Knowledge Base

Commissioning begins at mechanical completion, also called commissioning, when the plant has been fully installed, connected, and tested. Under a Turnkey scope, this is when the plant is handed over to the client, transferring responsibility and starting the warranty period; under Engineering & Key Components, handover takes place once the client has received the equipment.  A Service & Maintenance contract with Bright, HoSt’s service brand, should be in place from this point, since it governs the warranty period. During cold commissioning, HoSt’s process engineers visit the site to confirm the equipment is mounted and connected correctly, troubleshoot issues, check signals and motor rotation, and confirm the wiring to the control container. The client’s technical operators are present throughout, and HoSt trains them on the equipment, the process, and the SCADA system, including how to set feeding diets based on the available feedstock.

Start-up, also called hot commissioning, is followed by feeding the digesters with inoculant or active digestate from a nearby biogas plant. Without a nearby source, the digesters can be started with fresh liquid instead, though this takes considerably longer, since the bacterial population needs to build up gradually through heating and mixing. As the empty digesters fill, the air inside is displaced by biogas; during this stage, the biogas is flared, since its quality, in terms of oxygen content and other impurities, does not yet meet requirements. Once digester quality is high enough and biogas flow reaches the minimum needed to run the compressors, typically at least half of their maximum capacity, gas is fed to the upgrading unit for the first time, a milestone known as First Gas. From there, the plant is fine-tuned and performance-tested until it consistently meets the agreed production and quality levels. Once performance tests are signed off, the client takes over daily operation, and HoSt continues to support the plant through a service and maintenance contract with Bright Renewables.