Where do you live? Is it possible to burn them in small quantities. Fires in fire pits are nice.

Is the area accessible to a car and trailer. If so you can rent a wood chipper for about $200 per day. You can make a lot of mulch with a 6" chipper/shredder for your flower beds, etc.

If the trees are not extremely large and not near any structures, have you considered taking them down yourself. Chain saw rentals are not expensive.

IF YOU, do watch some of the videos on Youtube for instructions on how to and how not to take trees down.

Besides it is fun to play lumberjack.

Healthy trees cut down can take a long time to decompose in most climates....think how long untreated fences or decks hold up. However, they can be a great habitat for wildlife IF you have the space and patience to deal with them.

The smaller the pieces the faster they will decompose :-)