The smock mill Goliath in front of the wind farm Growind in Eemshaven in the Netherlands. A windmill is a mill that converts the energy of wind into rotational energy by means of vanes called sails or blades. Centuries ago, windmills usually were used to mill grain (gristmills), pump water (windpumps), or both.
When bat guano is harvested, it is in a powdered form. Plants that can benefit from the use of bat guano fertilizer include vegetables, herbs, ornamentals, and fruit and nut trees.
Guano can appear in a wide range of colors including white, yellow, brown, hazel, gray, black, or red, but color does not indicate or influence its quality. One of the factors that can determine the fertilizer quality of bat guano is the dietary habits of the different bat species who inhabit a cave. Some bats are vegetarian, eating primarily fruits. Other bats are carnivorous; their diet usually consists of insects and similar small critters.