The report, which provides an inventory of greenhouse gas emissions for the region, was commissioned by a consortium of councils – Wellington City Council, Porirua City Council, Hutt City Council, Upper Hutt City Council, Kāpiti Coast District Council and Greater Wellington Regional Council – and prepared by consultants URS New Zealand Limited.
Increases in emissions are usually closely linked to growth in population and GDP so this reduction is seen by the councils as an important step in the right direction. In the Wellington region, the population has increased by 12 percent and regional GDP by 26 percent since 2000/01.
The 3 percent decline does not include emissions from the forestry sector; when forestry is included, emissions are very similar, decreasing by one percent over the 12-year period (2000/01–2012/13).
The relatively stable regional trend contrasts with rising national emissions although differences in methodology prevent a direct comparison. Nationally, gross emissions (excluding forestry) increased by 5 percent and net emissions (including forestry) increased by 30 percent from 2000 to 2011.
The Wellington region councils want to improve their understanding of the sources of greenhouse gas emissions and trends in their region, including urban areas, and identify actions they can take to mitigate this. More broadly, the study will inform strategic decision-making by the councils and provide useful information to researchers, the business community, central government and Wellington residents.
The inventory sets out annual rates of greenhouse gas emissions for the Wellington region as a whole with a breakdown by district. It measures greenhouse gas emissions from the following sectors: stationary energy (such as electricity and gas), transport (including domestic aviation), industrial processes (such as gases used in refrigerators and air conditioning systems), agriculture and waste. It also measures changes in the forestry sector.
In 2012/13, regional gross emissions (excluding forestry) were about 3.8 million tonnes of greenhouse gases (carbon dioxide equivalent). Net emissions for the region (including forestry) were 1.7 million tonnes – around 3.5 tonnes per person. Over the 12-year period, gross emissions per person decreased from 9 tonnes to about 8 tonnes.
In Wellington City, Porirua City, Hutt City, Upper Hutt City and the Kāpiti Coast district, most emissions come from stationary energy and transport, compared to the Wairarapa where most come from agriculture. The main factors in reducing greenhouse gas emissions in the Wellington region are:
- more electricity being generated from renewable sources (wind and geothermal), with some of this coming from new renewable developments such as Project West Wind
- a decline in electricity consumption
- relatively stable overall consumption of road transport fuels (petrol use has declined while diesel has gone up)
- landfill gas recovery systems being installed
- more waste being diverted from landfills
- waste water treatment changing from oxidation ponds and septic tanks to sludge treatment processes in Kāpiti Coast district
- a decline in animal stock rates in Wairarapa.
Notable emission increases were seen in domestic aviation (based on regional activity) and industry (based on national trends).
The Wellington region councils took part in an international pilot project to test the methodology used by URS New Zealand, called the Global Protocol for Community-Scale Greenhouse Gas Emissions. This method is emerging as international best practice in developing community-scale greenhouse gas inventories.
The study also identifies areas for further work by the councils to improve data quality for emissions monitoring. Due to data limitations the inventory excludes emissions from international aviation and shipping, estimates regional industrial process emissions based on national trends, and does not account for forest carbon storage in harvested wood products.
More analysis will be required to properly assess what factors are driving regional emissions and opportunities for mitigation. The next stage of the project will focus on developing projected scenarios for regional emissions to 2020.
The table below provides the gross emission results for each city/district and the Wellington region as a whole. The three Wairarapa district authorities were grouped into one Wairarapa area for the purpose of the inventory.