Biomethane to Grid

Biomethane injection into the gas grid.

The Green Gas Certification Scheme (GGCS) enables biomethane (‘green gas') to be tracked through the supply chain, ensuring certainty for those that buy it.

CNG Services along with six other companies including National Grid, Eon, Centrica and Bio Group founded the scheme, which is run by a subsidiary of the Renewable Energy Association (REA), the Renewable Energy Assurance Ltd.

The scheme works on the basis that each unit of green gas injected into the grid displaces a unit of fossil-derived natural gas. The GGCS tracks each unit of green gas from its injection into the gas grid through any number of trades to its sale to a consumer. It monitors the contractual rather than physical flows to ensure there is no double-counting of the gas. Each kWh of green gas is electronically labelled with a unique identifier, the Renewable Gas Guarantee of Origin (RGGO), that contains information relating to where, when and how the gas was produced. This acts as an assurance that the green gas traded or bought is authentic and has not been sold to another party.

The following schematic shows how the GCCS system will work:

 Green Gas Certification Scheme

  1. A participating green gas producer will register the biomethane injected into the grid on a monthly basis, based on the actual volume and CV of the gas produced from an independent meter reading.
  2. The producer then registers the details of the supplier or trader it has contracted with to sell the units of injected gas (normally via a Gas Purchase Agreement).
  3. A participating gas supplier or trader must acknowledge a transaction with the producer (or previous supplier/trader) registered to their account.
  4. The supplier/trader registers each kWh of green gas it has contracted to sell to another supplier/trader or consumer.
  5. If the sale is to another supplier/ trader the transaction registered to their account must be acknowledged. If the sale is to a consumer, each kWh of green gas sold must be registered
  6. Once the supplier/ trader registers the sale of gas to a consumer, the GGCS IS system will automatically generate a certificate in each consumer's name with the relevant RGGOs listed the relevant RGGOs will then be retired from the GCCS system and log them as having been sold to a consumer
  7. The GGCS will go live in early March 2011 at which point any green gas that has been injected into the gas distribution network to date can be registered.

There are a number of possibilities being considered. One tonne of food waste from a supermarket would make around 80 m3 of methane which is around 60kg of CNG or 80 litres of diesel. This would fuel a Sprinter for around 500km. The Green Gas Certificates could track this gas and show that the Sprinters were actually fuelled by gas made from the food waste.