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2 Greenhouse Gas Mitigation – General

The goal of this study is to quantify the economic benefits of positive health impacts due improved air quality through various greenhouse gas mitigation options. The focus is on the domestic, transport and industrial energy sectors, since it is known that these sectors have the largest health effect with respect to air pollution (Fisher et al, 2007). The energy sector represents the second largest source of greenhouse gas emissions in New Zealand, after agriculture. Agriculture is responsible for about half of all New Zealand’s greenhouse gas emissions; since few air quality benefits beyond odour can be achieved through reductions in agricultural emissions, they will not be addressed in this study. According to New Zealand’s latest UNFCCC greenhouse gas inventory 1990–2005 (MfE, 2007b) the energy sector collectively represents 42.4% of all greenhouse gas emissions. Table 2.1 shows the sources of greenhouse gas emissions within the energy sector in New Zealand.

The focus of this study is on carbon dioxide (CO2), which accounts for about half of New Zealand’s total emissions – the rest being mainly methane from agricultural processes. Agricultural processes that generate methane do not generally emit other contaminants with health effects; consequently they have no significant public health cost associated with air pollution.

The majority of the figures from Table 2.1 are sourced from the greenhouse gas inventory (MfE, 2007b) with the exception of the road transport and residential heating breakdowns. The breakdown in emissions by vehicle type was achieved using the Vehicle Kilometres Travelled (VKT) from Transit’s New Zealand Dynamic On-Road Transport (DOT) Model Fleet Hub. Similarly the residential heating breakdown was achieved using heating statistics from the Ministry for the Environment’s Warm Homes Project. Emissions from biomass (wood and biogas) are included in the greenhouse gas inventory (MfE, 2007b) and are not included in totals, whereas here they have been included in the analysis, but excluded in the final accounting. Note that, with more recent data (Warm Homes) it is possible that the greenhouse gas inventory (MfE, 2007b) slightly underestimates the emissions from residential sources.

Table 2.1: Breakdown of annual greenhouse gases in the energy sector (2005)

Source of greenhouse gas emissions by sector

CO2-e (kilotonnes)

Summary commentary
Actions that may have a co-beneficial effect on air quality and greenhouse gas emissions reductions

Energy industries





There is potential for reducing the need for existing and new thermal power generation. Phasing out thermal power generating plants would reduce both GHG emissions and air pollution. However, air pollution from thermal generation affects relatively few people, so the health benefits are small.

Measures such as large-scale use of solar hot water and domestic-scale renewable energy, use of energy efficient appliances, and reducing the use of electrical space heating, all have potential to decrease the demand for new and existing thermal power stations.

Substituting heat pumps for electrical resistance heating could reduce the peak winter heating load. Some of the gains could be offset by increased use of air conditioning in summer.

Public electricity and heat production   6,066
Petroleum refining   824
Manufacture of solid fuels and other energy industries   294

Manufacturing industries, building and construction



Substantial energy savings could be achieved through co-generation or by making use of the waste heat produced at various industrial and electricity generating and heating operations.

Similarly industrial symbiosis could be examined. These initiatives involve industries working together to engage traditionally separate industries and other organisations in a collective approach, to add competitive advantage involving physical exchange of materials, energy, water and/or by-products together with collaboration on the shared use of assets, logistics and expertise.





Pollution and GHG emissions from personal transport could be decreased by reducing the total number of vehicle kilometres travelled (VKT). This could be achieved through a number of social, technical, and economic initiatives.

Use of ethanol and biodiesel represent one such technical solution, however careful analysis of the ‘embodied energy’ is required to ensure an overall net positive GHG effect. Overseas research indicates that wide-scale use of biodiesel, more so than ethanol, can result in reductions in particulate emissions.

Heavy commercial vehicles represent 16.6% of all toad transport GHG emissions in New Zealand (or 3.0% of total GHG emission); they are also major emitters of air pollution. Greater utilisation of rail for transporting freight represents a possible method to prevent HCV from entering heavily populated areas.

Road transport     12,602
a Cars (petrol)   8,645  
b Cars (diesel)   598  
c LCV (petrol)   76  
d LCV (diesel)   723  
e HCV (petrol)   99  
f HCV (diesel)   2,096  
g Buses (petrol)   68  
h Buses (diesel)   298  

Civil aviation



Railways     172
Marine     336

Other sectors


The need for domestic heating can be reduced by improving building envelopes (eg, better insulation, weatherproofing, etc). There is evidence to suggest that some efficiency gains will be negated by increased home temperatures. Measures aimed at reducing humidity levels in homes would allow for lower indoor temperatures with no impact on comfort levels.

Biomass fuel represents a renewable energy supply with little or no net greenhouse gas emissions. However, air pollution due to large-scale burning in populated areas has serious health implications. Pellet burners and low-emission wood burners represent one possible solution.

Commercial/institutional     1,705
Residential     3,457
a Open-fire wood   386  
b Open-fire coal   74  
c Pre-1994 wood burner   1,097  
d 1994–1999 wood burner   836  
e Post-1999 wood burner   291  
f Multi-fuel burner – wood   371  
g Multi-fuel burner – coal   289  
h Gas   114  
Agriculture/forestry/fisheries     1,170

Fugitive emissions from fuels



Not covered in this study