30 December 2011

Composting to Lighten our Carbon Footprint

There are a variety of ways to calculate your carbon footprint. Online calculators ask you for all kinds of information about your household, flights and car use. On carbonfootprint.com they even ask you about food preferences and how much of your waste is recycled. Composting is mentioned in one of the recycling options. However, I think it deserves more prominence if we want to make decisions about how to tread lighter.


I looked around the Internet to find out how much organic waste people produce on average and I found very little information. One survey reported that “households taking part in the Central Vermont Solid Waste Management District's Bin & Cone Pilot diverted an average of 345kg (760 lbs.) of food scraps per year,” while the Austrialian government reports that Australians generate an estimated 361 kilograms (794 lbs.) of food waste per person per year or approximately  936 kilograms (2059 lbs.) per household per year. The Environmental Protection Agency in the US asserts that North Americans throw away an average of 214 kg. (474 lbs.) of food scraps per family per year.

In summary:

Household Food Waste Generation per Year
Source 1: Central Vermont
345 kg.
Source 2: Australia
936 kg.
Source 3: EPA (USA)
214 kg.

These figures are wildly inconsistent, they come from developed nations and I don’t trust surveys about kitchen waste production. Think about it, if somebody asked you how much your daily compostable kitchen waste weighs, what would you say? So, I decided to find out for myself.

I did what any respectable scientist would do: I weighed our compost before taking it to the compost pile every day for six months (May to November, 2011). Here are the results:

Scoggin Household Food Waste Generation
Average per day
2.64 kg.
Average per week
18.36 kg.
Total for the year
954.80 kg.

Pretty high, no doubt. Six people live in this house, similar to the average Ecuadorian household.  Also, I am vegetarian, and we consume a lot of fresh fruit and vegetables.  Further, our maid composts all leftovers, and they tend to be pretty heavy. When I say that these figures are high, I am not only comparing them to the reported results from other countries, but also to our neighbors who participate in our community composting project. Based on daily observations, my household contributes approximately one third of all compost to the project, even though seven families participate.

Why are these results significant? According to Wikipedia, Ecuadorians emit 3,090 kg. (6,800 lbs.) of carbon per capita per year, considering all sources of carbon emission (compared to 22,182 kg. per American!) Also, each kilogram of food waste emits the equivalent of 6 kilograms of CO2 in a landfill, under anaerobic conditions, and 0 when it is composted in aerobic conditions.

This means that taking into account only CO2 emissions from food waste, my family saves 5728.80 kg. of equivalent CO2 emissions per year, or 955 kg. per person per year. In other words, my family saves 31% of the average CO2 emissions for Ecuadorians only by composting.

Of course the average Ecuadorian household would save considerably less by composting because of the average diet composition and how much food is consumed at home. But even if it turns out to be 20% or even 15%, the effect of composting on greenhouse gas emissions would still be significant.

The fact that my family saves nearly one third of the average CO2 emissions only by composting deserves attention by any authority keen on making this country greener.