Biomass recycling, traceability, and defined material routes across the SDL Group

This case study shows how material is separated, graded, and directed to the right end use to protect value, maintain quality, and support traceability across the group.

From the outside, the SDL Group can look like a collection of separate operations. Forestry and harvesting. A sawmill. Site clearance. Biomass collections. Houndswood recycling at Watford. CHP fuel. Wood pellets. In practice, those operations are connected by one thing: material flow.

Each part of the group handles a different material stream. Each stream has its own requirements, risks, and best end use. Some material is suitable for timber products. Some is better suited to fuel. Some can be processed into pellet feedstock. The key is not treating everything as one stream with one destination.

That is why the SDL Group uses defined material routes. We separate, grade, process, and direct material based on quality, suitability, and value. That helps protect higher-value outputs, make better use of lower-grade material, and keep the wider system controlled.

What counts as material across the SDL Group?

Across the SDL Group, material includes far more than standing timber or cut logs. It includes a range of inputs, byproducts, and recovered wood streams, including:

• Standing timber harvested through forestry operations

• Sawlog and cordwood routed for processing

• Chipwood for chipping and controlled downstream use

• Brash, lop and top, and lower-grade whole-tree material from site clearance for fuel use

• Sawmill byproducts such as chip, dust, and offcuts

• Arboricultural material received through Houndswood recycling at Watford

• Clean wood streams collected through biomass collections

The aim is not to force everything into a single output. The aim is to keep each material stream moving into the most suitable route, with the highest practical value and the right level of control.

Where traceability starts

Traceability starts at the point material enters the SDL system.

That might be in the forest, on a site clearance job, through a biomass collection, or at Houndswood. From that point, material should follow a defined route supported by records and operational checks.

Depending on the stream, those records may include site packs, job references, haulage records, weighbridge tickets, intake records, grading decisions, batch records, and dispatch records.

This matters because traceability is not just about tracking movement. It is about supporting better decisions. It helps keep suitable material in higher-value uses, helps to prevent contamination issues, and provides a clearer picture of how the group functions as an integrated operation.

Stage 1: Forestry and harvesting

Forestry is one of the clearest starting points for material control.

Material begins as standing timber. Once trees are felled and extracted, separation becomes important straight away. Higher-grade trunk material is assessed for sawlog. Smaller, less straight, or less suitable cordwood is directed into chipwood routes. Brash, lop and top, and other lower-grade material are separated for fuel use.

That early split matters. If streams are mixed too early, higher-value timber can be downgraded and lower-grade material can create problems further downstream.

This is also where the evidence chain begins to form. Site details, job references, and load movements start to build the record behind the material journey.

Scheme compliance may also matter at this stage. FSC or Grown in Britain status will apply depending on the source of the material and the chain of custody requirements in place. As all of the products we produce at SDL Sawmills are both FSC and Grown in Britain Certified the material has to be as well.

Stage 2: Sorting and grading

Sorting and grading are the decision points that protect value.

Within the SDL Group, suitable sawlog is directed to the sawmill. Chipwood moves into controlled chipping and downstream processing. Lower-grade material, such as brash, and lop & top material, is directed into fuel routes.

Contamination must be identified early. Metal, mixed waste, rot, soil, and other unsuitable inputs can affect equipment, reduce fuel quality, and undermine controlled feedstock standards.

This is where the integrated structure of the group becomes important. Because SDL has more than one outlet for material, routing decisions can be based on suitability rather than convenience. That creates better control over what enters each process and what comes out of it.

Stage 3: Sawmilling

The sawmill is the highest-value destination for suitable log.

Where sawlog quality is good enough, the best use is timber production. That is the first priority in the route hierarchy.

But the sawmill is not just a timber output. It also produces byproducts, including chip, dust, offcuts, and edgings. In many businesses, those materials might be treated as waste or as a low-value side stream. Within the SDL Group, they are planned inputs into the wider system.

Suitable sawmill chip and dust can be routed into pellet feedstock. Offcuts can be chipped adn reprocessed to make sawmill chip and sawmill dust also to be used as wood pellet feedstock.

This is one of the clearest examples of how the group works. The best material stays in the highest-value use, and the byproducts remain part of a controlled internal material flow.

Stage 4: Site clearance material

Site clearance introduces a more variable material stream.

That can include heavy timber, cordwood lengths, lop and top, mixed species, and irregular shapes and sizes. No two site clearance jobs are exactly the same, which means the handling route has to stay flexible while still remaining controlled.

Where it is practical and commercially sensible, material can be processed on site using equipment such as chippers or shredders. Lop and top and other suitable lower-grade material can then move into fuel routes. Where processing on site is not the right option, material can be brought back into the group for sorting, grading, and further processing.

The important point is that even with a variable input, we can plan for a valuable output. Where the material mix changes from site to site, the route should still be driven by grade, suitability, and end use.

Stage 5: Biomass collections

Biomass collections provide a controlled route for external clean wood material to enter the SDL system.

This may involve collecting wood material from customer sites where it arises as a byproduct of another operation. Once collected, it is transported via walking-floor trailers and HGV's back into the wider group as a planned intake stream.

This route is an important part of biomass recycling. It turns clean external wood material into a usable input rather than leaving it unmanaged or underused.

Control is what makes that possible. External material should only enter the system through a route that includes sorting, recording, and suitability checks.

Stage 6: Houndswood recycling at Watford

Houndswood at Watford is an important part of the SDL Group’s biomass recycling infrastructure.

It acts as an intake and processing point for arboricultural waste from sources such as tree surgeons, arborists, and site clearance operators. The material received can vary significantly in size, form, and cleanliness, which makes sorting and processing essential.

Suitable material is sorted and processed into usable arb chip using a variety of screeners and other machinery. That chip can then move into SDL’s wider fuel routes where appropriate.

This stage is especially important because arboricultural arisings can carry a higher contamination risk. Metal, litter, soil, and green waste can all affect suitability. Without proper sorting and processing, the material cannot be treated as a credible controlled input.

Stage 7: CHP fuel

CHP fuel is the defined route for material that is not suitable for higher-value timber production or pellet feedstock, but is still suitable for controlled energy use.

That may include brash, lop and top, suitable lower-grade forestry material, suitable site clearance arisings, and suitable processed arb chip.

This route gives lower-grade material a clear commercial purpose. But it depends on consistency. Inconsistent sizing, moisture, or contamination can affect plant performance and fuel quality.

That is why the earlier stages matter. Good sorting and grading upstream help protect performance downstream.

Stage 8: Wood pellets

Wood pellet production depends on clean feedstock, process control, and traceable production.

Suitable pellet feedstock may include sawmill chip, sawmill dust, and other suitable clean chipped material that meets specification.

The pellet production process typically includes intake, screening, drying, milling, pressing, and dispatch. Quality control runs alongside that process through sampling, batch control, and production records.

Certification and audited standards matter here because pellet production depends on consistency. ENplus certification is essential to this route because it supports product quality, testing consistency, and batch traceability within pellet production.

How traceability is maintained across the group

Traceability only has value if it is backed by records.

Across the SDL Group, the material journey should be supported by linked operational evidence. That may include:

• Site packs and job references

• Haulage records and weighbridge tickets

• Intake and grading records

• Processing records

• Production batch records

• Dispatch and delivery records

Taken together, those records show how material is identified, directed, processed, and turned into defined outputs across the group.

Why defined material routes matter

Defined material routes help explain how the SDL Group operates as an integrated business rather than a set of separate activities.

They also help protect value. Higher-grade material is kept in higher-value uses. Lower-grade material is given a defined purpose. Unsuitable or contaminated material is identified early, helping protect downstream processing and product quality.

That is the practical value of traceability. It is not just about saying material is tracked. It is about showing that material has a defined route, a defined purpose, and records behind it.