Ash Content and Quality of Premium Grade Wood Pellets

Compared to industrial wood pellets, which have looser specifications, particularly regarding ash content, which can reach 6%, premium-grade wood pellets, for use in space heating, have stricter specifications, specifically a maximum ash content of 1%. Premium-grade wood pellets generally have a diameter of 6 mm, while industrial pellets are generally 8 mm. The color or appearance of premium-grade wood pellets also plays a role, with brighter colors generally preferred. This is why premium-grade wood pellets are naturally more expensive. Demand for premium-grade wood pellets increases during the winter due to the increased need for space heating.

Regarding ash content, several standards even stipulate ash content lower than 1%, such as DIN Plus with a maximum of 0.5%, ENPlus-A1 with a maximum of 0.7%, and Ö NORM M7135 which requires a maximum of 0.5%. This is why strict control of raw material selection and treatment is applied in the production of wood pellets to meet these specifications. Although the ash chemistry for premium grade wood pellets may not be as stringent as for industrial pellets because the application operation is at lower temperatures, the production of wood pellets with very low ash content requires high-quality raw materials.

In premium grade wood pellets, even a slight difference in ash content can significantly impact the selling price. For example, wood pellets with a maximum ash content of 0.55% can differ by around USD 30 per ton compared to wood pellets with a maximum ash content of 0.35%. Because they are used for space heating, premium grade wood pellets are generally packaged in small plastic bags, such as 15 kg, while ordinary industrial pellets are packaged in jumbo bags or even bulk due to the much larger volume requirements.
 

Problems of Wood Harvesting from Calliandra Energy Plantation and High Potassium Content in Wood Pellet Ash: Two Things That Need Attention

The factor of production efficiency and standard and stable product quality is the mindset of the industry, including for the wood pellet industry from the calliandra energy plantation. Manual wood harvesting operations make production efficiency low. The high daily need for wood pellet raw materials from energy plantations requires mechanization equipments for harvesting the calliandra plantation. Meanwhile, calliandra wood pellet products with high ash content containing potassium also require certain treatments so that the wood pellet products meet the standards for power plants in general. The stability of production quality and quantity is closely related to the quality of the production equipment used. These two things must be an important concern for wood pellet producers from calliandra energy plantations with large capacity and export orientation.

The wood pellet industry from the calliandra energy plantation is new, so there are not many references. The history or the origin of this industry comes from the project of the Ministry of Forestry of the Republic of Indonesia at that time which created an incubator-scale industry as a pilot for the production of wood pellets from the calliandra energy plantation located around Geger Hill, Bangkalan, Madura, East Java about 12 years ago. At that time, there were actually several wood pellet industries operating, but all of these wood pellet factories or industries used raw materials from wood industry waste, such as sawmill industry waste, barecore industry waste, plywood industry waste and so on.

Calliandra trees are also not new plants to the public. This tree has been widely planted but previously with different purposes, namely for reforestation, for animal feed or for honey bee farming. While for bioenergy purposes or wood pellet production, planting calliandra trees in the form of energy plantations is something new. That is why in the early stages, calliandra wood harvesting was still done manually and this was ineffective and inefficient on large-capacity plantations. In addition, the wood pellet product has not been analyzed or examined completely / comprehensively so that the high potassium content (ash chemistry) in the ash has not been detected. When the requirements for the maximum content of potassium / potassium must be met, special treatment needs to be done.

In addition, an important thing to note is the target types of products produced. If the calliandra plantation not only produces wood as raw material for wood pellet products, but also processes leaves for animal feed, then the harvesting mechanism is very influential. The leaves from the calliandra plantation must also be harvested effectively and efficiently or the same as the wood products. This could be, for example, the trees and leaves are harvested together and then taken to a place and separated to be processed individually. Or it could be that the wood and leaf products have been separated at the time of harvesting, then each goes to its respective processing unit. The equipment used must also be different according to the choice of the harvesting mechanism. Meanwhile, honey products from bee farms that utilize calliandra nectar are not affected by this mechanism, this is a separate honey production process and is related to the flowering season of the calliandra tree itself.

Along with the global decarbonization trend, the prospects for calliandra plantations are increasingly bright. It is predicted that many calliandra plantations will be created, which are intended primarily for bioenergy production such as wood pellet production, and this is in line with the carbon neutral scenario that supports the net zero emission program. The use of wood pellets is mainly for fuel in coal-fired power plants through the cofiring mechanism. In the next stage, it is possible to use 100% of the power plant fuel using wood pellets (fulfiring). The high potassium content is generally a problem in applications for this power plant, although there are types of power plants that technically do not have a problem with the potassium content, but the production of wood pellets from calliandra with low potassium content is certainly preferred.

Charcoal Production for Activated Carbon Raw Material

Charcoal characteristics are influenced by the raw materials used and the conditions of the production process. The use of charcoal for certain applications or industries also requires certain specifications or characteristics. For example, charcoal used for fuel can have different specification requirements from charcoal specifications for agriculture (biochar), or charcoal used as raw material for activated carbon. A number of parameters that are acceptable in certain applications may not be acceptable in other applications.

Charcoal products used as raw materials for activated carbon production are also the same. Parameters in the form of high fixed carbon (~80%), high hardness, low ash content (~3%) and low volatile matter (<10%) are prerequisites for the specifications or quality of charcoal as a raw material for activated carbon. As a comparison, charcoal for agriculture (soil amendment) or commonly called biochar has a wide range of quality or specifications, namely lower fixed carbon (FC), higher ash content and higher volatile matter, especially in agro type biochar according to WBC (World Biochar Certificate), while premium type biochar according to WBC has a higher or highest quality and can be used for various purposes. While the material type biochar according to WBC has the lowest quality with use mainly in certain industries such as cement, asphalt, plastic, electronics, and composite materials or cannot be used for agriculture, soil applications and consumer products.

 Raw materials for charcoal production for activated carbon production because it requires stricter parameters, especially high fixed carbon, low ash content and high hardness so that raw materials suitable for this purpose are more limited or not all biomass can be used for charcoal production for activated carbon raw materials. This is what makes coconut shells the best and most popular raw material for charcoal production as activated carbon raw materials today. And palm kernel shell raw materials (especially from dura variety) are expected to be the next candidate. The availability of abundant palm kernel shells (PKS) is a special attraction. But indeed with this palm kernel shell (PKS) charcoal raw material, there is still the smell of palm oil, so it is a challenge for activated carbon producers.

Biomass Pellets in India

India has hundreds of millions of biomass waste, especially from agricultural wastes or about 230 million tons per year. Hundreds of millions of tons of biomass waste is of course an environmental problem, especially because most of the waste is simply burned in fields where the smoke pollutes the environment, but on the other hand it will be a solution, namely for decarbonization programs and climate change. Technically, the biomass waste from agricultural waste will be processed into fuel pellets (biomass pellets) which are used for fuel in power plants by cofiring. In the early stages, the Indian government targeted 5% for the cofiring ratio in their coal power plants, where the 5% figure when translated into biomass pellet production would reach around 50 million tons of biomass pellets per year. This is a very large amount, especially with a short time target, which is only one year since it was ordered on October 8, 2021 and will take effect in October 2022 or this year, so hard efforts are needed to achieve this target. Meanwhile, in 2021, the world's demand for wood pellets for power plants will only be around 23 million tons.

The establishment of factories for the production of biomass pellets must be carried out immediately to achieve the production target. These factories must also be supported by logistical readiness to supply raw materials so that the factory can be completed, so that the production of biomass pellets can be carried out as soon as possible. With an average power generation capacity of 275 MW in India, with a cofiring ratio of 5%, the annual need for biomass pellets is estimated at 50 thousand tons or 170 tons per day. With the number of power plants reaching around 900 units with an average consumption of 50 thousand tons of biomass pellets per year or a total of almost 50 million tons per year, the distribution of biomass pellets is also a challenge. A factory with a capacity of around 5 thousand tons/month is likely to be suitable, and even if each factory supplies one power plant, the need for a biomass pellet factories will also be the same as the number of power plants, which is 900 units. A huge amount.

Biomass pellets or agri-waste pellets, namely pellets from agricultural wastes do have a number of differences with wood pellets. Wood itself is also a part of biomass so it can also be called biomass pellet. Biomass has a wider range, including wood pellets and agri-waste pellets. Agri-waste pellets have higher ash content, and some have higher chlorine, potassium and silica content in the ash. The content of these substances is not friendly to the heat exchanger pipes in the boiler which will cause fouling and corrosiveness, so that in addition to decreasing boiler efficiency, the service life of the boiler is shortened. In addition, the harvest of agricultural products usually coincides at certain times, while the pellet factory must continue to produce every day. This is why it is necessary to store and allocate raw materials in the form of agricultural waste for the routine production of these pellets. And because these agricultural wastes cannot be left alone in the agricultural area, they need additional investment in the form of storage warehouses and to be able to store more agricultural waste they need to be temporarily compacted by baling. These things usually don't happen in wood pellet production, so the agri-waste pellet production approach is different.

And because the ash chemistry of agricultural wastes causes many problems in the operation of power plants, their use is also limited. With a cofiring ratio of 5%, the problem can still be tolerated, but when the ratio is enlarged, the impact will be more pronounced. The exception is the CFB (circulating fluidized bed) type plant which can use 100% of the agricultural waste pellets, but in India the power plants using CFB technology are very small, around 1% (9-10 units). Indonesia and Malaysia also produce biomass fuel that is almost similar to pellets and even in the international market is the pellet competitor, namely palm kernel shells or PKS. The volume of PKS also reaches millions of tons, so it can be exported to India to help meet India's needs for biomass pellets, which so far have been mainly for export to Korea and Japan. PKS is also produced by a number of countries in West Africa. But it seems that the Indian government for now will prioritize the use of their agricultural waste first, so it has not provided financial support for the import of the biomass fuel.

Currently, India must make every effort to accelerate the construction of biomass pellet factories to achieve this target. However, 1 year to achieve this target is very difficult. With these conditions in the future, it is possible that power plants in India will import biomass fuels such as wood pellets and PKS to meet their needs. With the currently planned cofiring ratio of 5%, the need for biomass pellets reaches around 50 million tons, if only 2% of the biomass fuel needs are imported, both PKS and/or wood pellets, it will reach 1 million tons, the amount is still very big.

Production of LOF and EFB Pellets at The Same Time

The leaching process for palm oil empty fruit bunches (EFB) so that it has potassium and chlorine content suitable for EFB pelletproduction on a commercial scale that can be used maximally on a pulverized combustion (PC) boiler at a power plant is not easy and inexpensive. That is because the leaching process requires a solvent to extract the potassium and chlorine content from the EFB material. Ideally the leaching process is carried out with acid solvents, agitation and heat and a long time so the extraction process can run optimally. In fact this is the bottle neck to carry out the leaching process, so that almost no one has done this process commercially today. It is different if the leaching process also has other objectives that also have commercial value, for example for the production of liquid organic fertilizer (LOF).

By simultaneously producing LOF, the costs for leaching can be compensated with the benefits of the LOF. In CPO business operations, especially in palm oil plantations the cost of fertilizer is one of the highest cost components, estimated at 35.75 billion rupiahs (around 2.5 million USD) per year for every 10,000 hectares. If the cost of the fertilizer can be saved from the use of self-produced LOF as well as pellet EFB production, then this is one of the optimization of biomass utilization in the palm oil industry. LOF will have the main content in the form of potassium because the potassium content is quite high at EFB about 30% of the ash produced is potassium. Potassium fertilizer is very beneficial for plants because it is an essential nutrient with benefits including transporting sugar, controlling stomata in leaves by maintaining electro-neutrality in plant cells, co-factor of more than 40 enzymes and reducing the occurrence of various diseases. Some plantations also need large amounts of potassium fertilizer, for example banana plantations. The process of making LOF by soaking EFB for several days is expected to significantly reduce the potassium and chlorine content in EFB and make it a material for pellets that are friendly to the PC boiler power plant.

The EFB pellets produced can then be sold for export as well as meeting domestic needs. With EFB pellet production as well as LOF, it is hoped that export bioenergy will not damage or reduce the fertility of the existing soil, something that is sometimes indeed dilemmatic. In addition, other materials in the plantation such as leaves and frond can still be composted if they are also intended as fertilizer. EFB pellet production also always requires energy in the form of electricity for its plant operations. And for that electricity can be produced from biogas by treating the palm oil mill effluent (POME), for more details, read here. The location of palm oil mills which are generally remote are required to be able to produce their own electricity, including if they are going to process EFB into LOF and EFB pellets, the electricity needs should also be fulfilled by themselves.

EFB pellets without leaching process actually can also be used for FBC (fluidized bed combustion) boiler technology and for a limited number percentage of PC boilers. With this leaching process EFB pellets can be used optimally on the PC boiler. Majority of power plants or coal power plants currently use PC boiler technology. So that if the EFB pellet produced can be friendly with a PC boiler the market is more open automatically. Production of EFB pellets which are agricultural waste pellets will usually be the second priority after the production of wood pellets is constrained mainly in terms of the availability and supply of raw materials.