The Engineer Q&A: ALL-Streams HTO – turning waste into resources

David Inman, innovation project manager at Anglian Water, takes The Engineer through the project, highlighting the challenges that lay ahead.

Can you outline the ALL-Streams HTO project?

Our work with Cetogenix is about taking biosolids and turning it into more valuable materials, such as renewable natural gas, biomaterials, and renewable chemicals. Over the next 18 months, our project with Cetogenix and Cranfield University will establish the market opportunities for the output of the hydrothermal oxidation and then develop a pilot site. This is really interesting opportunity because we have to be thinking about how we maximise resource recovery if we are to achieve the net zero targets that Anglian Water has and help develop technologies and markets that can be leveraged by others to do the same, both in the water industry and further afield.

Is an offtake agreement in place?

Once the project is scaled up, the focus is to demonstrate the feasibility of recovering and valorising all resource streams from the HTO effluent (i.e. ammonia, volatile fatty acids, phosphorus etc.) at a scale relevant to the water industry. A market research deliverable within the project is investigating whether those recovered resources are best valued within water companies, or in other industries. Any offtake agreement would involve navigating end-of-waste regulations, which adds an additional layer of risk so would need to be evaluated in terms of the trade-off between end-point value, market resilience, and regulatory risks.

Why hydrothermal oxidation?

What is really interesting about the hydrothermal oxidation process is how it opens up lots of different avenues for resource recovery. Through the process we can remove emissions associated with our current water treatment and anaerobic digestion processes, it produces phosphorous and nitrogen to be used in agriculture, you can convert some of the outputs into biogas, and it produces biogenic carbon dioxide which can be used in food production. It is also interesting because of its ability to process unwanted additional elements that can be found in the biosolids used.

The potential opportunity here is significant. Based on the work that we have done, we believe that the process can at least double, and potentially triple, the amount of energy being recovered compared to that being recovered by anaerobic digestion alone today. When you consider that at Anglian Water produced 125MW of energy last year, you start to get a sense of how impactful this technology could be if scaled up across our network and the wider UK water industry.

Will you be using Cetogenix’s Ceto-Boost solution?

The project will make use of results from Cetogenix Ceto-Boost solution for the full-scale design planned to be based on Anglian Water’s Cotton Valley Sludge Treatment Centre near Milton Keynes. The ALL-Streams HTO (hydrothermal oxidation) project’s demonstration at Cranfield University will use a bespoke designed pilot-scale reactor that will allow us to replicate the range of pressures and temperatures used in the Ceto-Boost system.

What does Cetogenix’s tech bring to the project?

We looked at a number of hydrothermal processing options, and chose the best technology for our needs. The unique focus for the ALL-Streams HTO project is how innovation can enable downstream refinery of recovered products, our collaboration with Cranfield University and development work on ammonia recovery via HTO and the wider implications for reducing process emissions on mainstream treatment is an example of developing innovation that is unique to the project. 

What role will Cranfield play in this project?

Cranfield University is one of our partners in this project and will be supporting by assessing the market opportunities and helping to develop the pilot site. It was also through Cranfield University that we were initially introduced to Cetogenix in the first place, after the two had worked on some joint projects for the Bill and Melinda Gates Foundation.

What are the top three challenges in coupling hydrothermal oxidation technology to a water treatment facility?

One of the challenges is the need to retrofit water treatment facilities to work with this new hydrothermal oxidation technology. However, current sites do not necessarily always have the space, so there may be a need to find new, larger sites, the availability of which can be limited given water treatment works are typically near urban centres.

Another challenge, which is applicable to the various energy recovery projects that we are working on at the moment, is the need for new types of expertise and skills. Whilst the water industry is well versed in the treatment and management of dangerous substances, it is nonetheless the case that the production of products for the energy sector is novel to the industry and will require the creation of new job titles and necessitate the hiring of people from other sectors that have the requisite skills. Finding these people may prove to be a challenge, and is one of the reasons that Anglian Water invests so much time in developing partnerships with organisations across industries to help tap into this expertise.

Finally, HTO is still a new technology and the markets for the products that it creates are still being established. For it to be successful, we need real world examples of the resource recovery and value creation so that more investment flows into scaling the technology and also developing supply chains for the outputs to flow into. It should be noted that, due to resource and land availability, the UK has invested more in resource recovery technologies than many other countries and so is further down the track than many in this regard.

The interest in this area is undeniable, as evidenced by the partnership with Cetogenix but also other projects such as that with Firefly Green Fuels, which is focused on producing sustainable aviation fuel specifically. Investing in and developing these use cases is an important part of our work at Anglian Water, developing solutions that are not only a benefit to us but that can be leveraged by others in the water industry and further afield. Through coordinated innovation and development, HTO technology and other similar solutions can be a critical part of our transition to net zero.