THE ROCKWOOL PROBLEM

Three reasons growers start looking for an alternative

It never goes away

Rockwool is spun from molten basalt. It can't be composted, can't be recycled, and won't break down in landfill. Every flat you use is permanent waste — and at commercial volume, a standing disposal cost with no end date.

It's uncomfortable to handle

Dry rockwool sheds fine mineral fibres. Most growers learn to wet flats before handling and to avoid working with them in an enclosed space. Manageable — but a daily annoyance that doesn't need to exist.

It needs conditioning first

Rockwool is alkaline out of the bag, typically pH 7.8 to 8.5. Before seeding, it has to soak in pH-adjusted water. That's an extra step, extra water, and extra pH-down on every single batch.

Side By Side

Rockwool Cubes vs Hemp Grow Mats

	Rockwool Cubes	TerraFibre Hemp Grow Mats
Pre-soak and pH conditioning	Required before every batch	Not required
Handling precautions	Wet before handling	None — no dust
Harvest	Roots grip the flat; residue in the cut	Clean lift, no residue
End of life	Landfill only	Compost, roots and all
Chemical binders	Varies by brand	None
Formats	Fixed sizes	10x20, 5x5, or cut from a 120ft roll
Manufacturing	Energy-intensive, imported	Mechanical, Drayton Valley AB
Water retention	Excellent	Excellent

Why It Works

What Hemp Does Differently

Nothing to do before you start

Rockwool needs soaking and pH conditioning before a seed touches it. A hemp mat doesn't. Take it out of the pack, lay it in the tray, saturate it, seed it. On a seven-day microgreens cycle, removing a prep stage from every batch is a meaningful share of your total handling time.

Moisture where the roots are, not on the surface

Hemp fibres hold up to 1,050% of their own weight in water — but they hold it inside the fibre structure rather than pooling on top. The surface dries as air and light reach it while moisture stays available below. Standing surface moisture is what mold needs to establish, so this matters more on densely sown crops than almost anything else.

Roots anchor into the fibre, and stay there

The needle-punched structure gives radicles something to grip immediately. Seedlings stand upright and uniform through blackout and into light. At harvest, cut above the mat and the greens lift away with nothing attached — no residue in the cut, no washing step, longer shelf life.

Cut to whatever size you actually need

Standard 10" x 20" for 1020 trays, 5" x 5" for smaller trays and retail, and a 10" x 120' roll for anything else. Fodder systems and custom rack dimensions are exactly what the roll is for. Standard weight is 300gsm; 500 and 750gsm are made to order for crops wanting more depth.

Common Questions from Rockwool Growers

Switching growing medium isn't a decision most growers make lightly, and the questions below are the ones we get asked most often.

Still deciding? Send us your crop, tray size, and weekly volume at info@biocompositesgroup.com and we'll tell you honestly whether a grow mat is the right fit.

No. Rockwool arrives alkaline and has to be soaked in pH-adjusted water before you can seed it. TerraFibre mats are mechanically separated hemp fibre with no chemical treatment, so there's no conditioning step. Saturate the mat and seed it.

For anyone running a lot of trays, that removes a prep stage from every batch — and the pH-down that goes with it.

Yes. The needle-punching process interlocks the fibres mechanically rather than binding them with glue, which is what gives the mat its structure. Hemp is one of the strongest natural fibres available.

Roots anchor into the fibre as they develop, and the whole mat lifts out of the tray in one piece at harvest. Breakdown happens in compost — where moisture, microbial activity, and no living root system work together.

In most cases, yes. Our 10" x 20" mats fit standard 1020 trays, and 5" x 5" suits smaller trays and retail displays. For fodder systems or custom tray dimensions, the 10" x 120' roll cuts to whatever size you need.

They work with bottom-watering trays, stacked blackout setups, and vertical racks. If you're running something unusual, get in touch — we manufacture in-house and can often cut to spec.

Hemp fibre is a natural material rather than an inert mineral, so it isn't identical to rockwool in how it interacts with solution. In practice, growers running standard microgreens and fodder programs report no meaningful change to their routine.

If you manage EC closely in a recirculating system, trial a single tray alongside your usual setup and watch your readings before switching the operation over.

Compost them. The mat goes in whole with the root mass still in it — nothing to separate, nothing to sort, nothing to landfill.

For commercial growers this is often the largest single difference. Rockwool disposal is a recurring cost line with no end date. Hemp fibre removes it rather than reducing it.

No — and we'd rather say so plainly than have you find out on a tray.

Grow mats are a flat medium built for densely sown, short-cycle crops: microgreens, wheatgrass, fodder, and sprouts. They don't provide the rooting depth a cutting or a transplant-up seedling needs. If you're propagating cuttings, rockwool cubes or a coir plug remain the right tool.

Where mats replace rockwool is in flat and sheet applications — and that's where the disposal problem hits hardest anyway.

Commercial Growers

Growing at volume? Let's talk.

If you're running rockwool flats across a commercial microgreens, wheatgrass, or fodder operation, the switch is worth costing out properly — and disposal is usually where the numbers move most.

We manufacture in Drayton Valley and cut to spec. Bulk rolls, custom widths, and heavier 500 or 750gsm weights are all available on request. Tell us your tray dimensions, weekly volume, and what you're growing, and we'll come back with pricing and a recommended format.

Request Bulk Pricing