My local nursery is selling bags of bat guano, and enriched compost that includes it. What is it good for, and is it safe to use? The company describes all their products as organic.
No matter what is in your compost, it is always a good idea to wear a dust mask when opening bags of soil amendments, and when spreading them in the garden. A mask will help protect you from breathing in airborne fungal spores.
Bat guano is used as a fertilizer, and provides supplemental nitrogen, according to this information from Oregon State University. It contains about 12 percent nitrogen. The ratio of N-P-K (nitrogen-phosphorus-potassium) is approximately 8-5-1.5.
A recent news story on National Public Radio highlighted the human health risks of exposure to bat waste (guano) in caves in Borneo. Both world travelers visiting bat caves and local harvesters of guano may be at risk of contracting very serious viruses, unless they take precautions (masks, gloves, and scrupulous hygiene). In parts of the United States (particularly the Ohio and Mississippi River valleys), there is a fungus called Histoplasma that is found in soil which contains bat or bird droppings. Gardeners who wear masks when digging in affected areas can avoid contracting
histoplasmosis.
Bat and bird guano are allowed as soil amendments “with restrictions” imposed by the U.S. Department of Agriculture. They must be decomposed and dried according to the USDA Organic Regulations requirements for raw manure. I recommend contacting the manufacturer of the products and asking them about where they obtain their bat guano, and whether they meet NOP (National Organic Program) and OMRI (Organic Materials Review Institute) standards. You can also ask about their veterinary and phytosanitary certificates for these products, and whether they make certain the guano is harvested sustainably and without harm to the bats and their ecosystem or to the health of harvesters (particularly in countries without strong worker protection laws).