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Annex D: Waste Emissions Projections provided by Ministry for the Environment

Introduction

Greenhouse gas emissions arise from three waste sector sources, being emissions from solid waste disposal sites and from domestic and industrial wastewater treatment plants.

Emissions from solid waste disposal sites comprised 79 per cent of the emissions from the waste sector in 2005. 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 21 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.

Recent trends

Waste sector emissions in 2005 are now 0.647 million tonnes of carbon dioxide (Mt CO2e) below the 1990 baseline value of 2.493 Mt CO2e, a reduction of 25.9 per cent.

This 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.

Modelling

Description of method

The emissions from solid waste disposal are projected using the methodology and variables used in New Zealand’s Greenhouse Gas Inventory 1990–2005 (MfE, 2007). 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 is 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 CH4 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 complied 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 Treasury’s December 2006 Half Year Economic and Fiscal Update model results. Other variables remain constant at the values reported in the latest national inventory (MfE, 2007).

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 using a linear projection of emissions from 1990 to 2003 (r2 = 0.96). Emissions are projected to be 0.39 Mt CO2e for 2010. This is an increase of 0.06 Mt CO2e from the 2006 net position report and reflects an improved methodology for estimating the biodegradable organic content of domestic and commercial wastewater.

Policies

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.

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 CO2e, 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 CO2e, 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.

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 CO2e, 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 6.5 Mt CO2e.

Projection

Total emissions

Emissions from the waste sector over the first commitment period are expected to range between 6.7 Mt CO2e and 7.3 Mt CO2e. Projected annual emissions for 2010 are expected to lie between 1.34 Mt CO2e and 1.45 Mt CO2e per annum with a most likely value of 1.4 Mt CO2e.

Figure D1 shows that since 1990 there has been a large decrease in emissions 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 sectoral emissions despite increasing 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)

Thumbnail of image. See figure at its full size including text description.

Reconciliation with 2006 projection

For the period 2008 to 2012, projected emissions from the waste sector have increased 0.5 Mt CO2e from the 2006 estimates due to several factors:

  • as discussed above, emissions from wastewater treatment have been revised upwards due to methodological improvements resulting in an increased methane emissions factor

  • adjustments to assumptions regarding the impact of the New Zealand Waste Strategy.

23 For the forestry sector this report only covers Article 3.3 which includes post 1990 afforestation and all deforestation.

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