What is the best way to compost bones?

It has been taking us about 4 years to compost hog heads.  Most of the other bones compost between 1 and 2 years.  What is the best medium to compost bones in?  We use the bury and flip method with wood chips and manure.  Is there a better solution?

I burn them in my woodstove.  After they are burned, they crush easily and breakdown quickly.

Larger bones take longer to break up in compost piles.

I have found breaking them/smashing them to increase surface area has been beneficial.

I also found that my roasted bones seem to disappear faster. I think the heat makes the internal structure weaker but that is anecdotal.

I make a lot of bone broth and after the slow cooking, many bones are easy to break up and would compost faster probably.

I like Gary's suggestion for burning them.

This might be helpful from the University of Missouri:

Composting dead swine requires the addition of a carbon source to ensure proper carbon-to-nitrogen ratios are present for the composting process. Experience thus far suggests that sawdust is an ideal carbon source due to its small particle size, ease of handling, absorbency, and high carbon content. Using straw as the only carbon source has been less successful, with lower composting temperatures, leaching of fluids from the composting pile, and longer composting times required. When sawdust is used as a carbon source, plan to provide about 100 cubic feet of sawdust per 1,000 pounds of carcass to be composted. For farrow-to-finish operations, sawdust requirements are about one-third to one-half cubic yards per sow in the herd on an annual basis. See Table 1 for a summary of compost criteria.

https://extension.missouri.edu/publications/wq351