Thursday, 3 December 2015

Tackling the haze in South-East Asia: a call to COP21 Paris

Reprint of my original article published first in the blog of The Grantham Institute.

Peat fires are raging in Indonesia and their extent is staggering. The dry season is not over and NASA satellites have already counted more than 12,000 active fires, which have emitted in excess of 1.6 Gton of carbon dioxide equivalent. This is more than Japan’s annual emissions and close to the footprint of the whole of India. In fact, if peat fire emissions were considered, Indonesia would be the 4th highest emitting country in the world. With COP21 climate negotiations on carbon emissions due to start in just over a week, this widespread haze is choking the population and fauna.

Driven by energy goals and climate change, international efforts are moving towards reducing anthropogenic greenhouse gas emissions and limiting the burning of fossil fuels. However, by ignoring smouldering fires, a major source of greenhouse gases is being overlooked.

The long slow burn

Smouldering fire is a natural phenomenon that burns Earth’s organic-rich deposits, primarily peatlands, soils and coal. Sometimes termed smouldering megafires, these are the largest and longest burning fires on Earth and take place not only in Indonesia, but also in Siberia, Alaska, Florida and Australia to name a few.

Peat megafires destroy essential peatland ecosystems, and release huge quantities of carbon dioxide, carbon monoxide and methane, making up 15% of annual global greenhouse gas emissions. This is the same amount attributed to the whole of the European Union, or all the vehicles worldwide – and yet it is not accounted for in global carbon budgets.

Moreover, the burning of deep peat affects older soil carbon that has not been part of the active carbon cycle for centuries to millennia, and thus creates a positive feedback to the climate system (see Figure 1).
Figure 1. The peat fire problem at the Earth scale, including climate feedback. By G Rein, CC BY 3.0 license

Why so large?

Smouldering combustion is the slow, low temperature, flameless burning of porous fuels. It is sustained by the heat released when oxygen directly oxidises the carbon on the surface of organic soil particles. Once ignited, subsurface organic layers such as those in peatlands or carbon-rich soils burn slowly for long periods of time, spreading deep into the ground and over extensive areas.

Possible ignition events can be natural (e.g. lightning, self-heating, volcanic eruption) or anthropogenic (land management, accidental ignition, arson). Smouldering fires can be initiated by weak sources of ignition and are typically the most difficult to extinguish. Smouldering suppression requires much larger amounts of water than extinguishing flaming fires (it requires actual flooding of the land).

Easy ignition and difficult suppression make smouldering fire the most persistent type of combustion phenomenon on Earth. These fires burn for very long periods of time, lasting months, years, or even decades, despite extensive rains, weather changes and fire-fighting attempts. Peat fires have been active in Indonesia this season for the last more six months or more. They have become endemic in some areas of the world.

Figure 2. Visual and overlaid infrared imaging of radial smouldering spread over a sample of peat ignited at the centre. Photo by Rackauskaite, Huang and Rein (CC BY 3.0 license)

The Triple Challenge

Given the scale of the problem, relatively little action is being taken. I have identified three major challenges hampering global action:

Challenge #1 – Scientific understanding is poor: There are still large gaps in our knowledge of how smouldering fires ignite, spread or extinguish, which impedes the development of any successful mitigation strategy. Poor scientific knowledge on smouldering even leads to fatal misunderstandings and confusion between flaming and smouldering combustion.

Challenge #2 – Non-existent mitigation technologies: Smouldering megafires are routinely fought across the globe with techniques that were developed for flaming fires. These techniques are ineffective for smouldering fires because the heat transfer and the chemistry involved are completely different. For instance, aerial tankers do nothing to stop smouldering fires because flooding is required instead, and satellite monitoring substantially underestimates the size of peat fires because smouldering can spread underground.

Challenge #3- Topic fragmented among scientific disciplines: Smouldering megafires are an intrinsically multidisciplinary theme requiring collaboration by combustion scientists, ecologists, atmosphere scientists and biochemists.

These three challenges must be overcome before effective mitigation strategies can be implemented. While the largest fires on Earth continue releasing naturally stored carbon into the atmosphere, we are failing to protect both people and the planet.

A Call to Paris

We can reduce the worldwide burden of smouldering megafires and create new technology drivers by pursuing greater experimental understanding and up-scaling our research in the field.

Science is an essential enabler of understanding of peat fires. By strengthening the importance of fundamental knowledge and by consolidating the disciplines interested in the phenomenon, I believe combustion science will serve as the basis for tackling wildfires.

COP21 in Paris has the chance to mobilise the resources needed to advance the science that can lead the way and pioneer technologies against this Earth-scale but unconventional source of emissions.

Further Reading

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