When the Prime Minister took to the airwaves on Sunday night, one of the first things she tried to sort out was the rather confused issue of who pays the carbon tax. One of the downsides of calling the thing a "tax", for the PM (and there are quite a few downsides) is that the term "carbon tax" carries the redolent sense of something that will attach itself leech-like to every conceivable extremity of the ordinary householder's life.

So Ms Gillard was exceedingly careful with her pronouns when she addressed the nation. "Around 500 big polluters will pay for every tonne of carbon pollution THEY put into OUR atmosphere," she said (I've added the capitals, not in order to make that quotation look shouty, but to identify the allocation of responsibility the PM's trying to convey here; WE are getting those polluters to pay for what THEY do to US).

Listen to talkback for 30 seconds and you'll pick up what the general presumption is - a sort of vague impression that Big Polluters and Big Business are pretty much the same thing.

But who are these 500 big polluters, exactly - this Misfortune 500, who are to be history's martyrs to the answering of our generation's greatest moral challenge?

Can we get a list?

No - we can't, according to the Government. The 500 companies are not an identified list. The figure of 500 is just an estimate of how many companies in Australia would be caught by the scheme's eligibility rules.

Here's how it works: any company which has a facility (plant, factory, premises or similar) directly emitting more than 25,000 tonnes of carbon a year will be forced to cough up $23 a tonne for that pollution. Now, this is a bit tricky, because it means a company with 20 facilities each emitting 24,000 tonnes of CO2 a year would not be liable, while some poor boob with one factory emitting 26,000 tonnes of carbon dioxide and 19 clean green beansprout-fired tofu smelters would still have to cough up.

Will this structure provide an incentive for companies to spread out their emissions between facilities? Well, it might at the lower end of things, where the emissions tonnage is measured in thousands. But for the biggest emitters, the ones who pump out millions of tonnes a year, the prospect of filleting operations off into a bunch of smaller premises is kind of unrealistic.

Companies are already required to report all this stuff under the National Greenhouse and Energy Reporting Act 2007 - and they do. But you can't get a list of all the facilities emitting more than 25,000 tonnes. "It is not possible to disclose facility-level pollution data collected under the National Greenhouse and Energy Reporting Act because this would breach confidentiality provisions under that legislation," a government spokesman says.

However, you can get kind of a good idea of where different companies stand by having a look at the last report of their emissions, from the 2009/10 financial year. It's online here.

As you can see, the biggest emitters by far are the power generators: Delta Electricity with 20 million tones of emissions, Macquarie Generation with 23 million, and so on.

The news at the weekend that Tim Tams would experience only the most infinitesimal of price increases was of course welcome. It was also kind of obvious, in the sense that there's bugger-all carbon in a Tim Tam really.

In 2009-2010, Arnotts reported 28,982 tonnes in direct emissions; given that they have several factories across Australia, their chances of copping the carbon tax are pretty slim. Ditto, for example, McDonalds - 2,871 tonnes, or Cadbury - 35,438. The reason, similarly, that your kilo of mince is only going up four cents is that agriculture is exempt from the scheme. Your between-meals snacks are much more likely to be affected if they include plate glass or zinc.

To get an idea of which sectors are being targeted for the biggest cuts in emissions, have a look at page 80-83 of this report, which is the Treasury's modelling document. Do not feel you have to read all of it.

Between now and 2050, Treasury expects that fully half of the planned emissions cuts will be made by electricity generators. Industrial processes - the emissions intensive manufacturing processes that give us aluminium, steel, flat glass, paper and so on - will give an estimated 9 per cent. Transport is expected to yield 8 per cent of the emissions savings in that time, even though it is exempt. The reason? We'll be using more public transport, driving cleaner cars, and using cleaner fuel.

And finally, the one we all forget about: rubbish. Landfill dumps emit a huge volume of greenhouse gases, and the scheme announced at the weekend will make operators pay. So your empty Tim Tam packet is going to cost a tiny bit more to toss than it used to.

Annabel Crabb is ABC Online's chief political writer.