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.

Why Has Large Capacity Wood Pellet Production from the Calliandra Energy Plantation Not Been Realized?

 

As a tropical country that has the largest land area in Southeast Asia, the potential for fuel or renewable energy from biomass, especially wood pellets, is very potential and promising. To maintain the stability of large capacity production volumes and their continuity, wood pellet production must use raw materials from energy plantations or biomass plantations. Energy plantations from short rotation coppice & fast growing species from legume groups such as red calliandra (Calliandra calothyrsus) have been a concern for quite a long time, but why has this large capacity wood pellet production not yet been realized or has no industry realized it? Below could be two main factors causing this:

1. Quality of calliandra wood pellets

The characteristics of rotational crops and fast growth of the legume group are that they contain quite high levels of potassium and sodium (K+Na) in their wood. Potassium has the property of having a low melting point so it will be problematic for heat exchangers in power plant boilers in general. The high potassium content makes its use unsuitable for power plants in general, namely those that use pulverized combustion (PC). Red calliandra (Calliandra calothyrsus)  in particular is the same, so with a large production capacity, the quality of export-oriented wood pellet products needs to be improved by reducing the content, especially potassium and sodium (K+Na). 

The process of reducing K + Na, which is part of the ash content, is carried out using a leaching / washing process. This unit needs to be added to the wood pellet production process from red calliandra. Apart from making calliandra wood, the raw material for wood pellets, this process becomes wetter, it also produces waste water. This will increase the production costs of red calliandra wood pellets.

Although it is possible that the leaching/washing process was not carried out so that the resulting wood pellets still have a fairly high K + Na content, they still have the potential to be used for certain types of power plants, such as those with fluidized bed and stoker technology. However, this type of power generation technology is not as common as the use of pulverized combustion (PC) technology. So that market acceptance for the production of calliandra wood pellets is large or can be used in all types of power plants, the leaching/washing process should be carried out.

2. Utilization of only certain parts (partial) of the plant, and not comprehensive (whole tree utilization)

When it only use wood for wood pellet production, it means that only part of the plant is used (partial) or there are other parts of the plant that are not used, namely the leaves and flowers. In fact, these two parts of the plant will be able to maximize income or profits which will provide the impetus to accelerate the realization of large capacity wood pellet production from the energy plantation. The additional costs incurred for the leaching/washing process will be compensated by the income/profits from leaf processing and flower utilization.

Calliandra leaves which have a high protein content are processed into animal feed, especially into flour or also pelleted into feed pellets. Meanwhile, the nectar from flowers is used as food for honey bees in beekeeping to produce calliandra honey. By maximizing the potential of all parts of the plant (whole tree utilization) of calliandra, various products (multiple products) are produced so that the driving force to accelerate the realization of large capacity wood pellet production from energy plantations becomes stronger.

One form of gratitude for Allah SWT's blessing in the form of a country with a tropical climate with vast land is to use it in an environmentally sound and sustainable manner. Tropical areas like Indonesia are a "paradise" for biomass production, especially for biomass energy (bioenergy) in the form of wood pellets. Optimizing this potential, especially with large capacity production of wood pellets and additional products, could be a boon and a blessing for prosperity as well as a solution to global climate problems (carbon neutral fuel). And basically business judgment is also needed from the entrepreneur's side so that the entrepreneur has the courage to decide to execute this business opportunity.

EFB Pellets with Low Potassium (K) and Chlorine (Cl) for Power Plants

Palm oil mills that have excess energy, especially electrical energy, will have more freedom to develop their business. The excess electrical energy could have come from the production of electricity from the use of biogas. Liquid waste (pome) from palm oil mills is the raw material for biogas production. A palm oil mill with a production capacity of 30 tons of FFB/hour will be able to generate 1 MW of electricity and so on. One of the products that can be processed from the utilization of palm oil solid waste as well as the development of this business by utilizing excess energy is EFB pellets production. With the high price of palm kernel shells or PKS and wood pellets, the driving force or need for EFB pellets is increasing. Global awareness regarding decarbonization or CO2 removal (CDR) or CO2 reduction is the main driving force.

Apart from that, the production of EFB pellets can also be carried out by a separate company by purchasing the raw materials for EFB from palm oil mills. With conditions in Indonesia where there are still very few palm oil mills that have biogas units so that they have electricity supply and can process EFB into EFB pellets, there is still a lot of EFB that has not been utilized and becomes waste that pollutes the environment. This makes EFB pellet producing companies not have to worry about the supply of EFB raw materials. In fact, because the amount or volume of EFB is very large, the EFB pellet plant will be overwhelmed by the abundance of this raw material.

However, due to the high content of EFB in potassium and chlorine (ash chemistry), the use of EFB pellets is limited or can only be used in certain types of power plants, especially stokers and fluidized beds. In fact, most power plants currently use pulverized combustion technology. This is so that the chemical content of ash in EFB must be made as friendly as possible to boilers, especially those with pulverized combustion technology. This can be done so that the chemical content of the ash in the form of potassium (K) and chlorine (Cl) is only less than 2000 ppm. Potassium (K) with a low melting point causes deposits or scale to form in the heat exchanger pipes in the boiler so that the efficiency of heat exchange decreases while chlorine (Cl) is corrosive which shortens the life of the equipment. The treatment was even successful in reducing K and Cl by up to 80% so that the problem of fouling thickness and corrosivity was also reduced by 80%. With the number of palm oil mills in Indonesia reaching around 1000 units, of course the amount of EFB that can be processed into EFB pellets is also very large.

Potassium and Chlorine, 2 Elements Need More Attention at Wood Pellet

Most of the current power plants use pulverized combustion technology which operates at temperatures greater than 1400 C. The high operating temperature makes the requirements for the fuel used quite tight, meaning that not all fuels can be received immediately. The standard power plant fuel is designed using coal, so that when using biomass fuels it might be necessary to modify it. In the ratio of small cofiring, for example, 5% of the power plant is likely to operate on a standard basis without modification. The big question is why the pulverized combustion technology power plant whose capacity can be hundreds or even thousands of MW can not directly use biomass up to 100% without obstacles? That's what we will try to review in the article below.

The main difference between biomass fuel and coal in terms of the power plant is the chemical ashes. The chemistry of coal ash is composed of inorganic materials which have very high melting points and tend not to be corrosive to metals at high temperatures. This makes technically coal fuel more friendly to pulverized combustion technology. Although reviewed environmentally, coal fuel is not friendly because there are many fly ash, ash waste is classified as hazard material / B3 and SOx emissions cause acid rain. While a review of climate change and global warming, it is clear that coal is a fossil fuel and is a carbon positive that increases the concentration of CO2 which is a greenhouse gas in the atmosphere. Many countries now reduce their use of coal in their policies.

While biomass fuels have a chemical content of ash consisting of inorganic materials that have low melting points and tend to be corrosive so that it becomes an obstacle to the pulverized combustion technology. Potassium is one of the chemical elements of ash in biomass which is in the spotlight, this is because potassium has a low melting point and in a large amount of biomass. The melted potassium ash will cover and be deposited on the heat exchanger pipes in the generator boiler. These deposits make heat transfer efficiency decrease so that fuel consumption will increase. This is indicated by the increased chimney temperature which means that there is a large heat loss.

Another element that is the main highlight besides potassium is chlorine. This chlorine is corrosive and is like a ghost for the pulverized combustion power plant. Corrosive properties will shorten the life span or operating life of the power plant, for example with high chlorine content in the fuel, making the operating life of the power plant to be half or a quarter of what it should be. Of course this is very detrimental, for more details can be read here. In addition to the two things above which are considered unfavorable from the use of biomass fuels, but along with the problem of environmental damage in the form of climate change and global warming, biomass fuels are the solution to the problem. This is because biomass fuels are renewable, sustainable, carbon neutral and various other environmental benefits.

The most popular biomass fuel today is wood pellets. When it turned out that wood pellet which is a biomass fuel containing potassium and high chlorine, it became less desirable and was even rejected by the pulverized combustion power plant. Wood pellet producers must pay attention to this issue if the market segment is electricity generation. Ensuring wood pellet products with chlorine and potassium content according to technical requirements are mandatory for these producers. When wood pellets have been produced but the specifications cannot meet the requirements, it is necessary to change the market or improve the quality of the wood pellets.

Basically to overcome the content of chlorine and potassium it can be in two ways, namely from the production side of wood pellets and from the user side. Wood pellet producers can choose raw materials that can meet the specifications requested or even do a number of treatments so that the specifications can be achieved. Whereas from the user side, that is by using electricity generation technology with lower operating temperatures so that the problem of potassium and chlorine can be reduced and even eliminated. The technology of electricity generation with fluidized beds and gasification can be a solution to this.