Arranging to having yiur future postmortem body used to fertilise plants, is a really cool option, in my opinion. A green/natural/eco funeral is one way to, basically, do that, and it’s pretty widely avalable too, in most places.
And cardboard coffins work, and tend to be accepted by mat green burial sites. Woven willow coffins, untreated wood coffins, as well as just classic biodegradable shrouds, are several other options that used for this. On that subject,Hheres some resources that might be helpful with planning for a green burial, ahead of time (and ensuring that thise wishes are carried out later) , for those that this appeals to and that haven’t allready: www.orderofthegooddeath.com/…/green-burial/ (the order also has information on n. o. r/terramation/composting, and on aquamatuon/water-cremation options, both of wchich are compatible with the ‘become plant ferileser if yiu wnat to’ idea) and www.greenburialcouncil.org/interactive-maps.html