Stages in the Utilization of Empty Fruit Bunches at Indonesian Palm Oil Mills

In addition to palm kernel shells (PKS) and mesocarp fiber, another solid biomass waste product available in large quantities at palm oil mills is the empty fruit bunch (EFB). EFB represents the largest volume of biomass waste generated by these mills. Mesocarp fiber, along with a portion of the palm kernel shells (PKS), is typically consumed as fuel for boilers. In fact, the volume of EFB produced exceeds that of the mill's primary product, crude palm oil (CPO). Despite this, EFB—which accounts for approximately 20% of the fresh fruit bunch (FFB) weight—remains largely unutilized. Given its substantial volume, it also poses a significant potential for environmental pollution. 

Many mills are striving to achieve a "zero waste" status, which necessitates the processing of empty fruit bunches (EFB). However, the challenges lie in determining the appropriate processing methods, the resulting products, and the overall economic viability. Ideally, this waste should not only cease to be an environmental pollutant but also generate additional profit—ideally, by produce products that maximize returns. A realistic approach, therefore, involves processing EFB in a way that prevents environmental pollution while minimizing the capital investment required for the necessary processing equipment. These factors are critical considerations, grounded in both current realities and future developments.

Empty Fruit Bunches (EFB) have significant potential for use in various bioenergy and biochar products. Through a process of biomass densification, EFB can be converted into pellets, which—much like palm kernel shells (PKS)—can be utilized within the energy sector. Given the massive volume of EFB available, the potential for EFB pellet production is substantial. EFB pellets are expected to emerge as a future trend, following in the footsteps of palm kernel shells (PKS), primarily due to their abundant availability and the fact that the vast majority remains unutilized. When compared to other potential raw materials for pellets—such as wood waste from forestry or the wood working industry—the volume of EFB is highly competitive, if not greater. Furthermore, unlike wood pellets derived from energy plantation (which require the cultivation of species such as calliandra or gliricidia), the production route for EFB pellets is significantly faster.

Another use for EFB (Empty Fruit Bunches) is the production of biochar. Biochar can serve as a soil amendment in the agricultural sector—specifically within oil palm plantations, whether company-owned or managed by smallholders. The application of biochar enhances nutrient use efficiency (NUE) by effectively turning fertilizers into slow-release products. Furthermore, biochar producers can generate revenue through carbon credits by adhering to methodologies established by recognized carbon standards, such as Puro, Verra, or Isometric. Industrial-scale slow pyrolysis equipment used for biochar production also generates excess energy—such as syngas—which can be utilized as fuel for palm oil mill boilers (via co-firing) or for other applications.

Currently, many palm oil mills utilize empty fruit bunches (EFB) by burning them in simple incinerators (as shown in the photo), which yields EFB ash—a substance rich in potassium that can be used as fertilizer. However, these simple incinerators not only generate smoke pollution but also fail to harness the heat produced during combustion. Upgrading to more efficient incineration systems—such as those employing reciprocating grate combustors—and incorporating pollution control equipment, like water scrubbers, would render the utilization of EFB environmentally friendly. Furthermore, the heat generated from combustion (waste heat recovery) can be harnessed for various purposes, including cogeneration with palm oil mill boilers, electricity generation, or other applications. 

Processing of Empty Palm Fruit Bunches (EFB) for Ash Production as Potassium Fertilizer and Energy

Palm oil mills produce a large amount of biomass waste, and one of the largest in their daily operations is empty fruit bunches (EFB). Comprising approximately 22% of the fresh fruit bunches (FFB) processed by the mill, the volume becomes enormous and piles up daily if not managed properly. For example, a palm oil mill with a capacity of processing 60 tons of FFB per hour for 20 hours per day produces 264 tons of empty fruit bunch waste per day (approximately 6,600 tons per month and 79,200 tons per year). This enormous amount would resemble a hill if piled up in one place.

Incinerators have recently become popular, particularly in Indonesia, for processing empty fruit bunches due to their speed and practicality. Furthermore, the ash produced by burning them can be used as fertilizer due to their high potassium content. However, these incinerators produce exhaust emissions that pollute the environment, including black smoke and particulate matter. These emissions, which pollute the environment and exceed the threshold permitted by the Ministry of Environment (KLH), have led to the prohibition of incinerators. This ban has led to an increasing number of unmanaged empty fruit bunches. Using empty fruit bunches for mulch is also less effective, and composting, a biological process, takes a long time.

Video link for conventional EFB incinerator here

This problem demands an immediate and effective solution. The quickest practical solution is to upgrade the incinerator to make it environmentally friendly or to reduce emissions below the required threshold. This can be achieved by using adequate emission control devices to meet these environmental requirements. While many emission control devices are available, cost and target output are crucial considerations when selecting them. This approach not only addresses the problem of empty fruit bunches, but the resulting ash can also be used as a potassium fertilizer.

Furthermore, by upgrading the incinerator with emission controls (basic type), the equipment can be developed into several types, as follows: the second type is a cogeneration boiler for palm oil mills, allowing 100% palm kernel shell (PKS) to be sold, even for export. The third type is by adding a new boiler and steam turbine for electricity production, which is then sold to PLN (Indonesia State Owned Electricity Company) under a power purchase agreement (PPA). The fourth type is equipped with waste heat recovery equipment, allowing for more general use. This also means the combustion process in the upgraded incinerator can also be upgraded so that the combustion process can run optimally. Several combustion technologies, such as chain grates, step grates, or reciprocating grates, can be considered to achieve maximum performance, including the removal and handling of ash product.

Empty fruit bunches (EFB) processing can vary, although the primary focus is addressing environmental pollution caused by them. However, their large volumes certainly represent a potential raw material for processing units. Therefore, in addition to addressing this waste, the technology used must also provide financial benefits. Of the numerous EFB processing technology options, the cost-to-benefit ratio of a technology application will be a crucial consideration for EFB processing.

In addition to combustion using conventional or this upgraded incinerator, thermal processing routes also include pyrolysis, with slow pyrolysis specifically for biochar production and fast pyrolysis for bio-oil production. Another pyrolysis variant is mild pyrolysis or torrefaction for the production of torrified biomass. Then there's gasification to maximize gas (syngas) production from biomass. Furthermore, empty fruit bunches of palm oil can be used as fuel or an energy source. To facilitate handling, storage, and reduce transportation costs, empty fruit bunches need to undergo biomass densification technology, with the final product being pellets or briquettes.