What to do with the fruit residue from oil palm seeds: refine it into bio-ethanol or use it as fertilizer?

When oil is harvested from the seeds of the oil palm tree, the fruit residue can be used to make bio-ethanol. However, it can also be used as a fertilizer on palm tree plantations; which option is best for the environment? Edi Wiloso compared the two green options at the Institute of Environmental Sciences Leiden (CML). His PhD defence is scheduled for 29 October.

A wet mass

The fruit of the oil palm tree

The fruit of the oil palm tree

Once the oil has been pressed from the seeds of oil palm fruit, you’re left with a wet mass of fruit residue. The oil is used in margarine, deep frying oil, potato crisps, taco crisps, sauces, biscuits and is even used to make soaps. In Indonesia, the world’s largest producer of palm oil, the idea was raised to turn the residue into ethanol, a green alternative for fossil fuels. However, Wiloso’s research shows that this isn’t always the best option for the environment.

Higher yields through fertilisation

Hundreds and even thousands of fruits are packed together in bundles that can weigh up to 25 kg

Hundreds and even thousands of fruits are packed together in bundles that can weigh up to 25 kg

The residue is currently usually returned to the plantations, where it are used as fertilizer. Nutrients leak into the ground, where they are absorbed by the trees. But when the residue is used for bio-fuels, the fertility of the soil decreases, which in turn affects the yields. In time, larger plantations will be necessary to compensate and to sustain production levels. Synthetic fertilizer could be used as an alternative, but is the green energy worth the substitution?

Life cycle assessment

To compare the options, Wiloso developed a method to measure the environmental impact of both products – green energy and green fertilisation. This included various aspects such as greenhouse gases and carbon dioxide emission. He used life cycle assessment, an approach that maps the environmental impact of a product throughout the course of its existence, from harvesting the materials, to processing, and use. This requires a lot of custom measuring, because the crucial characteristics differ per product. Wiloso included all possible applications for oil palm fruit residue in this study. The residue isn’t just suitable as a green fertilizer or as a bio-fuel; it can also be used as a source for fibres that are used in the production of mattresses or in the food industry.

Not a single clear result

The current process, in which the residue is returned to the plantations and used as fertilizer, turns out to be the most environmentally friendly process in most situations. Wiloso: ‘But this isn’t always the case, as the local situation influences the results; this means that every location needs to be analysed separately. Upon returning to Indonesia, Wiloso wants to promote the life cycle assessment method in the palm oil industry to make production more environmentally friendly.

Geoogste trossen op een plantage

Geoogste trossen op een plantage

CML was the best option

Wiloso works at the Research Center for Chemistry of the Indonesian Institute of Sciences (LIPI, Puspiptek, Indonesia). The production of bio-ethanol from harvest residues has been on the agenda of the institute since 2010. Wiloso was asked to study the environmental impact of the use of palm oil residue. ‘I was checking out different universities online, looking for the best location to study this issue. I soon found myself on the website of the CML.’ He also founded the Indonesian Life Cycle Assessment Network in 2014.

Edi Iswanto Wiloso ‘Development of life cycle assessment for residue-based bioenergy’ on 29 October 2015. >

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Studying in Leiden


  • Environmental Sciences isn’t a separate programme in Leiden, but the Biology bachelor’s does include a number of courses on environmental sciences, which can also be chosen as elective courses. You can also choose one of the following minors: Biodiversity and Natural Environment or Sustainable development (interdisciplinair). You can, of course, also write your thesis on an environmental subject.

  • Another route can be found via Cultural Anthropology and Development Sociology (CAOS).There, you can choose a relevant theme, such as Sustainability as well as a region, such as Southeast Asia or Sub-Saharan Africa. CAOS also offers a course in Water Course Management in the Philippines.

  • The Liberal Arts and Sciences: Global Challenges programme at Leiden University College The Hague offers very broad perspectives, but allows students to choose a theme as early as the first year. Students will follow three courses on the chosen topic during the first year, with the specialism expanding over the following two years. One of the themes is Sustainability, with global problems being treated within that theme including climate change and the exhaustion of natural resources.


Last Modified: 27-10-2015