Case study - Biogas monitoring for upgraded biomethane

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Courtesy of Geotech

By working with a range of partners worldwide, Geotech is involved in a range of projects at the cutting edge of biogas production and processing.  The recent landmark deal agreed between Marks & Spencer (M&S) and Future Biogas, a major biogas plant operator, is for the purchase of biomethane certificates.

The deal sees M&S purchase 35,000 Mega-Watt hours (Mwh) of certificates, which represent the 'bio' element of biomethane produced at anaerobic digestion (AD) plants.  The certificates will help to generate the equivalent amount of energy to heat 15 M&S Simply Food stores all year round, reducing the retailer's carbon footprint by more than 6,400 tonnes.

Geotech has worked with Future Biogas to supply biogas monitoring equipment for a number of projects.  The company uses Geotech’s fixed and portable gas analysers; the ATEX certified GA3000 PLUS fixed gas analyser measures and monitors the gas being produced on site.  Geotech’s portable biogas analyser, the BIOGAS 5000, supports gas analysis by providing consistent and reliable collection of data.  Whilst the fundamental requirements of reliable equipment for measuring the composition of hot, corrosive biogas remain the same across projects, there can be additional demands.

Future Biogas produces biomethane and electricity from biomass in a number of Anaerobic Digestion facilities across the country.  Geotech’s monitoring equipment is used to monitor the health of the fermentation and also check the condition of the biogas entering the gas upgrade unit to prevent damage to the upgrading membranes.  Typically the methane (CH4) yield, which can vary depending on the feedstock used, is the gas most closely monitored.  Methane is measured to indicate the revenue being generated and that the process is optimised.  Small deviations in methane levels can be significant so reliable and accurate equipment is critical.  A fast, local response is also particularly important for the fixed monitoring system, which may be linked into site alarms and without which the plant cannot fully function.

Other gases monitored include oxygen (O2) and hydrogen sulphide (H2S). An increase in oxygen, which can seriously damage expensive CHP engines, can be caused by a leak of air into the system.  H2S is generated, to different extents, by anaerobic digestion of different feedstocks and is also a major threat to efficient running of the engines.

M&S is the first UK retailer to buy biomethane to use in this way.  Biomethane gas is 50% more carbon efficient than average gas supplies and is generated by AD fuelled by farm waste.  The £8m Vulcan AD plant near Doncaster will use non-commercial crops from farms across Yorkshire and the North East.  Future Biogas is working on introducing sustainable break cropping feedstocks such as wildflower mixes, sunflower and ryegrass mixes.

The Biomethane Certification Scheme (BMCS) that M&S has signed up for is an independent certification scheme run by Green Gas Trading (GGT), a private limited company, which hopes to broaden the market and further facilitate links between green gas producers and buyers.  The scheme is backed by the Anaerobic Digestion & Biogas Association (ADBA), as well as other operators using Geotech’s biogas monitoring equipment, such as Tamar Energy.

To find out more about the project and Geotech’s biogas product portfolio please contact us or see us at ADBA’s R&D Forum on 14-15 April 2015 at the University of Southampton.

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