Global Warming

(Vanessa Pike-Russel photo.)

Open the Future calculates the environmental cost of a drive-through cheeseburger here.  The result: a carbon/product ratio of 23.7, or 23.7 pounds of CO2 equivalence per pound of burger.  (Like me, they estimate that beef contributes better than 10 pounds of CO2 equivalency per pound of product– encouraging after my error on the rice calculation.)

Compare that with, say, a three-egg omelette (from local, non-factory-farmed chickens) cooked at home and containing onions, spinach, and tomatoes from your garden. That’d emit less than 0.1 pounds of CO2. 

Or a bowl of organic, seasonal strawberries (0.07 pounds of CO2) and a slice of home-baked bread (0.01 pounds of CO2).  Or a quarter-pound baked potato (0.15 pounds of CO2).

So what’s for lunch today?

(Tamaki photo.)

I have received answers back from two experts on ricew and climate change.  Dr. Reiner Wassman, scientist at the International Rice Research Institute, writes:

“The proximate amount can be derived based on the IPCC guidelines (http://www.ipcc-nggip.iges.or.jp/public/2006gl/vol4.html):

Emission of methane: 130 kg CH4/ ha/ season (assuming 100d cultivation period)
=> 3250 kg CO2eq/ ha/ season

Emission of nitrous oxide: 0.3 kg N2O-N/ ha/ season (assuming 100 kg N fertilizer per ha)
=> 229 kg CO2eq/ ha/ season

TOTAL: 3479 kg CO2eq/ ha/ season

LOW YIELDING RICE PRODUCTION (3000 kg rice/ ha) ===> 1.16 kg CO2eq/ kg rice
HIGH YIELDING RICE PRODUCTION (5000 kg rice/ ha) ===> 0.7 kg CO2eq/ kg rice.”

So, what about that 35 pound figure from the Climate Change Institute? They write,

“The reported value for the Climate Institute is incorrect. The article on Thailand’s emissions mistakenly says Thailand emits 91.6 million tons of methane annually when citing the EPA 2006 Report on Non-CO2 Gases. The actual statistic is 91.6 million metric tons of CO2 equivalent from methane. The conversion factor from methane to CO2 is already included in the statistic. Therefore, dividing your calculated 35 pounds of CO2 equivalent per pound of rice by a CH4 to CO2 conversion factor of 25 gives a result of 1.4 pounds of CO2 equivalent per pound of rice…”

Now, one last verification: does this reconcile with the estimated global contribution of rice to global warming? World rice production is estimated at 645 million tons.  EIA puts CO2 equivalence of global methane emissions at 605 million tons.  USDA says, “Some studies show that up to 20 percent of global methane emissions come from flooded rice fields.”  But other studies put rice’s methane emissions at 20-100 million tons, or 400 – 2,000 million tons of CO2 equivalency.  This suggests that it’s not the rice methane estimates that are off, but EPA’s world methane inventory.

One study uses a low-end figure consistent with other data: 25.6 million tons of methane from rice production worldwide, which equates to 538 million tons of CO2 equivalnce.  Based on rice production of 645 million tons, that’s 1.2 pounds of CO2 equivalence per pound of rice.  And that’s perfectly consistent with these figures– but it also represents 89% of makes EPA’s methane inventory, making EPA’s figure look ridiculously low.

NASA, in a 1996 study, puts methane emissions for rice much higher, at 146 million tons, or around 3,000 million tons of CO2 equivalency, or 4.8 pounds per pound of rice.  But I’m mostly willing to concede this as an aberration.

How does 1.2 pounds of CO2 stack up against other foods?  That’s far less than beef’s (by my calculation) 10.75 pounds.  But it’s far more than soy (0.3), eggs (0.2), chicken (0.5) or turkey (0.6), and roughly the same as cheese (1.6) or pork (1.2).  Other grains, such as rice and corn, can be grown in a carbon-neutral manner, making rice all the more decadent.

To be clear, rice can be grown in a more environmentally-friendly manner by not flooding the fields throughout the cultivation cycle.  But it isn’t, and for that reason it remains an environmentally expensive food that much of the world relies on for survivial.

(Jeff Youngstrom photo.)

In my post “Consider Your Diet,” I erroneously used a figure of 276 pounds of CO2 equivalency per pound of rice.  It seems I put the decimal point in the wrong place– oops. 

EPA reports U.S. rice production at 223,235,000 cwt for 2005, which is 10.126 billion kg.  EPA puts methane emissions for rice for 2005 at 6.8 Tg (or 6.8 billion kg) of CO2 equivalency.  That’s a factor of 0.7 pounds of CO2 equivalency per pound of rice.

But  a site from the Climate Institute that says Thailand produces 28M tons of rice creating 46.7 M tons of methane in the process.  That’s 1.67 pounds of methane per pound of rice, or 35 pounds of CO2 equivalence per pound of rice. 

The UN’s Food and Agriculture Organization (FAO) quotes a study indicating that for 2006, India’s rice production contributed 6,600 Gg of methane, or 6.6 billion kg.  They give India’s rice output for 2006 as 91 million tons, or 91 billion kg.  That’s .0725 kg of methane per kg or rice, or 1.5 pounds of CO2 equivalency per pound of rice.

Alter Eco quotes a study from the Internationa Rice Research Institute saying, “on average the production of one kilo of rice represents the emission of 120g of methane.” That’s 2.5 pounds of CO2 equivalency per pound of rice.

But the IRRI itself notes that in one study, “Emission rates [from rice paddies] varied in a very wide range from 5 to 634 kg CH4 ha-1 depending on season and crop management”– a range varying by more than 100-fold.

Heinz-Ulirch Neue states,  “Recent global methane budgets from rice fields range from 20 to 100 Tg/yr,” or 20 to 100 billion kg.  According to IRRI, world rice production for 2007 was 645 million tons, or 645 billion kg.  That gives a range of 0.03 to 0.16 kg methane per kg of rice, or 0.63 to 3.4 pounds CO2 equivalency per pound of rice.

So, estimates of the CO2 equivalency of rice production appear to range from a low of 0.6 to a high of 35.  Which is correct?  I have no idea– but I’m still trying to find out.

(Photo via AFP.)

“British explorers in northern Canada to measure the thickness of floating Arctic sea ice ended their expedition short of reaching the North Pole due to an early summer ice melt, the team said Thursday.”

According to the AP article, they also found that most of the ice they traveled over was “first year ice”– meaning that the old ice appears to have already melted.

Ironically, the three explorers had traveled north to gauge the effect of global warming on the Arctic ice.  I guess they found out…