Documentation > Greenhouse effect > Greenhouse gases and us > How much greenhouse gases in our plate ?
Eating would lead to greenhouse gases emissions ? You must be joking...... And though, eating is a heavyweight, in France (and probably in many other occidental countries), among the activities that disturb the climate system. We owe this to the fact that agriculture is the main source of the principal non CO2 greenhouse gases : methane and nitrous oxide.
On the other hand, these two gases (methane and nitrous oxide) account today for almost one third of the national total in France.
Without much surprise, a conclusion of these two pieces of information is that agriculture ranks first in the french emissions.
But if we want to be exhaustive, we must also take into account other processes that are necessary to feed the population, and therefore have a wider look than just concentrating on direct emissions from agriculture. Indeed :
All agriculture, except from organic farming, uses fertilizers and pesticides that come from chemical industries. These fertilizers and pesticides have to be produced, what is done with fossils fuels and therefore leads to CO2 emissions (modern fertilizers are manufactured from natural gas : in the true sense of the word, with modern agriculture we eat oil and gas !).
Fertilizers manufacture represents the main source of upstream emissions, pesticides manufacturing being much more marginal because....the weight of pesticides used per hectare of land is much smaller than the weight of fertilizers. In addition, the chemical reactions that happen in a fertilizer plant also emit a little N2O. Of course, the emissions linked to the production of these products are not accounted for in the "agriculture" sector, but with the "industry" sector. It must be noted that France produces only a half of the fertilizers it uses, so that part of the corresponding emissions are nowhere in the national total, but will appear in the national total of other countries (too bad for them !).
In France, only 20% of the money spent on food is devoted to "raw" products, such as fruit, vegetables, or fresh meat of fish. The rest is used to buy processed food : pasta, canned food, frozen food, biscuits and sweets, drinks, etc. Well all the processing industries consume energy, and therefore emit greenhouse gases that will be accounted for in the "industry" total or the "energy industries" total (for electricity), and not in the "agricultural" total. In France, 15% of the energy used by the industry sector is consumed by food processing industries.
Then, most of the processed foods are packed (just take a look inside a kitchen cupboard !). It happens that manufacturing the packaging consumes a significant part of the "raw materials" that we produce (steel, aluminium, plastics, etc), and producing those "raw materials" accounts for 70% to 80% of the overall emissions of the industry. Hence the products that we buy at the supermarket "include" part of the emissions of the industry that correspond to raw material production :
Breakdown by destination of the raw materials production (steel, aluminium, cement, plastics, glass, cardboard) in Europe in 2001. Packaging, that is certainly not restricted to food products, represents a fourth of the emissions deriving from this "raw material production" : almost the same amount than what is emitted for construction materials ! Data reprocessed from Eurostat & APME
Let's go on with our inventory : a significant part of road transport - in France - is linked with food production and delivery :
Breakdown by nature of goods of the road transportation in France in 2001 (it is the share among the tonnes.km). Source : Ministry of transportation
As it can be seen on the above chart, a third of the trucks that get us so mad on the roads carry intermediate or consumer goods of the agricultural and food processing sectors. It can be living animals, fodder, milk, frozen foods, etc. Incidentally, it is obvious that every time we buy oranges coming from Spain or grapes coming from Italy, we French buy at the same time the road transportation that goes along with it, and we can hardly complain about later on ! The above chart does not include the share of food related products in the maritime and air transport, for which I do not have data.
at last, processed food is generally bought in supermarkets (when open markets sell mostly fresh products), which generates additional energy consumptions :
it requires electricity to keep foods frozen in supermarkets, especially in display units that are open but customers that do not intend to walk around in a coat in the store !
a store is heated in the winter and cooled in the summer : heating and cooling stores represents, in France, between 1,5 and 2 million tonnes carbon equivalent carbone (electricity included, but most of it is zero emission for it is nuclear and hydroelectric), that is roughly 1 to 2% of the national emissions,
supermarkets, that represent 80% of the sales of food products (roughly) are generally located in the suburbs, hence we need a car to get there (those emissions are not accounted for here),
at home, we need energy again : fridges and freezers, stoves and ovens, and even the coffee-grinder ! In France, the electricity consumption linked to eating (fridges, freezers, dish-washers, stoves and ovens, not to mention small appliances) represents 22% of the kWh consumed at home,
then all packagings end up in the waste bin, and their end of life is again a source of greenhouse gases emissions (even if we recycle).
Last, 25% of our domestic waste is composed of food waste, and when landfilled this waste leads to methane emissions, that are not negligible in the national total.
If we now try to sum up all that is mentionned above, we get to the following table, certainly perfectible, but that gives a general idea of the various contributions :
|Direct emissions from the agricultural sector||
|Corresponds to the emissions of the French fertilizer industry, but we import more than half our domestic consumption. Manufacturing all fertilizers used in France might lead to 2 to 3 times that amount.|
|Road transport for goods||
|French share only|
|Road transport for people||
|This is a prudent personnal estimate. French cars emit 20 million tonnes carbon equivalent overall, so the mentioned figure supposes that 5% of the total corresponds to food purchases.|
|Truck manufacture and diesel oil refining||
|Store heating (20% of national total)||
|Figure valid in France only, elsewhere multiply by 5|
|Personal estimate from EEC data|
|End of life of packaging||
|The overall emissions of the waste sector are roughly 4 million tonnes carbon equivalent in France, therefore this figure assumes that a fourth are linked to plastic incineration or methane emissions from land filled food waste|
|Methane emissions from landfilled food waste|
|National French emissions in 2001 (CITEPA)||
|Share linked to eating||
The conclusion that we may draw from the above rough calculation is that if we take all the processes we call on to eat into account, we get closer to a third of the french emissions to fill up our stomachs ! Of course, a rigourous calculation should take into account exports (for which our national emissions actually occur to fill up somebody else's stomach) and imports (which, with my calculation, allow us to eat as much as we want without increasing much the national total), but still we are probably not very far from the truth.
Summing up sectoral emissions is not the only exercise that we can do with greenhouse gases emissions induced by food production and delivery. Another calculation which is not without interest is to know "how much greenhouse gases" has been emitted to get this or that product, without bothering if the emissions happened at Pierre's, Paul's or John's place.
For example, we might want to know how much greenhouse gases have been emitted to produce a kg of industrial chicken. We must then look at all that was necessary to get the beast, regardless of the country where it happened (such an approach is called a life cycle analysis) :
Emissions linked to the heating of the hen house,
Fossil fuels used to manufacture the fertilizers used to grow the grain eaten by the chicken,
Fossil fuels burnt by the tractor used to grow the grain eaten by the chicken,
Nitrous oxide (N2O) emissions that occur when the fertilizers are spread on the field (see page on greenhouse gases),
Fossil fuels required to manufacture chicken food (industrial chickens rarely eat "raw" cereals, but rather processed foods) from the cereals,
Emissions linked to the manufacturing of tractors, to the drying of grain, and even to the refinery of the diesel oil used by the tractor....
At last, if the food is obtained from a ruminant (which is not much the case of a chicken !), such as milk, beef meat, etc, we also must take into account the methane burped by these nice animals. Indeed, ruminants produce methane in their stomachs because of the fermentation of the plants they eat (I recall that a cow has 4 stomachs !), and in France the weight of the cattle is superior to the weight of the population (we have 20 million heads of cattle, weighing several hundred kilograms in average). This is also true for the world as a whole : there are 1,4 billion heads of cattle for 6 billion people, and on average a head weights more than a human being.
The results of an estimation "from the oilfield - or the gas field - to the stomach" (figures are valid ±50%) are presented below :
Greenhouse gases emissions linked to the production of a kg (roughly 2 pounds) of food. Meat is with bones (the proper term would be "carcass equivalent") but without processing, packaging, or transportation.
To allow a reference, the bar on the far right represents the emissions linked to driving 100 km in an average european car.
Source : Jancovici/Ademe, 2007 (in press)
What happens when we turn to organic farming ?
We avoid fossil fuels required to the manufacture of synthetic fertilizers, that are not allowed (at least in France) for organic farming, and therefore the associated emissions disappear,
Ditto for pesticides,
There still remains N2O emissions linked to the psreading of manure and other "natural" nitrogen inputs,
Outputs per hectare are lower, when the number of hours of tractor driving per hectare remain roughly the same, hence CO2 emissions per production unit increase for some uses,
last but not least, organic or not, ruminants go on burping methane !
If we analyze all these opposite effects, here is the result :
Eating organic is definitely a good thing, but to preserve the climate we must also eat less meat. Furthermore, eating as much meat as today prevents converting a large fraction of the agriculture to organic farming, because as organic farming has lower yields for cereal production (about half the output per hectare), going organic for 100% of agriculture while keeping the same animal production would need much more arable land than we have at present, and it will be a goal even harder to meet if in the same time we want to turn crops into biofuels !