5 Control of Greenhouse Gas Emissions at Landfills
5.1 Background
The objective of the national environmental standard is for the effective management of discharges to air of greenhouse gases generated from large landfills. The focus of this standard is on the control and destruction of methane, one of the most important greenhouse gases in terms of the level of emissions and its global warming potential.
The national environmental standards 'lock in' existing best practice of capturing and flaring landfill gas at all large landfills. It also provides flexibility to encourage the beneficial use of methane, and facilitate the management of organic waste outside of the traditional landfill (eg, via composting initiatives).
The standard requires the collection and destruction of methane gas at all landfill sites with a total design capacity greater than 1 million tonnes of refuse. The regulations set standards for the flaring of the gas, but also allows for destruction of collected gas via beneficial uses of methane - such as electricity generation.
An understanding of the Resource Management (Energy and Climate Change) Amendment Act 2004 provides important background to the development of this standard.
5.2 Resource Management (Energy and Climate Change) Amendment Act 2004
The Resource Management (Energy and Climate Change) Amendment Act 2004 came into force on 2 March 2004.
One of the motivations for the Amendment Act 2004 was to remove the potential for duplication of regulation of greenhouse gas emissions at the local and national levels. It is the Government's preference for national coordination of controls on discharges to air of greenhouse gases.
The Amendment Act 2004 achieves national coordination by removing the power of regional councils to consider the impacts of discharges to air of greenhouse gases on climate change when making rules in regional plans or determining air discharge consents, except where necessary to implement a national environmental standard.
The Amendment Act 2004 states:
- rules can be made that are necessary to implement the standard (not the policy)
- the rules have to be no more or no less restrictive.
5.3 What does the standard say?
Regulation 25 outlines which landfills the standard applies to.
25 Application of regulations 26 and 27
(1) Regulations 26 and 27 apply to a landfill if -
a. the landfill -
i. has a total capacity of not less than 1 million tonnes; and
ii. contains not less than 200,000 tonnes of waste; and
iii. is or is likely to be accepting waste; and
b. the waste in or to be included in the landfill is likely to consist of 5% or more (by weight) of matter that is putrescible or biodegradable.
(2) However, regulations 26 and 27 do not apply to a landfill until 8 October 2007 if the landfill -
a. has a total capacity of not less than 1 million tonnes of waste; and
b. on 8 October 2004 -
i. contains not less than 200,000 tonnes of waste; and
ii. is accepting waste; and
c. does not operate a gas collection system.
(3) Regulations 26 and 27 do not apply to a cleanfill.
5.3.1 Applies to landfills that are designed to accept over 1 million tonnes of refuse throughout their design life
Subclause 25(1)(a)(i) states that the standard applies to sites with a design capacity of greater than 1 million tonnes of refuse. Whilst landfills smaller than 1 million tonnes can generate methane at volumes that could be collected, it is usually not likely to be at a volume that makes it economically viable.
5.3.2 Applies immediately for sites with existing gas collection systems
Gas collection systems are normally not installed until adequate volumes of methane have been generated. This is dependent on the period of time the refuse has been in place and the total quantity of refuse. The time anaerobic conditions start varies, but is usually between 80 and 260 days after refuse placement. Methane volumes usually only reach viable options for gas control after approximately 200,000 tonnes of refuse is in place.
The standard requires that the gas collection system must be operating when 200,000 tonnes of refuse has been placed within the landfill.
5.3.3 Applies only to operating sites
Subclause 25(1)(a)(iii) states that the regulation only applies to sites that are operating. It does not apply to closed landfills.
Existing gas management control systems at closed landfills may continue to operate as per existing consent conditions to manage health and safety, and/or odour effects.
Closed landfills can still produce significant quantities of methane over an extended period. It is also usual for gas to accumulate in an old landfill site and for there to be periodic uncontrolled emissions of gas. Site-specific investigations and specialist advice should be sought if any development is proposed on or within 50 metres of a closed landfill site.
5.3.4 Applies to large landfills with more than five percent putrescible matter
Subclause 25(3) states that the regulation does not apply to a cleanfill site, as these sites produce only minor amounts of methane. The regulation defines cleanfill as follows:
Cleanfill
(a) means a landfill that accepts only material that, when buried or placed, will not have an adverse effect on the environment; but
(b) does not include a landfill that contains 5% or more (by weight) putrescible matter.
The standard therefore, does apply to industrial monofills such as bark or sawdust dumps that are over 1 million tonnes in size and have more than 5 percent (by weight) of matter that is putrescible or biodegradable.
5.3.5 Transitional period for operating sites without gas collection
25 Application of regulations 26 and 27
(2) However, regulations 26 and 27 do not apply to a landfill until 8 October 2007 if the landfill -
a. has a total capacity of not less than 1 million tonnes of waste; and
b. on 8 October 2004 -
i. contains not less than 200,000 tonnes of waste; and
ii. is accepting waste; and
c. does not operate a gas collection system.
Existing operational sites that do not currently operate a landfill gas collection and destruction system have a transitional period of three years to install and commence operation. This provides time for the landfill owner to fund, design, install and operate a landfill gas collection and destruction system.
5.3.6 Control of gas
26 Control of gas
(1) No person may allow the discharge of gas to air from a landfill.
(2) Subclause (1) does not apply if the landfill has a system for the collection of gas from the landfill -
a. that is designed and operated to ensure that any discharge of gas from the surface of the landfill does not exceed 5000 parts of methane per parts of air; and
b. in which the gas is -
i. flared in accordance with regulation 27; or
ii. used as a fuel or for generating electricity.
Gas collection efficiencies are variable and so measurements are relatively inaccurate and unreliable. It is therefore not possible for the standard to specify a percentage efficiency for a gas collection system. Measuring methane emissions at the landfill surface and at monitoring points around the landfill is currently common practice in resource consent conditions at major landfills, including many recently closed sites. The surface emission limit is commonly 0.5 percent methane (by volume in air) in New Zealand which is approximately 5000 ppm and corresponds to approximately 10 percent of the lower explosive limit (LEL) for methane.
Monitoring of surface methane emissions is a requirement of resource consent at most landfills and is used at some closed landfills to assess risks. Factors to consider when designing a surface methane monitoring programme are outlined in section 5.6 of this report.
Subclause 26(2)(b)(ii) allows for collected landfill gas to be used as a fuel, or for the purposes of generating electricity. Potential beneficial re-uses are outlined in section 5.5 of the report.
5.3.7 Flaring standards
27 Flaring of gas
(1) If gas collected at a landfill is destroyed by flaring, -
a. the system for the principal flare or flares must -
i. comply with the requirements in subclause (2): or
ii. achieve at least the same effect as the system in subclause (2); and
b. the system for the backup flare must -
i. comply with the requirements in subclause (3); or
ii. achieve at least the same effect as the system in subclause (3).
(2) The system for a principal flare must -
a. have a flame arrestor; and
b. have an automatic backflow prevention device, or an equivalent device, between the principal flare and the landfill; and
c. have an automatic isolation system that ensures that, if the flame is lost, no significant discharge of unburnt gas from the flare occurs; and
d. have a continuous automatic ignition system; and
e. have a design that achieves a minimum flue gas retention time of 0.5 seconds; and
f. be designed and operated so that gas is burned at a temperature of at least 750 degrees C; and
g. have a permanent temperature indicator; and
h. have adequate sampling ports to enable emission testing to be undertaken; and
i. provide for safe access to sampling ports while any emission tests are being undertaken.
(3) The system for a backup flare must have -
a. a flame arrestor; and
b. an automatic backflow prevention device, or an equivalent device, between the backup flare and the landfill; and
c. an automatic isolation system that ensures that, if the flame is lost, no significant discharge of unburnt gas from the flare occurs; and
d. a continuous automatic ignition system.
(4) A principal flare must be operated at all times unless it has malfunctioned or is shut down for maintenance.
(5) A backup flare must be operated if, and only if, a principal flare is not operating.
Regulation 27 outlines the performance standards a landfill consent holder is required to meet if they elect to destroy the collected gas by flaring. The standard requires that any principal flare must operate at a minimum temperature of 750 degrees Celsius and be designed to achieve a minimum flue gas retention time of 0.5 seconds. The standard also requires that any principal landfill gas flare has:
- a flame arrestor and automatic back-flow protection device or an equivalent system between the flare and the landfill to prevent flash-back and landfill fires
- a continuous automatic ignition system
- an automatic isolation system to ensure that there is no significant discharge of unburnt landfill gas from the flare in the event of flame loss
- a permanent temperature indicator
- adequate sampling ports to enable emissions testing to be undertaken
- provision for safe access to sampling ports while any emission tests are being undertaken.
The standard also requires that a landfill have a backup flare that is available to operate when the principal flare is not operational due to malfunction or maintenance requirements. The backup flare must have:
- a flame arrestor and automatic back-flow protection device or an equivalent system between the flare and the landfill to prevent flash-back and landfill fires
- a continuous automatic ignition system
- an automatic isolation system to ensure that there is no significant discharge of unburnt landfill gas from the flare in the event of flame loss.
Subclause 27(1) of the regulations allow for differing technologies to be adopted if these alternatives can achieve at least the same effect as the systems outlined in the regulations.
5.3.8 Perimeter monitoring
The standard does not require the monitoring of landfill gas at the perimeter of a site. Landfill gas can migrate horizontally through the ground and discharge at a point remote from the landfill refuse footprint. Perimeter monitoring probes are typically provided around the edge of the landfill to monitor for gas movement away from the site.
Perimeter probe gas limits have historically been set at five percent methane (by volume in air), which corresponds to approximately 100 percent of the lower explosive limit (LEL) for methane. However, there is an increasing trend in New Zealand and overseas to set the perimeter probe limits based on neighbouring land use activities and a limit figure of 1.25 percent methane (which is approximately 25 percent of the lower explosive limit (LEL) for methane).
5.4 Exclusions from the standard
5.4.1 Less than five percent putrescible or biodegradable matter
There may be situations where a landfill exceeds the refuse quantity threshold of 1 million tonnes but through the effective diversion of putrescible or biodegradable matter will generate low methane volumes. In this case effective operation of a methane collection and destruction system may not be warranted or feasible.
To encourage the diversion of organic matter, the standard provides an exemption to install and operate a landfill gas collection system, if the site owner can demonstrate that the landfill contains, and is continuing to accept, less than five percent (by weight) of matter that is putrescible or biodegradable.
5.4.2 How can I demonstrate that I have less than five percent putrescible or biodegradable matter?
The best way to assess putrescible or biodegradable matter content in a landfill is to collect data about the composition of waste deposited over the life of the site. The Solid Waste Analysis Protocol (Ministry for the Environment, 2002c) provides a methodology for sorting waste into 12 primary categories including 'putrescible' (or organic) waste.
A typical Solid Waste Analysis Protocol survey programme would include:
- two years of quarterly surveys (to establish seasonal variations)
- an ongoing programme of annual surveys, with each season surveyed once per four-year cycle
- individual surveys designed to determine putrescible waste quantity to ± 20%.
For further information about developing, designing and interpreting surveys see the Solid Waste Analysis Protocol document and the survey design and analysis resources on the Ministry for the Environment website (www.mfe.govt.nz/issues/waste/waste-data). Regional councils and the landfill consent holder will need to agree an acceptable monitoring programme.
For further information on alternatives to landfill disposal for organic wastes see www.mfe.govt.nz/issues/waste/
5.5 Beneficial re-use of landfill gas
The standard requires the collection and destruction of landfill gas, however subclause 26(2)(b)(ii) specifies that it does not require collected landfill gas to be flared. Landfill owners may choose to harness the collected landfill gas for use as a fuel or for electricity generation.
Beneficial re-use options could therefore, include:
- electricity generation
- direct use of the gas, such as in boilers, kilns, heating or off-gas destruction
- low pressure gas supply (as fuel) to a dedicated user
- compressed natural gas.
The most common use of landfill gas (used in more than 80 percent or more of gas utilisation schemes) is in the production of electricity. Approximately 600 cubic metres per hour of landfill gas at 55 percent methane will support a 1 MW electric scheme. However, the life of a scheme is highly site-specific and detailed site-specific gas and commercial assessments assist before sizing a gas utilisation option. The economics of a 'gas-to-electric power' scheme will also be dependant on the proximity of the landfill to the nearest power grid connection point.
Direct use of landfill gas as a fuel for heating is considerably more efficient than converting the gas to electricity where approximately 60 percent to 70 percent of its energy value is lost.
Direct use as a fuel in brick kilns, boilers, production of steam or in co-generation plants (being facilities that produce electricity and usable heat) are the next most common group of gas utilisation options. Landfill gas has a unique composition and a dedicated landfill gas customer who is specifically set up to use the gas 24 hours a day, 365 days a year is preferable. Gas generation rates, quantities and quality vary from site to site. The gas usually requires pre-treatment before burning/use and, together with the need to provide a gas transmission system, these additional add-on costs can make a project uneconomic.
Compressing the gas for use in vehicles or for use by a dedicated gas user away from the site has been practised. A higher level of gas treatment is required for this option over other gas utilisation options.
5.6 Designing a surface methane monitoring programme
There are a number of different surface emission procedures worldwide. The surveys are commonly termed Instantaneous Surface Monitoring (ISM) surveys. The survey uses methane as an indicator for landfill gas and volatile organic emissions from the landfill surface.
ISM surveys are conducted on both final and intermediate capping but are not conducted on open refuse faces due to the danger to site personnel and the variable nature of the ground.
ISM surveys are also not typically conducted on daily cover.
Monitoring on intermediate capping is typically done only if the intermediate capping is to be in place for more than a few weeks.
The common factors to all ISM surveys are:
- a suitable instrument has to be used that is capable of measuring to parts per million (ppm) of methane
- the instrument is hand carried, is intrinsically safe and is suitably calibrated
- the walkpaths on the landfill are set before the survey
- the weather conditions have to be within certain parameters to ensure representative results can be obtained and that the instrument is not damaged
- where a surface emission is detected the ISM survey deviates from the walkpath to determine the extent of the exceedance area
- all details of the survey are recorded on a plan and tabulated to include an explanation (where possible) of why an exceedance occurred.
Recommended procedures for undertaking an ISM survey are available from the Ministry for the Environment. Note that the details of an ISM are not part of the regulations, but are available as guidance on how to design a system.
5.7 How does the standard take effect?
5.7.1 Who does this affect?
The standard places requirements on consent holders of operating landfills that have a total design capacity of 1 million tonnes or greater.
Regional councils are responsible for compliance with the standard. Enforcement action would be expected against landfill consent holders that are found to be in non-compliance with the standard.
5.7.2 What is the impact on existing resource consents?
The standards do not automatically apply to consents that have commenced before 8 October 2004. The introduction of the standards allows regional councils to review existing consents as outlined in section 128(1)(b)(a) of the RMA.
Landfills with greater than 5 percent putrescible or biodegradable matter (by weight) that are over 1 million tonnes in design capacity, but which do not operate a landfill gas collection and destruction system, have until 8 October 2007 to install and commence operation of a system.
5.7.3 What is the impact on new resource consent applications?
Regional councils will be required to place consent conditions requiring the installation of a landfill gas collection and destruction system on any new resource consents granted for landfills with a projected total capacity of over 1 million tonnes, unless the applicant can demonstrate that the landfill contains less than 5 percent (by weight) of putrescible or biodegradable matter.
The Resource Management (Energy and Climate Change) Amendment Act 2004 has resulted in the introduction of section 70B, which states that:
If regulations are made under section 43 to control the effects on climate change of the discharge into air of greenhouse gases, a consent authority, when considering an application for a discharge permit or coastal permit to do something that would otherwise contravene section 15 or section 15B, -
(a) may grant the application, with or without conditions, or decline it, as necessary to implement the regulations; but
(b) in making its determination, must be no more or less restrictive than is necessary to implement the regulations.
Therefore when deciding on resource consent applications for new landfills, regional councils are not able to impose conditions to control greenhouse gas discharges that vary from those specified in the national environmental standard.
5.7.4 What is the impact on regional plans?
There is no requirement for regional councils to initiate a review of their regional plan to bring them in compliance with the national environmental standards - the standards apply automatically. The Ministry recommends the use of clerical annotations to regional plans to inform readers that the relevant sections have been superseded by the national environmental standards.
Note that the Resource Management (Energy and Climate Change) Amendment Act 2004 has resulted in the introduction of section 104F, which states that:
if regulations are made under section 43 to control the effects of climate change of the discharge into air of greenhouse gases, a regional council may make rules that are necessary to implement the regulations, provided the rules are no more or less restrictive than the regulations.
5.8 Reporting requirements
The standards do not require the reporting of landfill gas monitoring information to the Ministry for the Environment.
