You are as green as you eat?
It has been suggested that our food is responsible for 20% of the UK's entire carbon footprint (Guardian 2007/06/07). Each one of us (the human body) burns an average of about 100W, ie 2.4kWh/day, which is getting on for 30% of my home's household energy use here in London for three of us, roughly the same as our electricity use. And food is not a very efficient way to capture and deliver that energy compared to (say) mains natural gas for heating, so that 100W probably has a disproportionately-high carbon footprint compared to our energy uses.
One way of reducing the carbon footprint is to eat more veg and less meat, and another is to source more of it locally to reduce 'food miles'. The BBC had a story on the "Fife Diet", for a family in Scotland, for example.
(Food miles are only part of the story: eg less energy may be used in growing a tomato in Spain and shipping it to the UK than in growing it in the UK with the assistance of more heating and fertiliser but closer to the consumer.)
Chef Barny Haughton said, "If you really want to cut down on the carbon footprint of your food eat seasonally, locally, and limit the amount of meat in your diet. Eat it maybe once a week, but choose locally reared, preferably organic, meat." I have my own views as to whether "organic" is necessarily better for you or the environment rather than just being a sop to the conscience, but Haughton's may well be a good guide.
Also in the Guardian piece it was suggested that: "A good rule of thumb to work out the potential carbon emissions of a fruit is to look at its perishability. If it will easily spoil, then it is more likely to need to be transported by air and cold-storage conditions and be prone to needless wastage."
Humans are omnivores by construction, and in more northern climes storing (or transporting) foods with a high concentration of energy and nutrients such as meat, especially in winter, is probably a good way of sustaining health. Also, meat, fish and non-local fruit and vegetables help maintain diet diversity with the micronutrients/vitamins/minerals/etc that we need, at least over intervals of days or months.
Presumably eliminating superfluous packaging helps also to reduce carbon footprint, and possibly even walking or cycling to a nearby shop to buy it does too.
It's not clear to me if, for bulky shopping, if it is better to have it delivered by the shop, since they presumably work hard to minimise fuel (etc) use by combining multiple nearby deliveries, or to use a private car. We don't own a car, and this is one more reason that we don't need to buy one while still being able have the odd larger-than-usual efficient bulk purchase.
In general, cooking is about getting things hot, and generating heat is much less carbon-intensive with mains natural gas (0.19kgCO2/kWh) than with mains electricity (0.43kgCO2/kWh), so cooking with gas is probably more climate-friendly overall.
However, in situations where relatively small amounts of energy can be delivered fairly precisely minimising energy loss and heating of containers such as pans, ovens, etc, then electricity is probably more effective. Two such methods where electricity may beat gas for cooking carbon-efficiency are the microwave and the plastic upright electric kettle.
Euan Murray, general manager for the Carbon Trust's Carbon Footprinting programme, said (2008/04) as regard to cooking method that: "We have learnt some very interesting things, such as there is a clear hierarchy when it comes to emissions from cooking. Baking a potato in an oven generates far more emissions than if you boil it in a pan with a lid on, which in turn generates more emissions than cooking it in a microwave."
I'm trying to work out the carbon footprint of the humble cup of tea. So far I have calculated the CO2 from the ~35Wh (130kJ) to boil the water (efficiently in an upright plastic kettle) producing about 15g CO2 given an average 0.43kgC02/kWh for UK grid-delivered electricity as of 2007 using UK government (DEFRA) figures. (Actually, with our new PV system and a lower-powered 1kW travel kettle then during daylight we should not actually need to import all or any of the energy to boil the water from the grid, though we have still lost the opportunity to export that energy and save someone else on the grid causing that CO2 to be released.)
At the end of the process my teabag is composted aerobically releasing the CO2 originally absorbed by the tea leaves and whatever made up the paper teabag: ie no further energy nor GHG (GreenHouse Gas, eg methane) costs from sending the teabag through the council-run domestic waster system, eg to landfill.
But I don't know about the cultivation, picking, preparation, shipping (etc) energy costs at all. I wrote at the end of January 2008 to Twinings as I drink gallons of their finest to ask if it had numbers, and similarly Typhoo as of the start of February.
Typhoo has sent me two holding replies as at 2008/03/31 (nothing from Twinings), and it seems to be working on the numbers but is not yet confident in them. Here's a snippet from Typhoo's helpful response of 2008/03/31:
Many of the key arguments revolve around questions such as to what [] the foot printing covers. Indeed many retailers or [s]upermarkets have proposed the simple route of counting the carbon foot print of the stores (but not the delivery of the product into the store or the manufacturer's foot print to make the product).
For tea manufacture we ultimately believe it should cover the whole process i.e. growing the tea bush, processing the tea leaves, shipping the tea, printing the packaging, packing the tea and shipment to the retailer. Although we are quite far down the road of carbon foot printing the Typhoo Tea factory i.e. the total amount of carbon used by the Moreton factory, the carbon foot print of the tea plantations still has to be defined. We will also have to average a value for a true reflection of a standard cuppa, as tea comes from many different regions (Africa, India, Sri Lanka, China and Argentina to name the main areas) and shipment from each area will have a different foot print.
I agree with Typhoo's approach, but I'd still like their best guess so far ASAP!
I also ought to at least consider the energy cost of getting potable mains water and flushing away the result later, and even the cost of (dish)washing my mug after a day's use. At (say) 300ml of water for my tea and to wash the cup (per cuppa), one source suggests that causes the release of ~0.09gCO2, or maybe the equivalent 0.2Wh of grid electricity. (As of 2008/02/07 I sent a request to our local water company, Thames Water, for some energy/GHG figures, and as of 2008/03/19 they wrote back confirming a 0.3gCO2/l average.)
I can make a stab at the dishwashing cost if I ignore any due to the cleaning agent (eg detergent/surfactant/etc): We tend to run our dishwasher once per day at a cost of 1.27kWh. I use one tea mug per day when at home for a daily average (say) 5+ cups, and it probably takes up ~5% of the top rack or maybe 2.5% of the total available space, so that might amortise to ~32Wh/day or ~6Wh per cup of tea.
The tally of computed elements so far:
This section is still very much a work-in-progress; I'm very interested to hear your views.
The figure quoted by Thames Water for our Green House Gas Emissions is calculated using a water industry standard Carbon accounting tool. A third party, the Water Research Council, has developed this tool. In calculating the figure we take account of the electricity used to treat and pump water. The average figure across the Thames Water region for Green House Gas Emissions is 0.3 grams/litre.
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