Why is rice agriculture the 3rd source of methane emissions worldwide?
Of all the information shared after COP28 in Dubai, one specific stat caught my eye: the difference in carbon emissions between the “worst” and the “best” type of rice is of a factor of 189 (0). In other words, the worst type of rice will emit 189 times more than the best one.
I was surprised by this data and started to ask myself a few questions:
- How is rice agriculture producing emissions?
- What proportions are we talking about here?
- Should I consider buying ecological rice?
Rice is a staple food for 60% of the world’s population and 80% of rice production globally is produced by small farmers in low income nations (1). As we often see in pictures of paddy fields across Asia, rice mostly grows in flooded fields. This aquatic environment is the perfect place for methane-producing bacteria to proliferate due to the presence of organic matter. Rice agriculture also produces carbone dioxide (CO2) from the irrigation pump system and nitrous oxide (N2O) from the fertilizers poured in.
Methane is a greenhouse gas with a lifetime of about a decade and Global Warming Potential about 30 times greater than that of carbon dioxide (CO2) during the 100 years after it is released into the atmosphere (2). Methane reduction is reaching a global consensus and the objective of bringing it down by 30% in 2023 (compared to 2020) was set by the participants of the Global Methane Pledge (3).
Like all emissions, methane is produced naturally in the atmosphere (surprising as it may sound, humans are not always needed!) in wetlands and by termites. Anthropogenic sources (i.e. linked to human activity) are still a significant driver of methane through ruminants, rice agriculture, coal mining, biomass burning, and gas and oil. In terms of proportions, here is what we are talking about:
Rice agriculture is the third source of methane and second anthropogenic (ie. human linked) one after cattle farming — that’s relevant!
The introduction of adjusted methods are being studied and implemented in order to limit emissions:
- Water management practices such as Alternate Wetting and Drying (AWT) mean that the methane-producing bacteria which proliferate in water will feel less at home (4). Certain AWT techniques can reduce methane emissions by 70%, which is pretty significative! (5)
- The System of Rice Intensification (SRI) is a holistic methodology which also reduces water usage across the process and therefore methane emissions (6).
- Fertilizers’ improved and more balanced used (7)
- Introduction of less water-loving rice plants (7)
What about ecological rice?
As a consumer, one of the main climate action that can be taken is to carefully select the products purchased at the (super)market. Each € spent is equivalent to a vote. So what are we buying when choosing ecological rice?Based on previous research, the EU ecological label is one of the most trusted. This label certifies that no pesticides were used in the cultivation process which is already a big step. However, it does not provide information regarding the cultivation technique and water use which would be the main factors to look into when it comes to methane.
As often is the case, reading the detail on each pack is the way to go. The most impressive actions I have seen described, in addition to no pesticides, are:
- Water efficient rice cultivation techniques (will impact methane emissions)
- Rice straw valorization in other ventures to save it from being burnt or composted onsite (will impact methane emissions)
- Organic fertilizers (will impact nitrous oxide emissions)
- Maritime transport (will impact carbone dioxide emissions)
- Crop rotation and hedge introduction in rice fields (will improve soil quality and biodiversity)
It is not always easy to know whether a brand is implementing those actions. If not highlighted on the pack of rice, looking a bit deeper on the brand’s website will generally help. As you will have understood, only very precise techniques will see methane emissions reduced in rice agriculture.
A different label from the EU ecological one might be needed to better understand the impact of each rice brand on the environment.
Rice is essential for the survival of many people around the world, the development of crops with lower emissions can have a major positive impact. Staying informed, reading the labels, and choosing the brands which have implemented the most relevant actions in terms of climate and biodiversity are the main routes I will go with for now.
References:
0. Source unfound.
1. Gathorne-Hardy, A. (2013), Greenhouse gas emissions from rice
2. UN Environment Programme — Facts about methane
