Carbon Zero

Trying to live a lower carbon life

Started October 2009. Charts updated June 2017

I'm playing with the CarbonZero household calculator to calculate the monthy greenhouse gas emissions for our household.

The calculator asks for either a monthly or yearly value for various consumption types:

  • electricity/gas/coal (kWh, litres, kg)
  • car travel (km or $)
  • bus and train transport
  • planes and long distance coaches
  • waste and recycling

The end result for September 2009 was: 172 kg estimated total CO2e emissions. They provide the ability to instantly buy high quality New Zealand based offsets for $28.75 per tonne (1000 kg) [as at 4 Feb 2015]. [The market price for NZU carbon credits is much lower, but that's for bundles of 100 units or more of variable quality. CarbonZero is one of the few (only?) places you can buy single NZU carbon credits.]

Then I added in data for every month going back to January 2004.

What is most useful about this exercise is the graph below. The spikes are almost all car related - holidays to see friends and relatives. In January 2009 my business had a cash-flow crises so we went cycle touring rather than drive to family. Then in June-July a friend lent us their grunty car and we enjoyed the convenience - a lot.

In 2011 a close family member had cancer which resulted in us travelling a lot more - so our transport related emissions went way up.

In January 2014 we went on a two week, 2319 km driving holiday around the South Island resulting in 551 kg CO2e emissions. A bit of a carbon blow out. For comparison; return flights to Sydney for the three of us (4446 km each) would have resulted in 3078 kg CO2e emissions.

In February 2014 I got an electric commuter bicycle which my public transport use. Over the previous few years I had been catching the bus/train home frequently with my folding bike.

Note: the above graph is per adult. Our son is 7 years old so his carbon is all our responsibility.

The table below gives emissions per person - that's to make it easier to compare against the country based emissions data. However - that's an unfair comparison because the CarbonZero measurement leaves out food and other consumption.

YearOur household kg CO2-e emissionsOur kg CO2-e emissions per person
Countrykg CO2-e per person
New Zealand18,800
South Africa9,000
Cook Islands2,900
Solomon Islands400

Source: 2005 data. Note that these country numbers are just the national total carbon emissions (including agriculture and industry, etc) divided by the population. I don't know what the average New Zealand household emissions are - so it's a bit unfair to compare them.


There are a lot of qualifications needed at this stage:

  • The calculator is easy to use - that means there are lots of average numbers in the formulas, eg
    • it doesn't differentiate between Meridians hydro electricity vs Genesys coal electricity - although, in reality the NZ grid is managed as a national entity so the electrons come from "the system" rather than a particular electricity retailer
    • it doesn't ask how much "stuff" I use/consume (so a vegan using a solar oven is equivalent to another person eating imported caviar every night)
    • on the plus side - the averages used in the formulas are New Zealand averages, so it's likely to be more accurate than overseas carbon calculators
  • My transport data is mostly guesswork before Oct 2009 (apart from the holidays). My electricity data is accurate) - I've factored in holiday driving trips but my bus and train usage is an educated guess.
  • It took me a while to properly work out how to use the calculator - I know I've make some errors. Once you've paid to offset a months emissions you can't go back and edit it. [I've discovered you can delete a months data after it's offsets have been paid. Then you can create a new months data and pay to offset it again. You'd have to be pretty obsessed to do that though.]
  • The tool doesn't have an option to buy more credits than you "need". It would be interesting to pre-pay for coming years emissions on 1st Jan then live to the target. What should my annual household "ration" be?
  • There is a school of thought that emissions trading is "a market based solution" and therefore a BAD THING (because the global economy depends on growth - and we have/will outgrow the planet). I'm inclined to think we need everything we can throw at the carbon emissions problem. So "market based responses" along with a whole bunch of other responses is what we need. Some of which are blindingly obvious; Reduce, Reuse, Recycle. It may be that it depends on your definition of the word market: "globalisation" or "how people swap/exchange things/services"?

I don't mind if the calculator is not perfect at this stage, and I don't mind that my previous data was lacking. It's a step in the right direction. The more I do this the better at it I'll get.

My next steps:

  • I'll start collecting accurate transport data [Done]
  • I'll pay for offsets back to 2005 over the next few months [Done]


Today global atmospheric carbon emissions average around 1.27 tonnes per person; in Australia the rate is 5.63 tonnes. For comparison, the earth's current capacity to absorb carbon is 0.62 tonnes per capita, estimated to decrease to 0.32 tonnes by 2030.
Source: Carbon taxes or a carbon ration? by David Spratt, Dissent Magazine, number 23, Autumn/Winter 2007

I'm not sure where Mr Spratt got these numbers from - the Australian number doesn't match up with the IEA number in the chart above. And he doesn't say if he's talking about carbon emissions or CO2 equivalent emissions. I'd love to have a robust estimate of the global capacity to absorb carbon. I'll keep looking.

Our household increased from two, to three people in October 2007.
Page last modified on July 24, 2017, at 02:02 am
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