Hazard Classification of Biogas and Risks of Large Scale Biogas Production

Abstract

This paper focuses on the approach that the Netherlands has chosen for large biogas-producing cofermentors that fall under the Seveso Directive and for which a Quantitative Risk Assessment (QRA) needs to be performed. In this context, two main questions arise: 1) when does an establishment with a large amount of biogas formally fall under the Seveso Directive?, and 2) what scenarios and failure frequencies should be used in a QRA? 1) Recently, a regulation containing new criteria for hazard classification of substances and mixtures for supply and use was implemented in the European Union. This has led to a revision of the Seveso Directive and changes to its scope. Under the revised Seveso Directive, a higher percentage of hydrogen sulphide is needed for biogas to be classified as acutely toxic and for it to come into scope of the Directive. For the flammable properties, limited changes are observed for uncleaned biogas. However, upgraded biogas will benefit from higher qualifying quantities in the revised Seveso Directive. 2) Because no systematic incident analyses are available, no appropriate scenarios and frequencies are available to calculate third party risks. For this situation, the RIVM (as the manager of the QRA approach in the Netherlands) suggested to consider typical fermentors as atmospheric vessels for which defined scenarios are available. Further investigations are needed to determine if this approach is valid.