They are the natural droppings of cows, when they go on grazing in forest or on grazing lands, such cow dung cakes are called Aaranyak, meaning those which are not hand made and that which does not contain grass. They are 100% Natural. They get dry, where they are dropped.
They are exclusively used for Yagnya and for agnihotra. As per Ayurveda their are specific medicines, for whose cooking only Aaranyak are used.
They are best natural, traditional and effective fumigant for antiseptic purification of home and office, as they contain medicinal herbs. Few pieces of Aaranyak can be burned every morning and/or evening with help of camphor and experience the effect.
Traditionally cows are taken for grazing in forest or/and reserved grass lands called Gou char in Hindi or Gay Ran in Marathi. This is very scientific as cow get physical exercise, they feed on various types of herbs and the grass land get cow urine and dung for rejuvenation.