The kite-flying robots aiming to help the water sector achieve net zero

18 December 2024

We explore the innovative technology that will plug the data gap around greenhouse gas emissions from sewage treatment works.

Greenhouse gas (GHG) emissions from anthropogenic activities have contributed to climate change and are an urgent problem. The water sanitation sector is a significant contributor to GHG emissions, including sewer-based and non-sewer sanitation technologies, which can contribute up to 50 per cent of the emissions of a city’s total emissions.

Water companies in England have committed to achieving net zero emissions by 2030, and intervention on emissions from sewage treatment works (STW) has become one of the major focuses of the water industry’s route to this goal. Measuring and monitoring GHG reliably and accurately, however, is a significant challenge faced by water companies, one further complicated by variations between sites, as well as temporally and spatially within a site.

Robots flying kites to track GHG emissions

Here at the University of Surrey, we are seeking to address that challenge with an innovative project that will see robots flying kites in locations where GHG emissions are a concern. Our multi-disciplinary team is developing a tool that comprises a low-cost sensor mounted on an aerodynamic balloon platform. The balloon, which resembles a miniature barrage balloon, is tethered to a go-kart-sized robot that is free to roam within a given set of parameters.

This tool – we call it a mobile robotic flux tower – will allow spatially representative measures in complex environments, thanks to the mobility of the robot and the adjustable height of the platform. Additionally, the balloon can stay in place over long periods, giving sufficient time and resolution to fully capture the gas dynamics of the study location. Real-time data transmission and AI modelling will enable automated data analysis and visualisation of GHG emissions.

Being tethered to a robot, the mobile robotic flux tower can be easily transported to sites where GHG measurements are needed. The system is scalable and transferable to a wide range of sites where GHG emissions are an issue.

An impression of the University of Surrey’s kite-flying robot

The challenges of decarbonising the water sector

Decarbonisation of the water sector faces many challenges. Indirect (scope 2) GHG emissions (those that come from where energy is produced) fell by 47 per cent from 2011 to 2019, mainly due to a move towards renewable energy sources. Tackling direct (scope 1) emissions is more problematic for the sector, with a lack of monitoring data a major barrier for designing and implementing suitable intervention approaches.

The UK is in a unique position in regard to its STW, with ageing infrastructure and centralised and decentralised activated sludge and trickling filter systems. Generating representative data that covers different process types, geographic variations, climate differences and seasonal changes requires dedicated and versatile tools. However, these tools can be expensive and time-consuming to deploy and face additional challenges such as the need for highly skilled human operators.

In addition, the tools currently available for monitoring GHG are rarely capable of covering the whole of an STW while also accounting for meteorological conditions and gas dispersion. This is especially the case for methane and nitrous oxide, which have, respectively, a global warming potential, over a century, nearly 30 and 300 times that of carbon dioxide.

The benefits of multidisciplinary working

Complex environmental challenges often need multidisciplinary expertise and collaborative efforts to create innovative solutions. Multidisciplinary working is an essential feature of our project: our team brings together disciplines and expertise from robotics to sensor technology, from fluid dynamics to environmental engineering, and from atmospheric science to advanced data analysis and AI modelling. We believe that multidisciplinary working is key to solving real-world problems, in this case addressing environmental challenges where multiple and complex physical phenomena are at play.

Previously, our team has developed automated robotics for applications in challenging environmental conditions and areas with limited accessibility – aquatic environments, for example. The robots flying kites project will be drawing on technologies that we’ve already demonstrated elsewhere. For example, our technology has already led to the development of a novel, miniature, high-precision, low-cost methane probe that can be powered by USB alone and is already being commercialised in collaboration with our industrial partners in sensor manufacturing. For developing and testing we are fortunate to have access to the Environmental Flow (EnFlo) Laboratory, a wind tunnel at the University of Surrey which is part of the UK’s National Atmospheric Measurement and Observation Facility (AMOF).

After building the prototype of our kite-flying robot in the lab, we will test it on fields at the University of Surrey’s campus. Following validation and optimisation, we will move to STWs and farmland to work with project partners on real-world applications.

Hydrocarbon probe for methane detection

One of those partners is Thames Water, with whom we have been working (with funding support from a Engineering & Physical Sciences Research Council (EPSRC) studentship and a Environmental Biotechnology Network (EBNet) grant) to investigate some fundamental principles of STW emissions. We’ve also been developing an AI model for predicting GHGs dissolved in wastewater. The robots flying kites project, which is funded by Natural Environment Research Council (NERC), will focus on monitoring GHG emitted into the air (gas phase). Our work will hopefully innovate high-efficiency, low-cost, user-friendly measurement tools and AI-based models which can be easily adapted for other STW sites, and other water companies.

Agricultural applications of the robots flying kites project

This new tool has applications beyond STWs, including monitoring GHG emissions from farmland. Agriculture is a significant contributor to global emissions, with practices like rice cultivation producing emissions comparable to the entire aviation industry. However, adopting regenerative agricultural practices can dramatically reduce these emissions (by up to 50 per cent for rice) and even transform farmland into carbon sinks. Understanding the emissions from various crops and how they change with different farming techniques is crucial, yet it remains a challenge due to the lack of accurate monitoring tools. We hope our robot may be able to help plug this data gap.

If the UK water sector is to meet its target of achieving net zero by 2030, it will require accurate, reliable and affordable measurement of its direct GHG emissions, especially nitrous oxide and methane. Our innovative and scalable mobile robotic flux tower will enable this task. By early 2026, these kite-flying robots will be roaming across STW sites and farmland up and down the UK, capturing and transmitting crucial GHG data.

Author: Bing Guo is a senior lecturer in the Department of Civil and Environmental Engineering, Giovanni Iacobello is a lecturer in the School of Mechanical Engineering Sciences, David Birch is the head of the Centre for Aerodynamics & Environmental Flow, and Belen Marti-Cardona is associate professor (reader) at the School of Sustainability, Civil and Environmental Engineering, all at the University of Surrey, UK.