【国际天然气联盟】低碳气体技术导论-2024.10

Summary of Low Carbon Gas Technologies

Core Content

This document provides an overview of low carbon gas technologies that are essential for the decarbonisation and diversification of the global energy system. It highlights the importance of these technologies in achieving carbon neutrality and supporting energy security and access. The report is structured into three main sections: Decarbonisation, Diversification, and Innovation, each focusing on different methods of producing and utilising low-carbon gases.

Main Sections and Key Technologies

Part 1: Decarbonisation

This section explores technologies that reduce emissions from the methane supply chain.

• Biomethane through Anaerobic Digestion

  • Process: Organic waste is decomposed by bacteria in an anaerobic environment, producing biogas (rich in methane).
  • Feedstocks: Food and feed industry waste, manure, green waste, sewage sludge, etc.
  • Biomethane can be purified and injected into the existing gas grid, acting as a carbon-neutral fuel.
  • CO₂ from the process is biogenic and does not contribute to net greenhouse gas emissions.

• Pyrogasification

  • Process: Waste is heated in the absence of oxygen to produce syngas (carbon monoxide, hydrogen, CO₂, methane).
  • Feedstocks: Dry biomass, solid recovered fuels (SRF), and other organic materials.
  • Syngas from SRF contains more pollutants and requires purification for industrial use.

• Hydrothermal Gasification

  • Process: Wet or liquid organic waste is processed under high pressure and temperature to produce syngas.
  • Syngas composition: Methane, hydrogen, and CO₂.
  • Purification: CO₂ is removed, leaving methane and hydrogen for further use.
  • Methane content can reach 50–60% in catalytic conversion, and up to 90% when hydrogen is co-injected.

• E-methane

  • Process: Methanation of CO or CO₂ with hydrogen to produce synthetic methane.
  • CO₂ sources: Biogenic CO₂ from biogas plants, industrial CO₂, or atmospheric capture.
  • E-methane can be used in existing natural gas infrastructure.

• Solar Photocatalytic Processes

  • Process: Uses solar energy to split water into hydrogen and oxygen through photocatalytic reactions.
  • Two main types:
    • Photocatalysed water splitting: Simple process with a photocatalyst immersed in water.
    • Photo-ElectroChemical (PEC) water splitting: Electro-assisted, increasing hydrogen yield.
    • PV-EC water splitting: Integrates multijunction III-V solar cells with electrolysis.

Part 2: Diversification

This section focuses on hydrogen production technologies and their role in the energy transition.

• Methane Reformation

  • Process: Methane reacts with steam and oxygen in the presence of a catalyst to produce syngas and hydrogen.
  • When carbon capture is used, the hydrogen is termed blue hydrogen.
  • Key reactions:
    • Steam Methane Reforming (SMR): $\mathrm{CH_4 + H_2O \leftrightarrow CO + 3H_2}$
    • Water-Gas Shift (WGS): $\mathrm{CO + H_2O \leftrightarrow H_2 + CO_2}$

• Water Electrolysis

  • Process: Uses electricity to split water into hydrogen and oxygen.
  • Green hydrogen is produced using renewable energy, while pink hydrogen uses nuclear energy.
  • Five main technologies:
    • Alkaline electrolysis
    • Photoelectrochemical (PCEC)
    • Proton Exchange Membrane (PEM)
    • Anion Exchange Membrane (AEM)
    • Solid Oxide Electrolysis (SOEC)
  • Ongoing research aims to improve efficiency, cost, and durability.

• Thermal Gasification

  • Process: Converts solid organic matter into syngas using high temperatures (700–1500°C).
  • Syngas is purified and then used in gas-water shift reactions to produce high-purity hydrogen (>99.9%).

• Methane Pyrolysis

  • Process: Uses energy to break methane into hydrogen and solid carbon.
  • Methods:
    • Plasma pyrolysis
    • Thermal pyrolysis
    • Catalytic pyrolysis
    • Microwave-assisted pyrolysis
  • Requires less energy than electrolysis and has a low GHG footprint.

• Biological Production

  • Two main methods:
    • Fermentation: Breaks down complex organic matter into hydrogen and short-chain molecules.
      • Dark fermentation: Uses bacteria and complex substrates.
      • Photo-fermentation: Uses light and small organic acids.
      • Microbial Electrolysis Cells (MEC): Uses low electrical current and simple carbon sources.
    • Biophotolysis: Uses cyanobacteria and green algae to split water into hydrogen and oxygen.

• Geological Extraction

  • Natural hydrogen ("white" hydrogen): Produced through water-rock reactions like serpentinisation.
  • Water injection induced hydrogen ("orange" hydrogen): Uses CO₂ sequestration and iron-rich formations to generate hydrogen.

Part 3: Innovation

The gas industry must innovate to support deep decarbonisation and energy transition.

• Key Priorities for Innovation:

  • Operational efficiency and decarbonisation.
  • Skills development and collaboration.
  • Investment in decarbonising technologies (CCS, CCU, renewable gases, hydrogen).
  • Enabling policy and financing to support scale-up of these technologies.
  • No-regrets infrastructure investments to facilitate renewable energy integration.

• Role of Innovation:

  • Supports energy security and access.
  • Addresses climate targets and GHG reduction.
  • Enables net-zero pathways by combining gas and renewable energy.

Key Information

• Over 140 countries have committed to carbon neutrality by 2050.
• Natural gas infrastructure can support the cost-effective deployment of low-carbon and renewable gases.
• Hydrogen is emerging as a key energy carrier with multiple production methods.
• Decarbonisation and diversification are critical for aligning with climate goals.
• Innovation is vital for scaling up these technologies and ensuring sustainability.
• Low-carbon gas technologies help address climate change, energy security, and energy access issues, especially for the 3 billion people lacking clean energy.

Conclusion

Low carbon gas technologies are crucial for the transition to a sustainable energy system. They offer flexibility, efficiency, and scalability, and are compatible with existing infrastructure. By combining decarbonisation, diversification, and innovation, the gas industry can play a leading role in achieving global climate targets and energy security.