Brand: Carbon Gold/Westland Compsot | Supplier: Marshalls | Price: £0.65/litre
Personal observations
The Carbon Gold range is now manufactured under licence via Westland through the Marshall’s division. The biochar element is intended to improve structure, water retention, and soil microbial activity. From the drying test, the dominant character is still the wood-fibre base and coir particles — you can see and feel the fibre fluff throughout the material, which is very characteristic of Westland’s approach across their range. The sieve result is telling: 31% of material passes through 2mm, 56% is retained in the 2–10mm fraction but 24% is retained on 10mm. This is not bit bits wood chip, it is fibres interlocking into mesh that will not sieve. Water retention is very good at 5.0 times dry weight, and dry-down is fairly fast at 25 minutes. The biochar addition does add some useful structure for repotting, but this is primarily a wood-fibre growing medium rather than a compost in the traditional sense. Good for pots and containers; less suited to seed trays or lawn work where fine texture matters.
Quick-test data (April 2026)
| Metric | Band | Value | Context |
|---|---|---|---|
| Bulk density (dry) | L | 0.142g/ml | Very light — fibre-dominant |
| Water held per g dry weight (WHC) | M | 5.0× | Top-end range — fibre and biochar contributing |
| Dry-down time | — | 25 min | Mid-range -fibre releases water readily, biochar more slowly |
| Sieve: <2mm fraction | — | 31.0% | Low — one of the coarser profiles in the test group |
| Sieve: 2–10mm fraction | — | 56.0% | Very high — fibre dominant |
| Sieve: >10mm fraction | — | 31.0% | Mid-range -fibr eleases water readily, biochar more slowly |
| Price per litre | £0.65 | Marshall’s online – incl. P&P |
WHC is above the baseline – likely assisted by the processed wood fibre and biochar. However, the fast dry-down confirms this is primarily structural/fibre water retention rather than chemically bound moisture.
Marshall’s online price only — purchasing online adds delivery cost.
Comparative hands-on testing, April 2026. Consistent method across all 18 products. See methodology note.g Breakdown.
| Category | Weight | Score | Notes |
|---|---|---|---|
| Ease of Use | 40% | 8.0 | Fibrous, but easy to use for potting. |
| Composition & Quality | 35% | 6.6 | Biochar and balanced coir fines give good structure and rooting. |
| Sustainability | 25% | 7.6 | Strong peat-free credentials with certified biochar. |
| Overall (Weighted) | 100% | 7.6/ 10 |
What we liked:
- Biochar improves aeration and root environment.
- Peat-free formula with a clear sustainability story.
- Versatile across pots, beds and mixes.
Points to consider:
- Premium price compared with standard MPC.
- Can appear slightly dry out of the bag; needs a good initial soak.
Summary: A technically refined peat-free compost where biochar adds durability and structure, backing up the brand’s regenerative claims.
Disclaimer.
Brand names such as Westland, SylvaGrow, RocketGro, Dalefoot, Carbon Gold, and others mentioned on this site are registered trademarks of their respective owners. MultipurposeCompost.co.uk includes these examples for informational and comparative purposes only and does not claim endorsement, affiliation, or suitability for any specific use. Gardeners and buyers should always check current product specifications and manufacturer guidance before purchase or application.
