Your friend may have bats in his barn, but he probably has more birds than bats. Either way, both types of poop are great sources of nitrogen, and both will burn the crap out of your plants (far too concentrated). If you compost the guano with other sources of organic matter for several months, the nitrogen will dilute and become less toxic. The rule of thumb for vegetable gardens is that horse/cow manure is a great source of nitrogen, but you should till it into the soil in the fall, so that it will not burn your plants in the spring. The same rule applies for other high-nitrogen sources.