Methane: Sources, Sinks and Uncertainties

A paper about methane that I have been working on with a team of scientists and practitioners is now published.

A nuanced understanding of methane is important for Aotearoa, as the dominant view positions methane emissions as a major problem. But our predominantly pasture-based agricultural systems operate in ways that emit methane, also support the processes that destroy methane.

We are frequently reminded how ruminants produce methane, but there is much less focus on how methane is removed. The hydroxyl (-OH) radical provides by far the largest pathway for removing methane from the air. Hydroxyl is produced from water vapour in reaction with ultraviolet light. So any farm that has actively growing pasture, will be supporting the production of hydroxyl. Here is a simple explanation of how methane is formed. In addition to hydroxyl, our farms can also support processes in the soil and in animals to reduce methane. We can expect significant variations between the amount of hydroxyl produced on healthy pasture compared to a concentrated animal feeding operation (CAFO). Other processes in the soil and the animal will influence the interplay of sources and sinks.

Our research identified significant variations in methane modelling that provides a shaky foundation for any quantification.

The global warming gasses, water vapour, carbon dioxide, methane, and nitrous oxide all cycle differently through the environment. Our dilemma is to understand how these differences need be reflected in policy and land stewardship, while recognising their dynamic interdependence.

The practices that support all manner of benefits, including carbon sequestration in soil – diverse, actively growing pastures, and healthy soil biome, will also increase methane sinks.

Here is one of the authors, Walter Jehne talking about methane.

If we persist with creating an artificial equivalence between carbon dioxide and methane, and use that to create policy and possibly levies, it will be another distraction from creating the best incentives for farming methods that will mitigate climate change. We have an opportunity now to develop a more nuanced appreciation of how methane cycles. If you are interested in helping, please comment below.