Understanding methane leakage from AD installations - a new methodology
The use of anaerobic digestion (AD) has increased significantly in the UK over the past decade, making significant contribution to greenhouse gas (GHG) savings. The majority of biogas from AD in the UK is used in combined heat and power (CHP) plants and biogas boilers. In the past few years, over 90 biomethane-to-grid (BtG) plants, where biogas is upgraded for injection into the gas grid, have been developed in the UK. Here at Ricardo, we have been auditing biogas CHP and BtG plants under the non-domestic Renewable Heat Incentive (RHI) since 2013. During this time, we have seen a wide range of developments in the market, but methane leakage from AD facilities remains an important issue for the AD industry in the UK.
Methane leakage is a potential issue for many biogas plants. Fugitive methane emissions result from the biogas production process (the AD plant) and biogas utilisation processes (e.g. biogas combustion in CHP engines/boilers or from biogas upgrade systems in BtG plants). Operators receiving Government support, such as the RHI, are required to comply with biomass sustainability criteria (BSC), which provides a framework to encourage operators to minimise fugitive methane emissions. As part of annual BSC reporting, operators are required to report on GHG emissions. As it is difficult to accurately measure fugitive methane loss – and there is no clear guidance from regulators on this issue – operators are required to use a default value of 1% (0.2 g methane/MJ) when reporting their GHG emissions. This may lead to operators with low methane leakage being penalised, but operators with lower standards benefiting.
Ricardo has extensive experience in methane monitoring techniques used in a wide range of applications. We were commissioned by the Department for Business, Energy and Industrial Strategy (BEIS) to undertake a review of techniques available on the market and to develop a methodology for monitoring methane leakage from AD plants. This new methodology is intended for use as part of a wider comprehensive measurement programme to estimate methane emissions and corresponding GHG savings from different types and categories of AD plants across the UK. This will be a large-scale programme requiring a practical and cost-effective methodology so that it can be applied to as many sites as possible.
In response to this, we have developed a methane monitoring methodology for use on different categories of AD plants comprising different types of feedstocks, biogas production systems and biogas upgrade technologies. It is based on a whole-site approach (i.e. undertaking measurements of methane concentrations at the site boundary).
For further details on the methodology >>click here
The methodology uses point sources and fugitive emission measuring techniques to detect and quantify emissions generated from digester roofs, seals and leaks that occur due to failures that are difficult to detect due to random occurrences.
I will be presenting this methodology at the UK AD and World Biogas Expo 2019 in Birmingham on 4 July. The event schedule is available at http://www.biogastradeshow.com/theengineroom/
The methodology developed is a comprehensive methodology which can also be applied for monitoring other species including for example ammonia. It can also be applied for different applications such as methane leakage from shale gas.
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