Let us walk you through some basic Non-CO₂ negative emission technologies
Non-CO₂ negative emission technologies (NETs) target greenhouse gases (GHGs) other than carbon dioxide. These include methane (CH₄), nitrous oxide (N₂O), and fluorinated gases (F-gases, such as hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride). These gases have higher global warming potentials (GWPs) compared to CO₂ and persist for varying durations in the atmosphere. See the primer below (or download it) for an overview of the primary GHGs amendable to NETs and the associated technologies.
1. Methane (CH₄)
Primary Sources: Agriculture (enteric fermentation, manure management), energy (natural gas leaks, coal mining), waste (landfills).
NET Approaches:
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Methane oxidation: Catalytic or photochemical oxidation converts CH₄ into CO₂ and water. While CO₂ is a GHG, its GWP is much lower than methane's.
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Biochar amendments: Applying biochar to soils or as a landfill cover can reduce methane emissions by enhancing microbial oxidation.
Methane-capture technologies: Utilizing methane-oxidizing bacteria or engineered solutions to capture methane emissions at the source (e.g., from landfills or livestock).
2. Nitrous Oxide (N₂O)
Primary Sources: Agriculture (enteric fermentation, manure management), energy (natural gas leaks, coal mining), waste (landfills).
NET Approaches:
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Methane oxidation: Catalytic or photochemical oxidation converts CH₄ into CO₂ and water. While CO₂ is a GHG, its GWP is much lower than methane's.
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Biochar amendments: Applying biochar to soils or as a landfill cover can reduce methane emissions by enhancing microbial oxidation.
Methane-capture technologies: Utilizing methane-oxidizing bacteria or engineered solutions to capture methane emissions at the source (e.g., from landfills or livestock).
3. Fluorinated Gases (F-Gases)
Primary Sources: Industrial activities, refrigerants, air conditioning, semiconductor manufacturing.
NET Approaches:
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Destruction technologies:
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Plasma arc destruction: Uses high-energy plasma to break down F-gases into less harmful compounds.
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Catalytic decomposition: Employs specialized catalysts to break F-gases into inert or less harmful components.
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Capture and reuse: Recovery and recycling of refrigerants or industrial gases to prevent their release.
Natural alternatives: Developing refrigerants and industrial chemicals with low GWPs as substitutes for F-gases.
4. Hydrofluorocarbons (HFCs) and Similar Substances
Primary Sources: Refrigeration, air conditioning, and aerosols.
NET Approaches:
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Thermal destruction: Controlled incineration in specialized facilities to destroy HFCs.
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Cryogenic separation: Freezing and separating HFCs for reuse or destruction.
Alternative technologies: Transitioning to cooling systems with natural refrigerants (e.g., ammonia, CO₂).
5. Black Carbon (BC)
Primary Sources: Incomplete combustion of fossil fuels, biofuels, and biomass.
NET Approaches:
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Improved combustion technologies: Deploying stoves and engines that achieve near-complete combustion.
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Filter technologies: Retrofitting filters to capture particulate matter from emissions sources.
Soil incorporation: Using captured BC as a soil amendment to sequester it long-term.
Research Frontiers and Challenges
Direct air capture for non-CO₂ GHGs is less mature than for CO₂ and often focuses on capturing these gases at point sources.
Policy and incentives are critical to scaling non-CO₂ NETs, particularly in sectors like agriculture where emissions are diffuse and challenging to manage.
Global standards for monitoring, reporting, and verifying (MRV) non-CO₂ removals are less developed than for CO₂.
These NETs represent a growing frontier in climate mitigation, addressing high-GWP gases that significantly contribute to climate change despite their lower atmospheric concentrations relative to CO₂.
Set forth below is a chart highlighting a cross-section of efforts to develop and implement technologies aimed at reducing non-CO₂ greenhouse gases. But, there are many more—which is exactly what Net350 is exploring.