Decarbonisation Technology August 2026 Issue

BIOMETHANE PRODUCTION From organic waste to renewable gas

Existing infrastructure

Renewable

Low carbon

Secure energy

1. Feedstocks

2. Production pathways

3. Upgrading

4. Uses

Anaerobic digestion

Agricultural residues

Grid injection

Biogas

Digestion

Upgrading

Food waste

Transport

Thermochemical conversion

Wastewater sludge

Industry

Biomethane

Syngas

Gasication

Upgrading

Industrial organic waste

Power generation

Key benets

Lower emissions

Circular solution

Energy security

Scalable & future-ready

Renewable energy

Figure 1 Biomethane production from organic waste to renewable gas

methanogenesis step, methane-producing microorganisms convert these intermediates into biogas. Raw biogas typically consists mainly of methane and CO 2 , together with water vapour and trace impurities, including hydrogen sulphide, ammonia, nitrogen, oxygen, siloxanes, and volatile organic compounds. The methane fraction determines the energy value of the gas, whereas CO 2 and impurities must be removed when the target product is biomethane for grid injection, transport fuel, or industrial use. In addition to biogas, anaerobic digestion produces digestate, a nutrient-rich residue containing organic matter and plant nutrients such as nitrogen, phosphorus, and potassium. When properly managed, digestate can be used as a fertiliser or soil conditioner, improving nutrient recycling and strengthening the circular economy value of biomethane systems (Neri, et al., 2023) . Biogas upgrading is required to increase methane concentration and meet end-use specifications. Water scrubbing is one of the most established technologies. It relies on the higher solubility of CO₂ and H₂S in water compared with CH₄. It is valued for its relative simplicity and robustness, although water use and methane slip must be controlled. Pressure swing adsorption (PSA) uses solid adsorbents to selectively retain CO₂ under pressure and regenerate them by depressurisation. Membrane separation is a modular and increasingly attractive option

in which CO₂ permeates through selective membranes faster than methane. Chemical absorption, typically based on amine solvents, provides very high CO₂ removal efficiency and high methane recovery; however, solvent regeneration requires heat and increases process complexity (Miltner, et al., 2017) . Beyond conventional anaerobic digestion, emerging biomethane pathways include biomass gasification and power-to- methane integration. Gasification converts dry lignocellulosic biomass into synthesis gas (syngas), which can subsequently be methanated to produce synthetic biomethane. Power-to-methane combines renewable hydrogen from water electrolysis with CO 2 from biogas upgrading or other biogenic sources, producing additional methane through catalytic or biological methanation. These approaches can increase carbon utilisation efficiency and strengthen the integration of renewable electricity and gas systems (Gotz, et al., 2016) . Biomethane production technologies exhibit a high level of technical maturity, with anaerobic digestion and upgrading technologies such as water scrubbing, PSA, membrane separation and chemical absorption already commercially deployed worldwide. Future developments are expected to focus on process optimisation, methane recovery, digestate valorisation, system integration, and cost reduction, rather than on fundamental technological