The Challenges of
Representative Sampling
of Waste Materials

Ensuring that SOCOTEC remains at the forefront of industry best practice, Sarah Gazzola, commercial manager for Energy & Waste Services, went along to last week’s RDF Industry Group to participate in the debate.

Having worked in the waste industry since graduation, I can vouch that “one woman’s trash is another woman’s treasure.” Never has this saying rung more truly than in the wake of the cessation of wide-spread coal use in the UK. Since then, the pursuit of a low-carbon economy has led to multiple fuel alternatives, including refuse derived fuel (RDF), to keep the home fires burning.

However, it’s not all plain sailing, with a new fuel comes new challenges and that is why we are supporting the ‘RDF code of practice’ that the RDF Industry Group is working on, to ensure that suppliers of refuse-derived fuel (RDF) meet the quality requirements of users. During last week’s session, we took the opportunity to share our thinking on “The challenges of representative sampling of waste materials.”

Suitable quality at every stage

To ensure quality requirements the specification of fuel must be tested for efficacy at every stage. Starting with the fuel producers, robust sampling and analysis is required to create consistent RDF/SRF so that they can ensure that their products meet the required specification or contracts. Next, exporters and brokers need to be considered, as, in addition to compliance with any TFS requirements, fuel shipments must be checked to ensure that the fuel is in specification, to avoid costly rejection of exports by the end user. By the end user stage, fuel analysis is an integral part of the renewable energy generation process; fuel quality can impact on plant efficiency, materials handling, environmental compliance and, in the UK, renewable subsidy claims, such as ROCs and RHIs. Analysis suites include fuel quality, energy content (also known as calorific value), biogenic content, levels of contamination and analysis of elements affecting fuel emissions.

Meeting the challenge

It is true that sampling and analysis of RDF/SRF can be challenging, with larger particle sizes, varied bulk densities and safe access for sampling to consider. And that’s just the start of it, samplers also have to contend with the potential introduction of errors from subdivision to reduce sample mass.

However, there is guidance out there, with the current SRF Sampling standard- BS EN 15442:2011. This standard mandates that one sample cannot represent more than 1500T and that a sample should be made up of a minimum of 24 increments. Further to this, minimum sample masses are based on nominal particle topsize and bulk density. To ensure accuracy, a compliant sampling tool should be used, which is three times the nominal particle topsize.

The business of fuel

There are genuine business reasons for ensuring consistent high quality of RDF/SRF. Fuel analysis is used for commercial settlement of fuel purchases, or gate fees. It is also submitted to support renewable subsidy claims, or calculate tax, providing a financial incentive. Furthermore, analysis highlights if fuel is within operating specification, if not, it could potentially damage expensive equipment, or the environment.

Providing quality analysis

Once a sample is received at the laboratory; the analysis that follows must be carefully controlled to ensure robust analytical data. ISO 17025 and UKAS accreditations are adhered to, with quality control checks and audits being put in place to back up the robust methodologies.

Setting the standard

Having been involved with international standard development for more than a decade, SOCOTEC is now the UK’s principle expert on the TC300 committee, which is converting current SRF EN standards to EN ISO standards - read our blog.

It was certainly an interesting session, hearing the points of view from leading members of the RDF industry group. Whatever our involvement in the industry, across the board, it is clear that we all share the goal of creating the highest standards for RDF.

For SOCOTEC, as we are no strangers to setting the standards, we are happy to stand shoulder-to-shoulder with other members of the RDF Industry Group to produce a code of practice that we can all be proud of.