The production of bio domestic cooling gas (biogas) and organic fertilizers using Palm Oil Mill Effluent (POME) involves several processes and procedures that utilize the organic-rich effluent in a sustainable and eco-friendly manner. Here's an elaborate overview of these processes:

1. Production of Biogas from POME
   Biogas production from POME involves anaerobic digestion, a biological process where microorganisms break down organic matter in the absence of oxygen, producing biogas (mainly methane and carbon dioxide) and digestate (a nutrient-rich slurry).

Process Steps:

1. Pre-treatment:

   • Screening: Removal of large solids and debris from POME using mechanical screens.
   • Balancing: Equalizing flow variations and homogenizing the effluent in a balancing tank.

2. Anaerobic Digestion:

   • Digester Design: POME is fed into anaerobic digesters, which can be of various designs such as covered lagoons, complete-mix reactors, or upflow anaerobic sludge blanket (UASB) reactors.
   • Temperature Control: Maintaining optimal temperature (mesophilic: 30-40°C or thermophilic: 50-60°C) to enhance microbial activity.
   • Retention Time: Ensuring sufficient retention time (typically 15-30 days) for effective digestion of organic matter.

3. Biogas Collection:

   • Gas Capture: Biogas produced is collected through gas-tight covers or domes on the digesters.
   • Gas Storage: Temporary storage of biogas in gas holders before utilization.

4. Biogas Utilization:

   • Cooling Applications: Biogas can be processed (cleaned and dried) and used in absorption chillers or other cooling systems to produce domestic cooling gas.
   • Energy Production: Biogas can also be used for electricity generation or as a cooking fuel.

Key Considerations:

• Safety Measures: Ensuring proper handling and storage to prevent leaks and explosions.
• Quality Control: Regular monitoring of biogas composition and digester performance.

2. Production of Organic Fertilizers from POME
   The digestate resulting from the anaerobic digestion of POME can be further processed to produce high-quality organic fertilizers.

Process Steps:

1. Solid-Liquid Separation:

   • Centrifugation: Using centrifuges to separate the solid and liquid fractions of the digestate.
   • Filtration: Employing filters or belt presses for further separation.

2. Solid Fraction Processing:

   • Composting: Composting the solid fraction either aerobically (using windrows or composting piles) or in-vessel composting systems.
     • Aeration: Providing adequate aeration to promote microbial activity.
     • Temperature Monitoring: Ensuring temperature control to facilitate pathogen reduction and organic matter stabilization.
   • Curing: Allowing the compost to mature and stabilize, improving its nutrient content and soil conditioning properties.

3. Liquid Fraction Processing:

   • Nutrient Recovery: Treating the liquid fraction through biological treatment processes (such as aerobic treatment or constructed wetlands) to reduce nutrient load.
   • Irrigation Use: Using treated liquid fraction for fertigation (irrigation combined with fertilization) in agricultural fields.

4. Final Product Formulation:

   • Blending: Mixing composted solid fraction with other organic materials (such as plant residues or animal manure) to achieve desired nutrient profiles.
   • Granulation: Pelletizing or granulating the organic fertilizer to improve handling and application.
   • Packaging: Packaging the final product for distribution and use.

Key Considerations:

• Pathogen Reduction: Ensuring adequate pathogen reduction during composting to produce safe and hygienic fertilizer.
• Nutrient Management: Balancing nutrient levels to meet specific crop requirements and avoid nutrient runoff.

Integration and Sustainability:
Integrating biogas and organic fertilizer production from POME not only mitigates environmental pollution but also creates valuable by-products. The processes should be designed to optimize resource recovery, minimize waste, and ensure economic viability. Key sustainability practices include:

• Closed-loop Systems: Recycling nutrients and organic matter back into agricultural systems.
• Energy Efficiency: Utilizing biogas for on-site energy needs, reducing reliance on fossil fuels.
• Community Engagement: Involving local communities in the use and benefits of biogas and organic fertilizers.

By implementing these processes, palm oil mills can transform POME from a waste product into valuable resources, contributing to environmental sustainability and economic development.