Yes, your mother loves the flowers, but maybe not the cost of flying them in

Twice a year, at Valentine’s Day and Mother’s Day, newspapers in the U.S. often print articles informing the public where their flowers come from. While the main purpose of these stories may be to remind people that they need to buy something for their loved ones, a post on USA Today online this week compelled me do something else – mostly because I already sent my mother a present. The article characterized the efforts both rose growers in Colombia and the aviation industry take to make sure the flowers are delivered to the States looking their best. I thought about how much jet fuel is burned importing the flowers and, in turn, how much carbon dioxide (CO₂) is emitted.

An article earlier this year detailing the Colombian rose industry stated flower imports from January 1 to February 14 have increased seven-fold between 2009 and 2015 and that the production of American roses have decreased 95%. As a result, in the three weeks prior to Valentine’s Day, 30 cargo planes with over a million flowers each flew from Colombia to Miami every day. And, as referenced in the USA Today piece, the roses that are flown out of Bogota in the cargo hold of United Airlines passenger jets may not be destined for vases in American homes. Many are placed on another flight from Houston to Japan, where roses can sell for a premium.

I quickly set out to model airline fuel burn for all nonstop passenger and dedicated freighter flights from all Colombian airports to the States, using operations data compiled by Airline Data, Inc. and Piano aircraft design and performance software. Over 17,000 passenger and cargo jets flew from Colombia to various American airports, carrying over 465,000 metric tons of payload (passengers and cargo). I’ve shown in a previous blog post, that adding payload increases the absolute fuel burn of a flight, but improves the fuel efficiency per unit of mass moved, because the aircraft is operated closer to its maximum payload. The airlines did a very good job of filling their aircraft on these routes, with both passenger-cargo and all-cargo flights operating at approximately 85% of maximum mass payload.

In 2017, an average of 0.57 kilograms of fuel was burned to transport a kilogram of payload between these North and South American countries. Using the assumption that each flower weighs 0.05 kilograms – an estimate given to me by a horticulturist I know who spent their graduate school career researching postharvest handling – 4 billion flowers from Colombia weigh 200,000 metric tons. That is over 40 percent of the total airline-reported payload (both passengers and freight) transported on flights from Colombia to the United States. Therefore, flying that much sweet-smelling cargo burns 114 million liters of fuel and emits approximately 360,000 metric tons of CO₂. That figure is just for the flowers, and does not include packaging that ensures that the product is not damaged during transport. To put this number into context, according to the U.S. Environmental Protection Agency (EPA), a forest larger than the area of Houston (1,624 km²) would be needed to sequester that amount of carbon.

Unfortunately, the carbon count doesn’t stop there. Shipping the roses on a United flight to Tokyo increases the carbon intensity of those flowers by 600 percent. Also excluded in my calculations are the emissions of the refrigeration trucks transporting the flowers from the farms to the airports (the grower in the USA Today article was an hour away from Bogota’s airport), to and from a warehouse where flowers are stored or bouquets are assembled (200 refrigeration trucks were needed in Miami each day during the Valentine’s Day season), to a second flight somewhere else in the U.S. or around the world, and then to a store that sells the prepared bouquets or a florist who will expertly design your bouquet for you. Perhaps estimating the total fuel burn and emissions of the floral industry is an area of further research that I should propose to our Green Freight team.

As I finish writing this blog post, I’m reminded I should probably buy a Mother’s Day present for my wife, a cat mom. I think I’ll buy her some flowers. But I’ll be sure that they are American grown, preferably somewhere local.