Over the past four years OTECSA have been involved in over 30 Anaerobic Digestion sites across the United Kingdom. From Thurso to the Isle of Wight we cover the length and breadth of the country carrying out process safety projects including biogas DSEAR risk assessment, HAZOPs and COMAH support. As part of a retainer contract with one client we also provide consistent process safety support on incident investigations, technical troubleshooting and risk assessments.
DSEAR Risk Assessment
One of the main activities we regularly carry out is Biogas DSEAR Risk Assessment studies and the aligned Hazardous Area Classification assessments that are required for ATEX zoning of equipment.
Key Process Stages
Each biogas system is different but involves key process stages:
- Material storage and preparation. This can involve the potential for combustible dust consideration in biogas DSEAR risk assessment
- Biogas production in digesters. At this stage the biogas is produced in the absence of oxygen, with methane produced in a gas mixture with carbon dioxide and a small amount of other gases. This can also include hydrogen sulphide which is also flammable under DSEAR, but is also toxic to personnel.
- Biogas processing. This is where the biggest variation in processes occurs. Most sites use a portion (if not all) the biogas for production of heat and power in CHP (combined heat and power turbines). This provides heat and power for the site operations. Some sites clean and upgrade the gas by removing contaminants such as CO2 and H2S. The gas is then upgraded with propane to make it suitable for injection into the gas network.
- Waste processing. The biogas liquid waste is processed for disposal, which can remove dewatering and storage. There is a very little biogas left at this stage. There however remains a risk in upset conditions of some gas production and build up if systems remain closed.
Following risk assessment of the operations from a DSEAR perspective, a hazardous area classification zone assessment is carried out. This allows for selection of suitable equipment in line with the DSEAR Regulations and ATEX Directives.
As part of our commitment to the industry in 2025 we joined the Anaerobic Digestion and Bioresources Association.
