The following is presented for your information and further research. The BCEMC does not specifically endorse any book, website, vendor, product or service.
What is natural burial?
Natural burial, also known as green burial is burying a deceased body directly into the soil where it will decompose and become compost after a period of time. Prior to burial, the body may be wrapped in a biodegradable shroud then put directly into the soil. Some choose to be buried in a biodegradable casket. No embalming or concrete vault is used.
This burial option is available for those who choose it, plan ahead, and prepare for it. The Green Burial Council says this is "a way of caring for the dead with minimal environmental impact that aids in the conservation of natural resources, reduction of carbon emissions, protection of worker health, and the restoration and/or preservation of habitat."
There are a few books written on the topic which you may find at libraries or your favorite bookseller.
Is natural burial legal?
Yes, natural burial is legal at both the federal and state levels. However, you should make yourself aware of federal and state laws.
The FTC states that "no state law requires routine embalming for every death." Source: The FTC Funeral Rule. Please see the final paragraph: Make funeral arrangements without embalming.
In New Mexico, a body must be embalmed or refrigerated only if final disposition will occur more than 24 hours after death. No law requires a casket for burial. However, certain cemeteries may require certain containers. Source: Burial and Cremation Laws in New Mexico.
Green Burial Council (especially see Natural Burial FAQ)