All sorts of garden and kitchen waste - the key elements you're looking to manage are the balance of carbon to nitrogen, the amount of moisture, and aeration.   The ideal - you want a mixture of Carbon (stalks, stems, and woody bits) and Nitrogen (from the soft, green, sappy stuffs), in a ratio of about 30:1.

In the allotment, it is far from an exact science (!) but you may find this table helpful in achieving a reasonable balance - where I have been able to find an approximate ratio for specific materials, I have put it in brackets in the listing.

• Anything with a ratio of less than 30:1 is listed as a "nitrogen"
• and a ratio of more than 30:1, as a "carbon".

I tend to use this only when I add high carbon materials - then I take care to add extra nitrogen materials to compensate for them, in the form of high-nitrogen fertiliser (posh name for lots of fresh grass cuttings!), commercial compost-maker additives (rarely), or - urine!

• From the Allotment and Kitchen
  • Most vegetables - N
    - including Brassica heads and leaves, - N
    and chopped Brassica stalks - C.
    DO NOT ADD Brassica roots, potatoes and potato plants.
  • Fresh Weeds - harvested BEFORE they set seed! (30:1)
  • Grass clippings (when fresh) (15:1)
  • Alfalfa (13:1)
  • Fruit peels and wastes
  • flowers
  • Corn stalks (60:1) and cobs
  • Hay and Straw (74:1)
• From Trees, Shrubs and Hedges
  • Deciduous leaves (especially oak) and deciduous hedge prunings - N
  • Bark and twigs (100:1); good for aerating a pile - C
  • Add woody and hedge waste sparingly - add extra nitrogen if you do use these!
      »  evergreen leaves (high in carbon)
      »  pine needles (acidic)
      »  saw dust from untreated wood (400-500:1)
• Other stuff - high in nitrogen
  • Manure - highest in nitrogen when fresh
      »  pig (5:1)
      »  poultry (10:1)
      »  horse (25:1)
      »  cow (20:1)
      »  rabbit
  • Seaweed (19:1) - if it is lifted fresh and moist after a storm.   The longer it's uprooted the more salt it absorbs!
  • Urine (1 part to 2 parts water - cheaper than commercial compost starters!!!!)
      »  Beer and brewing wastes
      »  Coffee grounds (good stuff - get some from Starbucks!) (20:1)
      »  Tea leaves
      »  (Coffee filters and tea bags add carbon)
      »  Hair (add sparingly!)
• Other stuff - high in carbon
  • Paper - use sparingly; it should not be more than 10% of your heap.
      »  scrunched/torn newsprint (200-500:1)
      »  shredded cardboard (200-500:1)
      »  Do look at what NOT to add, below!
• Some materials will add neither carbon nor nitrogen, and can be added to your compost heap.   Things like small quantities of wood ash (from burning untreated woods), lime (as a compost heap is likely to be slightly acidic; but this should not be necessary, especially if lime is part of your crop rotation), and egg shells.

DON'T ADD THESE!

• Brassica roots, and potato plants (to avoid problems of plant disease in your plot).
• Animal products.   Apart from the stink, they attract vermin, and may carry disease.
  • Dairy products
  • Fish
  • Faeces of carnivorous animals - like cats and dogs
• Cooked food - which will also attract vermin.
• Glossy or coated papers, because of the chemicals used in their manufacture, or the metal-based inks used.
• Sewage sludge - which can contain concentrations of heavy metals.
• Ash from burning treated woods, coal, charcoal, or "mixed" fires.