Bin capacity and collection frequency: sizing the waste line

Four hundred spent pads a day, a sixty-litre bin, and one collection at six in the morning. On paper the bin is nowhere near full. In practice it is overflowing by Thursday afternoon, the bags are splitting, and someone is stacking pads in the yard because there is nowhere else to put them. The bin was sized on volume. Spent pads are a weight problem.

Waste from a fresh department is denser than the packaging it came from, and pads are the densest part of it. A dry sheet weighs almost nothing. The same sheet after a shift weighs 150 to 250 grams, and it does not compress. Nothing in the waste stream settles, so the bag takes the full weight from the first hour.

Weight, not volume, is the constraint

Run the arithmetic once and the picture changes. Four hundred pads at 200 grams is 80 kg a day, 560 kg a week. A standard 120-litre wheelie bin has a safe working load well below that, and the bag will fail long before the bin does. Most sites are not measuring weight at all, which is why the failure always arrives as a split bag on a Friday.

Two numbers fix it: kilograms per trading day, and kilograms per collection. Weigh one day’s bag on a platform scale. It takes two minutes and it will be heavier than you expect.

Check the bin rating too. Most wheelie bins are rated by volume and tested by weight, and a bag of wet pads at the base can deform the axle within a year. If the bin is being dragged rather than rolled, it is already overloaded.

Drain before you bin

The single cheapest intervention is a drain step. Tip the pads into a perforated tray, let them stand for ten minutes over a sink or a floor drain, and then bag them. Free liquid goes down the drain instead of into the bag, and the same bag carries roughly a third more sheets.

The drain step also removes most of the smell. Liquid sitting in a sealed bag at 18 °C for two days is what turns a waste room into a problem the neighbours notice.

Setting frequency against trading days

Collection frequency should follow the trading pattern, not the calendar. A store that does 60 percent of its week between Friday and Sunday needs a collection on Saturday or Sunday, and a quiet Monday collection is a waste of a pick-up.

• Count pads per day for two weeks, not per week.
• Multiply by the average wet weight to get kilograms.
• Size the bin at 1.5 times the heaviest day, not the average.
• Match pick-ups to the two heaviest days, then add one.

A depot doing 1,200 pads a day will generate around 240 kg, which is a small skip rather than a wheelie bin. Getting that wrong is how pads end up stacked on the ground, and stacked pads attract birds within a day.

The overflow that became a pest issue

A shop doubled its fresh range in the spring and kept the same bin and the same three collections. By the second weekend the bin was full, the overflow went into a cage in the yard, and the cage was not lidded. The pest contractor’s report three weeks later listed the cage as the likely source, and the shop spent more on proofing than a year of extra collections would have cost.

If you are changing range, changing case size or changing trading hours, re-run the weight calculation in the same week. The waste line is the part of a fresh operation that fails first and gets noticed last.

One more thing worth doing: keep the spent pads separate from general waste if your contractor offers a food-waste stream. Pads are not food, but they belong with the wet stream rather than the dry, and separating them stops a load being rejected for contamination. The polymer data sheets give the dry mass per sheet, which is the number you need for the calculation.