Developing a Pressure-Based Measuring System for Determining Biogas and Methane Production for Biochemical Methane Potentials and Anaerobic Toxicity Assays

Abstract

Data collection for Biochemical Methane Potentials (BMPs) and Anaerobic Toxicity Assays (ATAs) can require a significant time commitment to measure the biogas production and methane content, especially for a large number of assays. Additionally, data collected requires precision and accuracy. A prototype measurement system was researched and developed to determine if laboratory personnel time requirements could be reduced and if measurement accuracy could be increased. Biochemical Methane Potentials and Anaerobic Toxicity Assays are laboratory tests performed on a substrate to determine the anaerobic biodegradability and toxicity of a waste, respectively (Owen et. al., 1979). Performing a BMP assay could provide helpful information about the anaerobic efficiency of converting the organics in a substrate to methane. An Anaerobic Toxicity Assay (ATA) is a method to determine the inhibition of gas production by the substrate. These tests have been performed in large quantities at the Agricultural Waste Management Lab (AWML) at Iowa State University using variations of the ISO-11734 BMP and ISO-13641-1 ATA standards. In the AWML, the current method for measuring biogas production has been via volume displacement in a wetted gas syringe, and the methane content of biogas has been quantified with an infrared methane analyzer to determine the methane content. This paper describes the concept of using pressure transducers and a non-dispersive infrared methane sensor to monitor real-time biogas and methane production. The concept was tested using a prototype that monitored fifteen assay bottles. Glucose BMPs were monitored using both the wetted gas syringe and the pressure based system. Biogas and methane production were compared. The concept evaluation produced positive results, and the selected components for the process appeared to be effective during the test. However, gas leaks around the system/BMP assay interface impacted the prototype results and additional modifications and evaluation are needed.