Caroline Dixey, Suresh Renukappa, Subashini Suresh, and Panagiotis Georgakis              RNC0004

Written evidence submitted by: Caroline Dixey, Suresh Renukappa, Subashini Suresh, and Panagiotis Georgakis, University of Wolverhampton

Natural Capital in the Green Economy:

Transport Infrastructure Perspective

Caroline Dixey, Dr Suresh Renukappa, Professor Subashini Suresh, and Professor Panagiotis Georgakis

Faculty of Science and Engineering

University of Wolverhampton

United Kingdom

Executive summary:

• In recent years, the asphalt industry has become increasingly aware of its sustainability impact in surfacing, namely to the three key pillars, being Societal, Economic, and Environmental. This awareness is now driving the leading asphalt companies to research and develop new methods of asphalt creation to make the surfacing industry more sustainable for years to come including the use of recycled asphalt paving (RAP), single-use and waste plastics, smart technology and biomaterials.

• As well as the issues that relate to the asphalt paving itself, there is also the impact of quarrying. Materials make up the largest carbon emitter in this sector. In recent times, there has been a realisation that the material in quarries is finite and when one quarry is depleted, another must be sourced ultimately resulting in disruption in eco-systems and surrounding areas from quarrying activities.

• More must be done to overcome issues within the industry to aid improvement in the green economy including the re-utilisation of abandoned quarries as nature reserves, use of more RAP within asphalt mixes, incorporation of single-use and waste plastics as aggregate binding agents, smart technology for monitoring of road surface quality and maintenance and research and development into biomaterials as an aggregate binder.

Written evidence:

1. Compared to other sectors, surfacing has only recently gained an awareness of the necessity to change its ideals and attitudes towards a more sustainable future, with recognition of the impact being in the very late 20th century. This is late compared to other industries and construction sectors which started looking into sustainable solutions as far back as the mid-19th century. With such a large scope for improvement in sustainable engineering within the surfacing industry utilising various methods such as recycled materials, permeable surface and smart technology, this sector is deemed to have a great opportunity and much potential to decrease the current impact.

2. One of the main areas of impact is the quarrying of materials to use in asphalt mixes. The quarrying of stone means that resources are being depleted over time and not being replaced. In 2019 alone, circa 133.5m tonnes of sand, gravel and crushed rock was sold in England, 25% of which was for surfacing. When looking at the surfacing elements alone, being base, binder and surface courses, typical carbon emissions by tonnage average at 52 kgCO2e/t. The total kgCO2e/t is calculated from direct and indirect sources which are emissions from the asphalt plant itself (Scope 1 - direct), and emissions from electricity consumption and the purchasing of goods and services, and distribution (Scopes 2 and 3 respectively).

3. Only a small number of quarries when depleted are being re-purposed, with the majority being left as ‘abandoned’. Being uneconomical, these quarries are recommended to be re-utilised as nature reserves, not only bringing back green areas but also improving economical prospects from users of the reserves. Additionally, the implementation of new nature reserves would also aid in carbon capture, offsetting some of the emissions produced by active quarries. Whilst there are well over 100 restored quarries in the UK to date, there is estimated to be many more that are currently depleted and abandoned.

4. To offset some of the carbon emissions being created by asphalt producing companies, some are using reclaimed asphalt pavement (RAP) from old surfacing that is being replaced or decommissioned, then mixing with virgin material from quarries to create a new surface mix. The implementation of this reduces the amount of virgin material required, thus reducing the amount of quarrying required. Currently only 10% RAP is permitted by the UK government for use within asphalt mixes. If the amount allowable were to be increased to a minimum of 50%, as utilised by FM Conway on the M25, this would decrease reliance on virgin material and slow the impact of quarrying.

5. Some companies are also utilising single-use and waste plastic within asphalt mixes. The concept replaces traditional aggregate binding agents with recycled and waste plastic and tests have shown that even a small amount of plastic can improve stability, strength and durability of asphalt when used in the surfacing mix. One surfacing project, based in Green Dragon Lane, Enfield utilised a mix of polymer-modified asphalt and recycled plastic-bound asphalt with a successful outcome. The asphalt performed very similarly to commercial polymer-bound asphalt and saved 600kg waste plastic from incineration/landfill and carbon saving of 1,416kg. The product used on this scheme is now being used internationally and should be encouraged further within the UK

6. Smart technology is also another area that is improving the asphalt industries’ credentials. A fairly new concept, companies can use technology to create ‘Smart Road Materials’. The asphalt incorporates sensors to monitor conditions of roads in real time, allowing for better addressing of issues by local authorities due to the provision of data that can predict when maintenance may be needed. This is done by data being transmitted to a data collection hub which, in turn, would then send the data to a database on a server to be analysed. This analysis can then be carried out via either human or artificial intelligence. Smart technology can also be used to monitor material quality at the asphalt plant without human intervention, create self-cleaning equipment and monitor asphalt plant emissions. By utilising smart technology, the overall benefit is improvement in material quality and road maintenance.

7. Another area smart technology in road surfacing could benefit is via the charging of electric vehicles as they drive over the road. One country that has already started looking into this is the USA. Installed in Detroit, Michigan, the road was created by installing electromagnetic coils under the surface course, powered by the city’s electrical grid. The coil then transmits energy to a receiver on the car’s battery, charging it as it drives. The benefit of this would be reducing the amount of charging required and potentially even not needing charging points at all in the future. If implemented in the UK, this would be certainly beneficial in aiding the UK government to achieve the target ban of petrol and diesel vehicles by 2035.

8. One other solution being investigated by asphalt companies is the use of biomaterials as an aggregate binder. In comparison to the other solutions investigated, this is a brand-new concept which was trialled in January 2024 in Canada and is a solution which is also being investigated in numerous other countries as an alternative to traditional or plastic-based asphalt. It can include materials such as plants, cooking oils, and animal manure. A study and testing undertaken at Chang’an University showed that the addition of plant fibres resulted in stiffer asphalt binder at lower temperatures, as well as a decrease in the cracking resistance of the asphalt.

9. As this is a new technology within asphalt creation, it may be some time before the industry recognises and starts to use this method due to not only extensive testing being required but also the current restriction on RAP being able to be used. As part of the development of biomaterials, a consideration that could be taken is the use of what is deemed to be invasive species in the UK, e.g., Japanese Knotweed and Giant Hogweed. If these plants were tested and identified to be a feasible part of the mix for sustainable surfacing, not only would this potentially result in the industry becoming more sustainable, but also aid in the eradication of these invasive species from UK shores.

10. With the reluctance from local authorities in the UK being high regarding recycled asphalt, only a limited number have allowed the use of biomaterials to be trialled in the UK. Whilst Canada have trialled it early 2024, Tarmac is another company to have produced a plant-based binding agent in their asphalt mix as part of the A452 resurfacing works in Birmingham. The mix enabled carbon savings of 6.5kg CO2e per tonne of asphalt as well as carbon capture and storage, showing what could be considered a highly sustainable option for road surfacing.

11. By further developing recycling methods, smart technology and biomaterials, the implications of this would be a reduction in quarrying of virgin material, thus lessening impact on the immediate environment, as well as putting single-use plastic and agricultural waste to better use than direct to landfill, also resulting in fewer harmful materials being released into the environment. A decrease in road maintenance may also be required from smart technology implementation thus also reducing maintenance costs and council tax from improved and automated monitoring.

12. The above can only happen, however, if governing bodies such as the Environment Agency and the UK government themselves invest the time, funding and research into these areas as well as the major aggregate producing companies, or preferentially, a combination of all with a particular emphasis on biomaterial research and development.

December 2024