chemicals – Cabot Institute for the Environment blog

Chemical industry failing to stop emissions of super-strong greenhouse gas HFC-23 – new research

Posted on September 4, 2024September 4, 2024 by amanda.woodman-hardy

The potent greenhouse gas HFC-23 is emitted from the industrial production of fluoroplastics and specific refrigerants.
Quality Stock Arts/Shutterstock

Emissions of a super-strong greenhouse gas could be substantially reduced if factories would properly implement existing “destruction technology” in certain industrial production processes. If operated properly, emissions of this greenhouse gas could be cut by at least 85% – that’s equivalent to 17% of carbon dioxide emissions from global aviation.

Our research, published today in the journal Nature, scrutinises emissions of one of the most potent hydrofluorocarbon (HFC) greenhouse gases, called trifluoromethane (HFC-23). One gram of HFC-23 in the atmosphere contributes as much to the greenhouse effect as 12kg of carbon dioxide.

This unwanted byproduct comes from the production of certain gases used as refrigerants and the manufacture of fluoropolymers (a class of plastic chemicals) such as polytetrafluoroethylene (PTFE), a key ingredient in most non-stick cookware.

black frying pan, single friend egg, dark background. — Fluoroplastics are used in the production of non-stick cookware.
J.Thasit/Shutterstock

More than 150 countries have pledged to significantly reduce their HFC-23 emissions as part of the 2016 Kigali Amendment to an international treaty called the Montreal Protocol on substances that deplete the ozone layer. The breakdown of HFCs in the atmosphere does not directly link to ozone depletion, but HFCs were introduced to replace ozone-depleting substances such as chloroflourocarbons (CFCs), so they have been included in this regulation.

HFCs are also strong greenhouse gases. While the Kigali Amendment aims to reduce emissions of widely used HFCs, an exceptional arrangement is made for HFC-23. Because HFC-23 is largely emitted from production processes and not from end-use applications, its destruction as a by-product is required “to the extent practicable” as of 2020 – that means as much as possible, but it’s a vague limit.

Even before 2020, many countries, including the biggest manufacturers of PTFE such as China, reported they had installed destruction technologies at PTFE factories and are successfully destroying HFC-23. In 2020, the reported global annual emissions of HFC-23 were only around 2,000 metric tonnes – but actual global emissions, derived from atmospheric measurements, amounted to around 16,000 metric tonnes.

To unravel this discrepancy between real and reported emissions, we analysed HFC-23 emissions from a major European PTFE factory in the Netherlands, which already operates destruction technologies – these include the incineration of harmful byproducts.

The aim of our experiment was to define what “practicable” actually means, and to identify how much HFC-23 can be easily destroyed by existing technology at a factory-wide scale, considering that emissions come from both the chimneys and leaks from other parts of the plant.

With the factory’s collaboration and the consent of the Dutch environment authorities, we released a controlled amount of a tracer gas directly next to the factory: this is a non-toxic, degradable gas that does not occur in the atmosphere. We then measured the concentrations of HFC-23, other byproducts of flouropolymer manufacture, and the released tracer at an observing site run by the Europe-wide greenhouse gas research centre, the Integrated Carbon Observation System, near the Dutch village of Cabauw.

This 213m-tall tower is located around 25km away from the factory. We knew exactly how much tracer we had released and how much of it arrived at the measuring point, so we could calculate the emissions of HFC-23 and other gases.

aerial shot of tall metal tower, green fields — Measurements of HFC-23 and the tracer were carried out at the 213m Cabauw measuring mast, operated by the Royal Netherlands Meteorological Institute.
ICOS RI/Tom Oudijk, Sander Karsen, Dennis Manda, CC BY-NC-ND

Results showed that even though our estimated emissions were higher than those reported by the factory, the technology at this particular factory was working properly and successfully destroying HFC-23.

Upscaling to global emissions

However, as the industrial manufacture of fluoropolymers is currently the major known source of HFC-23 to the atmosphere, we suspect that destruction technologies are not as effectively operated as reported by manufacturers.

Our findings indicate that if all factories globally were controlling emissions in the same way as the Dutch site, HFC-23 emissions could be cut by at least around 85%, representing emissions equivalent to 170 million metric tonnes of carbon dioxide per year. This reduction equates to almost one-fifth (17%) of carbon dioxide emissions generated by all aviation traffic.

Real and reported emissions of HFC-23

An independent auditing framework for fluoropolymer production would ensure that HFC-23 is destroyed properly at factories around the world. Targeted monitoring of greenhouse gas emissions resulting from the production of fluorochemicals would further the understanding of emission sources and ensure that countries are fully compliant under different international climate and environment agreements.

Our results show that destruction technologies can effectively be implemented – in this case, at factories producing fluoropolymers such as PTFE, to significantly reduce the emissions of a highly potent greenhouse gas.

This blog is written by Dr Dominique Rust, Research Associate, School of Chemistry, University of Bristol; Dr Kieran Stanley, Senior Research Fellow, School of Chemistry, University of Bristol, and Stephen Henne, Senior Scientist, Group Atmospheric Modelling and Remote Sensing, Swiss Federal Institute of Technology Zurich. This article is republished from The Conversation under a Creative Commons license. Read the original article.

The last ozone-layer damaging chemicals to be phased out are finally falling in the atmosphere

Posted on June 18, 2024 by amanda.woodman-hardy

The high-altitude AGAGE Jungfraujoch station in Switzerland is used to take measurements of Earth’s atmosphere.
Jungfrau.ch

Since the discovery of the ozone layer, countries have agreed and amended treaties to aid its recovery. The most notable of these is the Montreal protocol on substances that deplete the ozone layer, which is widely regarded as the most successful environmental agreement ever devised.

Ratified by every UN member state and first adopted in 1987, the Montreal protocol aimed to reduce the release of ozone-depleting substances into the atmosphere. The most well known of these are chlorofluorocarbons (CFCs).

Starting in 1989, the protocol phased out the global production of CFCs by 2010 and prohibited their use in equipment like refrigerators, air-conditioners and insulating foam. This gradual phase-out allowed countries with less established economies time to transition to alternatives and provided funding to help them comply with the protocol’s regulations.

Today, refrigerators and aerosol cans contain gases like propane which, although flammable, does not deplete ozone in Earth’s upper atmosphere when released. However, ozone-friendly alternatives to CFCs in some products, such as certain foams used to insulate fridges, buildings and air-conditioning units, took longer to find. Another set of gases, hydrochlorofluorocarbons (HCFCs), was used as a temporary replacement.

A collection of used refrigerators. — HCFCs can leak to the atmosphere from discarded fridges.
RichardJohnson/Shutterstock

Unfortunately, HCFCs still destroy ozone. The good news is that levels of HCFCs in the atmosphere are now falling and indeed have been since 2021 according to research I led with colleagues. This marks a major milestone in the recovery of Earth’s ozone layer – and offers a rare success story in humanity’s efforts to tackle climate-warming gases too.

HCFCs v CFCs

HCFCs and CFCs have much in common. These similarities are what made the former suitable alternatives.

HCFCs contain chlorine, the chemical element in CFCs that causes these compounds to destroy the ozone layer. HCFCs deplete ozone to a much smaller extent than the CFCs they have replaced – you would have to release around ten times as much HCFC to have a comparable impact on the ozone layer.

But both CFCs and HCFCs are potent greenhouse gases. The most commonly used HCFC, HCFC-22, has a global warming potential of 1,910 times that of carbon dioxide, but only lasts for around 12 years in the atmosphere compared with several centuries for CO₂.

As non-ozone depleting alternatives to HCFCs became available it was decided that amendments to the Montreal protocol were needed to phase HCFCs out. These were agreed in Copenhagen and Beijing in 1992 and 1999 respectively.

This phase-out is still underway. A global target to end most production of HCFCs is set for 2030, with only very minor amounts allowed until 2040.

Turning the corner on a bumpy road

Our findings show that levels of HCFCs in the atmosphere have been falling since 2021 – the first decline since scientists started taking measurements in the late 1970s. This milestone shows the enormous success of the Montreal protocol in not only tackling the original problem of CFCs but also its lesser known and less destructive successor.

Two graphs side by side showing a the climate warming and ozone-destroying influence of HCFCs declining from 2021. — The influence of HCFCs on the atmosphere is set to fall steadily.
Western et al. (2024)/Nature

This is very good news for the ozone layer’s continuing recovery. The most recent scientific prediction, made in 2022, anticipated that HCFC levels would not start falling until 2026.

Despite HCFC levels in the atmosphere going in the right direction, not everything has been smooth sailing in the phase-out of ozone-depleting substances. In 2019 a team of scientists, including myself, provided evidence that CFC-11, a common constituent of foam insulation, was still being used in parts of China despite the global ban on production.

The United Nations Environment Programme also reported that HCFCs were illegally produced in 2020 contrary to the phase-down schedule.

In 2023, I and others showed that levels of five more CFCs were increasing in the atmosphere. Rather than illegal production, this increase was more likely the result of a different process: a loophole in the Montreal protocol which allowed CFCs to be produced if they are used to make other substances, such as plastics or non-ozone depleting alternatives to CFCs and HCFCs.

Some HCFCs at very low levels in the atmosphere have also been shown to be increasing or not falling fast enough, despite few or no known uses.

Most of the CFCs and HCFCs still increasing in the atmosphere are released in the production of fluoropolymers – perhaps best known for their application in non-stick frying pans – or hydrofluorocarbons (HFCs).

HFCs are the ozone-friendly alternative that was developed and commercialised in the early 1990s to replace HCFCs, but their role as a potent greenhouse gas means that they are subject to international climate emission reduction treaties such as the Paris agreement and the Kigali amendment to the Montreal protocol.

The next best alternative to climate-warming HFCs is a matter of ongoing discussion. In many applications, it was thought that HFCs would be replaced by hydrofluoroolefins (HFOs), but these have created their own environmental problems in the formation of trifluoroacetic acid which does not break down in the environment and, like other poly- and per-fluorinated substances (PFAS), may pose a risk to human health.

A column of air-conditioning units attached to the exterior of a building. — HFOs enable air-conditioners to use less electricity than competing alternatives.
AndriiKoval/Shutterstock

HFOs are at least more energy-efficient refrigerants than older alternatives like propane, however.

Hope for the future

In discovering this fall in atmospheric levels of HCFCs, I feel like we may be turning the final corner in the global effort to repair the ozone layer. There is still a long way to go before it is back to its original state, but there are now good reasons to be optimistic.

Climate and optimism are two words rarely seen together. But we now know that a small group of potent greenhouse gases called HCFCs have been contributing less and less to climate change since 2021 – and look to set to continue this trend for the foreseeable future.

With policies already in place to phase down HFCs, there is hope that environmental agreements and international cooperation can work in combating climate change.

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This blog is written by Cabot Institute for the Environment member Dr Luke Western, Research Associate in Atmospheric Science, University of Bristol. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Why we’re looking for chemicals in the seabed to help predict climate change

Posted on January 30, 2019April 13, 2023 by janet.crompton

File 20190128 108370 ansjbe.jpg?ixlib=rb 1.1 — Alex Fox, Author provided

Hidden in even the clearest waters of the ocean are clues to what’s happening to the seas and the climate on a global scale. Trace amounts of various chemical elements are found throughout the seas and can reveal what’s going on with the biological reactions and physical processes that take place in them.

Researchers have been working for years to understand exactly what these trace elements can tell us about the ocean. This includes how microscopic algae capture carbon from the atmosphere via photosynthesis in a way that produces food for much marine life, and how this carbon sequestration and biological production are changing in response to climate change.

But now scientists have proposed that they may also be able to learn how these systems were affected by climate change long ago by digging deep into the seabed to find the sedimentary record of past trace elements. And understanding the past could be key to working out what will happen in the future.

Trace elements can teach us an amazing amount about the oceans. For example, ocean zinc concentrations strikingly resemble the physical properties of deep waters that move huge quantities of heat and nutrients around the planet via the “ocean conveyor belt”. This remarkable link between zinc and ocean circulation is only just beginning to be understood through high-resolution observations and modelling studies.

Dissolved zinc concentrations in the oceans.
Reiner Schlitzer, data from eGEOTRACES., Author provided

Some trace elements, such as iron, are essential to life, and others, such as barium and neodymium, reveal important information about the biological productivity of algae. Different isotopes of these elements (variants with different atomic masses) can shed light on the types and rates of chemical and biological reactions going on.

Many of these elements are only found in vanishingly small amounts. But over the last few years, an ambitious international project called GEOTRACES has been using cutting-edge technological and analytical methods to sample and analyse trace elements and understand the chemistry of the modern ocean in unprecedented detail. This is providing us with the most complete picture to date of how nutrients and carbon move around the oceans and how they impact biological production.

Carbon factories

Biological production is a tangled web of different processes and cycles. Primary production is the amount of carbon converted into organic matter by algae. Net export production refers to the small fraction of this carbon bound up in organic matter that doesn’t end up being used by the microbes as food and sinks into the deep. An even smaller portion of this carbon will eventually be stored in sediment on the ocean floor.

As well as carbon, these algae capture and store a variety of trace elements in their organic matter. So by using all the chemical information available to us, we can get a complete view of how the algae grow, sink and become buried within the oceans. And by looking at how different metals and isotopes are integrated into ancient layers of sedimentary rock, we can reconstruct these changes through time.

Sampling the seabed.
Micha Rijkenberg, Author provided

This means we can use these sedimentary archives as proxy records of nutrient use and net primary production, or export production, or sinking rates. This should enable us to start answering some of the mysteries of how oceans are affected by climate change, not only in relatively recent Earth history but also in deep time.

For example, as well as enlightening us on active processes within the modern ocean, scientists have analysed what zinc isotopes are in seabed fossils from tens of thousands of years ago, and even in ancient rocks from over half a billion years ago. The hope is that they can use this information to reconstruct a picture of how marine nutrients have changes throughout geological history.

But this work comes with a note of caution. We need to bring our knowledge about modern biogeochemistry together with our understanding of how rocks form and geochemical signals are preserved. This will enable us to be sure that we can make robust interpretations of the proxy records of the prehistoric seabeds.

Collecting the samples.
Micha Rijkenberg, Author provided

How do we go about doing this? In December 2018, scientists from GEOTRACES met with members of another research project, PAGES, who are experts in reconstructing how the Earth has responded to past climate change. One approach we developed is to essentially work backwards.

First we need to ask: what archives (shells, sediment grains, organic matter) are preserved in marine sediments? Then, which of the useful metal and isotope signatures from seawater get locked up in these archives? Can we check – using material from the surface of deep-sea sediments – whether these archives do provide useful and accurate information about oceanic conditions?

The question can also be turned around, allowing us to ask whether there new isotope systems that have yet to be investigated. We want to know if GEOTRACES uncovered interesting patterns in ocean chemistry that could be the start of new proxies. If so, we might be able to use these ocean archives to shed light on
how the uptake of carbon in marine organic matter responds to, and acts as a feedback on, climate in the future.

For example, will a warmer world with more carbon dioxide enhance the growth of algae, which could then absorb more of this excess CO₂ and help to act as a break on man-made carbon emissions? Or will algae productivity decline, trapping less organic matter and spurring on further atmospheric warming into the future? The secrets could all be in the seabed.

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This blog is written by Cabot Institute member Katharine Hendry, Reader in Geochemistry, University of Bristol and Allyson Tessin, Visiting research fellows, University of Leeds. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Neonicotinoids: Are they killing our bees?

Posted on September 11, 2013April 20, 2023 by janet.crompton

The UK government has announced that whilst it accepts the European Union ban on neonicotinoid pesticides, it does not believe that there is enough scientific evidence to support this action.

In April, the EU banned the use of neonicotinoid pesticides for two years starting in December because of concerns over their effect on bees. The use of these pesticides will not be allowed on flowering crops that attract bees or by the general public, however winter crops may still be treated. Fifteen countries voted for this ban, with eight voting against it (including the UK and Germany) and four countries abstaining.

Neonicotinoids were originally thought to have less of an impact on the environment and human health than other leading pesticides. They are systemic insecticides, which means they are transported throughout the plant in the vascular system making all tissues toxic to herbivorous insects looking for an easy meal. The most common application in the UK is to treat seeds before they are sown to ensure that even tiny seedlings are protected against pests.

Image by Kath Baldock

The major concern over neonicotinoids is whether nectar and pollen contains levels of pesticide is high enough to cause problems for bees. It has already been shown that they do not contain a lethal dose, however this is not the full story. Bees live in complex social colonies and work together to ensure that there is enough food for developing larvae and the queen. Since neonicotinoids were introduced in the early 1990s bee populations have been in decline and there is a growing feeling of unease that the two may be connected. Scientific research has provided evidence both for and against a possible link leaving governments, farmers, chemical companies environmentalists and beekeepers in an endless debate about whether or not a ban would save our bees.

Several studies on bees have shown that sublethal levels of neonicotinoids disrupt bee behaviour and memory. These chemicals target nicotinic acetylcholine receptors, one of the major ways that signals are sent through the insect central nervous system. Scientists at Newcastle University recently showed that bees exposed to neonicotinoids were less able to form long-term memories associating a smell with a reward, an important behaviour when foraging for pollen and nectar in the wild.

Researchers at the University of Stirling fed bumble bee colonies on pollen and sugar water laced with neonicotinoids for two weeks to simulate field-like exposure to flowering oil seed rape. When the colonies were placed into the field, those that had been fed the pesticides grew more slowly and produced 85% less queens compared with those fed on untreated pollen and nectar. The production of new queens is vital for bee survival because they start new colonies the next year. Studies in other bee species have found that only the largest colonies produce queens, so if neonicotinoids have even a small effect on colony size it may have a devastating effect on queen production.

So why does the government argue that there is not enough scientific evidence to support a ban on neonicotinoids?

Image by Kath Baldock

In 2012, the Food and Environment Research Agency set up a field trial using bumble bee colonies placed on sites growing either neonicotinoid-treated oil seed rape or untreated seeds. They found no significant difference between the amount of queens produced on each site, although the colonies near neonicotinoid-treated crops grew more slowly. The study also found that the levels of pesticide present in the crops was much lower than previously reported.

I personally think that both laboratory and field studies bring important information to the debate, however neither has the full answer. Whilst more realistic, the government’s field trial suffered from a lack of replication, variation in flowering times and various alternative food sources available to bees. Only 35% of pollen collected by the bees was from the oil seed rape plants, so where oil seed rape comprises the majority of flowering plants available to bees the effect on neonicotinoids may be more pronounced. The laboratory research can control more variables to establish a more clear picture, however the bees in these studies were often given only neonicotinoid-treated pollen and nectar to eat, which clearly is not the case in a rural landscape. Flies and beetles have been shown to avoid neonicotinoids, which could mean that bees would find alternative food sources where possible. This would have a major impact on crop pollination.

We desperately need well-designed field studies looking at the effect of neonicotinoids on bees and the environment in general. Despite an EU moratorium on growing neonicotinoid treated crops, an allowance should be made for scientists to set up controlled field trials to study the effect of these pesticides on bees during the two year ban. It could be our only chance to determine the danger these chemicals pose to vital pollinators and the wider environment.

This blog is written by Sarah Jose, Biological Sciences, University of Bristol

Sarah Jose