Cremation might be preferable for environmental reasons. Burial is a known source of certain environmental contaminants, with the coffin itself being the major contaminant, however in some countries e.g. the UK, legislations now requires that cremators be fitted with abatement equipment (filters) that remove serious pollutants such as mercury.
Each cremation uses about 28 gallons of fuel and releases about 540 pounds of carbon dioxide into the atmosphere. Thus, the roughly 1 million bodies that are cremated annually in the United States produce ~270,000 tons of carbon dioxide. That’s more CO2 pollution than 22,000 average American homes generate in a year. The environmental impact may be reduced by using cremators for longer periods, and not cremating on the same day as the coffin is received, which reduces the use of fossil fuel and hence carbon emissions. Cremation is therefore becoming more friendly toward the environment though natural burials are also possible. Some funeral and crematorium owners offer a carbon neutral funeral service incorporating efficient-burning coffins made from lightweight recycled composite board.
Another environmental concern is that traditional burial takes up a great deal of space. In a traditional burial, the body is buried in a casket made from a variety of materials. In the United States, the casket is often placed inside a concrete vault or liner before burial in the ground. While individually this may not take much room, combined with other burials, it can over time cause serious space concerns. Many cemeteries, particularly in Japan and Europe as well as those in larger cities, have run out of permanent space. In Tokyo, for example, traditional burial plots are extremely scarce and expensive, and in London, a space crisis led Harriet Harman to propose reopening old graves for "double-decker" burials.
Some cities in Germany do not have plots for sale, only for lease. When the lease expires, the remains are disinterred and a specialist bundles the bones, inscribes the forehead of the skull with the information that was on the headstone, and places the remains in a special crypt.