Solid Recovered Fuel

Solid Recovered Fuel (SRF) is distinct from Refuse Derived Fuel (RDF) in that its quality as a fuel is far superior. It is typically used in processes that require a high quality, small particle size, high Calorific Value, low Moisture Content material – such as Cement Kilns and new-generation ATT plants. There is a move in the UK towards the production of pellets from SRF for subsequent use in industrial processes.

Picture of loose SRF, source Geminor all rights reserved

Context

Solid Recovered Fuel (SRF) is distinct from Refuse Derived Fuel (RDF) in that its quality as a fuel is far superior. It is typically used in processes that require a high quality, small particle size, high Calorific Value, low Moisture Content material – such as Cement Kilns and new-generation ATT plants. There is a move in the UK towards the production of pellets from SRF for subsequent use in industrial processes.

Solid Recovered Fuels are covered by international technical specifications which set, amongst other parameters, the chemical and physical parameters of an SRF

Composition of Solid Recovered Fuel

The composition of SRF is defined in the international specification set out above, but often an SRF in the UK can be a more refined RDF rather than something that complies entirely with the specification standard. The main chemical parameters that vary between an RDF and SRF mentioned above are broadly as follows:

Parameter	RDF Example	SRF Example
Net CV	11 MJ/kg	18 MJ/kg
Moisture Content	25%	15%
Chlorine	<1%	<0.6%
Particle Size	300mm	40mm

Chlorine is a particular issue due to its tendency to form Hydrochloric Acid in an energy recovery process, which then requires specific abatement/clean-up technologies. With limited such arrangements in Cement Kilns this means that they generally have a lower tolerance for Chlorine closer in a final specification RDF or SRF. In addition, the use of any Waste Derived Fuel in Cement Kilns has the potential to impact the final quality of the cement produced, and so the composition of an RDF or SRF is critical in the decision to use it in such an application in terms of the ash content of the RDF/SRF.

Export of Solid Recovered Fuel

Whilst the data reported for 2019 suggests in excess of 400,000 tonnes of RDF and SRF were used in Cement Kilns in the UK, there has been a growing and steady export market since 2014 for SRF into cement kilns. Whilst the export of SRF from the UK is often reported within the overall Waste Derived Fuel/RDF statistics, data for England alone from the EA shows a proportional growth in SRF export in the context of a reduction in RDF, as shown in the graph below.

RDF and SRF Export - analysis of EA data by Monksleigh

Nascent SRF Pellet Market

Increasingly the market is considering further refinement (including reducing moisture and increasing NCV) of SRF to produce a high quality fuel pellet for ease of storage, haulage, and introduction into a Cement Kiln, with some companies seeking to achieve End of Waste Criteria classification that would then enable the material to be used in other applications as a blended substitute for coal. There are three main organisations pursuing this approach in the UK market at the present time, each with a different 'brand name' for their pellet:

N+P (Subcoal®)

N+P have been producing a pellet in their operation in the Netherlands and are in the process of producing their Subcoal® pellets in their first plant in the UK in Teeside, with plans to expand to this at their recently acquired facility at Crayford

Waste Knot (SIRF Pellets)

Waste Knot's SIRF pellet is to be produced in their first plant, which is under construction in Middlesborough

Eco-PowerFuels (Eco Power Pellets)

Eco-PowerFuels have been producing their Eco-Power Pellets in their facility in Humberside and in January 2021 was reported to have signed a contract to supply Tarmac's Tunstead Cement Kiln