ILUC factors and palm oil yields: Resolving an apparent contradiction

Posted Thursday, 31 May 2018, 09:33

Farmers and other biofuel stakeholders sometimes express disbelief in the magnitude of indirect land use change (ILUC) emissions that researchers say is associated with palm oil biodiesel. For example, a recent study using the Global Biosphere Management model (GLOBIOM) estimates that ILUC emissions from palm biodiesel are more than triple those for rapeseed (also known as canola) biodiesel. Palm plantations, critics counter, have a much higher yield of vegetable oil per hectare compared to rapeseed and other oil crops. How could the ILUC emissions for palm oil biodiesel be so much higher than for those crops, then?

These only seem contradictory. In reality, they're not.

Do palm plantations have higher vegetable oil yields than other oil crops? Yes. The figure below shows that palm oil delivers almost twice the energy yield per hectare as rapeseed and, as a result, requires half the amount of cropland to supply a certain amount of biofuel. Do ILUC models disregard this important parameter? No. Economic models do take this factor into account. The GLOBIOM modeling study incorporates accurate historical yield data for a number of major crops, including palm oil.

carbon emissions for biofuels
Figure: a) Biofuel yield in liters diesel equivalent per cultivated hectare projected, and b) global land expansion due to increased biofuel demand in the year 2020 in Valin et al. (2015)

So, if palm oil leads to only half as much total land expansion as rapeseed oil, how could it possibly cause higher ILUC emissions? Because not all land use change is equal.

Most palm oil is produced in Malaysia and Indonesia, and these countries are characterized by a rare ecosystem: tropical peat swamp forests. These forests grow on soil which is permanently waterlogged so that deadwood, leaves and other organic debris accumulate in oxygen-free conditions. This carbon is stored for centuries in an organic material called ‘peat’. Tropical peat swamp forests thus contain large amounts of carbon, typically in the range of 150 tonnes per hectare in the biomass and 3,000 tonnes per hectare in the underlying peat.

Palm oil expansion at the expense of these ecosystems has a compounded negative effect on carbon emissions: natural forest is replaced by palm oil plantations; and peatland swamps are drained and oxidised slowly, releasing the carbon that has accumulated over millennia. One study found that emissions from peat oxidation amount to around 95 tonnes of CO2 per hectare each year. Therefore, tropical deforestation and peat drainage are the main causes of the high ILUC emissions for palm oil biodiesel. By comparison, models suggest that rapeseed expansion would take place mostly on relatively low-carbon abandoned land in EU. Each hectare of cropland expansion caused by palm biodiesel demand drives much higher emissions than that caused by other biofuel crops.

There’s more to the story than carbon. Deforestation of tropical forests in Indonesia and Malaysia also has dreadful consequences for biodiversity. A single hectare of tropical rainforest harbors over 200 plant species and more than 60% exist only in a particular region. For example, Borneo has experienced great forest loss, and the population of Bornean orangutans (Pongo pygmaeus) could decline by 86% by 2025.

It is clear that policies promoting the use of palm oil biodiesel do not lead to any greenhouse gas emission reduction but rather contribute to destruction of one of the Earth’s richest biodiversity hotspots: causing devastating losses of carbon stocks, endangering rare species, polluting air and water, and contributing to the suffering of indigenous Indonesians.