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ACR Carbon Markets 101: High GWP Pollutants

By: Megesh Tiwari

Senior Technical Manager, American Carbon Registry

ACR’s Carbon Market 101 blog series explores and explains carbon markets and how ACR tackles various issues in our ongoing mission to set the bar for carbon credit quality. 

At ACR, we have a strong focus on incentivizing actions to reduce and eliminate extremely potent non-CO2 climate pollutants like methane, hydrofluorocarbons (HFCs), and ozone depleting substances (ODS) like chlorofluorocarbons (CFC) and hydrochlorofluorocarbons (HCFC). Given the potential to deliver significant climate impact, we thought it would be useful to introduce some of the central concepts associated with our innovative and industry-leading methodologies for refrigerants, foam blowing agents, ozone depleting substances, landfill emissions, and orphaned and abandoned wells.

What is Global Warming Potential?

To better understand the impact that different greenhouse gasses (GHG) have gasses have in contributing to the rise in the Earth’s temperatures, scientists established the concept of Global Warming Potential (GWP).

The GWP compares the emissions of one metric ton of different GHGs against the emissions of one metric ton of carbon dioxide (CO2) over a given period of time, most commonly over 100 years. GWP is a relative term and is calculated by dividing absolute GWP of a GHG by absolute GWP of CO2. As such, CO2 is the reference GHG with GWP value of 1. The higher the GWP value, the more it contributes to global warming. For instance, if a pollutant has a 100-year GWP value of five, it contributes to global warming at a rate of five times higher than CO2 over the period of hundred years from the date the pollutant was released into the atmosphere.

What are short-lived climate pollutants (SLCP)?

Another important distinction in comparing harmful pollutants is distinguishing short-lived GHGs from long-lived GHGs. For instance, CO2 can last for centuries in the atmosphere before breaking down, while methane, which has a high GWP, remains in the atmosphere for a much shorter period - only around a decade.

It takes 100 years for around 60-70% of the carbon dioxide to decay in the atmosphere. The rate of decay decreases over time, taking around 500 years for the additional 10% CO2 to decay and over thousands of years for all CO2 to decay. However, in the case of short-lived climate pollutants, like methane, HFCs and HCFCs, over half of the decay happens within first 20 years. In other words, these short-lived GHGs heat the atmosphere at a much higher rate in the initial years after their release, several times higher than their 100-year GWP values. For example, even though HCFC-22 (the most commonly used refrigerant in refrigeration and air conditioning) traps heat around 2,000 times more than CO2 over 100 years; but in the first 20 years, it traps heat around 5,000 times more than CO2. Because of these alarmingly high heat trapping properties, reducing emissions from these short-lived pollutants is critical for avoiding rapid warming of the planet in the short term.

Where are high GWP pollutants used?

High GWP pollutants are present in hundreds of manufacturing, industrial and agricultural processes. High GWP pollutants are often paid less attention than CO2 emissions, but they make a significant contribution in the rise of global temperatures. Global phaseout of HFCs can alone prevent 0.5C warming of the planet by 2100. 

Methane, which has a GWP of between 27 and 30 over a 100-year period, is often found in agricultural production (which accounts for 23 percent of U.S. methane emissions), landfills (17 percent), and oil and natural gas operations (30 percent).

HFCs and perfluorocarbons (PFCs) - which can have GWP in the thousands - are used in a wide variety of applications, including air conditioning units, refrigerators and foam insulation. 

HCFCs, which are also ODSs, were the most widely used compounds for refrigeration, air-conditioning and foam insulation before they were started to be phased out in 2020 in the US. However, many other countries have not yet begun to completely phase out use of HCFCs. And even in countries where HCFCs are being phased out, the market for recycled and reclaimed HCFCs in still huge, especially to service existing equipment. On top of this, even as old equipment gets replaced with new equipment that uses lower GWP alternatives, the remaining gas sits in stockpiles and eventually vents into the atmosphere.

What can be done to limit the use of high GWP pollutants?

Some groups of pollutants have been targeted by governments and international bodies and are strongly regulated or banned. For instance, the Montreal Protocol, which was ratified by all 198 United Nations Member States, calls for the phasing out of ODS, which are also high-GWP climate pollutants, through target dates and strong reporting measures. 

But other high GWP GHGs like HFCs and methane are still present in hundreds of manufacturing, industrial and agricultural processes And while production and consumption of virgin HCFCs are banned in the US, the market for reclaimed HCFCs to service old (leaky) existing equipment is still robust.

Carbon markets can incentivize projects that remove or avoid the release of GHG emissions into the atmosphere. Revenue generated from carbon credits allows for the collection and safe destruction of these harmful pollutants, along with financing the transition to alternatives that contribute less to global warming.

For example, in the case of refrigerants, air conditioners and foam insulation, there are often low-GWP alternatives that already exist. Unfortunately, many of these alternatives are cost prohibitive and have not been widely adopted in the marketplace. Carbon markets can play a role in supporting industries to transition more quickly to low GWP alternatives.

The destruction of, and transition away from, these high GWP GHGs is irreversible,  permanent and fully additional and has significant short-term impact on preventing global temperature rise.  It is expected that as more companies continue to signal interest in purchasing these kind of carbon credits, the price of the credits will rise, creating more revenue for projects and catalyzing wider adoption of alternatives.

Examples of ACR methodologies focused on high-GWP, short-lived climate pollutants 

Advanced Refrigeration Systems, version 2.1

Certified Reclaimed HFC Refrigerants, Propellants, and Fire Suppressants, version 2.0

Destruction of Ozone Depleting Substances and High-GWP Foam, version 1.2

Destruction of Ozone Depleting Substances from International Sources, version 1.0

Transition to Advanced Formulation Blowing Agents in Foam Manufacturing and Use, version 3.0
Capturing and Destroying Methane from Coal and Trona Mines in North America
, version 1.1

Landfill Gas Destruction and Beneficial Use Projects, version 2.0
Plugging Abandoned & Orphaned Oil and Gas Wells
, version 1.0 (in scientific peer review)