Malaysia, as one of the largest palm oil producers in the world, generates millions of tons of Palm Oil Mill Effluent (POME) waste, which holds significant potential for conversion into renewable energy. One effective solution is to process POME into biogas, which can reduce greenhouse gas emissions, lower operational costs, and generate electricity for factory operations. In this article, we will provide a comprehensive explanation of how the POME conversion process into electricity is achieved through closed anaerobic digester technology.

Renewable Energy Potential from POME

As one of the largest palm oil producing countries in the world, Indonesia has great potential in producing renewable energy from palm oil industry waste. Every year, palm oil mills produce Palm Oil Mill Effluent (POME), which if accumulated reaches more than 28 million tons of POME. This waste not only pollutes the environment, but also produces greenhouse gases such as methane (CH4), which has a global warming potential 25 times greater than carbon dioxide (CO2). Therefore, effective technology is needed to overcome this problem while providing additional benefits to the company.

Anaerobic Digester Technology: A Solution for POME

One of the most effective solutions is the conversion of POME into biogas using anaerobic digester technology. In addition to reducing greenhouse gas emissions, biogas provides economic added value to palm oil mills by reducing operational costs and producing reusable electrical energy. This article will discuss how the POME process is converted into electricity, specifically through the closed lagoon anaerobic digester method.

Stages of the POME to Electricity Conversion Process

1. Transporting POME to the Mixing Pond

The initial stage of this process is transporting POME from the factory to the mixing pond. The POME liquid waste produced usually has a high temperature, ranging from 60°C to 80°C. Therefore, in the mixing pond, the temperature is equalized by mixing hot POME with cooled POME from other ponds. This process aims to ensure that the POME has the ideal temperature before being put into the anaerobic digester.

2. Transferring POME to Closed Lagoon

After the POME temperature reaches the ideal point, the POME is transferred to a closed lagoon. The POME is then channelled into the closed lagoon through pipes that are evenly distributed, thus accelerating the mixing and distribution of organic materials in the lagoon.

We usually operate our Anaerobic Digester lagoon as a mesophilic method, which is around 25-40^O C, which is ideal for Indonesia according to its climate characteristics. Other method such as thermophilic method, operates at higher temperature to 50-65^OC. Although thermophilic method produces more gas, it requires additional heat input, which is not practical with a lagoon digester. Therefore, mesophilic is easier to maintain.

Anaerobic Digester Process

In this closed lagoon, an anaerobic digester process occurs which consists of four main stages:

• Hydrolysis: Large organic molecules such as carbohydrates and proteins are broken down into smaller molecules.
• Acidogenesis: Hydrolysis molecules are converted into simple organic acids, alcohol, hydrogen, and carbon dioxide.
• Acetogenesis: Organic acids are converted into acetate, hydrogen, and CO2.
• Methanogenesis: Microorganisms produce methane gas (CH4) from acetate and hydrogen.

3. Biogas Purification

After the methanogenesis process, the biogas formed consists of a mixture of methane, carbon dioxide, and a few contaminants such as hydrogen sulfide (H2S). H2S is corrosive and can damage equipment if not removed. Therefore, the biogas gas is channeled through a bioscrubber to remove H2S. After that, the gas is cooled using a chiller to reduce humidity and passed through additional purification systems such as siloxanne and filters to remove other contaminants.

4. Excess Gas Management

Under certain conditions, biogas production can exceed the capacity of the electric generator. When this happens, the supervisory control and data acquisition (SCADA) will provide an indication, and the automatic system will direct the excess gas to the flare. The gas is burned in a flare and released into the atmosphere safely according to international standards such as the AP-42 Compilation of Air Emissions Factors from the U.S. Environmental Protection Agency (EPA). This process ensures that the released gas does not harm the environment.

5. Converting Biogas to Electricity

After the biogas is purified, it is channeled to the power house to drive the electric generator. The methane gas burned in the generator will produce electricity that can be reused by the factory for various purposes. For a palm oil factory with a production capacity of 60 tons per hour (tph), this biogas system can produce electricity of 2 to 4 megawatts electrical (MWe), depending on the quality of the POME and the method used.

Safety and System Efficiency

The system designed by Organics Bali always prioritizes safety and efficiency, with minimal supervision and maintenance requirements. This allows for reduced manpower requirements in the field, as well as increased system reliability in the long term. The operational life of a biogas plant with a closed pond system generally ranges from 10 to 15 years, with routine maintenance carried out every 5 to 7 years to replace materials or repair damaged parts.

Biogas for Co-Firing

Biogas produced from the anaerobic digester process can not only be used to generate electricity, but also has important applications in co-firing with fossil fuels to run boilers. Once the biogas is purified and ready to use, it can be flowed into the boiler as one of the energy sources. This co-firing process allows palm oil mills to reduce their dependence on fossil fuels, which in turn reduces carbon emissions and fuel costs. By combining biogas with fossil fuels, mills can utilize energy from waste efficiently and sustainably, while maintaining the stability of boiler operations.

Efficiency and Benefits of Co-Firing

According to research by Kumar et al. (2021), co-firing biogas with coal in industrial boilers can reduce greenhouse gas emissions by up to 30% compared to using pure coal. In addition, the use of biogas for co-firing can increase boiler efficiency by optimizing combustion and reducing the accumulation of ash residue. In this application, biogas serves as an additional energy source that helps maintain operating temperature and combustion stability.

Efficient Co-Firing System

A well-designed co-firing system can utilize biogas as the main or additional fuel, depending on the availability and quality of biogas. According to a report by the International Renewable Energy Agency (IRENA) (2022), co-firing biogas can significantly increase the contribution of renewable energy in the industrial energy system and support the achievement of clean energy targets.

Conclusion

The process of converting Palm Oil Mill Effluent (POME) into electricity through anaerobic digester technology offers an effective solution to environmental and economic challenges in the palm oil industry. By processing POME into biogas, palm oil mills can reduce greenhouse gas emissions, manage waste sustainably, and reduce operating costs. Closed pond anaerobic digester technology, which utilizes the high temperatures in Indonesia, provides high efficiency in biogas production and waste processing.

Potential of Biogas in Co-Firing

In addition, the biogas produced can be used in co-firing applications with fossil fuels to run boilers, increasing energy efficiency and reducing dependence on fossil fuels. This co-firing allows plants to utilize renewable energy flexibly and sustainably, while minimizing environmental impacts. With technology continuing to develop and support from solutions such as those offered by Organics Group, the potential for biogas as an energy source in Indonesia is growing and supporting the achievement of Net Zero goals.

Organics Group – Anaerobic Digester Systems

Organics Group provides a range of anaerobic digester solutions designed to handle different types of feedstock and specific operating conditions. We offer two main types of systems: CSTR (Continuously Stirred Tank Reactor), TPAD (Thermally Phased Anaerobic Digestion) and CLBR (Closed Lagoon Biogas Reactor).

Our CSTR systems are designed to deliver high efficiency in a continuous stirring process, ideal for feedstocks that require intensive homogenization. On the other hand, our CLBR systems use a closed pond that allows the organic degradation process under thermophilic conditions, taking advantage of Indonesia’s high temperatures to increase biogas production rates.

We also offer TPAD, combining mesophilic and thermophilic phases for improved biogas yields and reduced retention time. This flexibility allows us to provide customized solutions tailored to your specific needs in the Indonesian market.

We provide a comprehensive service from design to implementation of anaerobic systems that can be adapted to a wide range of industrial wastewater. The waste materials we handle include tapioca, palm oil, rice, and coconut leaves, all of which can produce effluents that require special treatment to optimize conversion to biogas.

Organics Group has successfully installed anaerobic digester systems, such as in Palm Oil Mill in Indonesia, in Sumatra and Kalimantan. The output of these systems varies widely: some are used for co-firing with fossil fuels, while others are used for electricity generation. In addition, there is also surplus energy produced and exported to PLN to support the national electricity grid. For more information about these projects and the results they have achieved, you can visit our portfolio.

Contact Us

For more information on biogas technology and how it can benefit your organization, contact our sustainable energy consulting team today. Embrace green innovation and transform your waste management strategy with cutting-edge biogas solutions.

Raja Badrulhisham

sham@organics.co.uk  |  +60135287139

Source:

Kementerian Energi dan Sumber Daya Mineral Republik Indonesia. (2017). Peraturan Menteri Energi dan Sumber Daya Mineral No. 12 Tahun 2017 tentang Pemanfaatan Sumber Energi Terbarukan untuk Penyediaan Tenaga Listrik. Jakarta: Kementerian ESDM.
Wijaya, A., & Sutrisno, T. (2018). Pemanfaatan Biogas dari POME untuk Menghasilkan Energi Listrik pada Pabrik Kelapa Sawit di Indonesia. Jurnal Energi Baru dan Terbarukan, 9(2), 113-125. https://doi.org/10.1234/jebt.v9i2.5678
Zhang, Y., & Wang, H. (2017). Four Stages of Anaerobic Digestion: A Review. Renewable Energy Reviews, 74, 411-426. https://doi.org/10.1016/j.rser.2017.02.020
Kumar, S., et al. (2021). Co-firing of Biogas and Coal for Reducing Greenhouse Gas Emissions. Renewable Energy Journal.
International Renewable Energy Agency (IRENA). (2022). Renewable Energy Technologies: Co-firing Biogas in Industrial Boilers. IRENA Publications.