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Why hemp fibre and shiv need different factory processes

Bioprefab Editorial Desk

Hemp bast fibre and woody shiv can become different factory insulation products because their physical forms suit different forming routes. One documented hemp-fibre mat process cleans and opens the fibre, forms it into a fleece by carding or air laying, then adds binder and dries the mat. A separate study pressed hemp shiv with a bio-based thermosetting binder into rigid panels. This mat-and-panel pairing describes the routes followed here, not a rule: factory-made hemp-fibre insulation can also be supplied as boards. [2] [3] [6]

The first decision is which stem fraction to process

Hemp stems yield bast fibre and woody shiv, but separation does not guarantee perfectly clean fractions. A patent describing an insulation-mat process specifies cleaning hemp fibre to remove foreign substances, dust and shives before fleece formation. That is one process description, not a universal grading specification; the sources here establish no general fibre-length or shiv-size limits for insulation manufacture. [1] [6]

Fibre can form a fleece for a mat

A patent for a hemp-fibre insulation mat describes two dry methods for forming fleece: carding and air laying. In its example, fibres are cleaned, opened, formed into a fleece, placed on a facing, bonded at selected fibre crossings and dried. The patent describes a particular process and product; it does not establish that all manufacturers use this sequence or recipe. The broader EOTA assessment document allows vegetable-fibre products, including hemp, as mats or boards, with optional binding or supporting fibres and facings. [2] [6]

Shiv can be bound and pressed into a panel

The woody shiv route depends on a mix that can be formed and consolidated into a panel. A 2017 industrial scale-up study examined wet and dry processes; its dry trials used a hydraulic press with heated plates and hemp shiv bonded with a bio-based thermosetting binder. The study varied binder content from 5% to 23% and target density from 155 to 245 kg/m³. These are experimental ranges from that study, not standard factory settings. [3]

Moisture, binder and density affect the panel process

Panel recipe and processing conditions affect both manufacture and the resulting properties. The study found binder formulation and proportion, water content and panel density to be important parameters. It reported that wet processing could require excessively long drying for rigid panels, while its dry process was more versatile and took less time. Its dry-process panels reached compressive and flexural strengths of 1 MPa and 1.7 MPa, respectively; those results belong to the tested formulations and are not product declarations. [3]

The fractions differ in sorption, not by a simple moisture rule

A study of hemp and flax found that fibre and shiv adsorbed similar amounts of moisture at a given relative humidity. It also found much higher sorption hysteresis in shiv than in fibre, linked to lignin content. These findings distinguish measured sorption behaviour; they do not establish that one fraction needs a particular factory preparation or performs better as insulation. [1]

Research results and assessed products are different stages

ISOBIO’s final reporting described a lightweight rigid insulation material as capable of continuous manufacture and ready for scale-up, while saying that its manufacturing partner was developing approaches to full-scale production and marketing. A separate project summary described a hemp board with a bio-based binder and reported an expectation of market entry in 2020. These are historical development reports, not confirmation that the specific board is currently sold. EAD 040005-00-1201 provides an assessment framework for eligible factory-made fibre insulation; it is not a certificate for every hemp product. Check the offered product’s current assessment, declared composition and intended use. [2] [4] [5]

Ask for evidence tied to the product being offered

For a hemp-fibre mat or board, ask for the declared fibre, binder or supporting-fibre composition, facing and product form, plus assessed properties relevant to its intended use. EAD 040005-00-1201 lists thermal conductivity, water-vapour diffusion resistance and reaction to fire; water absorption applies only for specific applications. For a shiv panel, ask for its particle grading, binder formulation, moisture limits, pressing conditions and product-specific test results. A research recipe or process patent does not establish the properties of a different factory product. [2] [3] [6]

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