Biomethane was already classified “Act now” in 2025, alongside the same proposals: UNC0894/0894A on reverse compression and UNC0900 on gas quality. SDS-2 retains that priority under Objective 7.2.
The timetable needs careful interpretation. Ofgem’s summary lists 2026–27 for implementation, but the detailed biomethane section expects decisions in that period, acknowledging possible delays from external safety and strategic assessments. This is not a guaranteed commissioning timetable.
As of 16 September 2026, the code register still lists both modification processes as awaiting Ofgem’s decision. The statement is the final 2026 publication; “preliminary” refers to the transition into the new code-governance framework, not an open consultation draft.
Low local gas consumption—particularly during summer—can limit how much biomethane a distribution network accepts. Reverse compression would move surplus network gas upstream into the National Transmission System (NTS), creating space for additional local injection.
UNC0894 and UNC0894A are alternative proposals, not complementary approvals. They pursue the same physical outcome but differ in commercial treatment:
For constrained producers, the potential benefit is more injection hours, less curtailment and scope for expansion. But additional capacity is not cost-free under either approach. Its commercial value depends on infrastructure funding, compression costs, access allocation and the treatment of outages—not simply whether NTS entry charges apply.
The resulting trade-off is between additional saleable production and the full cost of making that production deliverable.
UNC0900 concerns contractual oxygen limits at the Murrow and Glentham entry points, through changes to their Network Entry Agreements. It does not automatically relax specifications for every biomethane producer.
Where higher oxygen concentrations can safely be accepted, reduced oxygen-removal requirements could lower treatment costs. Workgroup discussions identify this potential saving, but also downstream sensitivities, including storage-related corrosion risks. The impact is therefore site-specific.
National Gas reported in March 2026 that it had submitted an Health and Safety Executive (HSE) exemption request to permit gas containing up to 1 mol% oxygen in the NTS and relevant higher-pressure distribution networks. That submission is not an approval: safety permissions, code provisions and agreed entry specifications remain distinct requirements.
Oxygen reform would not eliminate propane enrichment. Propane addition addresses calorific-value and billing arrangements; NESO identifies alternative billing approaches as a separate route to reducing that cost.
SDS-2 connects distributed renewable-gas production with network repurposing, decommissioning and cost recovery. However, the extent and timing of network changes remain dependent on wider government decisions.
For biomethane, declining gas consumption does not necessarily create spare injection capacity. NESO warns that local constraints can intensify as production rises, demand falls, or both occur together.
The implication for project assessment is spatial and long-term: feedstock availability, seasonal network demand and access to upstream capacity need to be considered together. This links biomethane development to decisions about which network assets are retained, adapted or retired.
Ofgem’s harmonised modification-prioritisation process has been in effect since 29 May 2026. It provides an existing route for progressing strategically aligned changes, but does not replace substantive approval requirements.
Support-scheme deadlines are separate. Government guidance retains 31 March 2028 as the deadline for new Stage 1 Green Gas Support Scheme applications—not the end of payments to existing participants. Network-development assumptions therefore need to be reconciled with each project’s application, tariff-guarantee and commissioning requirements.
For biomethane investment, SDS-2 identifies the regulatory work ahead. The commercial consequences remain conditional on approved rules, funded network works, acceptable gas-quality terms and enforceable injection arrangements.