Renewable natural gas

Renewable natural gas, also known as sustainable natural gas, is a biogas which has been upgraded to a quality similar to fossil natural gas. A biogas is a gas methane obtained from biomass. By upgrading the quality to that of natural gas, it becomes possible to distribute the gas to customers via the existing gas grid, within existing appliances. Renewable natural gas is a subset of synthetic natural gas or substitute natural gas (SNG).

Renewable natural gas can be produced economically, and distributed via the existing gas grid, making it an attractive means of supplying existing premises with renewable heat and renewable gas energy, while requiring no extra capital outlay of the customer. Renewable natural gas can be converted into liquefied natural gas (LNG) for direct use as fuel in transport sector. LNG would fetch good price equivalent to gasoline or diesel as it can replace these fuels in transport sector.

The existing gas network allows distribution of gas energy over vast distances at a minimal cost in energy. Existing networks would allow biogas to be sourced from remote markets that are rich in low-cost biomass (Russia or Scandinavia for example).

The UK National Grid believes that at least 15% of all gas consumed could be made from matter such as sewage, food waste such as food thrown away by supermarkets and restaurants, and organic waste created by businesses such as breweries.

A biomass to SNG efficiency of 70% can be achieved. Costs are minimised by maximising production scale, and by locating plant next to transport links (e.g. a port or river) for the chosen source of biomass. The existing gas storage infrastructure would allow the plant to continue to manufacture gas at the full utilisation rate even during periods of weak demand, helping minimise manufacturing capital costs per unit of gas produced.

Renewable gas can be produced through three main processes; anaerobic digestion of organic (normally moist) material, thermal gasification of organic (normally dry) material and produced through the Sabatier reaction. In these cases the gas from primary production has to be upgraded in a secondary step to produce gas that is suitable for injection into the gas grid.

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