Managing gas from operational and closed landfills is typically a complex undertaking. It involves extended periods spanning many decades and engages multiple stakeholders including the regulator, the local community, the landfill owner/operator and often, the landfill gas power generation company. Under most contractual scenarios, the power generation company is required to extract enough gas from the field to prevent migration from the site.
On one of FCC’s sites in Scotland, routine borehole monitoring was giving rise to confusing findings. Certain boreholes had either very high methane or low/none during weekly monitoring rounds. The data density made it difficult to identify trends and understand the root cause. For example, comparing the migration data to atmospheric pressure or GUP variations or liquid levels onsite. Without a root cause, it was impossible for FCC or the gas contractor to take appropriate remedial measures.
In addition to measuring and verifying gas concentration levels, FCC was also looking at how they could measure flow-rates from the borehole on a continuous basis to allow them to quantify the extent of the gas migration problem. Reporting all the data in real-time enabled FCC to share the data with the gas contractor and to get to establishing the root cause quickly.
One GasfluX™ unit was deployed on a perimeter well, located closest to a risk receptor. The unit was set up to measure bulk gases, pressures & flow-rates, to get a true sense of the risk. The deployment ran for 4 weeks on a perimeter well and then was extended by a further two weeks on an in-waste well.
The system was measuring every three hours and the client had email alerts set-up at half and full LEL. A customised data portal was built for the project displaying real-time data, accessible to the client via a username and password on the Ambisense online reporting tool.*
Given that GasfluX measures both gas concentration and flow-rate, continuously and in real-time, it was possible for the client for the first time to quantify the extent of the gas migration from each location. While barometric pressure had some degree of influence on the recorded gas levels, it was evident that the borehole pressure behaviour and resulting flow-rates was not driven by that alone. This held true both for measuring from the perimeter and an in-waste well. As a result, the power generation company agreed to drill additional gas wells to maximise the capture of landfill gas and eliminate a long-standing regulatory issue.
*Since this case study Ambisense has launched Ambiliytics, a smart platform that connects to and integrates data from any IoT sensor and combines it with contextual data such as satellite and geophysical all on a single platform. Then it uses machine learning to generate statistical models, letting users get incredibly deep insights into their data and make faster and better risk assessment decisions.