As the demand for renewable gas climbs, researchers at the Paul Scherrer Institute (PSI) have developed a highly sensitive method that detects two of the most problematic impurities in biogas – siloxanes and organic sulfur compounds – simultaneously. Published in Progress in Energy, the method uses gas chromatography coupled with inductively coupled plasma mass spectrometry (GC-ICP-MS) to achieve detection limits down to 15 parts per billion.
Siloxanes, often originating from personal care products, and sulfur compounds, derived from the microbial breakdown of proteins, are both commonly found in biogas. Though present only at trace levels, they interfere with energy conversion processes and can damage infrastructure. For example, when siloxanes are combusted, they form silicon dioxide, which fouls burners. Sulfur compounds, meanwhile, disrupt fuel cells, limiting their use with biomethane.
In Switzerland, biogas is increasingly fed into the national grid. “Despite their tiny concentration, these cause huge problems,” explained Ayush Agarwal, lead author of the study, in a press release. The new method allows for both classes of contaminants to be measured from the same sample with exceptional selectivity, thanks to the element-specific detection capabilities of ICP-MS.
The GC step first separates volatile components of the gas, after which ICP-MS detects sulfur and silicon isotopes, ignoring non-target elements. “To our knowledge, this is the first method of its kind that can measure sulphur and silicon compounds simultaneously,” said Agarwal.
To complement the lab-based workflow, the team also developed a portable field sampler that captures gas-phase analytes into a liquid. The samples remain stable for up to 28 days, making them suitable for off-site analysis. This is particularly important for small or remote biogas plants without on-site analytical infrastructure.
“This is a good example of how we conduct applied research at PSI, providing concrete solutions to current challenges,” said Christian Ludwig, senior author and co-director of the PSI Center for Energy and Environmental Sciences.
The authors suggest that the method will support the integration of biogas into fuel cell systems, grid injection, and other high-value applications as part of a cleaner energy future.
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