SRF vs RDF: What’s the difference between the alternative fuels?

Recycling is an important part of the waste hierarchy, preventing waste from being dumped in already burgeoning landfills and putting it to good use instead.

But the reality is that not all waste is suitable for recycling. Cardboard contaminated with food and a lot of plastics are rejected at recycling plants, so we need to be investing in alternative ways to keep these materials in the circular economy.

Energy from waste (EfW) is the solution that SunSkips favours to get the maximum value possible from the rubbish we manage and minimise what’s sent to landfill.

There are two common types of waste that can be burned to generate useful energy: RDF (refuse derived fuel) and SRF (solid recovered fuel). But what’s the difference and is one more valuable or sustainable than the other?

What is RDF?

RDF is a fairly crude energy source usually derived from municipal waste. The most valuable recyclable waste like wood, metal, paper, and glass is removed before it’s shredded and packaged as fuel, with minimal separation involved.

In its final form – which may be raw or compressed into pellets, logs or bricks – good RDF is mostly made up of the lightest, driest, fluffiest, most combustible material.

The alternative fuel is used in specialist EfW facilities, which can power homes and industry or supplement traditional fossil fuels.

The UK doesn’t have a very strong infrastructure for generating energy from waste (although it is improving), so waste management firms typically export to Europe where RDF is in high demand.

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What is SRF?

SRF is a more refined subset of RDF in that it needs to go through a more sophisticated process of separation before it can pass the quality criteria.

It is usually sourced from industrial and construction waste and typically contains higher calorie materials that make it more valuable due to the level of heat it’s capable of generating.

Because of SRF’s higher quality, it can be used in industrial kilns like those used for making cement.

SRF is what SunSkips produces from the waste managed across Suffolk and Cambridgeshire. Thanks to the skip hire company’s meticulous screening line, operators at the East Anglian sites are able to leverage flip-flow screens, overhead magnets, and air classifiers to get a final end product with smaller particles, sufficient moisture levels and high caloric content.

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But RDF and SRF are quite similar to the layman, so let’s break down the key differences between the two waste derived fuels…

What’s the difference between RDF and SRF?

The key difference between RDF and SRF is essentially how well it’s refined and processed.

A lot of material that could otherwise be recycled is wasted with RDF, whereas the time invested in separating it from SRF not only gives you an extra revenue stream via the recyclable materials, but you also end up with a better quality, more valuable energy source.

SRF is considered a zero-to-landfill fuel because once it’s been burned, the ash that’s left over can also be used as aggregate in cement production.

Because RDF doesn’t go through as rigorous a process as SRF, it doesn’t have as many applications due to its lower efficiency.

How is SRF used in industrial kilns?

Once the waste is separated into high-quality SRF at SunSkips’ sites, it’s sent off for further cleaning and drying before being ground up into a fluffy substance, which makes it burn hotter.

Waste is burned in a furnace at 1000ºC, creating steam that powers turbines. Metals from the burned waste that were missed in the initial processing are picked out to be recycled and the ashes are taken to be used as aggregate.

Why SunSkips invests in SRF

SunSkips is a sustainable skip hire company that understands how much the country’s landfills are struggling with the amount of waste a growing population generates.

Therefore, we feel it’s our responsibility to operate to high environmental standards and be part of the solution.

The waste hierarchy puts EfW on the fourth step after prevention, preparing for reuse, and recycling, but before disposal, which is deemed less environmentally friendly. Burning SRF does, of course, generate CO2 (250-600kg per tonne), but far less than fossil fuels and it’s better for the atmosphere than the methane that’s emitted from rubbish rotting in landfill for hundreds of years.

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Because it needs relatively little pre-treatment (compared with petroleum production), EfW is an incredibly efficient method not only of energy generation, but also waste management.

About half of non-recyclable waste is biogenic and therefore can be burned as a sustainable alternative to fossil fuels. At a time when energy prices are sky high and the reliance on foreign supply is creating economic and political chaos, a readily-available fuel is a very appealing proposition.

Burning SRF is heavily regulated. The smoke is filtered, carefully monitored and strict failsafes are put in place to stop them reaching above what the Environment Agency deems unacceptable.

Plastic waste is an especially good material for SRF because it’s notoriously difficult to recycle and there isn’t a huge market for certain pieces – and those that do exist have very strict criteria.

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SunSkips is passionate about sustainable alternatives to landfill and is always looking into new, efficient processes to adopt as more sites pop up around East Anglia – SRF is a big part of how we’ll continue to get as much value as we can from the 6,000+ tonnes of waste we process every month.

Want to learn more about how SunSkips can get more value out of your industrial and commercial waste via SRF? Schedule an appointment with our team and let us explain.