Building an Innovative Renewable Energy Ecosystem in a Wastewater Treatment Plant through Co-location of Food Waste Digestion and Biomethane Generation

Aims of the project:

GENeco operates the only co-located food waste recycling facility and wastewater treatment plant (WWTP) in the UK, with a biomethane generation plant and a biomethane vehicle refuelling station.

By building these facilities on a WWTP, the activities of each plant are fully integrated, forming a unique renewable energy ecosystem. The strategic design means that resources and energy are used to their fullest potential, the practical embodiment of the circular economy. The foundations of GENeco’s ecosystem were built on engineering excellence and optimisation of each plant’s performance through real-time monitoring.

At this innovative facility, GENeco is able to offer cost effective and sustainable solutions to a variety of commercial customers and local residents, helping them to reduce the environmental impact of their activities.

GENeco treats significant volumes of varied waste and transforms it into useful products. This includes 40,000 tonnes of food waste, and sewage sludge from over 1 million people. GENeco also provides around 300 industrial waste customers from across the UK an alternative disposal route to landfill. From this waste, GENeco produces renewably-sourced energy and a nutrient bio-fertiliser. It also provides process water to local industry for cooling.

GENeco’s activities are positively contributing towards reducing the UK’s carbon footprint and reliance on a finite amount of resources.

GENeco operates the only co-located food waste recycling facility and wastewater treatment plant (WWTP) in the UK, with a biomethane generation plant and a biomethane vehicle refuelling station.

By building these facilities on a WWTP, the activities of each plant are fully integrated, forming a unique renewable energy ecosystem. The strategic design means that resources and energy are used to their fullest potential, the practical embodiment of the circular economy. The foundations of GENeco’s ecosystem were built on engineering excellence and optimisation of each plant’s performance through real-time monitoring.

At this innovative facility, GENeco is able to offer cost effective and sustainable solutions to a variety of commercial customers and local residents, helping them to reduce the environmental impact of their activities.

GENeco treats significant volumes of varied waste and transforms it into useful products. This includes 40,000 tonnes of food waste, and sewage sludge from over 1 million people. GENeco also provides around 300 industrial waste customers from across the UK an alternative disposal route to landfill. From this waste, GENeco produces renewably-sourced energy and a nutrient bio-fertiliser. It also provides process water to local industry for cooling.

GENeco’s activities are positively contributing towards reducing the UK’s carbon footprint and reliance on a finite amount of resources.

How long has the project been operational:

The Bristol WWTP, built in the 1960s, is the foundation of GENeco’s innovative activities. Since GENeco took over the operation of this WWTP in 2008, it has been at the centre of GENeco’s bid to become more sustainable and help others to do the same.

It was in this year that the sewage sludge anaerobic digestion process was split in to two phases. By providing optimal conditions for bacteria responsible for the production of acetic acid and methane in separate reactors the volumes of methane (biogas) produced can be maximised. In addition, two-phase digestion can produce a compliant digestate (bio-fertiliser) without the need for any secondary storage. This process optimisation allowed GENeco to convert two secondary storage tanks into anaerobic digesters.

In 2012, GENeco built the UK’s only food waste recycling facility to be co-located on a WWTP. The food waste recycling facility was able to utilise the two anaerobic digesters GENeco had released through optimisation of the sewage sludge anaerobic digestion process. GENeco’s food waste recycling facility processes 40,000 tonnes of food waste per year, converting this waste into useable resources, biogas and bio-fertiliser.

GENeco produces more biogas than it required to satisfy its heat and power requirements. GENeco identified that the excess biogas produced would be better utilised if converted to biomethane than if used as fuel for a combined heat and power (CHP) engine. This is because energy efficiency in GENeco’s CHP engines are on average 33% electrical efficiency and 38% heat efficiency, whereas energy efficiency in GENeco’s biomethane generation plant is 98%. In 2014 GENeco opted to install a biomethane generation plant, which uses high-pressure water to strip CO2 and other contaminants from the biogas to produced biomethane. This biomethane generation plant converts enough biogas into biomethane to power 7,000 homes every year, and the plant is currently injecting around 1,000m3/hr of renewable gas into the national gas grid.

In 2015 GENeco employed real-time monitoring system (Bentley’s AssetWise Amulet) to help them further optimise biogas production and to reduce the consumption of chemicals and raw materials. AssetWise Amulet enhances process-monitoring capabilities of the plant by combining raw data signals and lab analysis results into useable performance parameters. Visualisation of these parameters has been configured into supervisory dashboards to achieve efficient process operation.

To further its bid to create a sustainable circular economy within Bristol, GENeco is launching the UK’s first food waste collection vehicle (the “Bio-Bee”) which will be powered by biomethane produced from food waste and sewage. Compared to diesel equivalents, this ground-breaking refuse truck is quieter, produces <90% less ‘well-to-wheel’ CO2, and has measurable reductions in particulate matter (PM) and NOx emissions. The Bio-Bee will be used to collect the food waste that feeds the anaerobic digesters.

In addition to biogas, the anaerobic digestion process produces bio-fertiliser, with which GENeco provides a safe and sustainable source of nutrients to the agricultural industry. It facilitates significant crop yields and improves soil condition whilst reducing the industry’s carbon footprint and reliance on inorganic fertilisers.

How long the project took from concept approval to implementation: Ongoing since 2008

Organisation: GENeco

Funding: Private company

Picture courtesy of: GenECO

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