There's a growing number of products in people's homes that work on the same quiet principle: the durable part stays, the consumable part gets replaced. A Gillette razor handle that you've had for fifteen years. A Method cleaning bottle refilled from a concentrate pod. A Nespresso machine where the machine outlasts a hundred capsule purchases.
Not all of these are designed with sustainability as the primary motive — some are primarily business models, built around recurring revenue rather than reduced waste. But the underlying architecture they share — a durable platform, a replaceable element — is one of the more effective structures available for reducing the material cost of everyday consumption.
That same architecture is the foundation of Culm. And we think it's worth explaining why we find it convincing — and where the limits of the model are.
What the refill model actually does
The core logic is straightforward. In a fully disposable product, every component goes to waste at the end of each use cycle — even the parts that aren't worn out. The trigger, the pump, the body of the bottle, the base of the scratcher. These components often have useful lifespans that are an order of magnitude longer than the consumable element they contain or support.
By designing products so that only the consumable element is replaced, you reduce the total material that needs to be produced, transported, and eventually disposed of. The maths isn't complicated. If the durable component lasts ten times as long as it would in a disposable product, you're producing roughly ten times less structural waste over the same period.
The handle lasts years or decades. Blades — the actual cutting surface — are replaced every few weeks. A metal handle versus a plastic disposable eliminates significant long-term plastic waste.
A glass or durable plastic bottle refilled from concentrate pouches dramatically reduces packaging versus a new bottle per purchase. The cleaning compound travels without carrying the weight of water.
The machine — the most material-intensive component — is produced once. The consumable is the coffee, not the delivery mechanism. Reusable capsule systems take this further.
The bamboo post is the durable platform. The jute sleeve is the replaceable surface. When the surface wears out, you replace the sleeve — not the post, not the base, not the whole product.
Why the model is growing — and who's driving it
Consumer demand for this kind of product architecture has been building for several years, and the data backs it up. Research from recent years consistently finds that younger consumers — particularly those in the 25–45 bracket — are more likely to pay a premium for products with lower environmental impact, and more likely to seek out refillable or long-lasting alternatives to disposables.
This isn't purely altruism. Economic logic is also at work. Buying a quality item once and refilling it is often cheaper over time than repeatedly buying the whole thing. A Culm sleeve replacement, ordered as needed, is considerably less expensive than buying an entirely new scratcher every six months — and produces considerably less waste in the process.
"The most sustainable product is often the one that doesn't need to be bought again. That's a design challenge, not just a marketing claim."
There's also a growing rejection of what's sometimes called planned obsolescence — the design practice of building products to fail or become unfashionable within a predictable window. Consumers who've watched a washing machine fail at exactly the moment the warranty expires, or a phone that slows with each software update, have become more attuned to the difference between built-to-last and built-to-replace.
The difference between a refill model and a subscription trap
It's worth being honest about the complexity here. Not all subscription or refill models are created equal. Some are genuinely designed to reduce waste. Others are primarily designed to create a recurring revenue stream — and the sustainability language is incidental.
Consumables are priced to maximise margin. The durable unit is often subsidised or given away. Cancellation is difficult. The model depends on lock-in.
The durable unit is priced to reflect its quality. Consumables are priced fairly. You order when you need to — no lock-in, no dark patterns. The model works because the product is better.
Culm's sleeve isn't a subscription unless you want it to be. You order a replacement when your cat has worn through the current one. There's no enforced cadence, no auto-renewal unless you choose it, no penalty for buying infrequently. We want the model to work because the product is genuinely better — not because we've made it painful to leave.
What this means for how you shop
The refill economy, at its best, asks you to think about two things when you buy: what's the durable component here, and what's the consumable? If a product doesn't make that distinction clear — if everything seems equally disposable — that's usually a sign that it's been designed for throughput, not longevity.
For cat owners, the question is simple: do you want a scratcher that's designed to be thrown away and replaced, or one where only the surface wears out? The rest — the post, the base, the structure — should be there for the life of your cat. Maybe longer.
Buy the post once. Replace the jute sleeve when it's worn. No enforced subscriptions. No lock-in. Just a product that's built to last and a surface that's designed to be replaced.
That's the refill economy applied to pet furniture. It's not a radical idea. But in a category where most products are designed to be entirely discarded every few months, it feels like a necessary one.