Are Zeolites the Solution to Help Curb Methane Emissions?

Contributed by: Emily Newton

Zeolites comprise a category of hundreds of minerals that form crystalline structures and have various beneficial uses, including, medicine cat litter, skin cream, soil conditioner, toothpaste, and shampoo.

Some scientists are interested in using them for carbon capture. The potential is fascinating, but how can zeolites reduce emissions?

Using Zeolites for Carbon Capture in Landfills
Landfills are carbon emission sources, partially due to the degradation of products dumped there. However, a collaborative research project at Griffith University will investigate the feasibility of applying manufactured zeolites to landfill cover soils [1]. Participants will study whether the minerals could capture and oxidize the emissions, significantly boosting the baseline oxidation activity occurring in the soil.

The project uses lab-based characterization and field trials to determine the potential applications for commercially manufactured zeolite products. As of February 2024, one business was moving ahead with a field-trial validation after its product showed promising results in the lab. Two of its items have shown oxidation rates greater than 70% for three months after the initial application [2].

Many people rightfully point out it’s better if products never end up in landfills. That’s why some researchers are exploring how to turn waste into energy, using everything from sludge to old food as source material [3]. Even so, the world will need many approaches to reduce emissions and improve sustainability.

READ: Decoding the EU Methane Regulation for the Energy Sector

Designing Zeolite Carbon Capture Methods to Reflect New Requirements
Humans have been interested in zeolite carbon capture possibilities for a while. Leaders of brands associated with above-average emissions are especially motivated to find effective solutions.

In 2017, scientists from ExxonMobil created a new material from silica zeolite, finding it could cause a 25% reduction in the energy required for gas-separation processes and their associated emissions [4]. More recently, leaders from emissions-intensive industries are under even more pressure to make meaningful reductions when possible.

In January 2024, the Environmental Protection Agency proposed a fee increase applicable to entities reporting more than 25,000 metric tons of carbon dioxide equivalents annually. The proposal would apply a fee structure of $900 per metric ton of methane in 2024, with a $300 per metric ton increase in 2025 and a further $300 charge for emissions reported in 2026 and later.

However, industry-specific thresholds apply, too. For example, there is a 0.05% threshold for natural gas sold by or through a facility [5]. The more industry decision-makers can do to reduce their emissions, the less their enterprises will pay in fees. Using zeolites for carbon capture should help, but responsible parties should also pursue other options, such as:

• Addressing leaks in end-use equipment, coal mines and wells
• Using data analytics to identify emissions-intensive activities
• Increasing investments in cleaner energy to power operations
• Prioritizing greener operations, such as by ending non-urgent flaring

Curbing emissions will be a multipronged effort and leaders should not expect universally applicable solutions. However, the more they learn about zeolite carbon capture possibilities and other options, the more readily they can apply that knowledge to develop long-lasting, practical solutions.

Confirming the Enduring Significance of Zeolite for Water Treatment
Although zeolites are a topic of interest among industrial sustainability leaders now, researchers recently learned that ancient civilizations also recognized their potential. An anthropologist from the University of Illinois Urbana-Champaign discussed her findings when examining reservoirs the Mayans used for more than 1,000 years.

Mayans living in parts of what’s now Guatemala faced a yearly five-month drought, but constructed reservoirs provided potable water for tens of thousands of residents. One relevant takeaway was that builders sourced zeolite sand at locations nearly 20 miles from reservoir sites to use as a filtration mechanism [6].

READ: Advancing Towards Reduced Flaring and Methane Emissions

More recently, researchers have applied nano zeolites to wastewater treatment activities [7]. These efforts often allowed them to use fewer chemicals or less water in their processing tasks, which could reduce emissions. In 2023, a pair of studies about the municipal wastewater industry revealed it puts twice the amount of methane into the atmosphere as initially thought [8].

One Irish project involves designing a passive zeolite carbon capture method for reducing methane associated with domestic wastewater treatment [9]. The chosen method relies on porous zeolites to capture the methane and organisms called methanotrophs to metabolize it.

Based on their in-depth understanding of the proposed process, the researchers working with this approach believe it will cause effective methane reductions, even in low-purity streams. Although the team must do more to test commercial viability, this early work can inform their work and others developing similar solutions.

Exploring Zeolite Clay for Low-Cost Methane Mitigation
Costiliness is a downside of many carbon-reduction methods. The expense — combined with the limited real-world trials of some options — can make some leaders reluctant to try them. However, scientists from MIT may have addressed one of those negative aspects by finding a reasonably priced method that involves zeolite clay.

The team discovered that treating zeolite clay with copper increases the material’s effectiveness at absorbing carbon dioxide from the air. They achieved this work by packing the treated zeolite clay particles — that looked similar to cat litter — into an externally heated reaction tube.

Next, they sent methane concentrations from two parts per million to 2% through the tube, knowing the broad range would cover all amounts existing in the atmosphere [10]. This system converts the methane into carbon dioxide, which is far less damaging to the Earth than methane. People may eventually pair this approach with other methods that use zeolites for carbon capture or view this option as an alternative to those possibilities.

Experiments suggested this method is maximally effective at about 300˚ Celsius. That’s approximately half the temperature required to run the reactors used in other carbon-capture methods.

LISTEN: Episode 9: Revolutionizing Methane Mitigation with Windfall Bio

Using zeolite clay for carbon capture by relying on the team’s method is also highly promising for the real world because it takes methane from the air rather than pure oxygen. The researchers say locations such as dairy barns and coal mines would likely be the best places for this capturing method due to their highly concentrated methane.

A Promising Outlook
This overview shows how people have many intriguing ways to apply zeolites for carbon capture. Even if not all these efforts result in commercially viable systems, the work is undoubtedly valuable for a greener future.

References:

https://news.griffith.edu.au/2022/12/23/partnership-trio-join-forces-to-tackle-methane-emissions/ 
https://www.aumanufacturing.com.au/zeolites-to-be-trialed-to-curb-methane-emissions 
https://revolutionized.com/waste-to-energy-technologies/ 
https://corporate.exxonmobil.com/news/news-releases/2017/1207_exxonmobil-and-instituto-de-tecnologia-quimica-discover-new-material 
https://www.all4inc.com/4-the-record-articles/waste-emissions-charge-for-petroleum-and-natural-gas-systems-rule/ 
https://news.illinois.edu/view/6367/2024119234
https://www.mdpi.com/2073-4441/14/2/137 https://engineering.princeton.edu/news/2023/02/28/wastewater-sector-emits-nearly-twice-much-methane-previously-thought
https://www.sfi.ie/challenges/2050-challenge/methane-biofilter/ https://news.mit.edu/2022/dirt-cheap-solution-common-clay-materials-may-help-curb-methane-emissions