Author: Hannah Armstrong

PhD Insights: Novel recycling of lead batteries for people and planet

By Enrico Manfredi-Haylock, a member of the Transition to Zero Pollution cohort.

Did you know that the battery in your car is the most recycled item in the world? Its recycling process is considered as a gold standard example for the future circular economy of consumer goods.

The humble Lead Acid Battery (or LAB for short) was invented more than 100 years ago and today it is widely used for starting cars, keeping data centres running and storing renewable electricity. The lead used in these batteries is relatively easy to recover through a smelting process with no loss of quality of the recycled product so it can be used again and again. In fact, the metal in your car battery may have already gone through several incarnations of batteries before getting to you! In Europe and the USA it is estimated that over 95% of batteries are collected and recycled to make new batteries.

Close-up of car battery pile

But if LAB recycling is so successful, what’s the problem? Firstly, this process has a relatively high carbon footprint of 0.12kg of CO2 per kg of lead recycled. While that doesn’t sound too bad, consider that the world recycles millions of tonnes of lead per day! Secondly, batteries that are recycled improperly cause a pollution that is much worse than CO2.

In many developing nations, car batteries are recycled by hand in small cottage industries, in homemade furnaces, by workers who hack batteries apart with improvised tools for a pittance. These workers are fully aware that the lead in the batteries they break could cost them their life. Nonetheless, they choose to go ahead with this work because they have no other source of income. Used LAB recycling in developing nations was classed by the WHO and the Blacksmith Institute to be the most polluting industry of all, shortening life expectancy significantly for both workers and their families.

Headshot of Enrico Manfredi-Haylock
Enrico Manfredi-Haylock

It is therefore imperative to solve the pollution problems of lead recycling for these small informal recycling activities in the developing world; both to save our planet and our people. However, it is also important to recognise how many rely on this activity for a living. Restricting it may simply make the problem worse. Instead in this project we propose to introduce a novel chemical technique for the recycling of lead based on a new class of solvent that can be easily synthesised from everyday natural ingredients. The aim would be to develop this process to be as cheap and reliable as possible and to provide this technology directly to the people who need it with the help of local partners and charities. It is hoped that this approach can clean up the pollution from this industry, while keeping that invaluable economic lifeline in place for the world’s most vulnerable communities.

PhD Insights: New ways to deal with waste

By Alex Bowles, a member of the Transition to Zero Pollution cohort.

My work is focussed around decarbonising society through the enhanced recovery of waste materials. The UK produces 600,000 tonnes of waste tyres per year and in 2018 over half were exported to developing nations such as India (Source: UN Comtrade), where they are burnt in brick kilns or converted to oil in systems with negligible environmental and safety standards.

I am working on developing pyrolysis (heating in the absence of oxygen) as an upcoming waste-recovery technique for these tyres. Pyrolysis can be used to treat any organic waste material, such as biomass, plastics and rubber, to produce a mixture of solid (char), liquid (pyro-oil) and gas (syngas) products. The liquid and gas can be combusted for energy recovery or converted into recycled chemicals. Recycling mechanisms for the solid pyrolysis char product are still developing. I work on developing this pyro-char into activated carbon, a material used to filter air and water.

An aerial shot of a tyre dump

In my lifetime, atmospheric CO2 has risen by 15%. Abatement of further CO2 emissions to prevent catastrophic climate change is the biggest challenge facing humankind. My PhD focusses on utilising this recycled pyro-char derived activated carbon as a CO2 adsorbent, which can be attached to the end of a fossil fuelled power plant, cement kiln or factory that uses industrial heat to capture the CO2 through a carbon-capture mechanism. This system would prevent the release of CO2 into the atmosphere. Preliminary experiments have shown the potential to capture CO2 quantities of over 10% of the weight of the carbon reversibly and rapidly.

Headshot of Alex Bowles
Alex Bowles

I am working closely with my PhD sponsor, Pyrenergy, to develop pyrolysis as an effective recovery process for waste tyres. Much of the pyro-char feedstock for my PhD is a product of the Pyrenergy industrial process. Tyres are an especially challenging waste material due to the a) heterogeneity between brands and parts of a tyre, b) complex chemistry of rubber, c) high energy of production, and d) their abundance (>2 billion tyres are produced every year). I am working to contribute to the improved recovery of this important resource, which would support circular economy principles whilst reducing waste (tyre) and atmospheric (CO2) pollution to the environment.

PhD Insights: Making electric vehicles work for a better future

By Waseem Marzook, a member of the Transition to Zero Pollution cohort.

Electric vehicles (EVs) are key to achieving a carbon neutral and pollution free society. Transportation makes up a significant proportion of the global carbon footprint; one of the quickest and easiest way to greatly reduce that footprint is through the mass adoption of EVs, replacing all the fossil-fuel-powered vehicles on the road.

The most important component in any EV is the battery pack. Primarily powered by several lithium ion cells, EVs need long driving ranges, fast charging, and long warranties to compete with their fossil-fuel powered counterparts. This requires high capacity battery packs that are efficiently cooled and optimised for weight and cell lifetime.

Batteries age?

Unlike a petrol fuel tank, batteries age over time; the more they are used, and the more time that passes, the more their performance deteriorates. They store less charge, become more inefficient and deliver less peak power. For EVs this means that the maximum range and power are always reducing. Slowing the rate of this ageing, therefore, is a key component in improving EVs.

There are many factors that affect the rate of ageing such as current and the amount of charge in the battery. One of the biggest factors is temperature, extreme temperature both hot and cold have negative effects on battery life.

Keeping them cool

The key problem with fast charging is keeping the battery pack within a safe operating temperature. The battery pack generates a lot of heat while fast charging and this heat needs to be removed efficiently to keep all the cells at a safe and uniform temperature. Battery packs need to be cooled uniformly, as if you have one side of you pack in an optimal range but the other getting very hot, the hot side will age faster than the cold side. This can lead to premature failure of the entire pack.

Cell Cooling Coefficient
Close up of Waseem Marzook
Waseem Marzook

The Cell Cooling Coefficient (CCC) is a new universal measurement metric for characterising how efficiently a cell can be cooled. It tells you the temperature difference that will occur in a cell when a specified amount of heat is removed from it. My research involves developing this metric for cylindrical cells. Carefully designed rigs are used to experimentally measure the CCC of cylindrical cells of different sizes and under different cooling schemes, such as cooling the base of the cylinder or the sides. Longer term testing will show which cooling schemes are better at slowing down the ageing rate, coupling this with modelling of the CCC, this work will help identify where the thermal performance of these cells can be improved.

Cell manufacturers can use this metric optimise to their cells and produce the best thermally performing cell. As well as helping pack manufactures to compare a wide range of cells from different manufacturers, they will also be able to pick the best cell based on thermal performance for their cooling system. Ultimately, this will help develop battery packs that can be charged faster and which last longer. This will help mitigate some of the biggest downsides to electric vehicles and increase their desirability over fossil-fuel-powered vehicles, taking us a step closer to achieving a zero-pollution and carbon neutral planet.

PhD Insights: Finding new ways to feed the world

By Albert Fabregas Flavia, a member of the Transition to Zero Pollution cohort.

According to a recent UN report, the world’s population is expected to rise from 7.7 billion to 9.7 billion by 2050 and reach 11 billion by 2100. Such an increase in population will inevitably lead to a proportional increase in the demand for food. Producing enough food to satisfy the needs of this growing population (and doing so sustainably) is, therefore, a pressing global challenge.

Aerial photo of a tractor ploughing a field

Currently, staple food production relies heavily on the use of synthetic nitrogen fertilisers. However, considerable amounts of synthetic nitrogen are lost to the environment in the form of nitrate leaching or as ammonia and nitrous oxide emissions, causing air and water pollution across the globe and contributing to global warming.

A photo of Albert Fabregas Flavia
Albert Fabregas Flavia

Interestingly, a few soil-dwelling bacteria have long been known to be capable of converting the nitrogen in the atmosphere into nitrogen fertiliser. Using these bacteria as bio-fertilisers has therefore been proposed as a way to reduce agriculture’s harmful over dependence on synthetic nitrogen fertilisers. Yet, the process for converting atmospheric nitrogen into fertiliser is highly demanding for the bacteria and is likely to result in a severe “fitness cost” (that is, a negative impact on the bacteria’s ability to grow and replicate and therefore its viability as an eco alternative), preventing the potential use of these bacteria as bio-fertilisers in agriculture.

As part of Imperial’s commitment towards a zero-pollution future, our project we will be taking an innovative approach to tackling the bacterial fitness cost associated with synthesising nitrogen fertiliser from the air. Because, to paraphrase Bob Dylan, we think the answer to the question of how to feed the world sustainably might well be “blowing in the wind”.

PhD Insights: Why Particulate Matter matters

By Marcus Annegarn, member of the Transition to Zero Pollution cohort of PhD students

The title of my project is ‘Understanding the electronic and physical structure of particulate matter through theory and experiment’, and its aim is to help experimentalists detect and analyse particulate matter in London’s air.

What is particulate matter?

Particulate matter (or PM for short) are microscopic particles that exist in the air that we breathe. They can consist of a wide range of materials and across many shapes and sizes. They are often categorised by their size.

For example, PM10 is used to denote particles which are less than 10 microns in size and PM2.5 denotes particles that are less than 2.5 microns in size.  For reference, a human hair is about 180 microns in width.

So what’s the big deal? Short answer: Your lungs! Exposure to PM has been linked to both minor and severe health risks. This can result in short term affects such as a runny nose, coughing and shortness of breath.  Prolonged exposure has been linked to increased mortality and prevalence of respiratory diseases, particularly amongst at risk groups such as children, the elderly, and those with pre-existing conditions such as asthma.

An image of a PM detector in front a cityscape
Detecting PM levels in the atmosphere is vital for public health.

The smaller particles are believed to be more dangerous as they can penetrate deep into your lungs, even so far as into the membranes where oxygen is passed into your blood. The smaller particles also have a large surface area to volume ratio and more surface area allows for more harmful interactions with your lungs; for example, it is believed that small metallic particles can promote oxidation and thus severe damage to lung tissues.

However, the mechanism by which they affect our lungs is not yet fully understood. Nor which sizes and materials may be the most harmful. It is also hard to identify the exact size and composition of the particles.

Where does PM come from? 

PM can come from a wide range of sources. Outdoor sources include any sort of combustion engine as well as other vehicular sources such as brake pads, car tyres, roads, train tracks etc. Factories, open fires, and power plants can also contribute.

Indoor sources can come from fires, using gas heaters and stoves, cooking oil and even other household appliances such as air-conditioners.

How do we detect them? (Where I fit in)

The techniques often used to detect and analyse PM include X-ray absorption spectroscopy (XAS) and Electron Energy Loss Spectroscopy (EELS).

Marcus Annegarn

Both techniques result in a characteristic spectrum that gives information about the energy of the core electrons in the PM. From this information you can deduce which elements are present in the PM and in what configuration (i.e what material). The difficulty is that, to get this information, you need to match the spectra to a pre-existing spectrum of a known material.

My work involves using quantum chemistry software to try and predict spectra from theory so that we can use them to fingerprint and identify experimental spectra.

The hope is that this can lead to better understanding of what is out there and, in the future, which forms of PM are the most dangerous so that we can develop a targeted approach to mitigating the effect of air pollution on human health.

PhD Insights: Carbon capture and why it’s key to combating climate change

By Catrin Harris, member of the Transition to Zero Pollution cohort of PhD students


Carbon Capture and Storage (CCS) – is the process by which CO2 is captured and permanently stored deep within the earth’s subsurface. Due to global warming it is vital that we reduce atmospheric CO2 emissions, and technological solutions will play a key role in solving the current climate crisis.

Incorporating CCS technology within fossil fuel energy production, as well as other difficult to eliminate emissions sources, reduces overall mitigation costs and increases flexibility in achieving a net zero-carbon society. By capturing CO2 directly from the atmosphere, the CCS process functions as a negative emissions technology, reducing atmospheric CO2 levels.

Headshot of Catrin Harris. She is smiling at the camera.
Catrin Harris

My research focuses on storage of CO2 within saline aquifers. Geological carbon storage uses physical and chemical trapping mechanisms to permanently sequester CO2 in the subsurface. It is these secondary trapping mechanisms – capillary and dissolution trapping – that I study. My aim is to understand the physics describing CO2 trapping within porous rocks, in order to make predictions about flow and trapping in the subsurface.

To view what is happening within a rock sample I use a medical CT scanner, the same as those used in hospitals. The information gathered from the experiment is used to create a model which mimics what is happening underground on a large scale. These key trapping mechanisms immobilise a significant proportion of the CO2, ensuring storage security and stopping CO2 leaking back into the atmosphere.

Landscape picture of a power plant. Three funnels, two of which are emitting steam.

Research is niche so it can be easy as a PhD student to become very specialised very quickly. The everyday reality of studying flow through porous media is far removed from the bigger CCS process.  Considering the bigger picture is important too as it gives purpose and motivation to research. Engaging with the CCS community allows me to educate myself on the whole CCS process, gaining skills and knowledge outside of my specialism.

I firmly believe that CCS will be a critical technology within our energy portfolio during the transition to a zero-pollution society.

Transition to Zero Pollution: Imperial’s initiative to achieve a sustainable zero pollution future

By Dr Alex Berry, Transition to Zero Pollution Initiative Manager

With the Transition to Zero Pollution initiative, our vision is to realise a sustainable zero pollution future. We want to go beyond thinking about zero carbon and consider pollution in all its forms.

The scale of the challenge is massive. Pollution caused by people can be found almost everywhere we look. Toxic metals from human activity have been detected in the Himalayan peaks and plastic fibres found deep in the Pacific Ocean. Air pollution is a major health hazard for urban and rural communities and CO2 levels are rising above the levels needed to meet the Paris targets of limiting global warming to 1.5°C.

Addressing these challenges will require radical shifts in consumption, technologies, and business models, underpinned by innovative policies and governance structures. Scientists, engineers, clinicians, and economists will need to work together to create new technologies and policies that address not just a single source of pollution but the entire system and life cycle. We want to instil a holistic, zero pollution mind-set among our researchers and inspire current and future students.

Considering the big picture through a systems approach will help us to avoid some of the unintended consequences that tackling pollution sources in isolation has caused in the past. For example, at the start of this century, governments incentivised the diesel vehicle market to reward their lower carbon dioxide emissions but this led to degraded air quality in cities through increased nitrogen dioxide pollution. The ban on new petrol, diesel, and hybrid cars from 2035 will help to mitigate this. However, whilst the switch to electric vehicles will lower exhaust emissions, there are still issues of pollution from tyres and brakes and the social and environmental issues caused by mining for critical materials needed in current batteries. We need to consider not just the whole lifecycle of the batteries and cars but the wider transport system and whether the current model of private vehicle ownership necessarily works for the future.

Taking a holistic view can also help us understand co-benefits of solutions. For example switching to active travel like walking and cycling reduces vehicle pollution but also has positive impacts on human health, something that is particularly important in the current Covid-19 pandemic.

Researchers at Imperial are already tackling pollution in many different forms. From reducing plastic pollution to eliminating greenhouse gas emissions and improving air quality, from understanding human behaviour to sustainable business, and systems thinking, there is a wealth of research happening across College. We’ll be using this blog to share posts from our students and staff on how their research will help realise a zero pollution future so keep an eye out for our next posts.

You can also read more about the thinking behind Transition to Zero Pollution in our long read on Imperial Stories and see some of our research highlights on the Transition to Zero Pollution website.