Development of Analytical Methods to Gain Insight into the Role of Terpenesin Biogas Plants

Terpenes have been shown to be the dominant VOCs present in biogas mostly in plants where food wastes are digested. In particular, p-cymene and D-limonene have been reported to represent up to 90% of all VOCs in the biogas. A number of problems have been linked to terpenes in biogas plants, including odor problems, indoor air quality issues at workplaces and operational problems. In order to study the faith of terpenes, there is a need to develop robust analytical methods to quantify terpenes in all the flows at biogas plants including substrates, gas, and water samples. In this study, reliable analytical methods for the detection and quantification of terpenes in these flows are presented. The methods have a common final step consisting of a TD-GC-MS/FID analysis using Tenax TA for the trapping of terpenes. The methods were then applied to some samples taken at a biogas plant where food waste is digested. The results show that D-limonene was the dominant terpene in the substrate whereas p-cymene was dominant in biogas and process water.