How much greenhouse gas do we produce?

Greenhouse gas emissions (GHGs) will need to be cut back if the worst of global warming is to be avoided. So, how much GHG do we produce in our daily lives?  Where can we make cuts on these emissions?

Here are some general numbers which may help us in our daily decisions.  Let’s start with transportation and consider the trip from Blenheim to Christchurch and back, a distance of about 614 km on Hwy 1. One litre of petrol produces about 2.4 kg of CO2 when burned in an automobile.  So, if your car uses 10 litres fuel per 100 km, each 100 km trip produces about 24 kg of CO2.  Every 50 litre tank of petrol creates 120 kg of CO2.  Diesel fuel produces slightly more, or about 2.7 kg CO2 per litre.  So, in a vehicle using 10 litres of petrol per 100 km, would create about 147 kg of CO2.

But what if we decide to fly instead?  Air New Zealand’s carbon offset calculator shows a flight to Christchurch and back to be 490 km and a single passenger produces 69 kg CO2, just under half the amount from driving.  With respect to emissions, it is better to fly to Christchurch and back than it is to drive, unless you have two or more persons in the car or your car gets double the fuel efficiency (i.e., 5 litres per 100 km).

And then there are the emissions from food to consider.  Information from USA[1] has calculated the emissions in CO2e (CO2 equivalents, to account for other greenhouse gases, as well as CO2) per kilogram of consumed product. Keep in mind though that these numbers include processing, transport, cooking, wastage and disposal.  Lamb tops the list, with 39 kg CO2e per kg consumed meat.  Beef is somewhat lower at 27 kg per kg consumed.  Mind you, these are US numbers, where beef and lamb are largely grain fed.  Nearly 5 kg CO2e per kg consumed beef is due to feed production, which would be much less here, where most beef is grass fed. The emissions from lamb are higher than beef because less of the animal is used for food.

These numbers show that it doesn’t take many barbeques to match the emissions of a road trip to Christchurch and back.  This example illustrates that cutting back on beef and lamb may go a long way to cutting a family’s greenhouse gas emissions.  Pork (12 kg CO2e/kg consumed), chicken (7 kg CO2e/kg consumed) and eggs (5 kg CO2e/kg consumed) are lower emissions alternatives. 

Cheese tops the dairy category, at 13.5 kg CO2e/kg consumed, with milk and yoghurt each around 2 kg CO2e/kg consumed.  Surprisingly, most vegetables, nuts and legumes range from 3 kg CO2e/kg consumed (potatoes & rice) to 1 kg CO2e/kg consumed (tomatoes & lentils), largely due to wastage of fresh vegetables or the energy needed to cook potatoes, beans and lentils.  A simple pressure cooker to cook beans and lentils will decrease emissions by decreasing cooking time.  Propane for your hob produces around 3 kg CO2 per kg burned.

And of course, buying local can reduce the transport costs.  A kg of fresh fruit airfreighted from California creates another 1.2 kg CO2e emissions.

What about waste?  All organic material decomposes to CO2 and methane in municipal landfills, creating emissions.  This includes paper (1042 kg CO2e/tonne), wood (828 kg CO2e/tonne) and mixed food & garden waste (587 kg CO2e/tonne).  Composting can reduce the emissions from food scraps and garden waste by roughly 50%.  We in Marlborough are lucky because the council flares (burns) the gas emitted by the Bluegums landfill, significantly reducing these emissions.
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Hopefully, these values will have you thinking about how you could decrease your household’s emissions.


[1] The Environmental Working Group