What is the ruling on environmentally-friendly burial (“tree-pod burial”)?
Question

Nowadays there is something that is called environmentally-friendly burial (“green” or “natural” burial that allows the body to decompose naturally, or “tree pod burial”). The way in which this burial is done is by placing the person in a biodegradable pod. The body is placed in the foetal position inside the pod, which is then buried in the ground and a small tree, chosen by the deceased or his relatives, is planted above the pod. What is meant is that this will be a new life for a soul by planting the tree, or a revival or bringing his life back. Usually the tree is of a long-lived variety, which with the passage of time will spread widely. What is the ruling on that?
Praise be to Allah.With regard to the method of burial described in the question, and planting a tree as mentioned, none of that is permissible, because of what it involves of innovated ideas and introducing new things. Allah, may He be exalted, has prescribed that bodies are to be buried in the ground. This is what His prophets and messengers did, and no attention is to be paid to anyone who claims that this is harmful to the environment.
Allah, may He be exalted, says (interpretation of the meaning):
{From the earth We created you, and into it We will return you, and from it We will extract you another time} [Ta-Ha 20:55]
{Have We not made the earth a container,
Of the living and the dead?} [al-Mursalat 77:25-26].
Al-Baghawi (may Allah have mercy on him) said in his Tafsir (8/305): {a container [kifat]} is a vessel. What is meant by the root word al-kaft is bringing something together. Al-Farra’ said: What is meant is bringing the living together on the surface of the earth in their houses and homes, and bringing the dead together under the surface; in other words, containing them. End quote.
Abu Dawud (3208), an-Nasa’i (2009), at-Tirmidhi (1045) and Ibn Majah (1554) narrated that Ibn ‘Abbas said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “The niche (lahd) is for us and the trench (shaqq) in the ground is for others.”
It was also narrated by Ahmad (19158) from Jarir ibn ‘Abdillah al-Bajali; classed as sahih by al-Albani in Sahih Abi Dawud.
The lahd (niche) and shaqq (trench) are both in the ground, but the lahd is in the side of the grave. See the answer to question no. 103880 .
Secondly:
It is not prescribed to plant trees on graves.
Shaykh Ibn Baz (may Allah have mercy on him) said: It is not prescribed to plant trees on graves, whether Indian figs or any other kind, or to sow barley or wheat or anything else on them, because the Prophet (blessings and peace of Allah be upon him) did not do that with graves, and neither did the Rightly-Guided Caliphs who succeeded him (may Allah be pleased with them).
With regard to what he did with the two graves when Allah informed him of the torment of their occupants, and he placed a palm branch on them, this is something that was only for those two graves, because he did not do that with any other graves.
The Muslims have no right to introduce any acts of worship or rituals that Allah has not prescribed, because of the hadiths quoted above, and because Allah, may He be glorified, says (interpretation of the meaning):
{Or have they other deities who have ordained for them a religion to which Allah has not consented?} [ash-Shura 42:21]."(Majmu‘ Fatawa ash-Shaykh Ibn Baz  5/407).
And he (may Allah have mercy on him) said: That is not prescribed, rather it is an innovation, because the Messenger (blessings and peace of Allah be upon him) only put the palm branch on the two graves when Allah, may He be glorified, informed him of the torment being suffered by their occupants, and he did not place palm branches on any other graves. Thus it is known that it is not permissible to place them on graves, because the Prophet (blessings and peace of Allah be upon him) said: “Whoever introduces anything into this matter of ours that is not part of it, it will be rejected.” According to a version narrated by Muslim: “Whoever does a deed that is not in accordance with this matter of ours, it will be rejected.”
Similarly, it is not permissible to write on graves, or to place flowers on them, because of the two hadiths quoted above. The Prophet (blessings and peace of Allah be upon him) forbade plastering over graves, building structures over them, sitting on them and writing on them."(Majallat al-Buhooth al-Islamiyyah  68/50).
This is in addition to the fact that the tree mentioned is not planted on the grave itself, and is not connected to the body of the deceased; rather the trees are planted between the graves, or the palm branches are placed on the graves; in either case, they are not connected to the body of the deceased person in his grave.
As for the way of planting trees that is mentioned, and saying or believing that this will be a new life for a soul by planting the tree, or a revival or bringing his life back, all of that is the misguidance of the people of ignorance, and it is more akin to deviant belief in the transmigration of souls. When life departs from a person, it will never come back to him until Allah resurrects those who are in the graves. His soul does not go to a tree or to an animal; rather the soul is with its Creator, Who will place it wherever He wills. It will not return to another body or to an animal or to a tree, according to the consensus of the Muslim scholars; rather those who say this and similar things are deviant people who believe in the transmigration of souls, and those who are influenced by them.
For more information, please see the answer to question no. 14379  .
And Allah knows best.