That depends as you don’t give enough information in your question.
!. What is the ambient temperature, I am assuming that you do not live on the edge of the, for example, the Sahara desert (hot) or the artic tundra (cold),
2. How much grass clippings? A teacup full? A bucket full? A oil drum full? A container lorry full?
3. Are you compostting just grass clippings? Or mixing them with other organic waste?
4. Are adding any compost additive to help the brekdown process?
5. IN what container are you intending to cpmpost your clippings?
6. Are they dry (brown) or moist (green)?

So, as you can see, it is virually impossible to answer your question.

However I can suggest that if you want to compost them quickly and effectively that you
A. do NOT compost thenm in a closed container. You need aeration - either by turning the clippings over at regular (define regular?) intervals.
B. I ritagli d'erba contengono molto materiale nitrogeno quindi mic con qualcosa come segatura di legno o vecchi giornali
C. Evita troppa acqua - comincerà a puzzare e diventerà molto sgradevole.

Se tu avessi dato più dettagli nella tua domanda la risposta sarebbe stata più breve e più utile