Kopi Luwak has given way to intensive farming methods in which civets in battery cage systems are force-fed the cherries. This method of production has raised ethical concerns about the treatment of civets due to "horrific conditions" including isolation, poor diet, small cages and a high mortality rate. Although kopi luwak is a form of processing rather than a variety of coffee, it has been called one of the most expensive coffees in the world, with retail prices reaching / per kilogram. Kopi luwak is produced mainly on the islands of Sumatra, Java, Bali and Sulawesi in the Indonesian Archipelago. It is
Metabolic waste excreta. Some mammals including humans excrete uric acid as a component of their urine but it is only a small amount. These compounds form during the catabolism of carbohydrates and lipids in condensation reactions, and in some other metabolic reactions of the amino acids. Oxygen is produced by plants and some bacteria in photosynthesis, while CO is a waste product of all animals and plants. Nitrogen gases are produced by denitrifying bacteria and as a waste product, and bacteria for decaying yield ammonia, as do most invertebrates and vertebrates. Water is the only liquid waste from animals and photosynthesizing plants.