As I did research on the internet, I discovered that for some bottled butter is a very controversial topic. I know that many of us (me included) bottle foods a certain way because that's the way we were taught by our mothers and grandmothers (and "no one has ever died"). I felt like it was important, though, for you to be aware of some possible dangers and then armed with the facts, you can decide how you'll proceed.
My research led me to the following articles:
Jana Darrington, family consumer science agent for Utah State University extension stated, "When canned at home, items like butter and breads can provide fertile grounds for the paralytic illness botulism. We're just in the beginning stages of researching and trying to develop a safe method. Commercial enterprises have certain equipment and an ability to process that we can't do in our own kitchen. . . We don't know if there is any safe method for canning butter at home at this point."
I rely on extension services for a lot of my information on storage and canning. I'm excited about the possibilities of extension services developing and recommending a method for canning our own butter. But it sounds like we'll need to be patient and proceed with caution.
These articles suggest that you are currently better off buying commercially canned butter. I've seen this product at my local grocery store recently. You can also purchase powdered butter in #10 cans at food storage stores. I have actually stored a little bit of both, but haven't tried either product. Let me know if you've tasted commercially canned butter or powdered butter and can comment on the taste!