The Commons Diner

Calculating Carbon Dioxide Emissions for

"Food, Carbon & The Commons"
an art installation by

Steffi Domike, Suzy Meyer, and Ann Rosenthal

created for
6 BILLION PERPS HELD HOSTAGE! Artists Address Global Warming
The Andy Warhol Museum, Pittsburgh
March 10-June 17, 2007

The distances traveled by food to the store where you buy it, or the restaurant in which you eat it, is only a fraction of the energy expenditure associated with the production and preparation of the food we eat. As science begins to look at energy expenditure in food production, some say that the greatest amount of energy is spent in the production of intensive, industrial (conventional) foods with their petroleum-based chemical inputs such as fertilizers, pesticides, fungicides, and herbicides. Others point to the packaging of food—the plastics wraps, glass bottles, paper boxes, metal cans, and food grade waxes—as another significant energy expenditure. In the end, energy expended in cooking, as in the boiling of potatoes must also be considered.

Transportation then, is one link in the chain. Perhaps we are attracted to the aspect of food miles because is it obvious. We can conjure up California, Idaho, Mexico, New Zealand. Most of us cannot conjure up agriculture soils exuding CO2 and methane gas as it breaks down soil-borne bacteria which also contributes to the atmosphere.

Food miles, is, of all food-energy expenditures and CO2 emitting processes, the most graphic, the most studied (albeit in nascent stages), and easiest for interested consumers to grasp. The oft-repeated “food travels 1,500 miles from field to plate” is, from my research, a gross understatement. (That research includes dumpster diving outside a popular produce store in Pittsburgh’s Strip District and calculating distances traveled from 19 types of produce.) Calculating the distances food travels and subsequent carbon dioxide emissions are imperfect exercises.

First, distance traveled: It is hard to know the field, rural town, or county in which food is grown (unless you buy it locally). It is also not impossible, but difficult (due to non-transparency), to track the miles traveled by, let’s say, a head of broccoli: from a field to a processor (for washing or spraying), to a distributor, and maybe to ports and U.S. Customs, to a warehouse, to a re-distributor, and finally to the store where you buy food.

In developing The Commons Diner menu, we did what is currently done by the EPA and the Leopold Institute for Sustainable Agriculture. First, we picked a source point, a real address if local, or a known distribution point if national or international, and calculated the miles traveled by different modes of transport (air, boat, 18-wheeler). For Sumatran coffee we selected a known growing region, a major seaport, a U.S. port, and highway miles to Pittsburgh.  For local grapes, we used the farm’s address (near Lake Erie) and calculated the driving distance to Pittsburgh.

Second, to calculate carbon dioxide emissions we sought out an expert. following is a full explanation of methodology and caveats from our consultant, Conrad Vispo, Ph.D, who calculated the CO2 emissions for The Commons Diner menu.

Suffice it to say, the energy expenditure of food production and transport has impacts on environmental health, it always has and always will. It’s the atmospheric impacts that seem to be creeping up on us.  But let’s face it: it gets to be slim pickins right about now in March in Pittsburgh when we look to local food to feed us. Besides, what would we do without chocolate, fresh oranges, and the daily dose of coffee? In historical perspective, we’re consumers now spoiled by the delivery of goods from exotic places. One hundred years ago, oranges and chocolate were rarities at the corner mom and pop store.

For seven months of the year, local food is better for many reasons: it’s fresh, tastes great, comes unpackaged, is grown two counties over, and is driven into town by a family farmer. Consumer dollars circulate in the local economy. It’s a paradigm with positive impacts and a smaller carbon footprint.

Suzy Meyer
March 10, 2007
 

Calculating Carbon Dioxide Emissions for

The Commons Diner

By Conrad Vispo, Ph.D., Coordinator, Farmscape Ecology Program
www.hawthornevalleyfarm.org/fep/fep.htm

Methodology

There are three basic components to an estimation of the food-transport energy associated with a given meal: weight of a given ingredient, its source (and hence the distance traveled), and its mode of travel (and hence the efficiency and dirtiness of transport).

Once one knows how much is coming from how far away, one needs to multiply that value by an efficiency of transport factor. For example, if 100 lbs. (for the calculations, it doesn’t matter if this is 100 lbs of potatoes or feather pillows) are being transported 1000 miles, one needs to know how much energy is being used per pound transported each mile. For calculating transport efficiency, I used the numbers provided by the US government at  http://intensityindicators.pnl.gov/trend_data.stm. I found general corroboration for these values in other publications, such as those in Table 7 of Rich Pirog’s Food, Fuel and Freeways (available at http://www.leopold.iastate.edu/research/marketing.htm). I used the government values because they were more recent (2004 vs. 1989 for the original data in Dr. Pirog’s table). A survey of other sources suggested that these values were generally comparable to others cited. The most variable energy efficiency figure seemed to be for trucks – I found a 10-fold difference in the values cited. I used the values found in the govt. resource mentioned above hoping that, at the least, the values would be internally consistent in so far as they were derived in similar ways.

The government values that I used were not paired with C02 production values, however those of Pirog’s Table 7 were. I therefore calculated C02 produced per gal. of gas equivalent used from that table and applied those values to the energy figures from the government. If one just takes the chemical stoichiometry and calculates the C02 production from one gallon (6 ¼ lbs) of gas, the result is about 20 lbs of C02, very close to the figures used. I did not have access to the original source of the C02 data in Pirog’s table, I assume that the author either calculated C02 production based upon the chemical equations and had a solid basis for doing so, or else has empirical measures that closely paralleled the calculated values.

I converted all energy use to gallons of gas equivalents based upon the energy expended by the given vehicle and the energy content of gasoline. Trucks, planes, boats, and trains may each use different fuels; I converted them to gallons of gas equivalents for illustrative purposes.

Unfortunately, I could not find one clean set of figures that gave me modern transport efficiency values and C02 emissions. Instead, I made do with what I could cobble together.  It may be that, given the differences amongst boats, planes, trucks and the trains and variation in the conditions under which they travel, there is no single, correct set of values. Indeed, one source I consulted stated as much. In such a case, the best we can do is look at the existing numbers and try to use values that are, at least, consistent with those figures. I hope that I have done that.

Caveats

These numbers should be seen only as relative estimates rather than precise calculations. I hope that they give you an approximate idea of the energy and C02 production involved, however there are several reasons why they are far from exact.

First, while we have tried to use true road distances, actual shipping distances and appropriate air mileage between the points we identified as source and the nearest receiving facility, we couldn’t know the path actually taken. For example, does salmon flown from Anchorage actually come directly to Pittsburgh or does the airplane make some stops along the way? Does a boat shipping wine from Australia really come straight to NYC without picking up or dropping off along the way? Does a truck carrying Colorado beef really drive straight to NYC or are there warehouses and distribution centers en route? Detours from the shortest distance are probably common, and yet for the purposes of these calculations we couldn’t go to that level of detail.

Second, our source locations are only more or less accurate. For example, we don’t know for sure where on the East Coast of Nova Scotia the cod on our menu would likely be caught. We chose Halifax as our point of departure rather arbitrarily. While more digging might lead to some greater precision, the truth is that exact source for many of our products might vary from week to week in any case. This is especially true when one is buying from a distributor rather than direct from the source.

Thirdly, distance is important because, obviously enough, distance along with cargo weight are major factors determining energy used in transport. However, there can be huge differences in transport efficiency amongst modes of travel as well. For example, with the estimates we used, it would require roughly the same amount of energy to carry a given cargo a given distance by train as it would by boat. However, it would require six times more energy to do the same deed with a truck and 37 times more energy by plane. The caveat is that our estimates of energy use and C02 production are based on published estimates for these values. Comparing such values, it becomes apparent that efficiency can vary substantially based upon age and style of the particular transport vehicle and travel conditions (snow on road, head wind/tail wind, favorable/unfavorable currents). Again, digging into such detail was beyond the scope of this work and, in any case, the efficiencies are  probably not constant.

Interestingly, I could not even find a consistent value for the energy content of automobile gasoline; I picked a middle value that, again, may not be precise, but should be generally accurate for our purposes.

Finally, even if our estimates were miraculously precise, they would only be part of the picture. Energy is used in growing or gathering the product, be that by tractors in the field, fishing boats on the high seas, or grain handling for some livestock. Additional energy is used in preparing the food for shipment: lettuce’s waxed boxes, the freezing and vacuum packing of fish, the energy for cleaning dairy facilities. Further, you usually use energy when you go to shop (or go out for a meal). Indeed, some estimates have put the energy used by the shopping consumer well above that spent in transporting the given goods from source to store. Lastly, comes the food preparation, be it at home or in a restaurant, there is often energy used for washing and/or cooking.

For these reasons, and the human fallibility to which I am particularly prone, the estimates should only be taken for what they are: illustrative examples of the approximate energy costs of food transport, tempered by the evident roughness of calculation and the realization that additional energy uses are associated with the food system.

Conrad Vispo
February 21, 2007