A consortium led by Yorkshire Water has been awarded £2.3m from the Ofwat Innovation Fund (OIF) for its Advanced Thermal Conversion (ATC) Gasification technology.
Yorkshire Water is leading this project in partnership with the gasification technology provider Enertecgreen (ETG) along with Queen’s University Belfast, Carbon Trust, Thames Water, United Utilities, Anglian Water, Scottish Water, Irish Water, Northern Ireland Water, Southern Water and Wessex Water.
The Gasification process will convert sewage sludge into usable products such as biochar, vitrified ash ‘stones’ and a hydrogen-rich synthesis gas (syngas). By operating at high temperature, the process aims to destroy other contaminants such as forever chemicals like PFAS, and microplastics.
If successful, the project will demonstrate the circular economy in action by testing the use of the biochar as a wastewater treatment media and also as an additive in brick manufacturing.
The carbon-rich biochar, which resembles small pieces of charcoal, could also be used as a soil improver to increase water and nutrient retention, and as it doesn’t readily decompose, it’s also a vehicle for sequestering carbon in soil.
The vitrified ash ‘stones’ could be used as ‘aggregate’ in the construction industry to reduce the embodied carbon footprint. The syngas – a blend of hydrogen, carbon monoxide, carbon dioxide and methane – can be used to produce green electricity, along with other high-value products such as aviation fuel.
Dr Danielle Hankin, innovation programme manager, Yorkshire Water, said:
“Converting sewage sludge into gas, biochar and ash ‘stones’ opens up new, more sustainable uses for this waste product. We’re proud to be pre-empting changes in legislation and consumer attitudes, by delivering a groundbreaking technology that benefits customers, the environment and future-proofs the water industry.
“Once proven, the Gasification process will produce sustainable wastewater treatment media and construction material, generate green electricity, and could create high-value products such as biomethanol, aviation fuel or hydrogen. Our work represents a pivotal step in driving the UK towards a greener, more resource-efficient future.”
Helen Campbell, senior director, Ofwat said:
“There are big challenges in the water industry that must be solved, some are well known and others are less so. In our fourth Water Breakthrough Challenge we called for solutions with potential to deliver wide-scale, transformational change for customers, society and the environment – and that’s exactly what today’s winners have done. From raingardens to prevent flooding to green energy from treated sewage, innovations to cut the water sector’s carbon footprint to robots that patrol the pipe network, the winners are all helping shape a more sustainable and efficient water sector.”
The Water Breakthrough Challenge is part of a series of competitions from Ofwat, run by Challenge Works with Arup and Isle Utilities, designed to drive innovation and collaboration in the sector to benefit individuals, society and the environment.
It supports initiatives that help to tackle the biggest challenges facing the water sector, such as achieving net zero, protecting natural ecosystems and reducing leakage, as well as delivering value to society.
Background
The ATC Gasification concept was created and designed to mitigate against legislative changes on the disposal of sewage sludge as well as reducing greenhouse gas emissions and delivering an option for energy self-sufficiency.
The UK currently produces 1.4 million tonnes of dry solid sewage sludge per year of which 87% is currently anaerobically digested and used on land. This process is under significant pressure and landfill or incineration are not environmentally sustainable or financially realistic alternatives.
Yorkshire Water has been looking at alternatives to the current process for over 12 years, beginning with a trial of a pyrolysis process at Esholt, culminating with the development of the small-commercial scale ATC Gasification facility at Lower Brighouse, Huddersfield in partnership with Enertecgreen (ETG).
After a number of interactions Yorkshire Water say they are delighted that the OIF bid has been successful. The project will be delivered in partnership with ETG, Queen’s University Belfast, Carbon Trust, Thames Water, United Utilities, Anglian Water, Scottish Water, Irish Water, Northern Ireland Water, Southern Water and Wessex Water. The project will dry and gasify batches of 100% sewage sludge over a period of 20 weeks, ultimately proving the technical and commercial viability of gasification as a sustainable sludge conversion process.
Gasification product utilisation
As a result of tightening phosphorus removal consents, Yorkshire Water is forecasting to increase its consumption of ferric sulphate coagulant from 7,000 to 77,000 tonnes per year by 2025 at an estimated additional cost of around £19m per year.
Initial lab-scale research at Queen’s University Belfast has shown that Gasification-derived biochar could be used as a wastewater treatment media to remove phosphorus and to deliver a lower-cost sustainable alternative to ferric dosing. The University will also evaluate the destruction of contaminants, such as PFAS and microplastics, by the Gasification process.
Enertecgreen is already in talks with the UK’s largest brick manufacturer regarding the use of biochar and the vitrified ash stones within the construction industry. Work elsewhere in the industry is looking at the use of biochar as a carbon source in the production of sustainable fertiliser.
The hydrogen-rich syngas could continue to be used to generate heat and power, either for use locally or to feed into the national power grid. Alternatively, it could be converted into other, high-value products such biomethanol, aviation fuel or hydrogen.
Once proven, a modular Gasification process could be utilised as a centralised, sludge processing hub, or will enable water companies to process sludge at source, converting it locally into valuable products and renewable energy. This will also be the first time that 100% sludge has been processed on a large scale.
Benefits
As well as addressing regulatory risks associated with sludge to land and presenting sustainable, commercial resource reuse options the Gasification process converts 80% of the energy in the sludge to usable energy. For every 10 tonnes of dry sludge 8MW of usable energy is produced in the form of gas and heat.
The plant generates more than enough energy to be self-sufficient in power and heat and surplus energy can be used to meet external power and heat demand.
Yorkshire Water produces around 160,000 dry tons of sludge per year. Using a power optimised plant configuration the Gasification process could generate around 50MWee of power so that the Gasification process will be energy self-sufficient. Any excess energy may be used to power other areas of the business and thus contribute towards Yorkshire Water’s Net Zero ambitions.
The UK produces around 1.2 million dry tons of sludge per year and this is increasing. The Gasification process could potentially covert this sludge into sustainable products, remove all sludge to land and generate 375 MW of renewable energy for use by the wider industry.
As important however is the fact that all the sludge will have been consumed and processed so there will be no solid residues returning to land and all contaminants like microplastics and forever chemicals such as PFAS will have been safely destroyed.
The gas produced will initially be used to generate power but over time further processing options are envisaged that will convert the syngas to bio-energy products like bio-methanol and sustainable aircraft fuel (SAF).
