By Eric Crampton 21/08/2018 8


That this one comes up so often speaks poorly of our basic numeracy and sense of scale. There’s basically no chance that landfills expand to take up any substantial part of the country.

This is the kind of back-of-the-envelope thing that everybody should be able to do in their head.

Kate Valley services Christchurch. It has 1000 hectares total, only a tiny part (37 hectares) of which is actual landfill – the rest is forest buffer and the like. But let’s call it 1000 hectares. It has a 35 year life expectancy. The Christchurch area is about half a million people. Let’s keep all the numbers round to make life easier – we’re looking for order of magnitude stuff here really.

If Kate Valley can handle 500,000 people’s trash in a 1000 hectares for 35 years, then it could handle a million people’s rubbish for 17.5 years. A thousand hectares divided by 17.5 is about 57 hectares per year per million population.

Let’s be conservative and round that on up to a hundred hectares per million population per year. It makes the numbers easier. I’m pretty sure that Kate Valley covers the whole Canterbury region of about 600,000 people, so I should be rounding down instead. But it really isn’t going to matter, and I can’t be bothered to check fiddly details.

New Zealand’s land area is about 26 million hectares. Let’s restrict ourselves to agricultural, non-arable land. Basically land that isn’t in crop but can be accessed. There’s about 10 million hectares of agricultural, non-arable land. I ruled out arable land because it’s more expensive and y’all have some kind of potato fetish that if anybody proposes doing anything on ground that could be growing potatoes, your heads explode because importing potatoes is somehow worse than importing anything else. So we won’t include that land in the calculations. Pukekohe is safe. But I’d expect there’s a pile of other land that could be used that I’m not including too. 10 million hectares is a nice round number for easy order-of-magnitude calculations.

Let’s suppose that New Zealand’s population doubled to 10 million people. Those ten million people would be using a thousand hectares per year. That’s another easy round number.

There are a thousand thousands in a million, and ten million hectares to play with, so it would take about ten thousand years to use up all of the non-arable agricultural land for landfill. Those are numbers big enough that it’s impossible for errors in my rough figures above to much matter. If the use rate is double what I’d put up, then it’s 5,000 years instead of 10,000 years.

“But we’ll run out of land!” arguments never have an appropriate sense of scale. Nor do they ever have any appreciation of basic economics. If scarcity did start biting, land prices would bid up. In the landfill case, that would mean tip fees would go up – and markets would do their usual thing. So don’t come away from this with the dumb-take that Crampton figures that all the paddocks should turn into landfills. I’m pointing out rather that land is far from scarce and putting some ballpark numbers on it for a sense of scale. And if land ever started becoming scarce, the price system already deals with scarcity.

Addendum: I’ve switched to screencaps from Twitter’s embed code because too many folks have started nuking their accounts and making my old posts that embed them look like bomb sites.


8 Responses to “A simple landfill calculation”

  • You are so right just look at the area of Tauranga harbour it just has water in it , what a waste . And how about we put all our green bags full of rubbish in a Hercules and fly it along the Kaimais chucking it all out onto the peaks , that will take a huge amount . Any more Ideas anyone .

  • Hi Robin.

    I wrote this in the last paragraph. “So don’t come away from this with the dumb-take that Crampton figures that all the paddocks should turn into landfills. I’m pointing out rather that land is far from scarce and putting some ballpark numbers on it for a sense of scale. And if land ever started becoming scarce, the price system already deals with scarcity.”

    Try reading the post again. I’m not saying the whole country should be a landfill. I am saying there is absolutely no way we will be running out of room for landfills anytime soon.

  • It’s not directly about the land consumed by the landfill, it’s about what the landfill does. The two usual problems are gas coming out the top and liquid coming out the bottom.

    The gas is normally easy to deal with once you grab it, it’s mostly CO2, water, methane and a couple of percent sulphur compounds. The problem is collecting it – if you don’t the sulphur makes the neighbours unhappy, but if you do it’s tricky to burn the methane in a useful way because the sulphur eats your combustion machinery. So you flare it off and never mind the complaints about the flaring.

    The more ugly part is leachate. It’s typically a delightful mix of mostly harmless stuff with enough not harmless to make it tricky to handle. So generally it’s discharged into the local rivers or aquifers… and that’s where people start to get grumpy. Ideally what you want is a nice waterproof basin that’s not too close to groundwater and isn’t seismically active. Sadly the nearest of those sites is in Australia. More seriously, we’re currently going through the whole “rivers of shit” dairy debacle so hopefully people will wake up to the landfill problem before it’s drawn to their attention by a contamination event. Fecal coliforms and nitrogen are trivial to deal with compared to the exciting mix of polycyclic hydrocarbons and heavy metals you get out of landfills like Mapua. The trick there is to stop people putting the nasty stuff into the landfill in the first place. Incinerate the organics, store the metals until they’re worth refining. IMO, obviously, it’s much cheaper to landfill them.

    It’s much easier to “artificially”* raise the cost of landfills to encourage waste reduction, and levy the production and import of waste to cover the cost of disposal. Otherwise you just encourage illegal dumping (I dunno about NZ, but Australia has a whole industry built around removing asbestos from buildings, dumping it illegally on the streets then picking it up again and putting it in landfill. Most of the cost is paid by ratepayers and taxpayers).

    * ideally to cover the full cost of monitoring and remediation, but in practice it’s almost impossible to stop illegal landfills if you do that, so the actual cost has to be close to the cost of the land purchase + operation. See also: the Four Corners doco on NSW waste problem http://www.abc.net.au/4corners/trashed/8770146

  • Thanks Moz,

    Those are all around landfill design though, right? A thick clay liner and a gas capture system can cure a lot of ills. Rather than raise the cost of landfill artificially, just set standards to mitigate emissions (on gas, use the emission trading system).

  • “Rather than raise the cost of landfill artificially, just set standards to mitigate emissions (on gas, use the emission trading system).”

    Kinda Moz’s point I suspect. Lets be honest, the track record of businesses in NZ complying with standards is, well, patchy.

    Big businesses cant sell reinforcing steel without lying about its qualities. Farmers regularly and routinely flout their resource consents. Product recalls for failure to meet relevant standards are commonplace.

    Leachate especially is a classic issue. A corporate gets paid upfront for landfill, and is easily (relatively) closed down at any time with no meaningful risk to the directors and managers when the going gets tough. Avoidance of corporate responsibility is a real and ongoing issue, and landfill is a situation where the problems arising from poor operation have ramifications for decades after. Its hard to imagine a process (short of very expensive long-running insurance, or permanent personal liability for directors and managers) that could mitigate this problem.

  • If you think that is the problem, a fixed higher tip levy hardly seems like the right solution unless you think that the most dangerous waste is the most easily deterred by an increase in fees.

  • When I was at school there was a line in a musical that sticks with me: “effluent disposal? No problem, plenty of sea”. Or as Mal Webb says “what have future generations ever done for me?”. Humans just suck at long term planning.

    The Australian experience that I linked to, and the NZ experience with both illegal dumping and places like Mapua is that we don’t have a system that’s capable of dealing with delayed risks. As Ashton says, our current system is expressly designed to allow a company to take the profit now, close down the company and walk away leaving the problem to be dealt with by the government and local residents.

    You also have the Mapua problem. Some activity takes place, then 10, 20 even 50 years later we discover that ooops, that was really bad. Mapua they made DDT etc in the 1960s. Then discovered that DDT is bad, so eventually shut the factory down. Sadly the land and water table was contaminated. So they made a landfill and put all the contaminated stuff in that. A “sealed by the standards of the day” landfill. Over time we got better at detecting the problems, and discovered that they were more extensive than first thought. 50 years later it’s a big, expensive problem… and the company that made it is long gone (so is the government).

    Now, the above is based on goodwill and good intentions all round. In Australia we have the “James Hardy” company who mined and sold asbestos. When they discovered how bad that was they… denied the problem, covered it up, paid people off, and eventually after decades of fighting lost a court case and had to pay compensation. So they moved the company to the Netherlands and declared the local subsidiary bankrupt… problem solved! Again, leaving behind a huge mess and some dead and dying people. So sad, but one must think of the shareholders first.

    Commercial landfills work in that environment: they take money now to deal with a long term problem. The only solutions to this involve fundamental changes like removing bankruptcy protection, and quite possibly indissolvable, inheritable personal liability. There’s no way to accommodate that in the current world system of governance. The main alternative is to have government do it… but these types of problems are widespread across a range of industry areas and nationalising them all is out of the question (cows emit methane which lingers for 70 years… livestock farming must obviously be owned and run by the government).

    It’s a hard problem, and landfills are just one instance of it. People much, much smarter than me are working on it.

    Sorry for the very delayed reply but I was on holiday.

  • Oh, and bonds/deposits/remediation funds don’t work very well. Is it cheaper to put a hundred million dollars aside, or to pay a couple of million to politicians in order to have the requirement waived? Either way the company is out some money for the foreseeable future, just… one number is smaller than the other. A lot smaller.