Digester Biogas from Cassava Mill Effluent

PT Cipta Agung Manis (CAM)

Kendari, Southeast Sulawesi

April 2015 – 2016

PT Organics Bali completed the design, installation, and commissioning of a Closed Lagoon Bioreactor (CLBR) on the settling lagoon used for wastewater generated from the production of cassava (tapioca) at the PT Cam mill.

The brief for this project focused on environmental responsibility, ensuring that the substantial amount of methane gas produced during wastewater treatment could not escape to the atmosphere, thereby reducing the facility’s contribution to the greenhouse effect. The biogas system is capable of generating significant energy, which is used to power the entire mill operation.

This large-scale biogas project is designed to handle the high organic loading characteristic of tapioca processing effluent. The system employs a CLBR over the large lagoon, providing stable and efficient treatment of the wastewater while converting the organic load into biogas.

With a design capacity to process 3,000 m3/day of wastewater, the system generates biogas equivalent to 4.5 MWe, providing ample renewable energy to fully power the entire operation and potentially export surplus energy.

• Waste Type: Cassava Mill Effluent (Tapioca Production)

• Mill Process Capacity: 1,000 tonnes of cassava per day

• Wastewater Flowrate: 3,000 m3/day

• Lagoon Capacity: 85,000 m3 of wastewater

• Biogas Production Potential: Over 3,000 Nm3/hour (~72,000 Nm3/day)

• Electrical Potential: 4.5 MWe

• Biogas Application: Powering the entire operation, with excess for export

• Achieving an estimated 80% COD removal efficiency, the system removes approximately 240 tonnes of COD daily, significantly cleaning the effluent.

• Generates 4.5 MWe equivalent of bioenergy, providing ample power to run the entire mill.

• Captures methane, preventing its release into the atmosphere, with an estimated capture of ~39,600 Nm3 of methane per day.

• Converts methane capture into climate action, achieving an estimated emission reduction of ~795 tonnes of CO2e per day.

• Meets the core brief by preventing methane escape, reducing environmental pollution, and supporting the mill’s compliance goals.

*Note (assumptions):

• COD Load: Initial Chemical Oxygen Demand (COD) load is estimated based on an industry standard Cassava effluent concentration (~100 kg/m3).
• Methane Fraction: Methane content in the biogas is assumed to be ~55%.
• GHG Reduction: Greenhouse Gas (GHG) reduction is calculated using the GWP100 for methane = 28 tCO2e per tonne of CH4.
• Carbon Credit Eligibility: Actual carbon credit issuance is dependent on project registration, verification methodology, monitoring data, and registry approval.