GENeco has built a supply of enriched biomethane that joins the national gas distribution network, and secured finance from the renewable heat incentive (RHI) scheme at the Department of Energy and Climate Change (DECC).
The “gas to grid” plant at Bristol sewage works uses anaerobic digestion (AD) to extract energy in the form of biogas from a mix of food waste, commercial liquid waste and domestic sewage, which is then refined to the same composition as natural gas. This then joins the national gas distribution network.
Construction and commissioning in a short time frame was necessary to secure the government funding that makes it financially viable.
As well as having the potential to provide enough biomethane to supply 8,300 homes with renewable fuel, the gas can be used as a substitute for petrol, for instance in the groundbreaking Bio-Bus.
GENeco was created by Wessex Water in 2008 to help it become carbon neutral and eliminate landfill waste by 2020. It treats huge volumes of varied waste and turns it all into commercial products, diverting 100% of waste from landfill and providing renewable energy for nearly 150,000 homes.
In 2013 the company was awarded zero-waste-to-landfill status and is carbon neutral.
Over the past five years, renewable energy output from biogas has exceeded expectations, says GENeco. While AD is relatively common in the agricultural and water industries, biogas is typically used to generate electricity using combined heat and power (CHP) plants, which means that 60% of the energy is lost – predominantly as heat. To combat this, GENeco’s plant turns the biogas to biomethane (98% methane), producing a versatile and efficient biofuel that can be used as a substitute for natural gas.
With the introduction of food waste recycling, the production of biogas is now at a scale where it can be injected to the grid, a much more energy-efficient outlet than CHP engines. Before 2013 the allowable oxygen content for grid injection was prohibitively low, but a change to regulations in 2014 raised this to an achievable level.
The achievement, said the Guardian judges, was “a great step forward for the circular economy”. They added: “Getting connected to the grid is technically and bureaucratically difficult, and GENeco has overcome those challenges.”
Waste comes into GENeco’s treatment works with no commercial value and is transformed into sustainable products. The goal is to “close the loop” on all systems and processes. For example, solid inorganics such as nappies and condoms are screened and treated using an aerobic composting system that the company claims is unique. This produces a soil conditioner that can be recycled for use on agricultural land.
In addition, a proportion of clean effluent from the sewage treatment plant is piped to a nearby power station for use as cooling water, saving significant volumes of water and providing revenues to offset operating costs.
In effect, GENeco’s goal is to recognise all forms of waste as a resource that can be transformed into usable and profitable products and services.
Biomethane production alone supplies renewably sourced gas to 8,300 homes. But injection to the grid generates revenue for the company, while its use as a vehicle fuel opens up new business opportunities in the transport sector. As well as the launch in November 2014 of the Bio-Bus – which gained global media coverage – the company has piloted the “poo-powered” Bio-Bug, a car powered by human waste.
The technology, claims the company, sets GENeco’s plant apart from others being developed by water companies because the raw materials include diverse waste types: 35,000 tonnes of inedible food waste; 600,000m3 of commercial liquid waste; and domestic sewage from over a million people in the Bristol and Bath area each year.
In addition, varied waste streams contributing to gas production include raw sewage, paint washings from car manufacture, cosmetics and the inedible by-products from jam manufacturing.
An added benefit is the potential to improve urban air quality compared to diesel fuel use: a 97% reduction in dangerous particulate emissions which can pass easily from the lungs to the bloodstream; 80-90% fewer nitrogen oxides, which contribute to acid rain formation; and 20-30% fewer CO2 emissions.
As a result, GENeco is talking to the local community, schools and university groups about the vital role of recycling and the Bio-Bus is being used to help promote Bristol’s 2015 European Green Capital status.
One of the main constituents of GENeco’s AD is domestic sewage and with the local population likely to grow in coming years, GENeco is confident of increasing supplies.
It has also secured long-term contracts with several local authorities for their food waste. With DECC figures showing that household food waste recycling has increased by 11% in the past year, this is an important growth area.
Longer term, biomethane production from varied waste sources is a sustainable alternative to fossil fuels, it says.
GENeco is the 2015 winner of the impact award in the waste category of the Guardian Sustainable Business Awards.