Kuusakoski Research Centre – Maria Lehtinen, Lab Manager

Significance of the topic

Analytical characterization of recovered materials and solid recovered fuels (SRF) is central to safe, efficient and value-driven recycling operations. Reliable elemental and calorific measurements determine material routing (smelters, steel mills, waste-to-energy), regulatory compliance (landfill acceptance limits, TOC thresholds), and economic valuation. The interview illustrates how a medium-sized research laboratory embedded in an industrial recycling group applies routine and specialized analytics to support day-to-day decisions and product quality in a circular-economy context.

Objectives and overview of the interview

This interview documents practices at Kuusakoski Research Centre (Lahti, Finland) through conversation between LECO and Maria Lehtinen, the lab manager. Goals were to: present Kuusakoski’s operation and analytical needs; explain how specific instruments (LECO CHN828, RC612, AC600 among others) are used in practice; and share sample-preparation and throughput challenges in a recycling laboratory handling metals and SRF.

Methodology

Operational context and sample flow:

• Kuusakoski is a family-owned recycling group active primarily in the Baltic Sea region; core business is metals and WEEE processing.
• Feedstock arrives mainly by truck; large items are shredded at three in-country shredder plants. Sorted and upgraded materials are sold to smelters and steel mills.

Sample preparation and handling for fuel and material analyses:

• Typical incoming fuel fractions are pre-shredded to 15–40 mm. Analytical standards require sample particle size below 1 mm; Kuusakoski uses a two-stage milling approach: a larger mill down to ~2–4 mm and a smaller cutting mill to reach <1 mm. An ultracentrifugal mill is available to approach <0.5 mm but presents operational issues.
• Standard preparative equipment includes drying ovens and ashing ovens for necessary pre-treatments.
• Staffing: the research centre is a small lab with two lab technicians, one melting technician, and a lab manager. Typical sample intake is ~600–800 unique samples per year, with total analytical determinations in the thousands due to multi-parameter testing.

Analytical approach:

• Metals: handheld X-ray screening in scrap yards, and laboratory analyses by ICP-OES, ICP-MS, and a benchtop X-ray analyzer (XRF) for compositional characterization.
• Fuel and carbon analyses: LECO instruments are used—RC612 for carbon phase/TOC profiling, CHN828 for elemental CHN determination (to convert gross calorific value to net calorific value), and AC600 isoperibol calorimeter for calorific determinations.
• TOC protocol: the lab follows temperature-dependent differentiation, measuring TOC400, ROC (~600°C), and TIC (~900°C). They offer a faster single-point TOC400 method when only that parameter is requested.

Used instrumentation

Key instruments and preparative equipment reported in the interview:

• ICP-OES and ICP-MS for trace and major elemental analysis.
• Benchtop X-ray fluorescence (XRF) analyzer and handheld X-ray devices for yard screening.
• LECO RC612 (carbon-phase/TOC analyzer).
• LECO CHN828 elemental analyzer (C, H, N).
• LECO AC600 isoperibol calorimeter for gross calorific value.
• Cutting mills (coarse and fine), ultracentrifugal mill (to reach <0.5 mm), drying ovens, and ashing ovens.

Main results and discussion

The interview yields practical observations rather than experimental data. Main takeaways include:

• Analytical portfolio and workflows reflect a dual focus on metal recovery and fuel characterization. Metal screening in yards accelerates sorting, while lab-based ICP/XRF provides detailed compositional control for customers.
• LECO instruments are important and trusted tools for SRF characterization. The CHN828 is routinely used to derive net calorific value, while the RC612 provides regulatory-relevant TOC/TIC/ROC differentiation used in landfill decisions.
• Method selection balances speed and comprehensiveness: TOC400-only runs are offered for faster turnaround, while full temperature-dependent analysis is used when complete carbon partitioning is required.
• Sample comminution is a persistent challenge for heterogeneous waste-derived fuels. Achieving reproducible particle sizes below 1 mm is difficult and can require multiple milling steps; ultracentrifugal milling can further reduce size but may introduce operational complications.
• Throughput and staffing dynamics mean a modest number of physical samples but a large number of analytical determinations, emphasizing the need for reliable instrumentation and efficient workflows.

Benefits and practical applications

Practical benefits observed at Kuusakoski include:

• Regulatory compliance: TOC/TIC/ROC profiling supports landfill acceptance and environmental reporting requirements.
• Energy evaluation: CHN analysis combined with calorimetry enables conversion between gross and net calorific values, important for SRF marketability and combustion performance assessment.
• Material valorization: Accurate elemental data from ICP and XRF informs sorting and sales to smelters, optimizing revenue recovery.
• Operational decision-making: Yard-screening X-ray devices and laboratory analytics together speed material routing and improve process control.

Future trends and applications

Potential directions and opportunities relevant to Kuusakoski-style operations:

• Improved comminution technologies and sample homogenization methods for heterogeneous waste to reduce sample-prep variability and analysis error.
• Faster or inline TOC and elemental methods to increase throughput and shorten turnaround times for routine QC.
• Greater integration between screening (handheld XRF) and laboratory data (ICP, CHN, calorimetry) through digital data platforms and LIMS to support traceability and commercial reporting.
• Expansion of standardized protocols (e.g., ISO 17505-type approaches) for temperature-dependent carbon differentiation to harmonize landfill and SRF acceptance testing across jurisdictions.
• Automation and remote/field-capable sensors for preliminary sorting and decision support at large yards.

Conclusion

Kuusakoski Research Centre operates a compact but versatile analytical laboratory that supports metal recycling and SRF characterization through a combination of yard-level screening and laboratory-grade instrumentation. Reliable LECO instruments (CHN828, RC612, AC600) play a central role in fuel and carbon analysis, while ICP and XRF enable compositional control for metal recovery. Key operational challenges revolve around robust sample preparation—especially comminution—and balancing method speed with the need for comprehensive data. The interview underscores the practical importance of dependable instrumentation and standardized methods for commercial recycling operations.