Indonesia National Standard (SNI) of Biomass Pellet and Energy Plantation

Indonesia National Standard (SNI) for Indonesian biomass pellet products has been out and officially used since the end of 2020 or last year. The main objective of implementing SNI for biomass pellets is to respond to the cofiring program at PLN's (state owned electricity company) coal power plants. With this cofiring program, renewable fuels, especially biomass pellets, are used as the main fuel mixture, namely coal. The ratio of the use of renewable fuels in the form of biomass is still small, namely around 1-5% or the equivalent of 9-12 million tons / year of biomass fuel. The total coal power plants as a cofiring target is 114 units spread across 52 locations with a total capacity of 18,154 MW with the target to be completed in 2024. Almost all of the biomass pellets in Indonesia today are wood pellets, all of which also use wastes. sawmills or wood processing industries. In other terms, if you refer to wood pellets, then it must be biomass pellets, whereas if you refer to the term biomass pellets, this is not necessarily wood pellets, but it could be pellets from agricultural wastes (agro-waste pellets). Agricultural wastes which are abundant in Indonesia are also potential as raw material for biomass pellets such as rice husks, empty fruit bunches of palm oil, coconut husk and so on. Below is the table for the SNI biomass pellets:

 

Energy plantations can be a source of woody biomass specifically designed for energy production or specifically for raw materials for the production of biomass pellets or wood pellets. With energy plantations, large production capacities and guaranteed good supply can be achieved. The production of wood pellets from energy plantations takes longer because it needs to prepare and make the energy plantations and wait several years for the wood to be ready to harvest and be processed further into wood pellets. Calliandra and gliricidia are two species of fast rotation and coppice which have been chosen because of their superiority. Another thing that is very important to note is the high heating value and high productivity of wood per hectare. But there is a slight drawback of this type of wood is the content of potassium in ash which is quite high. This makes its use more limited, especially power plants with pulverized combustion (PC) technology.

 

Based on an experiment conducted with calliandra wood from the slopes of Merapi mountain, Central Java; Bangkalan, Madura and Aceh, Sumatera have an average potassium content of above 1000 ppm (0.1%). Indeed, the characteristics of fast-rotating crops tend to produce wood with higher levels of potassium. Meanwhile, from fruit plants, banana trees also have a high potassium content. This potassium has a low melting point and causes fouling in the heat exchanger pipes, thereby reducing the efficiency of the power plant. While chlorine compounds are other compounds that also need attention because they are corrosive at high temperatures, for more details, please read here. And in general, there are significant differences in ash chemistry between biomass and coal. But with a cofiring ratio of 1-5%, power plants generally do not modify their equipment or more specifically on PCs that are most sensitive to ash chemistry problems, because the cofiring percentage is still low.

 

With an average level above 1,000 ppm (0.1%) and still far from 50,000 ppm (5%), there is no problem for wood from energy plantations to be produced into wood pellets and supply to the coal power plants in Indonesia according to SNI the. But if it is exported to foreign countries, especially Japan and Korea, the circulating fluidized bed (CFB) and stoker type power plants are the best market share and the PC type is more limited. With the vast land available and Indonesia's tropical climate, it must further promote energy plantations both to meet domestic needs and to export markets. The energy plantation program also indirectly encourages the ruminant livestock sector, because the leaves can be used as animal feed. 

PKS for FBC Powerplant Part 2

Between the two variants of fluidized bed combustion (FBC) technology, the type of CFBC (circulating fluidized bed combustion) is more widely used for power generation than BFBC (bubbling fluidized bed combustion). That is because the level of efficiency is higher, the use of large capacity and the amount of flue gas produced is less. Stoichiometric air requirements for CFBC (1.1 - 1.2) are less than BFBC (1.2 - 1.3), this also results in less flue gas produced at CFBC compared to BFBC. The main difference between CFBC and BFBC is that there is a circulation of the use of bed material in CFBC and CFBC using air velocity greater than BFBC.

The fuel used for CFBC has a smaller particle size compared to BFBC so it will require higher preparation / pretreatment costs. This is one of the drawbacks of CFBC. The usual preparation is foreign material control and size reduction. Fuels used like coal must be cleaned of a number of impurities such as metals. Magnetic separator is a equipment commonly used to separate the impurities of these metals. The metals that pollute the coal apart from damaging the screen on the crusher (if using a hammer mill type crusher) it is also possible to cover the perforated plate at the bottom of the fluidized bed furnace. The closure of these pores causes disruption of air circulation which will certainly affect the output of the unit.

PKS or palm kernel shell is a biomass fuel that are widely available in Indonesia and have characteristics close to wood pellets. The PKS can be used for CFBC fuel both for cofiring and fullfiring (100% PKS). Regarding the preparation or pre-treatment of fuel before it is fed or used in CFBC, it also needs to be done for PKS. PKS measuring 2-5 cm need to be cleaned from a number of impurities and size reduction before use. In cofiring, when equipments for coal preparation can also be used for PKS, it means no new line is needed for that. But if it can't, a new line needs to be made. Some power plants in Japan even use 100% PKS as fuel with the CFBC technology and especially in the framework of environmental and climate change solutions supported by the government.

CFBC biomass power plants in Japan with 49 MW capacity
which has been operating since 2015 with PKS

The use of fluidized bed combustion (FBC) technology has actually been carried out since the 1960s, which at that time was mainly used to treat municipal and industrial waste. At present it is estimated that more than 300 FBC units are installed and operating throughout the world. PKS as palm oil mill solid waste (CPO mill) is available in abundance in Indonesia which is estimated to reach more than 10 million tons / year and in Malaysia is estimated to be more than 5 million tons / year. This is so that the use of PKS on FBC is very possible because the volume and availability is sufficient. Economic factors are especially limiting the use of the PKS, although in terms of the environment and climate change, it is strongly supported. The location of the palm oil mills which is in the middle of the plantation commonly in very remote locations also makes logistical costs expensive so it affects the selling price of the PKS.