ministry of Agriculture and Forestry commissioned a report investigating nitrous oxide emission factors and activity data for crops. Agricultural Production Survey activity data for wheat and maize was verified with the Foundation for Arable Research Production Database between 1995 and 2007. Data for wheat and maize between the two data sources was very similar.

Fertiliser sales data received from the New Zealand Fertiliser Manufacturers’ Research Association was verified with data collected from the Agricultural Production Survey from Statistics New Zealand for year end June 2008. Data from the New Zealand Fertiliser Manufacturers’ Research Association was year end May. The Agricultural Production Survey data for fertiliser use in New Zealand was within 26,000 tonnes (~10 per cent) of the fertiliser sales value supplied by the New Zealand Fertiliser Manufacturers’ Research Association. The New Zealand Fertiliser Manufacturers’ Research Association data is used rather than the Agricultural Production Survey data as 95 per cent of New Zealand fertiliser is provided from two large companies. Therefore this information will be more accurate than the survey as there is a multitude of differently named nitrogen fertilisers and the Agricultural Production Survey respondents often have problems filling in the fertiliser question in the questionnaire. Ten per cent variation in nitrogen fertiliser data between the New Zealand Fertiliser Manufacturers’ Research Association and the Agricultural Production Survey is considered to be good.

Dicyandiamide data obtained from the Agricultural Production Survey was verified with data from the main supplier of DCD. This company has a 90 per cent share of the market. Values obtained from this company were approximately 87 per cent of the reported DCD usage data obtained from the Agricultural Production Survey, indicating the values were reasonably accurate.

Table 6.5.4 compares the New Zealand-specific values for EF1 and EF3PR&P with the 1996 IPCC default value and emission factors used by Australia and the United Kingdom. In both cases, the New Zealand value is lower than the IPCC default value. This is due to the large proportion of well-drained soils within New Zealand as well as the type of soils as indicated in Table A-1 of the revised 1996 IPCC guidelines (IPCC, 1996). In Table A-1 (IPCC, 1996) it demonstrates that New Zealand silt loams have significantly less nitrous oxide emissions from dung and urine deposits on the silt loams than other countries and soil types.

Table 6.5.4 Comparison of IPCC default emission factors and country-specific implied emission factors for EF1 and EF3PR&P
  EF1
(kg N2O-N/kg N)
EF3PRP
(kg N2O-N/kg N excreted)
IPCC (2006b) developed temperate climate/Oceania default value 0.0125 0.02
Australian-specific IEF 2008 value 0.0125 (except animal production = 0.01) 0.004
United Kingdom-specific IEF 2008 value 0.0125 0.02
New Zealand-specific 2008 value 0.01 0.01

Note: IEF is implied emission factor.

Table 6.5.5 compares the New Zealand-specific values FracGASF, FracGASM and FracLEACH with the 1996 IPCC default and fractions used by Australia and the United Kingdom. Details on these three fractions can be found in further detail in section 6.5.2. Although New Zealand has taken a country-specific value for FracGASF of 0.1, it is the same as the IPCC default and that of Australia and the United Kingdom. This is because research showed that this value was appropriate to New Zealand conditions.

However, research showed that the default value of 0.2 for FracGASM was too high and therefore New Zealand has taken on board a lesser value of 0.1. The reduction is due to the different sources that make up this value. In New Zealand, 97 per cent of animal excreta is deposited onto pasture whereas the 1996 IPCC default value was calculated taking into account a much higher percentage of manure management and storage. This results in a much higher proportion of nitrogen being volatised and hence the higher FracGASM default value.

New Zealand also has a much lower FracLEACH. Research showed that New Zealand applies a much lower rate of nitrogen fertiliser than what was assumed when developing the 1996 IPCC default value. When the OVERSEER® nutrient-budgeting model (Wheeler et al, 2003) took this lower rate into account, the rate of leaching was much lower than when compared with farms with a high nitrogen fertiliser rate than can be typical in other developed countries.

Table 6.5.5 Comparison of IPCC default emission factors and country-specific implied emission factors for FracGASF, FracGASM and FracLEACH
  FracGASF
(kg NH3-N
and NOx-N/kg of N input)
FracGASM
(kg NH3-N and NOx-N/kg of N excreted)
FracLEACH
(kg N/kg fertiliser or manure N)
IPCC (1996) developed temperate climate/Oceania default value 0.1 0.2 0.3
Australian-specific IEF 2008 value 0.1 0.21 0.3
United Kingdom-specific IEF 2008 value 0.1 0.20 0.3
New Zealand-specific 2008 value 0.1 0.1 0.07

Note: IEF is implied emission factor.

6.5.5 Source-specific recalculations

A country-specific value of 0.1 has been adopted for the emission factor FracGASM. As this differs from the 1996 IPCC default value of 0.2, recalculations have been carried out for all years from 1990. This resulted in a reduction of 685.3 Gg CO2-e in 1990 and 737.2 Gg CO2-e in 2007.

The FracGASF value of 0.1 has been verified as appropriate to New Zealand conditions and has therefore been adopted as a country-specific emission factor. This value is no different to the 1996 IPCC default value, therefore it did not result in any recalculations.

Due to improvements in how dairy emissions are calculated (ie, using regional data rather than a national average) Nex applied to soils have been recalculated for all years. Details of how activity data is sourced can be found in section 6.2.2. The impact of this change to the inventory is reported in chapter 10.

Estimates of emissions from alpacas have been incorporated into this submission and emissions have been recalculated back to 1990. See section 6.2 for further details. The impact of this change to the inventory is reported in chapter 10.

All activity data was updated with the latest available data (Statistics New Zealand table builder and Infoshare database (2009), Meat and Wool statistics (2009), Livestock Improvement Corporation statistics (2009)).

Potatoes have been identified as an important crop in New Zealand (Thomas et al, 2008). Estimates have therefore been incorporated into this submission and emissions have been recalculated back to 1990. This resulted in an increase of 9.4 Gg CO2-e in both 1990 and 2008.

An error in the calculation of crop residues has also been corrected. Prior to this submission, in the calculation for emissions from crop residue activity, data on maize was being adjusted for a proportion that was burnt. However, maize residue is not burnt in New Zealand and was therefore not included in the calculations of the agricultural burning of crop residue resulting in a small proportion of maize crop not being accounted for. This oversight has now been corrected.

6.5.6 Source-specific planned improvements

New Zealand scientists are continuing to research N2O emission factors for New Zealand’s pastoral soils. This includes development of New Zealand-specific emission factors for sheep and cattle dung and emission factors for New Zealand hill country pastures. New Zealand is also continuing research to refine the methodology used to estimate N2O emission reductions using dicyandiamide (DCD) nitrification inhibitors.

The calculation of DCD effectiveness is being improved. This is through the development of the programming for the Tier 2 model used to determine animal methane emissions and nitrogen excretion rates. Reductions in emissions factors due to DCD will be applied monthly and only during the respective months that it can be used. In this way it can be applied more precisely to the relevant animal populations during the year.

Forage brassicas have been identified as an important crop in New Zealand but activity data is currently inadequate to be able to carry out emission calculations. Therefore improvements to this data collection are under way so that this crop can be included in future submissions.

Assessment of the fertiliser question in the Agricultural Production Survey is being carried out with the view to try to improve data obtained from the questionnaire and therefore improve the verification of fertiliser data from Fertiliser Manufacturers’ Research Association.

Further, Monte Carlo simulations on the uncertainties in N2O emissions from agricultural soils are planned for future submissions.

6.6 Prescribed burning of savanna (CRF 4E)

6.6.1 Description

In 2008, prescribed burning of savanna was not a key category in New Zealand. The inventory includes burning of tussock (Chionochloa) grassland in the South Island for pasture renewal and weed control. The amount of burning has been steadily decreasing over the past 50 years as a result of changes in lease tenure and a reduction in grazing pressure. In 2008, prescribed burning emissions accounted for 1.0 Gg CO2-e, a 2.2 Gg CO2-e (68.0 per cent) reduction in emissions from the 3.2 Gg CO2-e reported in 1990.

The revised 1996 IPCC guidelines (IPCC, 1996) state that, in agricultural burning, the CO2 released is not considered to be a net emission as the biomass burned is generally replaced by regrowth over the subsequent year. Therefore, the long-term net emissions of CO2 are considered to be zero. However, the by-products of incomplete combustion – CH4, CO, N2O and NOx – are net transfers from the biosphere to the atmosphere.

6.6.2 Methodological issues

New Zealand has adopted a modified version of the IPCC methodology (IPCC, 1996). The same five equations are used to calculate emissions. Instead of using total grassland and a fraction burnt, New Zealand uses statistics of the total area of tussock grassland that has been granted consent (a legal right) for burning, under New Zealand’s Resource Management Act 1991. Only those areas with consent are legally allowed to be burned. Expert opinion obtained from local government is that approximately 20 per cent of the area allowed to be burnt is actually burnt in a given year.

Current practice in New Zealand is to burn in damp spring conditions, reducing the amount of biomass consumed in the fire. The composition and burning ratios used in calculations are from New Zealand-specific research (Payton and Pearce, 2001) and the revised 1996 IPCC guidelines (IPCC, 1996).

6.6.3 Uncertainties and time-series consistency

The same emission factors and sources of data were used for the whole time series. This gives confidence in comparing emissions through the time series. The major sources of uncertainty are the percentage of consented area actually burnt in that season, extrapolation of biomass data from two study sites for all areas of tussock, and that many of the other parameters are the IPCC default values (ie, the carbon content of the live and dead components, the fraction of the live and dead material that oxidises, and the nitrogen-to-carbon ratio for the tussocks). Uncertainty in the New Zealand biomass data has been quantified at ±6 per cent (Payton and Pearce, 2001). However, many IPCC parameters vary by ±50 per cent and some parameters do not have uncertainty estimates.

6.6.4 Source-specific QA/QC and verification

There was no source-specific quality assurance or quality control for this category in 2008.

6.6.5 Source-specific recalculations

There were no source-specific recalculations for this category in 2008.

6.6.6 Source-specific planned improvements

Investigations into improving the tussock burning activity data have been carried out (Thomas et al, 2008). A new question on the burning on tussock land in New Zealand has been added to the Agricultural Production Survey. Assessment on this data will be carried out to determine if it represents an accurate area of tussock land burned, and the potential to include this data in future inventory submissions.

6.7 Field burning of agricultural residues (CRF 4F)

6.7.1 Description

Burning of agricultural residues produced 19.1 Gg CO2-e in 2008. This was a decrease of 9.6 Gg CO2-e (33.6 per cent) below the level of 28.7 Gg CO2-e in 1990. Burning of agricultural residues was not identified as a key category in 2008.

New Zealand reports emissions from burning barley, wheat and oats residue in this category. Maize and other crop residues are not burnt in New Zealand.

Burning of crop residues is not considered to be a net source of CO2, as the CO2 released into the atmosphere is reabsorbed during the next growing season. However, the burning is a source of emissions of CH4, CO, N2O and NOx (IPCC, 1996). Burning of residues varies between years because of climatic conditions.

6.7.2 Methodological issues

The emissions from burning agricultural residues are estimated using the equation on page 4.82 of the revised 1996 IPCC guidelines (IPCC, 1996). This calculation uses crop production statistics, the ratio of residue to crop product, the dry-matter content of the residue, the fraction of residue actually burned, the fraction of carbon oxidised and the carbon fraction of the residue. These parameters were multiplied to calculate the carbon released. The emissions of CH4, CO, N2O and NOx were calculated using the carbon released and an emissions ratio. Nitrous oxide and NOx emissions’ calculations also used the nitrogen-to-carbon ratio.

IPCC good practice guidance suggests that an estimate of 10 per cent of residue burned may be appropriate for developed countries, but also notes that the IPCC default values: “are very speculative and should be used with caution. The actual percentage burned varies substantially by country and crop type. This is an area where locally developed, country-specific data is highly desirable” (IPCC, 2000). For the years 1990 to 2003, it was estimated that 50 per cent of stubble was burnt. For the years 2004 to 2008, experts assessed this to have decreased to 30 per cent. These values were developed from opinions of the Ministry of Agriculture and Forestry officials working with the arable production sector (M Doak, pers comm). Neither legume nor maize crops are burnt in New Zealand but rather crop residue is incorporated back into the soil or harvested for supplementary feed for livestock. The proportion of stubble burnt each year varies greatly and depends on climatic conditions and the value of using or selling the waste stubble as supplementary feed for cattle.

6.7.3 Uncertainties and time-series consistency

No numerical estimates for uncertainty are available for these emissions. The fraction of agricultural residue burned in the field was considered to make the largest contribution to uncertainty in the estimated emissions.

6.7.4 Source-specific QA/QC and verification

There was no source-specific quality assurance or quality control for this category in 2008.

Table 6.7.1 compares the New Zealand-specific values FracBURN with the IPCC default value and fractions used by Australia and the United Kingdom. New Zealand’s value is higher than that of the 1996 IPCC default value, Australian and the United Kingdom values. This is because the IPCC default value was based on the assumption that little field residue burning was carried out in developed countries. This appears to be the case for both Australia and the United Kingdom. However, in some regions of New Zealand, burning of barley and wheat is still carried out, although this has been dropping since 1990. This fraction is also being looked into further as detailed in section 6.7.6.

Table 6.7.1 Comparison of IPCC default emission factors and country-specific implied emission factors for FracBURN
  FracBURN
(kg N/kg crop-N)
IPCC developed temperate climate/Oceania default value 0.1
Australian-specific IEF 2008 value NA 8
United Kingdom-specific IEF 2008 value 0
New Zealand-specific 2008 value 0.3

Note: IEF is implied emission factor.

6.7.5 Source-specific recalculations

All activity data was updated with the latest available data (Statistics New Zealand table builder and Infoshare database (2009)).

6.7.6 Source-specific planned improvements

In a report commissioned by the Ministry of Agriculture and Forestry (Thomas et al, 2008) there was discussion on the proportion of the total area of barley, wheat and oats that are burned. The report suggested that the demand for products from the crop residues may have increased and therefore a smaller proportion of residue burning may occur in some instances. However, there is no information available on the amount of cereal crop residues that are baled and therefore we cannot currently revise our expert judgement on FracBURN. The report also recommended changing the method for how crop residue is calculated for barley, wheat and oats. These recommendations will be assessed for feasibility of incorporation into future inventory submissions.


4  The number of beef breeding cows was assumed to be 25 per cent of the total beef breeding cow herd and other adult cows slaughtered were assumed to be dairy cows. The carcass weight of dairy cattle slaughtered was estimated using the adult dairy cow liveweights and a killing-out percentage of 40 per cent. The total weight of dairy cattle slaughtered was calculated (carcass weight × number slaughtered) and then deducted from the national total carcass weight of slaughtered adult cows. This figure was then divided by the number of beef cows slaughtered to obtain an estimate of the carcass weight of adult beef cows. Liveweights were calculated assuming a killing-out percentage of 50 per cent.

5  Percentage of carcass weight in relation to live weight.

6  For example, Blaxter and Clapperton, 1995; Moe and Tyrrel, 1975; Baldwin et al, 1988; Djikstra et al, 1992; and Benchaar et al, 2001 – all cited in Clark et al, 2003.

7  All values, except for New Zealand, include lambs in implied emission factor calculation.

8  Australia report that there is no field residue burning and therefore they do not use FracBURN.