Drying Palm Kernel Shells (PKS) by Utilizing Waste Heat from Palm Oil Mills and POME Biogas Units

The need for palm kernel shells or PKS is getting bigger because its use is increasing and diversifying. PKS can be used as boiler fuel in industry and in power plants. In addition, it can also be used as a raw material for activated carbon whose needs are also increasing, for more details, read here. The global trend to decarbonize or replace fossil fuels with renewable energy including biomass fuels, especially PKS is the main driving force for the increasing demand for PKS. Even oil-rich countries with economies driven from oil (petrodollars) are also gradually implementing the decarbonization program.

To be used as fuel or further processed into a number of derivative products such as torrified PKS, PKSC or palm kernel shell charcoal and activated carbon, the PKS must be dried first. The process of drying or reducing the moisture content to a certain level requires energy. PKS, which are palm oil mill waste, are generally just piled up in the backyard of the palm oil mill, so they are usually dirty and wet, resulting in a low selling price. If the palm oil mill can dry and clean its PKS, the selling price will also increase, so that there is added value as well as additional income for the palm oil mill. A number of energy sources from waste heat from palm oil mills can be used for the drying process.

Heat is an energy source that can be used for various purposes, either heat generated directly from the combustion process or from waste heat which is the residual heat from the combustion or other sources such as electricity and so on. In palm oil mill operations there is a certain amount of waste heat that can be extracted or harvested or recovered as a heat source for drying such as heat from combustion in the boiler, heat from steam turbine and heat from the FFB sterilization process. If the palm oil mill also processes its liquid waste for electricity production, the waste heat from burning biogas in the generator can also be used as a heat source for drying the PKS. A number of heat sources which are waste heat when integrated, the amount is large so that it can be sufficient for drying the PKS.

In addition to producing CPO (Crude Palm Oil) as the main product, palm oil mills generally also produce palm kernel. Currently, there are still a few palm oil mills (CPO mills) that also have PKO (Palm Kernel Oil) mills , meaning that there are palm oil mills that process fiber for CPO production and palm kernel for PKO production. The palm kernel is produced from the separation of palm kernel with its shell (PKS). Separation is done by breaking the palm kernel shell in a nut cracker drum, then it can be separated between the palm kernel shell and the kernel or core based on differences in specific gravity. If the palm oil mill wants to get added value from its palm kernel shells (PKS), then as soon as it leaves the palm oil mill it goes straight into the dryer (with waste heat as the heat source) after which it is cleaned with a sieve (screening) so that it becomes the final product in the form of dry and clean PKS, so that higher sale value. The size of the shell and fibers that pass the sieve (undersize), can also be used as boiler fuel. Palm oil mill boilers currently operate using fiber fuel (mesocarp fiber) and part of the palm kernel shell (PKS). The rejected material in the form of undersize can be used as boiler fuel so that less PKS are used.

Post Mining Land Reclamation With Bamboo

Bamboo is a tree that is easy to grow, tall quickly and has many benefits. One of them is the use of bamboo trees for post-mining land reclamation. Damaged and barren post-mining land is indeed not easy to plant directly. Certain treatments or efforts are needed so that the land can be planted with certain plants. When the land has become fertile soil, of course almost all plants can be planted on the land. And to achieve these conditions it takes time and a process that is not short.

Soil improvement efforts in the sense of improving soil fertility are the first thing to do so that plants can grow well on the land. Plants that can be planted at this stage are also only certain types of plants such as pioneer plants in the form of fast growing plants such as legumes. And bamboo as a group of grass plants is also easy to plant and grow on marginal lands such as post-mining land. Availability of water, adequate nutrients, pH or adequate soil acidity are some of the things needed to achieve optimal growth.

As an illustration, sand is a bad planting medium because there are almost no nutrients in it and this is almost the same as the condition of post-mining land in general. Substances or organic materials need to be added so that they become fertilizers or nutrients for the land. Animal dung is the best organic material for this, so integration with livestock is the best concept for post-mining land reclamation. Biochar with its various advantages also needs to be added to the land. Biochar can be produced from biomass wastes from plantations, agriculture and forestry for this purpose. The use of biochar on a wide scale can also provide income in the form of carbon credits because biochar is applied to the soil as a carbon sink with carbon sequestration.

Bamboo trees as a type of grass plant have fibrous roots. Large bamboo clumps have a large network of fibrous roots as well. The success of bamboo roots is one of the keys to bamboo growth. The use of biochar in bamboo nurseries will also improve the roots of the bamboo seedlings produced. While in bamboo plantations, the use of biochar also has many benefits, especially on post-mining land the results will look more real, such as maintaining moisture, more available nutrients, not acidic soil pH and so on. Biochar is useful for improving soil fertility, so it can be used in nurseries and plantations.

Currently a number of mining companies have carried out land reclamation with these trees, but most of them are still testing and do not yet have a comprehensive concept. Post-mining land reclamation with bamboo in Indonesia is estimated to start in 2010 or has been going on for about 12 years until now. A number of bamboo species have also been identified as suitable for the post-mining area. Scale up or capacity enlargement is an important and current challenge, especially when it is supported by information on 12 years of reclamation with these bamboo trees. With this capacity expansion, besides bamboo production, commercial production can also be achieved, the application of biochar will also find its optimum benefits, namely improving soil fertility and carbon sinks (carbon sequenstration).

The use of bamboo in particular is an aspect that has not received serious attention in these reclamation projects. Whereas only with the use of bamboo which is a plantation product can the reclamation effort be known to provide economic benefits or not. The lack of serious attention to the use of bamboo is thought to be because the bamboo reclamation is still in the experimental stage with a small area. But if it has been pursued professionally, the economic aspect will become an important concern.

The use of bamboo, for example, is to make people's houses around the mine. With bamboo treated first and also using the art of building architecture, the bamboo house produced will be of high quality, in the sense of being sturdy and beautiful and far from being cheap. This will reduce the use of certain wood for houses, some of which have limited types, such as ironwood in Kalimantan. Indeed, there are many ways to use the bamboo, but it is necessary to choose the best one based on the related conditions and situations. Ruminant farming, especially for the production of organic matter or land fertilizers, will also require cages or in rotational grazing, poles for paddock will also be required. The cages and poles can also be made with these bamboo products.

And when bamboo production is used for biomass production and then used for biochar production, it is also technically possible. But economically, it is necessary to study whether it also provides benefits, both from the effect of improving soil fertility and carbon credit. In this case, the most important thing is the production of the biomass itself so that the bamboo species that produce the most biomass are selected. The more soils that can be repaired with biochar treatment, the more land that can be recovered so that it becomes productive land. When the soil is fertile again, various food crops are also very possible to be planted on the land. The increasing population also demands more food needs, so food production needs to be increased, including the use of these recoverable lands.