"Thou shalt make compost unceasingly' is the first commandment of environmental gardening. The cry went up long before "pollution' and "conservation' became vogue words, and the humble compost heap remains the best example of a recycling project. The world would be a better place if cities could find ways of recycling a larger proportion of their organic wastes. Compost contains both organic matter, which provides good physical conditions for plant growth, and a better range of nutrients than any chemical fertilizer.
Vegetable waste is converted to compost by the natural process of rotting. This requires air and moisture. Air supplies oxygen to worms and other bio-material. Water is always necessary for life but if the compost is saturated there will be no air and no life. The rotting of compost is faster in warm conditions and since the biological process generates heat, compost heaps can become very warm.
The art of making good compost lies in keeping a balance between air, water and heat:
Compost-making is assisted by turning the compost. The mixing process breakes up lumps of material and mixes dry matter with wet matter. It also helps the circulation of air. Mechanical compost tumblers are a convenience.
A variety of compost-making containers can be purchased and some help with turning the compost, like a cement mixer. But none of them are automatic. You have to keep an eye on the compost heap or compost bin, making adjustments to achieve the necessary balance between air, water and warmth.