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The gasification of coal provided a much cleaner and sustainable way of utilising the resource when it was first introduced, offering a more versatile form of the energy source. The process converts coal into a gaseous fuel, known as syngas, which still retains most of its useful energy and can be readily purified and transported/distributed.

As well as coal, biomass can be used to produce SNG which could be advantageous from an emissions point of view.

What is Bio-SNG?

SNG produced by the gasification of any type of biomass is known as bio-SNG. Bio-SNG can be used in a similar way to biomethane generated via anaerobic digestion with the added advantage that the production can accommodate for a much wider range of input biomass feedstocks and waste. This is also the reason why bio-SNG is believed in some quarters to be crucial to the use of renewable gas to achieve large reductions in greenhouse gas emissions past 2050.

Bio-SNG production

The process and technology for bio-SNG production is similar to that required for the production of SNG from coal. A wide range of gasifier types are be available, all of which can be categorised into two main types: dry ash gasifiers and slagging gasifiers. The ash formed from the gasification of any hydrocarbon fuel is thermoplastic i.e. it doesn't turn from solid to liquid at a single phase change temeperature. Operating the gasifier between 850°C and 1000°C produces predominantly dry ash at the bottom of the vessel while operating between 1400°C and 2000°C produces ash that is melted to a liquid slag with relatively low viscosity at the bottom.

Below is an overview of the the bio-SNG production process:


Bio-SNG feasibility

Although proven technically feasible, the bio-SNG option is not as widespread as other renewable options for gas. In the UK, bio-SNG needs to be considered because of the potential benefits it can offer. Some of the recognised benefits of this option include:

  • High process speed for conversion of feedstock to energy (process speed is of the order of hours)
  • Potential to execute on a gas-grid scale at cost-competitive capital per GWtherm of energy input
  • Versatile/flexible fuel/feedstock types which include dry solid fuel, municipal commercial and industrial wastes, woody and contaminated biomass, coal, petcoke, plastics, sewage sludge, solvents, inks, bio hazardous/chemical/genetic wastes, persistent organic pollutants, landfill and slag tip mined material, etc.
  • High process efficiency (77% for BGL Oxygen-blown gasifier)
  • Potential to reuse waste produced from the process as an environmentally friendly construction material or fracking material
  • Potential to capture CO2 using highly efficient post-methanation technologies

IGEM's involvement

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