Modern cremation process

The cremation occurs in a crematorium, consisting of one or more cremator furnaces or cremation retorts for the ashes. A cremator is an industrial furnace capable of generating temperatures of 870980°C (16001800°F) to ensure disintegration of the corpse. A crematorium may be part of chapel or a funeral home, or part of an independent facility or a service offered by a cemetery.

Modern cremator fuels include natural gas and propane. However, coal and coke were used until the early 1960s.

Modern cremators have adjustable control systems that monitor the furnace during cremation.

A cremation furnace is not designed to cremate more than one body at a time, something that is illegal in many countries, including Australia

The chamber where the body is placed is called the retort. It is lined with refractory bricks that resist the heat. The bricks are typically replaced every five years due to thermal fatigue.

Modern cremators are computer-controlled to ensure legal and safe use; e.g., the door cannot be opened until the cremator has reached operating temperature. The coffin is inserted (charged) into the retort as quickly as possible to avoid heat loss through the top-opening door. The coffin may be on a charger (motorised trolley) that can quickly insert the coffin, or one that can tilt and tip the coffin into the cremator.

Some crematoria allow relatives to view the charging. This is sometimes done for religious reasons, such as in traditional Hindu and Jain funerals.

Most cremators are a standard size. Typically, larger cities have access to an oversize cremator that can handle deceased in the 200kg (441 pounds)+ range. Most large crematoriums have a small cremator installed for the disposal of foetal and infant remains.

Body container

In Australia, the deceased are cremated in a coffin supplied by the undertaker. Reusable or cardboard coffins are becoming popular with several manufacturers now supplying them. If cost is an issue, a plain, particleboard coffin (known in the trade as a "chippie") will be offered. Handles (if fitted) are plastic and approved for use in a cremator. Coffins vary from natural cardboard or unfinished particle board (covered with a velvet pall if there is a service) to solid timber; most are veneered particleboard.

Cremations can be "delivery only," with no preceding chapel service at the crematorium (although a church service may have been held) or preceded by a service in one of the crematorium chapels. Delivery-only allows crematoriums to schedule cremations to make best use of the cremators, perhaps by holding the body overnight in a refrigerator. As a result, a lower fee is applicable. Delivery-only may be referred to in industry jargon as "west chapel service."

Burning and ashes collection

The box containing the body is placed in the retort and incinerated at a temperature of 760° to 1150°C (1400° to 2100°F). During the cremation process, a large part of the body (especially the organs) and other soft tissue are vaporized and oxidized due to the heat, and the gases are discharged through the exhaust system. The entire process usually takes about two hours.

All that remains after cremation are dry bone fragments (mostly calcium phosphates and minor minerals). Their colour is usually light grey. They represent very roughly 3.5% of the body's original mass (2.5% in children). Because the weight of dry bone fragments is so closely connected to skeletal mass, their weight varies greatly from person to person, although it is more closely connected with the person's height and sex than with their simple weight. The mean weight of adult cremains in a Florida, U.S. sample was 5.3 lb (approx. 2.4 kg) for adults (range 2 to 8 lb/900 g to 3.6 kg). This was found to be distributed bimodally according to sex, with the mean being 6 lb (2.7 kg) for men (range 4 to 8 lb/1.8 kg to 3.6 kg) and 4 lb (1.8 kg) for women (range 2 to 6 lb/900 g to 2.7 kg). In this sample, generally all adult cremated remains over 6 lb (2.7 kg) were from males, and those under 4 lb (1.8 kg) were from females.

Jewellery, such as wris****ches and rings, are ordinarily removed and returned to the family. The only non-natural item required to be removed is a pacemaker, because it could explode and damage the cremator.

After the incineration is completed, the bone fragments are swept out of the retort and the operator uses a pulverizer called a cremulator (also known informally as a crembola) to process them into what are known as cremains, which exhibit the appearance of grains of sand (note that this varies with the efficiency of the cremulator used, and recognizable chips of very dry bone may be seen in some final product cremated remains, depending on origin and facility). Cremulators usually use some kind of rotating or grinding mechanism to powder the bones, such as the heavy metal balls on older models.

In Japan and Taiwan, the bones are not pulverized unless requested beforehand, and are collected by the family.

This is one of the reasons cremated remains are called ashes, although a technical term sometimes used is "cremains (a portmanteau of "cremated" and "remains"). The ashes are placed in a container, which can be anything from a simple cardboard box to a fancy urn. An unavoidable consequence of cremation is that a tiny residue of bodily remains is left in the chamber after cremation and mixes with subsequent cremations.

Not all that remains is bone. There will be melted metal lumps from missed jewellery; casket furniture; dental fillings; and surgical implants, such as hip replacements. Large items such as titanium hip replacements are usually removed before grinding, as they may damage the grinder. After grinding, smaller bits of metal are sieved out and later interred in common, consecrated ground in a remote area of the cemetery.

Methods of keeping or disposing of the cremated remains

Cremated remains are returned to the next of kin in a rectangular plastic container, contained within a further cardboard box or velvet sack, or in an urn if the family had already purchased one. An official certificate of cremation prepared under the authority of the crematorium accompanies the remains, and if required by law, the permit for disposition of human remains, which must remain with the cremains.

Cremated remains can be kept in an urn, sprinkled on a special field, mountain, in the sea, or buried in the ground at any location. In addition, there are several services in which the cremated remains will be scattered in a variety of ways and locations. Some examples are via a helium balloon, through fireworks, shot from shotgun shells, or scattered from an airplane (this is not illegal in most jurisdictions, in part because laws prohibiting it would be difficult to enforce). One service sends a lipstick-tube sized sample of the cremains into low earth orbit, where they remain for years (but not permanently) before re-entering the atmosphere. Another company claims to turn part of the cremains into a diamond in an artificial diamond manufacturing machine. These converted grown diamonds can then be cut, polished, and mounted, as would a real diamond into jewellery as a keepsake for the family. Cremains may also be incorporated, with urn and cement, into part of an artificial reef, or they can also be mixed into paint and made into a portrait of the deceased. Cremated remains can be scattered in national parks in Australia, with a special permit. They can also be scattered on private property, with the owner's permission. A portion of the cremated remains may be retained in a specially designed locket known as a keepsake pendant. The cremated remains may also be entombed. Most cemeteries will grant permission for burial of cremains in occupied cemetery plots that have already been purchased or are in use by the families disposing of the cremains, without any additional charge or oversight.

The final disposition depends on the personal wishes of the deceased as well as their cultural and religious beliefs. Some religions will permit the cremated remains to be sprinkled or kept at home. Some religions, such as Roman Catholicism, insist on either burying or entombing the remains. Hinduism obliges the closest male relative (son, father, husband, etc.) of the deceased to immerse the cremated remains in the holy river Ganges, preferably at the holy city of Haridwar, India. The Sikhs and Punjabi Hindus immerse the remains in Sutlej, usually at Sri Harkiratpur. In Japan and Taiwan, the remaining bone fragments are given to the family and are used in a burial ritual before final interment.

Reasons for choosing cremation

Apart from religious reasons (discussed below), some people find they prefer cremation for personal reasons. For some people, it is because they are not attracted to traditional burial. The thought of a long, slow decomposition process is unappealing to some; many people find that they prefer cremation because it disposes of the body immediately.

Other people view cremation as a way of simplifying their funeral process. These people view a traditional burial as an unneeded complication of their funeral process, and thus choose cremation to make their services as simple as possible.

The cost factor tends to make cremation attractive. Generally speaking, cremation costs less than traditional burial services, especially if direct cremation is chosen, in which the body is cremated as soon as legally possible without any sort of services. However, there is wide variation in the cost of cremation services, having mainly to do with the amount of service desired by the deceased or the family. A cremation can take place after a full traditional funeral service, which adds cost. The type of container used also influences cost.

Cremated remains can be scattered or buried. Cremation plots or columbarium niches usually cost less than a burial plot or mausoleum crypt, and require less space. Some religions, such as Roman Catholicism, require the burial or entombment of cremated remains, but burial of cremains may often be accomplished in the burial plot of another person, such as a family member, without any additional cost.

Environmental impact

To some, cremation might be preferable for environmental reasons. Burial is a known source of certain environmental contaminants. Embalming fluids, for example, are known to contaminate groundwater with mercury, arsenic, and formaldehyde. The coffins themselves are another known source of contamination. Another concern is contamination from radioisotopes that have entered the body before death or burial. One possible source of isotopes is radiation therapy, although no accumulation of radiation occurs in the most common type of radiation therapy involving high energy photons. However, cremation has no effect on radioisotopes other than to return them to the environment more rapidly (beginning with some spread into the air). Thus, cremation is of no overall help with pollution from this source.

Yet another environmental concern, of sorts, 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 America, 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, or are starting to 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.

However, there is a growing body of research that indicates cremation has a significant impact on the environment as well:

The major emissions from crematories are nitrogen oxides, carbon monoxide, sulphur dioxide, particulate matter, mercury, hydrogen fluoride (HF), hydrogen chloride (HCl), NMVOCs, and other heavy metals, in addition to Persistent Organic Pollutants (POP).

According to the United Nations Environment Programme report on POP Emission Inventory Guidebook, emissions from crematoria contribute 0.2% of the global emission of dioxins and furans.