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Appendix D: Waste Sector Emissions Projections

1 Introduction

Greenhouse gas emissions arise from three waste sector sources: emissions from solid waste disposal sites (landfills), from domestic and industrial wastewater treatment plants, and from solid waste incineration.

Emissions from solid waste disposal sites comprised 79 per cent of the emissions from the waste sector in 2006. These emissions are the result of anaerobic decomposition of organic matter: primarily garden, food, paper, textile and timber waste. The net amount of emissions produced depend on many factors including the composition of solid waste to landfill, waste disposal practices, and the efficiency of any landfill gas collection system.

Wastewater treatment processes produced 20 per cent of emissions from waste. Both methane and nitrous oxide are emitted through treating domestic, commercial and industrial wastewater. Factors influencing the amount of emissions include the type of treatment process, the volume of wastewater and the nitrogen content, and whether any resulting emissions are flared.

Emissions from solid waste incineration produced less than one per cent of waste sector emissions in 2006. These emissions include carbon dioxide (from combusting materials with some fossil fuel content, such as plastics), nitrous oxide and methane. The emissions arise from hospital and quarantine waste incineration. There has been a significant decrease in incineration emissions since 1990 due to the implementation of national regulations controlling air quality effects and the availability of alternative treatments such as steam sterilisation.

1.1 Recent trends

Waste sector emissions in 2006 were 1.858 million tonnes of carbon dioxide equivalent (Mt CO2-e). This is a reduction of 0.648 Mt CO2-e (25.9 per cent) below the 1990 baseline value of 2.506 Mt CO2-e.

This reduction has occurred across all waste sub-sectors. The largest reduction has occurred in the solid waste disposal on land category as a result of initiatives to improve solid waste management practices and increase landfill gas capture rates in New Zealand. Improvements in wastewater treatment technologies and solid waste incineration practises have resulted in smaller inventory reductions.

2 Modelling method

The emissions from solid waste disposal are projected using the methodology and variables used in New Zealand’s Greenhouse Gas Inventory 1990–2006 (MfE 2008a). The methodology uses data specific to New Zealand on waste generation rates, waste composition, percentage of waste disposed to types of landfills, and landfill gas extraction and combustion. Data on waste generation has not been collected routinely in the past; however, all assumptions have been clearly expressed in the national inventory and reviewed by international experts.

The national inventory uses a Tier-2 model to estimate gross methane emissions from solid waste disposed to landfills. This methodology is recommended by the Intergovernmental Panel on Climate Change (IPCC) and assumes that the degradable organic components in waste decay slowly throughout a few decades. Emissions of methane are highest in the first few years after the waste was disposed, then gradually decline.

The methodology requires an estimate of solid waste generated per capita. This data has been compiled through the landfill surveys in 1995 and 2002. Other limited data sets exist for waste composition and have been used. The only variable input into the projections methodology is that of national population, which determines the total volume of waste to landfills. The projection used is from Statistics New Zealand’s National Population Projections (2006 base, series 5). Other variables remain constant at the values reported in the latest national inventory (MfE, 2008).

Projected effects of the New Zealand waste strategy are deducted from the modelled gross methane emissions. The effects of the national environmental standard for landfill gas collection are also deducted from the remaining emissions, and were estimated using a survey of landfill operators in 2005 (Waste Management, 2005).

Emissions from wastewater treatment have been estimated using a combination of country specific methodologies and IPCC good practice models. Emissions are sourced from anaerobic treatment of domestic, commercial and industrial wastewater in municipal and some industrial treatment plants. Some larger treatment facilities flare the resulting methane. Projected emissions for 2010 were estimated by pro-rating the 2006 emission values against projected population, using the same Statistics NZ data as in the projections of solid waste described above. Emissions are projected to be 0.35 Mt CO2-e for 2010. This is a decrease of 0.04 Mt CO2-e from the 2007 Net Position report, which reflects an improved methodology for estimating emissions from industrial wastewater treatment.

Emissions from solid waste incineration were estimated and reported for the first time in the latest national inventory (MfE, 2008). IPCC 2006 good practice guidance was followed. Emissions of carbon dioxide, nitrous oxide and methane are sourced primarily from the burning of quarantine and hospital waste. There were 10 such incinerators emitting such gases at the start of 2006. Carbon dioxide is counted in the inventory where materials with a fossil fuel origin are burnt. Projected incineration activity was assessed through obtaining expected activity estimates from individual incinerators. Emissions are projected to be 1.44 Mt CO2-e for 2010.

3 Policies

3.1 Policies in place

The effects of the New Zealand Waste Strategy and the National Environmental Standard for Landfill Gas Collection are included in the total emissions from the waste sector. These are currently the only policies directly affecting emissions from the waste sector. Emissions from solid waste disposed on land are proposed to enter the scope of the New Zealand emissions trading scheme from 1 January 2013.

3.2 The New Zealand Waste Strategy

The New Zealand Waste Strategy was launched in March 2002 with the objective of moving towards zero waste by 2010. The strategy extends to all waste streams including landfill waste, mine and quarrying waste, and sewage. In the initial estimate of emissions over the first commitment period, the New Zealand Waste Strategy was projected to deliver an estimated reduction of 2.4 Mt CO2-e, or 13.5 per cent, in gross emissions from solid waste disposal sites. This projection is retained as the optimistic value. The most likely estimate is that 75 per cent of the reduction occurs, ie, 1.8 Mt CO2-e, with a pessimistic value assuming 50 per cent of the reduction. The impacts of the New Zealand Waste Strategy are applied to the data progressively, with a two per cent impact in 2008 to a maximum of 13.5 per cent by 2012 in the optimistic scenario.

3.3 The National Environmental Standard for Landfill Gas Collection

A National Environmental Standard for Landfill Gas Collection and Destruction was introduced under Sections 43 and 44 of the Resource Management Act (RMA) to be applied to landfills that will accept over one million tonnes of refuse throughout their design life (MfE 2004).

Landfill gas collection estimates were updated for the 2004 Inventory by Waste Management in 2005. The consultants projected that 7.4 Mt CO2-e, or 55 per cent, of gross emissions from solid waste disposal sites would be collected by landfill gas systems over the years 2008 to 2012. These estimates did not include the effects of the New Zealand Waste Strategy on gross emissions. Consequently, the landfill gas collection estimates were reduced by the same proportions used to reduce gross emissions. The most likely scenario now holds that landfill gas collections systems will reduce gross emissions by 6.8 Mt CO2-e over 2008 to 2012.

4 Projection

4.1 Total emissions

Emissions from the waste sector over the first commitment period are expected to range between 7.8 and 7.5 Mt CO2-e. Projected annual emissions for 2010 are expected to lie between 1.56 Mt CO2e and 1.51 Mt CO2-e per annum with a most likely value of 1.54 Mt CO2-e.

Figure D1 shows that since 1990 there has been a large decrease in emissions which, as explained above, is primarily due to decreased waste volumes and less organic matter entering landfills. The New Zealand Waste Strategy (MfE 2002) and National Environmental Standard for Landfill Gas Collection and Destruction are projected to further decrease waste sector emissions despite expected increases in solid waste volumes and increases in emissions from wastewater treatment.

Figure D1: Projected annual emissions for 2010 and the inventory time series of emissions from the waste sector (million tonnes carbon dioxide equivalent)

 

 

High range 2010

Low range 2010

Reported in national inventory

Mid range 2010

1990

2.505201

2.505201

2.505201

 

1991

2.534392

2.534392

2.534392

 

1992

2.492507

2.492507

2.492507

 

1993

2.507629

2.507629

2.507629

 

1994

2.483785

2.483785

2.483785

 

1995

2.285843

2.285843

2.285843

 

1996

2.298191

2.298191

2.298191

 

1997

2.287272

2.287272

2.287272

 

1998

2.2287

2.2287

2.2287

 

1999

2.104976

2.104976

2.104976

 

2000

2.128806

2.128806

2.128806

 

2001

2.079279

2.079279

2.079279

 

2002

2.040067

2.040067

2.040067

 

2003

2.026378

2.026378

2.026378

 

2004

1.96572

1.96572

1.96572

 

2005

1.912604

1.912604

1.912604

 

2006

1.788507

1.788507

1.788507

 

2007

1.773573

1.757031

 

1.765302

2008

1.602478

1.573142

 

1.58781

2009

1.583531

1.539952

 

1.561741

2010

1.567091

1.509443

 

1.538267

2011

1.550755

1.479264

 

1.515009

2012

1.536148

1.450918

 

1.493533

 

4.2 Reconciliation with 2007 projection

For the period 2008 to 2012, projected emissions from the waste sector have increased 0.7 Mt CO2-e (10 per cent) from the 2007 estimates due to several factors:

  • inclusion in the estimates, for the first time, of emissions from solid waste incineration. These emissions are projected to have decreased 86 per cent from 1990 levels by 2010
  • methodological changes in modelling emissions from industrial wastewater treatment
  • adjustments to assumptions regarding the composition of solid waste disposed to landfills since 2003 leading to a higher emission factor per tonne of waste
  • correcting an overstatement in the estimates of landfill gas collection.

5. References

MfE 2002. The New Zealand Waste Strategy: Towards zero waste and a sustainable New Zealand. Wellington, Ministry for the Environment.

MfE 2004. National environmental standards for air quality. Wellington, Ministry for the Environment.

MfE 2008. New Zealand’s Greenhouse Gas Inventory 1990–2006: An Overview. Wellington, Ministry for the Environment.

Waste Management 2005. Landfill methane recovery estimate and national greenhouse gas inventory. Report by Waste Management New Zealand to Ministry for the Environment.