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ANAEROBIC DIGESTION TIME TO TACKLE BIOGAS LEAKS


Without leak detection


surveys, it could be


argued that generating


biogas and then losing it to the atmosphere is worse than


allowing the natural


decomposition of organic


materials, and is simply


unsustainable


equate to a potential loss of 37 GWhe a year, resulting in: • 6,000 tonnes of methane escaping into the


atmosphere annually; • a financial loss of more than £7 million; • and the global warming effect of more


than 215,000 tonnes of CO2. Also, in the worst-case scenario, biogas in


combination with air can form an explosive gas mixture which, in a confined space near an ignition source, can result in explosion. While explosions are thankfully extremely rare, they do bring the risk of serious injuries and even fatalities. Biogas also contains hydrogen sulphide


Tim Elsome, General Manager of FM BioEnergy, outlines why now is the ideal time to tackle unidentified biogas leaks – and how to protect your plant, profits and the planet


biogas and digestate. The aim is to convert the biomethane into usable energy either as heat, electrical power or as a replacement for fossil-derived gas fuels, including for use as a transport fuel. However, what happens if the biomethane


A


escapes from the digester through leakage? Not only does it reduce the efficiency of the AD plant, but it can also pose a threat to health and safety, as well as being a significant greenhouse gas (GHG) pollutant. According to the Intergovernmental Panel


on Climate Change (IPCC), methane (CH4) emissions have been responsible for a significant proportion of the 1.1°C rise already experienced in global temperatures. Although leakage from biogas plants represents just a small proportion of global methane emissions, for those plants affected, the impacts can be significant. Furthermore, the solutions to prevent such leaks are readily available and quickly pay for themselves. Over eight years up to 2020, FM BioEnergy


surveyed 964 AD plants in the UK and Germany and found that 85% were suffering from biogas leakage. More recently, in December 2021, we surveyed nine UK plants representing different feedstocks, technologies and locations with capacities


4 JUNE 2022 | PROCESS & CONTROL 8


naerobic digestion (AD) plants are designed to convert biological feedstocks into biomethane-rich


between 500 kWe and 3 MWe, including three gas-to-grid plants with the largest site exporting 1,000m3


/hr. All nine sites had one or more leaks. These


comprised a total of: • 20 ‘minor’ leaks (< 100l CH4/h); • 25 ‘moderate’ leaks (< 1,000l CH4/h); • and one ‘significant’ leak (>1,000l CH4/h),


which was causing the operator financial losses and represented a safety risk. Extrapolating this data shows that the issue


of biogas leakage is not going away. More than 70 plants in the UK are likely to be in danger of financial or safety breaches, and almost all plants have some leaks. If 85% of plants in the UK were to leak an average of just 0.5% of their capacity, it could


(H2S), a toxic gas which has been the cause of a number of deaths in the UK agricultural industry in relation to slurry tank management. As H2S is heavier than air, it will fall to the ground. In confined, poorly ventilated spaces it can accumulate and remain unnoticed until someone enters, and the result could be fatal. The current high energy price (forward gas


prices have exceeded £2/therm since December) means that every cubic metre of lost biogas is costing your business money. The sooner leaks can be fixed, the sooner you can recover that lost revenue. Furthermore, at least year’s COP26 climate


talks in Glasgow, methane took on a greater significance in the global race to reduce climate change. The event saw more than 100 countries sign up to the Global Methane Pledge which aims to cut global methane emissions by at least 30% of 2020 levels by 2030. This could curtail up to 0.3°C of near- term warming, which scientists say could have a significant impact on the severity and frequency of severe weather events. Because of its higher global warming


potential (GWP), which is 28-36 times that of carbon dioxide, methane is considered to account for around half of the climate warming being experienced, and reducing methane emissions is seen as ‘low-hanging fruit’ in the fight against climate change. From August 2022 the Environment Agency (EA) is due to announce new regulations on


Leakage hotpots include valves and covers


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