Using the agricultural emissions Calculator

This tool is available to farmers, growers or small block-holders who want a quick, initial estimate of their farm’s emissions. It is especially useful for farms with many livestock types, some of which are not covered by sector-specific tools.   

Knowing your land's greenhouse gas emissions and where they come from is the first step towards reducing them. 

The calculator uses emissions factors derived from New Zealand’s National Inventory for methane and nitrous oxide emissions. These factors are national averages. The factors for forests are based on our Land Use and Carbon Analysis System (LUCAS) national sample. 

See Measuring emissions guide for more details.

The approach used to calculate emissions is simple so the calculator will give you a ball-park estimate of emissions and sequestration. For example, it does not account for the age of livestock and trees or management practices, which could reduce or increase emissions such as bought-in feed and manure management. It also relies on national average default values for emissions factors. 

The data you enter and the results the calculator generates will only be visible to you. No record is kept of the data and results so save or print them if you want to keep a copy.

The calculator is focused on: 

• methane and nitrous oxide from livestock and nitrogen fertiliser 
• carbon sequestered in vegetation.  

The term agri-soils in the calculator refers to the nitrous oxide lost from dung and urine in soil, rather than soil carbon. The nitrogen in dung and urine is used by soil micro-organisms such as bacteria and fungi and, as a result, some is released as nitrous oxide into the atmosphere. Nitrogen from fertiliser can also be converted to nitrous oxide and this is accounted for in the fertiliser section of the calculator.

The calculator uses the New Zealand Emissions Trading Scheme definition of a forest in which the forest:  

• covers at least 1 hectare  
• contains trees that can reach at least 5 metres in height when mature in that location 
• has (or is expected to reach) crown cover of more than 30% in each hectare 
• is at least (or expected to reach) 30 metres across on average. 

It does not include shelterbelts (unless their average width is at least 30m), and trees primarily for fruit and nut production. 

In the calculator, tall natural forests (such as mature native trees) are assigned a zero value for sequestration. This is in line with the approach taken in New Zealand’s Greenhouse Gas Inventory. The zero value may change in future (either up or down), as we discover more about sequestration in New Zealand’s forests through the monitoring programme managed by the Ministry for the Environment. 

For farms where livestock numbers fluctuate widely over the year, an average will need to be estimated. For example, a rough average can be calculated by summing the monthly numbers and dividing by 12. Where this information is not available, an estimate will need to be made.

The calculator requires that nitrogen fertiliser data is entered as kilograms of fertiliser, not as kilograms of nitrogen, to enable different emissions factors to be applied. For non-urea nitrogen fertilisers, you will need to enter each type that you use separately, along with the percentage of nitrogen in each. However, the calculator has the percentage of nitrogen in urea (with and without urease inhibitor) built into the calculation, so all you need to enter is the total kilograms of urea applied.