Feedstock Characterisation for a Torrefaction Feasibility Study

A feedstock label is not a design basis

Names such as wood residue, rice straw, RDF, municipal waste or sludge identify a broad material family. They do not say what reaches a receiving hopper on a particular day. A feasibility study needs an input description that a process engineer, laboratory and eventual operator can all recognise.

Start with the physical route. Where does the material arise? Is it segregated at source or after processing? What happens before it reaches storage? Is it baled, chipped, screened, dried or mixed with another stream? The answers often matter as much as the headline quantity.

Build a traceable feedstock pack

Our suggested checklist is practical screening guidance, not a technical standard, sampling plan or plant-design procedure. A project team should decide what is appropriate for its feedstock, process and receiving route.

This is not a universal test list. A wood-residue project and a mixed municipal-waste route do not face the same risks. The point is to make uncertainty visible early, then select suitable tests with the process and receiving-equipment teams.

Sampling is part of the evidence

A laboratory can only report on the sample it receives. Record how the sample was selected, where it was taken, whether material from different points or times was combined, how it was sealed and how it was prepared. If the material is variable, one convenient grab sample should be described as a screening sample, not as a definitive site average.

For solid biofuels, ISO 18125 specifies a method for determining gross calorific value and gives formulae for calculating net calorific value. ISO 18125:2017 summary (ISO, accessed 3 November 2026). Its published scope is calorific-value determination; it does not establish whether a site sample represents a supply stream or whether a design is adequate. Keep the sample identity, moisture basis and method alongside every number used in a feasibility discussion.

Look beyond heating value

Heat content is one question in an early review, not the whole question. The project team can investigate physical size and shape, moisture basis, ash and mineral characteristics, contaminants, storage condition and the receiving plant’s own stated constraints. Which properties matter, how they are tested and what they mean for a proposed route depend on the defined feedstock, process and receiving equipment.

Separate screening evidence from design evidence

Early samples can identify questions worth investigating. They should not be treated as a definitive design basis unless the sampling plan, variation and intended application support that conclusion. Keep preliminary observations separate from later engineering inputs, and record which values are measured, calculated or still unknown. This preserves a useful audit trail when the feedstock source, preparation route or receiving-plant requirements change. If the project team combines material from several sources, it should record the combination rule and each component’s evidence rather than treating the blend name as a measured property. Retain the raw reports and sample photographs where permission allows, so a later reviewer can trace the summary back to its physical evidence.

Turn unknowns into a feasibility plan

A useful early deliverable is a short register with three columns: evidence available, evidence missing and the decision each missing item could change. For example, unknown particle size may affect preparation scope; unknown moisture variation may affect storage and energy balance; unknown receiving-plant constraints may prevent a meaningful output specification.

Do not convert assumptions into guarantees. A feasibility study can state a provisional scenario, provided the input, method and limitation are clear. Before investment or contracting, replace those scenarios with agreed evidence, defined interfaces and an acceptance plan.

Read how to compare fuel-test results  ·  Use the procurement checklist  ·  Discuss a project requirement