A biofilm-based biocatalyst system for capturing low-concentration methane from air and converting into biomass

Background

Methane is a highly potent greenhouse gas, with a global warming potential significantly greater than carbon dioxide over a 20-year period. Its atmospheric concentration has been steadily increasing due to both natural and human-related sources, such as landfills, agriculture, and fossil fuel extraction. Unlike point-source emissions, many of these sources emit methane at low concentrations and in a diffuse manner, making it especially challenging to capture and mitigate. Addressing emissions from low-concentration, widespread sources is critical for meeting climate targets and minimizing the environmental impact of methane.

Current approaches to methane mitigation face significant technical and practical limitations, particularly at low concentrations. Traditional catalytic oxidation methods require high temperatures and are energy-intensive, making them unsuitable for dilute methane streams. Biological approaches, such as aqueous bioreactors using methanotrophic bacteria, are hampered by the poor solubility of methane and oxygen in water, leading to low reaction rates and high energy costs for gas-liquid mixing. Biofilters, while improving gas-to-cell contact, often suffer from operational issues like clogging, increased pressure drop, and uneven airflow due to biomass accumulation. These problems are exacerbated when processing large volumes of air with low methane content, resulting in reduced efficiency and reliability over time. As a result, there is a clear need for innovative solutions that can efficiently and sustainably capture methane from diffuse, low-concentration sources without the drawbacks of existing technologies.

Technology

The described technology is an advanced biocatalyst system engineered to capture and convert methane from air, especially from low-concentration, diffuse sources such as landfills, agricultural fields, and wastewater treatment sites. Central to its design is the use of methanotrophic microorganisms immobilized as biofilms on substrates, which are arranged on multiple horizontally positioned trays stacked vertically within a reactor. Methane-containing air flows upward between these trays, directly exposing the biofilms—typically 50 μm to 2 mm thick—to the gas stream without the presence of a bulk liquid phase. This configuration minimizes mass transfer resistance and energy consumption, as nutrients are delivered via carriers like cellulose beads to maintain biofilm moisture without immersion. The methanotrophs oxidize methane into carbon dioxide and convert it into microbial biomass (single cell protein), operating efficiently at ambient temperature and pressure, and at methane concentrations as low as 200 ppm. The system supports continuous operation, stable methane removal, and straightforward harvesting of biomass for use as animal feed.

This technology is differentiated by its innovative elimination of the bulk liquid phase, which traditionally hampers methane mass transfer in biological systems due to methane’s low solubility in water. By directly exposing biofilms to the gas phase, the system achieves significantly higher methane conversion rates and lower energy requirements compared to conventional aqueous bioreactors or biofilters, which often suffer from clogging, channeling, and performance degradation. The modular, tray-based architecture allows for scalable deployment and easy maintenance, while the use of diverse substrate materials and nutrient delivery methods ensures robust and adaptable biofilm growth. Experimental validation demonstrates over 100% improvement in methane removal rates compared to traditional systems, with stable long-term operation at low methane concentrations. This makes the solution uniquely suited for mitigating methane emissions from challenging, low-concentration sources, offering both climate benefits and the potential for valuable biomass production.

Benefits

• Efficient methane capture and oxidation from low-concentration diffuse sources at ambient temperature and pressure
• Elimination of bulk liquid phase reduces mass transfer resistance and energy consumption
• Vertically stacked tray design enhances gas flow and methane conversion rates
• Biofilm-based methanotrophic microorganisms enable stable, high-rate methane oxidation
• Use of natural and synthetic substrates supports robust biofilm growth and nutrient delivery
• Production of valuable biomass (single cell protein) as a byproduct for animal feed
• Scalable and continuous operation suitable for diverse methane emission environments
• Reduced operational issues like clogging and pressure drop compared to traditional biofilters

Applications

• Landfill methane emission abatement
• Wastewater plant methane capture
• Oil and gas site emission control
• Single cell protein production
• Agricultural methane mitigation

Additional info

A biocatalyst system captures atmospheric methane using methanotrophic biofilms, 50 μm to 2 mm thick, immobilized on substrates within vertically stacked trays. Operating without a bulk liquid phase, it directly exposes the biofilms to the gas stream, significantly reducing mass transfer resistance and energy consumption. Nutrients are delivered via carriers. Methane is oxidized to CO2 and converted into biomass (single cell protein) at ambient conditions, even at low concentrations.