2 The 2006/07 National Landfill Census
2.1 Aims
The 2006/07 National Landfill Census has two main aims:
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to build on the results from the previous National Landfill Census reports in 1995 and 1998/99 and the Landfill Review and Audit in 2002
-
to check on progress towards landfill-related targets in the New Zealand Waste Strategy.
In doing this, it aims to help identify areas where guidance is required or where further attention is warranted by the Ministry.
2.2 Method
Core questions from previous surveys were retained in the 2006/07 Census in order to ensure comparisons could be made over time. The majority of questions focus on the design of the landfills, but there are also questions on the siting, monitoring and operation of landfills.
Data for the 2006/07 Census were collected using a survey completed by site operators and some regional authorities (60 responses in total). Some surveys were followed up by telephone conversations to improve completeness. The content of the survey questionnaire is contained in Appendix 1.
2.3 Results
A comparison of the summary results from the National Landfill Census (1995, 1998/99 and 2006/07) and Landfill Review and Audit (2002) is shown in Table 1. Further discussion of the results follows the table. Overall, the results indicate that landfill design and operation in New Zealand has continued to improve.
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The total number of operating landfills continues to decrease.
-
All landfill sites in operation have the appropriate consent to do so.
-
The management of leachate, landfill gas and hazardous waste has improved.
-
The large majority of landfills now weigh or measure waste disposed of, and charge for disposal.
Table 1: Summary results from the National Landfill Census (1995, 1998/99, 2006/07) and Landfill Review and Audit (2002)
|
1995 |
1998/99 |
2002 |
2006/07 |
|
|---|---|---|---|---|
|
Total number of operating sites |
327 |
209 |
115 |
60 |
|
Sites with consent to operate |
-a |
157 |
104 |
60 |
|
Low-permeability underlying material |
- |
10% |
15% |
12% |
|
Leachate management system |
||||
|
Engineered liner |
- |
4% |
20% |
54% |
|
Leachate collection system |
13% |
35% |
47% |
77% (47)b |
|
Leachate recirculation |
- |
7% |
10% |
- |
|
Stormwater management system |
||||
|
Stormwater diversion |
41% |
67% |
74% |
- |
|
Stormwater monitoring |
- |
23% |
50% |
- |
|
Stormwater treatment |
9% |
27% |
36% |
- |
|
Landfill gas management system |
||||
|
Landfill gas monitoring |
3% |
11% |
27% |
- |
|
Landfill gas collection (flaring or beneficial use) |
- |
5% (10) |
10% (12) |
22% (13) |
|
Landfill fires |
52% |
24% |
17% |
0%c |
|
Hazardous waste management |
||||
|
Hazardous waste accepted |
33% |
20% |
- |
50% (30)d |
|
Documentation required |
- |
33% |
53% |
83% |
|
Quantifying waste and disposal charges |
||||
|
Measuring the quantity of waste |
39% |
63% |
83% |
93% |
|
Charging for the disposal of waste |
- |
45% |
82% |
93% |
Notes
a A dash (-) indicates that information was not requested in the survey.
b Two landfills replied that a natural collection of leachate occurs at their respective landfills. These two landfills have been included as having a leachate collection system.
c Landfill fires are now banned under the National Environmental Standards for air quality.
d Five landfills replied that the only hazardous waste they accept is wrapped asbestos or special waste. These five landfills have been included as accepting hazardous waste.
Note: figures in brackets represent the total number of landfills discussed.
2.3.1 General
Numbers of consented landfills
The number of operating landfills in New Zealand continues to decrease. There were 327 operating landfills in 1995, 209 in 1998/99, 115 in 2002 and 60 in 2006/07. One hundred per cent of landfills operating in New Zealand now have consent to operate. This has increased from 90 per cent (104 sites) in 2002 and 75 per cent (157 sites) in 1998/99.
Landfill siting
Twelve per cent of landfills (seven sites) are situated on low-permeability underlying material. This has decreased from 15 per cent (17 sites) in 2002, but is an increase from 10 per cent (20 sites) in 1998/99. Clay is the only material in New Zealand considered low permeability for landfill sites. Other common underlying materials include alluvial gravels, greywacke and sandstone/siltstone, which are permeable.
2.3.2 Landfill design
Leachate prevention
Fifty-four per cent of landfills (33 sites) have some form of engineered liner. This has increased from 20 per cent (23 sites) in 2002 and 4 per cent (eight sites) in 1998/99. The liner of choice is an engineered clay layer (26 sites). Other systems use a high-density polyethylene/geomembrane design (21 sites) or a geosynthetic layer (15 sites). Many landfills use more than one system of liner.
Leachate collection
Seventy-seven per cent of landfills (47 sites) have a system in place to collect leachate. This has increased from 47 per cent (54 sites) in 2002, 35 per cent (73 sites) in 1998/99 and 13 per cent (42 sites) in 1995. There are various systems in place to do this. The majority of landfills use an under-drain (34 sites) and many use cut-off drains (17 sites). Other systems include collection ponds, cut-off walls and perforated pipes feeding into sewer lines. Two landfills indicated that a natural collection of leachate occurs at their respective landfills. These two landfills have been included as having a leachate collection system.
Leachate treatment
Eighty per cent of landfills (48 sites) treat their leachate. The majority send it off-site to local wastewater treatment plants or settling ponds (30 sites). On-site leachate treatment occurs at 19 sites. Two landfills treat leachate on-site before sending it off-site for further treatment.
The most common on-site treatment system is settling ponds (17 sites), with a small proportion choosing irrigation to land (five sites). Other on-site treatments include leachate recirculation through landfill (two sites) and leachate dispersal to enhanced wetland (one site). Some landfills use more than one form of on-site treatment.
Gas treatment
Twenty-two per cent of landfills (13 sites) collect gas for flaring or beneficial use. This has increased from 10 per cent (12 sites) in 2002 and 5 per cent (10 sites) in 1998/99. Beneficial uses include reticulating the gas for industrial use and electricity generation. In total, 14 sites collect gas, 11 flare it and six generate electricity from it. A handful of sites do all of these. Three sites have indicated they are moving towards implementing some form of gas usage system.
2.3.3 Landfill operation
Quantifying waste
Ninety-three per cent of landfills (56 sites) measure the amount of waste they dispose. This has increased from 83 per cent (95 sites) in 2002, 63 per cent (132 sites) in 1998/99 and 39 per cent (128 sites) in 1995. Two privately owned and operated landfills indicated that this information was commercially sensitive. These sites were included as measuring the amount of waste disposed.
Disposal charges
Ninety-three per cent of landfills (56 sites) charge for the disposal of waste, up from 82 per cent (94 sites) in 2002 and 45 per cent (94 sites) in 1998/99.
2.3.4 Hazardous waste
Acceptance
Fifty per cent of landfills (30 sites) accept hazardous waste. This has increased from 20 per cent (41 sites) in 1998/99 and 33 per cent (108 sites) in 1995. This may reflect the increasing number of new sites that are designed to accept hazardous materials. Five landfills replied that the only hazardous waste they accept is wrapped asbestos or special waste. These five landfills have been included as accepting hazardous waste.
Documentation
Of the 50 per cent of landfills (30 sites) that accept hazardous waste, 83 per cent (25 sites) require documentation. This has increased from 53 per cent in 2002 and 33 per cent (14 sites) in 1998/99.
