Machines rarely fail because the technology doesn’t work. They fail because of decisions made weeks before the machine arrived. These are the seven that recur.

1. Buying Before Fixing Segregation

The mistake: treating the machine as the solution to a waste problem, when the actual problem is that wet and dry waste arrive mixed.

Why it goes wrong: no machine separates a plastic spoon from potato peel. Contaminated input produces contaminated output, meaning visible plastic fragments in material meant for the garden, and it blunts blades, jams shredders and wears seals. Worse, once the output is visibly contaminated nobody wants it, so it accumulates, and a machine whose output has nowhere to go stops being loaded.

What to do instead: get segregation working first, with colour-coded bins, trained staff and a supervisor who checks. Run it for a month before the machine arrives. If segregation cannot be made to work at your site, the machine will not fix it, and you should solve that problem before spending the capital. Start with our guide to wet and dry waste segregation.

From a TGMC site: A residential complex we supply was putting garden trimmings and coconut shells in with its food waste. The laboratory result on that output showed a C:N ratio of about 35:1, far above the 20:1 benchmark for finished compost. The machine was doing its job; what went into it was the problem.

2. Sizing on the Average Day

The mistake: taking a week’s average waste figure and buying a machine to match it.

Why it goes wrong: half your days are above average, including every banquet, every festival and every full-occupancy weekend. An overloaded machine doesn’t stop, it under-processes. The cycle doesn’t complete, output comes out wet and sour, odour starts, and within a few months somebody concludes the machine doesn’t work.

What to do instead: size on your realistic peak day, then add 20 to 30% headroom for growth and for the improvement in segregation that follows installation. See how to size a composting machine.

3. Comparing Prices Instead of Specifications

The mistake: lining up three quotations for 100 kg/day machines and choosing the lowest.

Why it goes wrong: capacity ratings are not standardised in this industry. One supplier’s 100 kg may be stated on input mass, another’s on chamber fill, another’s at a moisture content nothing like your waste. Add differences in stainless grade, heater control, gearbox selection and panel IP rating, and the three machines may have very little in common beyond the number on the cover page.

What to do instead: normalise the quotations before you compare them, on the same capacity basis, the same MOC breakdown and the same load figures. OWC specifications decoded has a comparison sheet for exactly this. The cheapest machine is sometimes right. It is only ever right after you have established what is being left out.

From a TGMC sale: A buyer recently compared our quote with a noticeably cheaper machine of the same rated capacity. Line by line, the gap came from the build: our SS 304 sheet from a branded mill against unbranded steel, branded motors and gearboxes against unmarked ones, and an engineered drive against an off-the-shelf one. The cheaper machine would have cost less on day one and more every year after.

4. Not Establishing What the Output Actually Is

The mistake: planning space for the machine without establishing what comes out of it and how long it has to sit there.

Why it goes wrong: machines differ. Some discharge material that is stabilised but not mature, needing two to three weeks of curing before it can be used, which means a covered area with bins or bays sized for that retention. Others complete the process inside the machine and discharge a finished soil amendment, needing only storage until collection or application. Buyers who assume one case and get the other end up with output sitting in sacks in a corridor, and once output stops being discharged, loading stops too. TGMC’s composters complete their machine cycle in 4 to 6 hours.

What to do instead: ask each supplier, in writing, whether the discharged material is a finished soil amendment or an intermediate, and ask for the laboratory report that establishes it. Then size the output area accordingly, before you sign the order.

From a TGMC site: At one household, the same machine produced output that passed both the maturity (C:N) and pathogen tests in June, and failed both in July. Nothing about the machine changed; how it was loaded and run did. That is why you should ask for laboratory results across several batches, not a single report.

5. Forgetting the Operator

The mistake: assuming that a fully automatic machine runs itself.

Why it goes wrong: every machine, of every type, needs somebody to load it, discharge it and clean it every single day. When that person is not identified before purchase, the task lands on whoever is nearest, gets done inconsistently, and stops entirely when that person moves on. This is the single commonest reason machines go idle. Not a component failure, just nobody whose job it is.

What to do instead: name the person and the backup before the machine arrives. Write the daily routine into their job description, not into a manual. Budget for training at handover and again after six months, because the person you trained will not be the person operating it in year two. On what automation does and does not remove, see fully automatic vs semi-automatic.

From a TGMC site: At a private home, early batches were inconsistent while different people took turns running the machine. Once we trained one person in the household on a fixed daily routine and made them responsible for it, output became steady.

6. Treating Exhaust and Drainage as Afterthoughts

The mistake: deciding where the exhaust vents and where the wash water goes on installation day, based on what is convenient.

Why it goes wrong: these two decisions generate the complaints that get machines switched off. Exhaust routed near guest rooms, a residential window, a restaurant seating area or an air-conditioning intake produces objections that no amount of process optimisation will resolve afterwards. Leachate and wash water discharging somewhere inappropriate creates its own problem, including a compliance one.

What to do instead: decide both at site-survey stage, with the prevailing wind direction and the nearest occupied windows on the drawing. Relocating an exhaust route after installation is expensive. Relocating the machine is worse. The site readiness checklist covers both.

From a TGMC site: On industrial sites, rodents are a real risk. At one steel and wire plant we serve, they reached a machine’s wiring through its cable entries. That is why pest risk is now part of our site readiness checklist, and why we fit sealed cable glands and mesh guards wherever rodents are present.

7. Choosing on Price Alone

The mistake: selecting the lowest quotation without examining what sits behind it.

Why it goes wrong: the cheapest machine in this market is usually cheapest because of a combination of thinner stainless in the wet zone, an unbranded gearbox with no service-factor margin, proprietary spares, and a supplier with no engineer within a day’s travel of your site. Each of those has a cost that appears later, and lands in year three or four rather than during warranty.

There is a second reason, and it is about capability rather than price. Some suppliers in this market have no engineering function at all. They order equipment to somebody else’s design, put a badge on it and sell it. When the drive fails in year four, you need people who chose that gearbox and can tell you why, and they may not exist.

What to do instead: compare on total cost of ownership over ten years, covering purchase, power, culture, bulking agent, labour, spares and AMC, rather than purchase price. And establish who owns the design of the machine you are buying, using how to vet an OWC manufacturer.

How to use price safely: Price matters, and nobody should overpay. Use it last, not first: shortlist only the machines whose specification, materials and service you have checked, then let price decide between them.

The Pattern Underneath All Seven

Six of these seven are not about the machine at all. They are about segregation, sizing discipline, space, people, siting and supplier relationships. Decisions made around the machine rather than in it.

Which is the useful conclusion. If you get those six right, a reasonable machine will serve you well. If you get them wrong, an excellent machine will still end up under a tarpaulin.

Frequently Asked Questions

What is the single most common reason composting machines go idle?

No named operator. Component failures get repaired. An unassigned daily task simply stops happening.

Can a machine handle waste that isn’t well segregated?

No. It shreds whatever it is given. Segregation must be working before the machine arrives.

How much space do I need beyond the machine itself?

Working clearance on all sides, plus covered space for the output. How much depends on whether the machine discharges a finished soil amendment or a material needing weeks of curing. Establish that first.

Is the cheapest machine always the wrong choice?

Not always, but it is only the right choice once you have identified what the price difference is buying, using a normalised specification comparison.