Preventing carbon losses in oil palm cultivation

Oil palm cultivation provides us with a vital commodity that is used around the globe in products from foodstuffs to cosmetics, but it is also one that presents a number of sustainability and environmental challenges. Dr Frances Manning from ADAS, an RSK group company, discusses solutions to mitigate carbon losses caused by farming on peatland in South-East Asia.

Oil palm cultivation across Malaysia and Indonesia provides global markets with a valuable commodity – palm oil. This vegetable oil is a staple ingredient in many processed foodstuffs, cleaning products and cosmetics and is even a component of some biofuels. Oil palm is such an important crop because it produces the highest yields of all vegetable oil plants. This high yield potential means less land is required to produce the same amount of oil when compared to other oil producing crops. In 2020, it was the most produced vegetable oil, followed by soybean oil, rapeseed oil and sunflower oil. To produce the same amount of these alternative oils, around four to six times as much land would be required. It is a highly efficient crop, accounting for 6% of all land cultivated for vegetable oil products but yielding over one third of total output.

Oil palm plants are grown across much of tropical South-East Asia, on both mineral and peat soils, with mineral soils being preferred due to the likelihood of higher yields. Agriculture on peat soils can present notable environmental challenges due to the necessity of introducing and maintaining an artificial water table depth, which prevents the crop roots from getting waterlogged and enables them to grow. Peat soil is highly saturated with water, a factor that enables it to thrive as a carbon sink. The waterlogging in peat soil creates the anaerobic conditions that prevent plant matter fully breaking down, storing the associated carbon deep in the ground. The high-water table, however, is not conducive to cultivation, which results in the peat being drained.

The practice of draining peat soil results in an increase in oxygen in the soil profile, which gives soil microbes the right conditions to break down the peat into carbon dioxide. This process is called peat oxidation and it can create problems for both the environment and for farmers. From an environmental perspective, peatlands are an important global carbon store and maintaining peatlands is one of the strategies recommended by the Intergovernmental Panel on Climate Change (IPCC) in order to reduce the impacts of climate change. On the ground, peat oxidation can lead to an increase in the rate of flooding in the plantation, impacting yields and the ease of using machinery. Management strategies exist, however, that enable the cultivation of this valuable product at the same time as increasing the protection of the soil it grows in.

Studies show that there are means of managing the soil that can reduce how much CO₂ is lost to the environment when it is used for oil palm cultivation. One such measure to reduce carbon losses from peat soils is to raise the water table. Monitoring the artificial water table depth to make sure that the peat is not accidentally overdrained can reduce CO₂ emissions while keeping oil palm yields at the same high levels. Recommended water table depths range between -0.4 m and -0.6 m.

A second effective means of reducing peat oxidation is by ensuring that the peat is shaded, particularly while the palms are young and the canopy is open. Ensuring sufficient shade cover can have a significant impact on reducing CO₂ emissions, principally because biochemical reactions tend to speed up at higher temperatures. Cooler soil temperatures slow the rate of oxidation, reducing the carbon emissions produced by the process. For example, it has been shown that shading the soil by 90% can reduce the rate of peat oxidation by 33%.

Implementing these solutions in oil palm cultivation will help reduce the rates of peat oxidation while maintaining the high yield potential of the crop. As oil palm is one of the world’s most important crops, resolving the challenge presented by the associated carbon losses from agriculture on peat soils will help enable global demand for vegetable oils to be met while making the most of the available land area and reducing the greenhouse gas emissions from production.

Dr Frances Manning is a sustainable agriculture consultant at ADAS Climate & Sustainability, providing consultancy and policy advice around mitigating and adapting to the effects of climate change in agriculture and across supply chains.