Carbon Neutral to Net Zero Pollution
Research lead– Ana Mijic, Marc Stettler, Rupert J. Myers
What is the problem?
Infrastructure is vital to society and provides us with energy, water, transport, telecommunications, and waste management. For most of human development, infrastructure was separated from environment. However, as the scope of human activities changed creating significant environmental impacts, the role of infrastructure has transitioned from supporting human systems to also managing natural environment. This raises a question of addressing systemic impacts of infrastructure projects and the role of civil and environmental engineering in creating and maintaining the built environment.
Global focus is currently on reducing greenhouse gas (GHG) emissions through setting the Net Zero Carbon targets at national levels and science-based targets for companies. This is of course beneficial to tackling global climate change. However, systemic impacts that refer to both direct and indirect long-term impacts extend beyond carbon footprint and spatial boundaries of an infrastructure project. These impacts, which cause the environmental damage – including biodiversity loss, and severe air, water, and soil pollution – are due, at least in part, to direct environmental pollution in some form or another. In addition, indirect environmental impacts due to infrastructure in the form of embodied pollution associated with infrastructure materials, and water and land footprints pose additional strain on the natural environment and affect its ecosystem services. The data portrait devastating impacts of pollution at a global scale, with annual number of cases of premature death linked to the use of natural resource and environmental damage currently reaching 19 million.
Our infrastructure decisions contribute to the pollution that our society generates; however, they can also determine how we manage the trends of population growth, urbanisation, and growing consumption. Within that context, infrastructure is critical in shaping the set of viable routes to reducing environmental pollution in the future. We argue that civil and environmental engineers must pay a crucial role in creating solutions that will promote sustainable development . This raises the question: how can we continue to improve quality of life through infrastructure provision, while minimising our impacts of pollution on the natural environment in the world that we have already created?
How does our research address this?
Our understanding of pollution impact pathways continues to evolve and improve, and while we understand some pathways quite well (e.g. the toxicity of leaded fuels ), new forms of pollution continue to emerge, such as microplastics and nanomaterials , which pollute our air, water and soil. More challenging aspect of the impact pathways assessment is the feedback between the environmental damage, which alters ecosystems and consequently impacts both humans and non-humans, and the structure of built environment. Concepts such as the natural capital have been developed to assess the value of ecosystem services provision for people , however, the link between the direct and indirect impacts assessment, as well as the implications for non-humans is still a scientific and practical challenge.
The need for holistic assessment is justified by four key aspects of the sustainable development debate:
1) Focusing on a single issue could potentially result in a range of unintended consequences that are already known, or yet to emerge (‘burden shifting’); for example the growth in the diesel cars market in the UK in the early 2000s, partly driven by lower taxes to reward their lower carbon dioxide emissions, degraded air quality in cities.
2) Focussing on a single form of pollution could miss synergistic opportunities for regenerative solutions: for example, there are often co-benefits of reducing carbon emissions and improving flood management and other ecosystem services that strengthen the case for change.
3) When discussing the future of infrastructure systems, we need to recognise their importance not only in the context of industry, innovation, and affordable and clean energy, but also for achieving other aspects of sustainable development, as embodied in multiple Sustainable Development Goals such as clean water and sanitation, sustainable cities and responsible consumption.
4) When reframing the debate in the context of a systems-level pollution expands the ‘burden of proof’ from regulators to include those causing or facilitating pollution, which is important for forms of pollution whose impact pathway is not well understood.
What have we achieved so far?
Systems-level pollution thinking will require fundamental revaluation of our infrastructure systems that necessitates inter-disciplinary research, innovation, and collaboration. Expanding the scope of analysis beyond approaches narrowly dealing with single environmental issues or pollutants, e.g., carbon accounting, has already revealed opportunities for thinking differently about infrastructure operations and planning. Analysis in the aviation sector has shown that minor changes to the altitude at which aircraft fly could significantly reduce the climate impact of flying attributable to contrails without significantly increasing CO2 emissions. The most effective way of achieving environmentally- and pedestrian- friendly urban design is to integrate transport infrastructure and public space planning, in addition to reducing pollution. Systems modelling of the urban water-energy nexus enabled us to analyse impacts of carbon policies on water infrastructure planning, while the water abstraction operational rules discovered through integrated modelling of urban water infrastructure have shown a potential to provide infrastructure equivalent benefits of up to £200 million. Finally, life cycle assessment has emphasised the role that materials can play in reducing environmental impacts of infrastructure systems, such as using alternative cement binders with lower CO2 emissions relative to conventional blended Portland cement binder.
What are What are the future directions for research and industry??
Examples across multiple infrastructure sectors provide a new conceptualisation of a system that is designed to support both built and natural environments. Understanding of pollution impact pathways resulting from human activities – and importantly environmental damage – is crucial for assessing the overall sustainability of the complex anthropogenic Earth system. We refer to this concept as a net zero pollution (NZP), which aims to achieve a systems-level balance between human footprint and the capacity of natural system to support life on Earth. This concept supports the debate about development within planetary boundaries, which needs to be revisited considering the role of built environment in managing natural systems.
Net zero pollution concept in the context of built and natural environment, which promotes balancing built environmental impacts with the capacity of the natural system to support life for all its inhabitants
For direct pollution, the concept implies either elimination of all pollution sources to the natural environment (zero pollution), or in case the pollution is released into environment, its removal to minimise damage, which could be in a different place or at a different time (net zero pollution). This principle works well in the context of managing GHG emissions through Net Zero Carbon accounting. It could also work in some cases where habitats are destroyed and rebuilt somewhere else, which is promoted by the biodiversity net gain approach. However, net zero pollution concept may be particularly challenging for the forms of pollution or cases when the damages are non-linear and spatially dependent. Such examples include impacts of agricultural diffuse pollution on river water quality, which needs to be removed at some point downstream for a water treatment, however, with potential significant damage in between the source of pollution and the abstraction location. In the context of air pollution, local impacts on health due to GHG emissions cannot be mitigated if pollutants can be taken out of the air somewhere else. Finally, the destruction of unique, old habitats due to the development and resources extractions may be impossible to replicate.
Seeing the coupled human-natural system through NZP lens poses multiple challenges with respect to understanding and quantifying the complexity of interactions across system components. It increases importance of, and need for, data and models to describe both infrastructure systems at the engineering level, and the infrastructure system-of-systems at the societal level, including:
- Modelling interdependences between physical (built and natural environment) and socio-economic (human activities) systems. Here, approaches such as system dynamics, surrogate and agent-based modelling may prove to be invaluable.
- Assessing feedbacks between environmental impacts, damage and state of the natural environment. This could be done by applying industrial ecology methods such life cycle assessment, material flow analysis, and footprint analyses, which could play a significant role in evaluation the systems-level sustainability indicators.
- Interdisciplinary expertise required to effectively develop and use these data and models to perform the more systematic analysis. This will be particularly important in the context of informing important societal decisions.
What is the long term vision for impact?
The natural world is in crisis and a different perspective is needed – transitioning to Net zero pollution enhances focus on the natural environment from a systems perspective, with a potential to facilitate better planning and decision making, and hopefully also environmental protection for the sake of future generations. In order to achieve that, we all need to change the way how we think about infrastructure systems and see them as enablers of the transition to zero pollution rather than acting as a barrier to sustainable development.
Dr Ana Mijic and Dr Marc Stettler, Dr Ruper Myers, Dr Michel-Alexandre Cardin
Carbon Neutral to Net Zero Pollution: Built and Natural Environments at our 10 year celebration event
- B. Dobson and A. Mijic, ‘Protecting rivers by integrating supply-wastewater infrastructure planning and coordinating operational decisions’, Environ. Res. Lett., Aug. 2020
- R. Teoh, U. Schumann, A. Majumdar, and M. E. J. Stettler, ‘Mitigating the Climate Forcing of Aircraft Contrails by Small-Scale Diversions and Technology Adoption’, Environ. Sci. Technol., vol. 54, no. 5, pp. 2941–2950, 2020
- L. Yang, L. Zhang, M. E. J. Stettler, M. Sukitpaneenit, D. Xiao, and K. H. van Dam, ‘Supporting an integrated transportation infrastructure and public space design: A coupled simulation method for evaluating traffic pollution and microclimate’, Sustain. Cities Soc., vol. 52, p. 101796, 2020.
- S. Miller and R. J. Myers, ‘Environmental impacts of alternative cement binders’, Environ. Sci. Technol., 2019
- S. De Stercke, A. Mijic, W. Buytaert, and V. Chaturvedi, ‘Modelling the dynamic interactions between London’s water and energy systems from an end-use perspective’, Appl. Energy, vol. 230, pp. 615–626, 2018
 For example, using science based targets: https://sciencebasedtargets.org/
 In this article, we define direct pollution to be the addition/change in quantity of any substance (solid, liquid, or gas) or any form of energy (such as heat, sound, or radioactivity) to the environment at a rate faster than it can be dispersed, diluted, decomposed, recycled, or stored in some harmless form. Sources of pollution are extremely diverse, and the specific harm caused by different pollutants depends on the environment in which they is released.
 It has been argued that the precautionary principle shifts the burden of proof onto the proponent of an activity, i.e. the proponent of an activity must show any resulting pollution does not cause harm