Food for thought - carbon footprint of rice

Since I started reading about meats and their carbon footprints, I figured I should check the carbon footprint for some of my favourite food. I grew up eating rice, so I googled rice carbon footprint. It was a huge surprirse to me when I found out that rice has a much higher carbon footprint comparing to beef on the same weight basis. According to this article, rice contributes 24 times more greenhouse gases to the environment than even beef and per pound rice is equivalent of 276 5 to 35? pounds of CO2-equivilant! NOTE: the author of the above mentioned article has had several discussions with readers to verify the actual CO2-equivalent figures based o n various literature sources. In one discussion he realizes that the calculation was off by 100 times, but does not believe that a number approximately 1000x smaller is the “right” number. Follow his discussions here. There has yet to be a conclusion - the number he still believed would to be 5 and 35 lbs of CO2-equivalent per lb rice produced. Something I should really look into as well…..

It might be one thing to stop eating beef, but it’s not really possible for me to stop eating rice!!

So why does rice have such a high carbon footprint? It is because methane is produced during flooded rice cultivation by the decomposition of organic matter in the soil. Details to the carbon footprint of rice cultivation can be found in the agriculture section of the 2009 Draft U.S. Greenhouse Gas Inventory Report.

So what can we do? Apparently the most significant factor for methane release is related to the amount of water that the rice is grown under! In some areas where rice fields are not flooded, no methane is created! Similarly, if the water level is more than 1m (so called deepwater rice fields), methane production is also limited. In other words, if rice production is from shallow flooding (which is most of the case), then the amount of methane and therefore its carbon footprint is much much more significant.

As someone growing up eating rice, most of the time I am quite picky about the type of rice (long grain, short grain, and so on) than the type of rice farming! I will need to do a bit more research to find out the carbon footprint of my favourite type of rice…

Tags: carbon footprint, climate change, food carbon footprint, vegetarian

Population and climate change | flo | April 11, 2009 12:35 am

14 Comments

By Jay, April 12, 2009 @ 9:38 pm

This is intriguing .. 276 lbs is a lot of mass. I wonder where on earth does this mass come from - organic matter in the soil? Let’s assume one square yard of land yields 1 lb of rice. How much is 276 lbs? This can give you some idea: one bag of topsoil from HomeDepot is around 40lbs - seven bags of them make about 276 lbs. Or, 1 cube yard of topsoil is about 1 ton, or 2200 lbs, so 276 lbs of topsoil translates into ca. 11 cm tall of topsoil over 1 square yard. The CH4 produced most likely comes from hydrocarbon (organic matter)- if it is CO2 then part of the mass comes from oxygen in air, but not the case for CH4. And think about it, the weight of topsoil is mainly water and inorganic matter.
Flora - maybe I misunderstood something?
By flo, April 12, 2009 @ 11:07 pm

Hey Jay - thanks for the comments. CO2-equivalent for rice production is indeed from the decomposition of organic matter under water anaerobically producing CH4. Because CH4 has a much higher global warming potential, in fact 72 times higher than CO2 gas! Therefore, when you convert the amount of CH4 produced due to the anaerobic digestion, it’s about 3.8lb of CH4 per lb of rice produced. I like how you helped us to visualize the physical size of the CO2 mass =p it’s very powerful to be able to demonstrate that!
By Jay, April 13, 2009 @ 12:58 am

Ah I see, that makes sense. Thanks!
But still now this fact makes us feel guilty eating rice ..
By the way I thought the picture was Taiwan but a closer look at the temple it seems Thailand?
By flo, April 13, 2009 @ 11:16 pm

Yeah, I was in shock when i realized how much CO2-equivalent we’re producing as a rice eater! I intend to explore some “dry” growing rice and see if they taste just as good. It would be a huge problems for rice farmers to deal with water management AND GHG emissions with growing concerns about climate change worldwide!
By GassyMan, May 15, 2009 @ 12:05 pm

It to bad we can’t capture the methane because methane burns very cleanly and could help decrease our dependants on fosil fuels.
By flo, May 19, 2009 @ 11:12 pm

It would be great to capture methane as you pointed out that methane is one of the cleanest burning fuel!! There must be something we can do about methane from rice fields…..
By Matt, May 28, 2009 @ 8:17 am

According to the EPA (http://epa.gov/climatechange/emissions/downloads09/ExecutiveSummary.pdf pg. 3) the global warming potential of methane is only 21, not 72.
By flo, May 28, 2009 @ 11:37 am

Hello Matt - thanks for pointing that out! I guess I should have clarified that GWP for methane is 12 in lifetime and 72 in the first 20 years. Since the report is produced by EPA, you’re right that most likely GWP of 12 is used for methane. I guess i’ll need to go back to the numbers again and see if they match!
By Andrew, July 5, 2009 @ 10:05 am

Please can you correct this article - if you scroll to the bottom of your reference “this article” the author admits that he got the decimal point wrong and his rice figure is 1000 times too big! He did not realise that the rice production figure was in ‘000s of CWT - he thought they were just CWT. Please can you correct this so people are not given false impressions - rice is much, much less bad for the environment than beef (around 10 to 20 times less)And I am not even a vegetarian!
By flo, July 6, 2009 @ 3:32 am

awesome comment Andrew!!! I should’ve checked the reference more carefully as well so that I didn’t make such mistake….. thanks again =). happy rice eating..
By DJ, July 7, 2009 @ 4:00 pm

In my post “Consider Your Diet,” I incorrectly stated that rice prodices 276 pounds of CO2 per pound of rice grown. I am unable to substantiate that figure.

In fact, estimates of CO2 equivalency for methane emitted from rice production range from 0.6 (much lower than beef) to 35 pounds (much higher than beef) per pound. This does not include the N2O emissions. And it’s a ridiculously large range, though scientific research by IRRI does indicate that rice-related methane emissions can vary by more than 100-fold depending on soil, temperature, and cultivation methods.

I am still trying to get at the truth of the matter, and have contacted several experts. When I have a better answer, I will provide an update.
By DJ, July 14, 2009 @ 3:11 pm

Here are my final results on rice and climate change, following the response of two experts in the field: http://asymptoticlife.com/2009/07/14/the-scoop-on-rice.aspx

They both put the figure for rice at 1.2 - 1.4 pounds of CO2 equivalency per pound of rice– far less than beef, but more than soy, eggs, chicken, or turkey, and about the same as cheese or pork. Considering other grains can (and often are) grown in a carbon neutral manner, rice still has quite an environmental cost.

I apologize for any confusion my earlier post caused.
By flo, July 15, 2009 @ 8:11 am

Thanks DJ!
By Oryzon, August 20, 2009 @ 10:23 am

The United States Geological Survey presents that rice SEQUESTERS carbon, and builds organic material into the soil, raising soil indexes by rice’s contributions which also mitigates subsidence.
Link:
http://www.water.ca.gov/deltainit/docs/rice_factsheet.pdf

A typical yield for organic rice is 60/cwt or 6000 pounds per acre. The organic material/straw residue that is returned to the soil is about 10,000 pounds per acre. Rice wetlands preserve a web of life and an inter-dependent set of ecosystems developed over geologic time; that include migratory and non- migratory birds & shore birds, land, sea & aquatic animals; amphibious animals and aquatic insects, invertebrates and mollusks.

Rice paddies erupt huge invisible plumes of oxygen into the atmoshere while seqestering carbon into the soil.

LoLee Green

Can we shop our way to sustainability?