Set 200 years into the future, humanity's footprints can be seen as far as Planet Nine in the Solar system. The most common propulsion engine is still ion drive and regrettably no one solves FTL. Since precious resources such as air and water are crucial for our species survival, what is the most economical way to dispose of the deceased in space? I suppose bringing the corpse back to Earth for cremation spends too much fuel and time; also, due to space constraints, taxidermy is an expensive option. I'm looking at space burial (space debris might endanger space-flight) or maybe recycling... (medicine then is still far from playing god)
The method your society uses depends on how the culture / religion / ethics have evolved in those 200 years.
In space, resources like water and biomass are expensive and precious. Since you have not developed FTL, humanity is restricted to the Sol system resources, plus whatever can be captured from Oort Cloud / Comets / Asteroids and other roving celestial bodies.
So, if humanity is resource-hungry, probably the bodies of the deceased would be (ritually or not) recycled, like the Fremen of Arrakis (Dune):
The fremen used still chambers to remove all the water of the deceased, based on their belief that the water in one's body belong to the tribe. After dissecating the body, this water was then ceremonially offered to the group leader, usually with the sayings "DeceasedName's body contained 30 litres of the tribe's water". This jug of water was then shared and drank by all the presents, to distribute this precious water around the tribe.
So depending on the ethics prevailing in your society, the deceased bodies would probably be buried in the habitat gardens, or placed in some resource recycling plant, ritually or not.
Putting the bodies on space caskets and launching them in a non-conflicting orbit could also be a possibility, if the resource abundance is high and/or religion / culture has it a a norm.
Can you afford to take them out of the biomass cycle?
- Put them into a transfer orbit to the sun or a gas giant.
- Slow decomposition: Burial in a park, plant a tree on top of the coffin, after a couple of decades/centuries the parkland becomes farmland and vice versa. Assuming a roughly steady population size, there would be a few trees per inhabitant of the habitat. That much might well be the "natural" size of the green spaces in the habitat. The kids play frisbee in the shadow of grandma's tree.
- Fast decomposition: Using mechanical or chemical processes, the corpse becomes fertilizer. That is finely distributed in a park area. Compost from the park goes into the farms. That reduces the "horror factor" or eating the dead. Parents can honestly explain that no, you're not eating grandma.
Transfer orbits to actually impact a planet would likely require significant fuel.
A large solar mirror could likely generate temperatures high enough to cremate a body if the water loss is affordable and total recycling isn't necessary. The grains left could just be scattered in space, or kept until planetfall.
Space debris would not be a problem, except in orbit around a gravity well (our current, actual space debris problem). Space is vast. Just fire the bodies at high velocity toward the Kuiper Belt, and no one will ever see them again.