In a previous post, we provided readers with an overview of what greenhouse gases are, how they impact our environment, and why we focus on carbon dioxide in climate discussions. However, there is another GHG that is a cause of concern that many climatologists have been talking about: methane.

Where do methane emissions come from?

Around 40% of methane emissions are naturally occurring. The two major anthropogenic sources of methane, constituting the remaining 60% are agriculture and energy generation. The former will be expanded on in the second half of this post.

Figure 1: Sources of methane emissions

Are the atmospheric concentrations of methane rising?

The atmospheric concentrations of methane have risen by a factor of 2.6 from pre-industrial levels. While the concentration remains relatively low compared to carbon  dioxide, methane has serious climatological implications in the short term.

In the introductory guide to greenhouse gases, we provided an overview of the lifetime of a GHG and its global warming potential (GWP). These are two crucial factors to understand the impacts of a GHG on the atmosphere.

Lifetime of methane

Carbon dioxide’s lifetime is variable. It stays in the atmosphere for anywhere between a few hundred years, and thousands of years. Meanwhile, methane has a much shorter atmospheric lifetime of 12 years on average.

Global Warming Potential of methane

The GWP is based on the warming potential of CO₂ in the atmosphere. The GWP is bound by a timescale to measure a GHG’s impact. Previously, we discussed the impact of CO₂ through a GWP with a 100-year timeframe. Methane, however, has a comparatively shorter lifetime and its GWP is therefore assessed on a 20-year timeframe. The Intergovernmental Panel on Climate Change (IPCC) has indicated that methane has a GWP₂₀ of 84-87, while it is only 28-36 on a GWP₁₀₀.

This means that on a 20-year timeframe, methane has more than 80 times the warming potential of CO₂.  It is noteworthy that we are not comparing methane on a 20-year timeframe to methane on a 100-year timeframe. When choosing to look at methane’s GWP on a 20-year timeframe, we are comparing its warming potential to the warming potential of CO₂.

Why do methane emissions matter?

Aside from the fact that the emission of methane is causing rapid warming, methane also has an impact on air quality. Methane is an ingredient in the formation of ground level ozone, which is a dangerous air pollutant.

The Global Methane Pledge (GMP) has recognised the risks caused by the emissions of methane into the atmosphere. A drastic reduction of our global methane emissions is regarded as “the single most effective strategy to keep the goal of limiting warming to 1.5 degrees Celsius within reach while yielding co-benefits including improving public health and agricultural productivity.”

The GMP was launched during the COP26 in Glasgow last November. The Pledge gained over 100 signatories who agreed to take action to reduce global methane emissions by 30%. This percentage is relative to 2020 levels and is set to be rolled out by 2030.

Methane emissions and agriculture

Estimates are that methane from livestock accounts for 14.5% of all global greenhouse gas emissions. In addition, the IPCC’s Sixth Assessment Report has disclosed that methane accounts for about 30% of global warming since the pre-industrial era. This is substantial, hence the GMP is essential to preventing drastic global warming.

Methane emissions from livestock mostly comes from enteric fermentation.

What is enteric methane?

Bacteria breaks down organic matter, producing hydrogen, carbon dioxide, and methane. This in a natural process called anaerobic fermentation and occurs in the digestive system of ruminants – like cows -, natural wetlands, and rice paddies.

Enteric methane is a by-product of the digestive process, and is expelled by burping.

How can we cut methane emission?

From 1990 to 2019, the UK experienced a 3.8% reduction of methane emissions from agriculture. This is unfortunately not sufficient to meet targets but is a first step.

Currently, the University of Edinburgh is leading research on ‘breeding planet-friendly cattle.’ Alireza Ehsani, a Marie Curie Fellow has been working on a method of breeding cattle which produces less methane and utilizes feed more efficiently. The aim is that the cattle eat and emit less, yet produce more milk. This research has received funding from the European Commission in 2020.

 

Reducing our emissions on all fronts is imperative. To learn more about what your options are as an organisation or individual, please contact a member of our team.

 

Edited by Tiffany Cheung