The split, and why it matters
Organic waste is anything that was once living and will biodegrade: food, garden waste, untreated timber, paper and card, natural textiles. Inorganic is everything else — plastics, metals, glass, ceramics, rubble.
The distinction matters because organic waste in landfill decomposes without oxygen and produces methane, a far more potent greenhouse gas than carbon dioxide. That is the reason for the national move away from landfilling biodegradable municipal waste, and it is why household waste to landfill fell to 254,000 tonnes in 2024.
Food and garden waste are both organic but go to different processes. Food goes to anaerobic digestion (breaking food down without air to make gas and fertiliser), producing biogas and a digestate (the fertiliser left after food waste is processed) fertiliser. Garden waste goes to open composting. They are not interchangeable, which is why councils collect them separately.
- Organic: food, garden, untreated timber
- Inorganic: plastic, metal, glass, rubble
- Food waste → anaerobic digestion
- Garden waste → composting
- Different streams, different processes
- Food in general waste is the big loss
Food waste specifically
Everything goes in the food caddy: cooked and raw, meat, fish, bones, dairy, bread, tea bags, coffee grounds, egg shells and plate scrapings. Anaerobic digestion handles material that home composting cannot, which is the point of the separate collection.
That is the opposite of the home composting rule, and it confuses people constantly. Meat, fish and dairy must not go in a home compost bin — they attract vermin and do not break down properly at the temperatures a domestic heap reaches. In the council caddy they are fine.
SEPA's analysis is that food is the largest single component of what remains in Scottish general waste bins. Using the caddy properly is the biggest available improvement in most households.
Garden beyond what the brown bin holds?
Green waste composted rather than landfilled, in one load.
Garden waste and home composting
Grass cuttings, hedge trimmings, leaves, prunings, small branches, plant material and spent compost are all green waste, and they compost well. Councils collect them seasonally in most areas and recycling centres have dedicated containers.
For a home heap, the working ratio is roughly equal parts green (grass, kitchen veg peelings) and brown (dry leaves, cardboard, small twigs), kept moist and turned occasionally. Too much grass alone goes slimy and anaerobic; too much brown alone does nothing.
Keep out: meat, fish, dairy, cooked food, diseased plant material, perennial weed roots and anything treated. And note that soil and turf are not green waste — they are inert (the heavy stuff — rubble, concrete, brick and soil) material handled with rubble and priced by weight.
The ones that fit neither cleanly
Compostable and biodegradable packaging is the biggest source of confusion. Most 'compostable' plastics require industrial composting conditions that a home heap never reaches, and many Scottish councils do not accept them in food waste because they contaminate the digestate. Check locally; when in doubt, general waste.
Treated, painted or engineered timber is organic in origin but not compostable — it goes with wood or general waste depending on treatment, as our scrap lumber guide explains.
Japanese knotweed is a category of its own: a controlled plant that cannot go in green waste or to a normal recycling centre, and spreading it — including in contaminated soil — is an offence. That needs a specialist.
