Hank Green: Everyone dies! It’s kind of a bummer, but it’s inevitable. Humans have entire philosophies and religions dedicated to the contemplation of what happens once our bodies stop working, but unless you’re a mortician, how much thought do you give to what happens to your flesh and blood after you die? Will it be burned up, buried underground, frozen, probed by queasy medical students or even displayed in a museum?

These days, once you’re dead, you actually have a lot of options, with more on the way. No wonder the US funeral services industry is a $20 billion business. And, whether you’re into the idea of a jazz funeral, Viking burial or 21-gun salute, once the ceremonies are over, there are some choices to make. Some options are simply honored by tradition; others are designed to let your body have the least impact on the world that’s becoming increasingly over-populated with corpses. Most of these options are illegal, and some are a little bit creepy.

(Intro)

So, dead bodies. Biologically speaking, as soon as the heart stops beating, cells stop receiving oxygen and start to die. Your brain cells go first, but skin and bone cells can live on for several days. Blood starts to pool in lower-lying areas as your capillaries drain. After a few hours, rigor mortis sets in as muscles suddenly stiffen, possibly scaring the bejesus out of bystanders, and within 24 hours, the body will have lost all of its internal heat in a process called algor mortis which, yeah, sounds kind of like a Voldemort curse there. The enzyme and bacteria-laden pancreas begins to digest itself before these hungry organisms start to spread to other organs. Things start to get smelly and bloated, as the bacteria produce strong gases. Hopefully by now the body has been put on ice or is getting processed for its final fate, and, like I said, there are many and actually surprisingly varied final options.

Back in the day, swiftly burying a corpse helped prevent the spread of disease and it also helped mourners psychologically to remove the body from view. Archaeologists have found multiple Neanderthal burying sites, indicating that the need to ritually dispose of corpses is a deeply-seated hominid need. Just laying a body in the earth and covering it is a pretty good way to let composition do its thing. It’s kind of the ultimate composting, but with population growth and the urbanization of many countries, burial has gotten a lot more complicated.

Mainstream Western burial is now very resource-intensive, involving an embalmed body placed within a reinforced coffin, buried with a vault of cement that doesn’t do much for timely decomposition. It also takes up a lot of space underground. The act of trying to preserve a body is nothing new. The Egyptians perfected mummification centuries ago using salty powders and resin. Oh, and it also doesn’t hurt that Egypt’s climate is naturally, y’know, dry.

But modern embalming developed during the Civil War to transport bodies of dead soldiers is different than mummification, chiefly because it doesn’t preserve a body indefinitely and because it uses lots of nasty chemicals. Embalming fluid is typically a mixture of formaldehyde, methanol and other solvents. It preserves bodies by irreversibly de-naturing—basically changing the shape of—cell proteins so that they are no longer a food source for bacteria, and also by killing the bacteria that are there.

It is estimated that the United States’ cemeteries alone bury over 3 million liters of toxic embalming fluid every year. Not only that, but we’ve got an estimated 90,000 tons of steel, 1.6 million tons of concrete and nearly 71,000 cubic meters of hardwood going into the ground each year. But even if a body is buried without all that stuff, if it’s much deeper than 50 centimeters, the decomposition process must carry on without the benefit of oxygen. This process of anaerobic digestion means that instead of producing carbon dioxide in water as it would in the open air or in top soil, the body just kind of turns to sludge and leaks methane. So-called ‘natural’ or unembalmed burials are on the rise in England, foregoing the chemicals and concrete and instead burying bodies in shrouds or biodegradable coffins so they can naturally decompose.

But if the thought of your body remaining in a bunker underground for decades to come isn’t so appealing and your religious views don’t prevent it, perhaps you’d rather end up as ashes or fine, gravel-sized bits of crushed bones, as it were. Humans have been cremating their dead since prehistoric times; it’s the mandated last rite of Hinduism. But the first modern crematoriums didn’t show up in England and America until the late 1800s.

While funeral pyres and shooting flaming arrows into boats at sunset seemed to work well enough, modern cultures have found ways to standardize and sterilize the process. Today, a body is kept cool until the time of cremation, when it’s placed in a flammable coffin and rolled into an incinerator that reaches temperatures of over 1000°C. I’ll spare you the particulars of what jet-engine flame does to flesh and muscle, but in the end, the heat is intense enough to deteriorate bones until they begin to crumble. The whole process usually takes about three hours and leaves loved ones typically with one to four kilograms of remains.

Today, about 41% of Americans choose cremation over burial, and while cremation may be cheaper or more spiritually appealing, it’s only marginally if at all better than traditional burial in terms of environmental impact. It doesn’t require as much physical space as full-body burials but, believe it or not, all that burning releases compounds like dioxin, hydrochloric acid and carbon dioxide into the atmosphere. In the UK, an estimated 16% of mercury emissions come from cremated vapor of old dental work. It also takes loads of energy to superheat a furnace for three hours, as in, it’s estimated that just one year worth of cremations in the US consumes as much power as it would take to go to the moon back over 80 times.

Once you’re left with an urn full of ashes, you’ve got various options. You can bury them in the family plot, keep them on your mantle or scatter them in a favorite spot, but you can also have your ashes launched into space or mixed with cement and sunk into the ocean as an artificial reef. Legendary journalist Hunter S. Thompson had his remains packed into fireworks and shot out of a cannon. If you’re more into keepsakes, there’s a company that will use your ashes to make pencils. Yes, apparently the average human yields enough ashes to provide graphite for 240 pencils, or you can turn those remains into a diamond through intense heat and pressure, which gives a new meaning to the term ‘heirloom jeweler’.

Now, if the thought of burying or burning your body doesn’t appeal, what about being liquefied? Alkaline hydrolysis uses an extremely alkaline solution to liquefy bodies. People have been using it to safely dispose of diseased livestock for years. In this process, a corpse is zipped into a silk bag, placed within a sort of mesh cage and loaded into a pressurized device. Once sealed, the chamber is filled with water and potassium hydroxide (also known as lye, a key ingredient in many liquid soaps) and then heated under pressure to 180°C.

It takes about three hours for the super-corrosive concoction to reduce a body to mush or, more specifically, a greenish-brown oily juice made up of amino acids, sugars and salts. Once that liquid seeps out, it can pretty much just go down the drain, or if you’re more poetic, say, put into a garden. What’s left of the calcium phosphate bones can be crushed to dust in your hand and scattered or buried wherever you please, just like ashes. The whole process uses far less energy than cremation, releases no greenhouse gases or mercury vapors, and unlike traditional burial, requires very few resources. Currently, this practice is only legal in a handful states, though it’s used by the Minnesota Mayo Clinic to dispose of donor bodies. It’s a promising alternative to burial and cremation, if you can get past the whole ‘puddle of green goo’ part.

But perhaps if you prefer the idea of ice over fire, then maybe the emerging practice of promession will hold some appeal. Remember in middle school when your science teacher busted out the liquid nitrogen and shattered a banana or a rose or something and it blew your mind? Well, that’s pretty much half of the promession process. Developed by a Swedish biologist, promession begins by freezing a body in a vat of liquid nitrogen. This makes the body so cold it becomes brittle, then a low vibration is applied and the body slowly crumbles into dust. A special vacuum then runs over the remains, removing the ice and evaporating the water.

What remains is a powder that weighs 50% to 70% less than the original body. From there, any tooth fillings, fake hips and bionic knees are removed, and the remaining human dust is tucked into a biodegradable casket and laid to rest in a shallow grave. From here, [aerobic] bacteria can work their magic and compost the remains within a year. At least, that’s how the theory goes. Swedish company Promessa has tested the concept using pigs, but it has yet to be put in practice on humans.

Now, if you’re of the mind that the dead body still has a good use or two left in it, you may want to consider donating your body to science or education. Temporarily preserved bodies can be used for lab dissections and medical procedure practices, or, if you’re into being preserved for all time and displayed in museum exhibits like body worlds, you could look into plastination. Developed by a German anatomist in the 1980s, the plastination process replaces a body’s water and fats with plastics such as epoxy and silicone, leaving hard, sturdy specimens that don’t smell or decay and that can be shaped into one of the many dance positions from ‘Thriller’.

So between burned, buried, frozen, liquefied or plasticized and put on display, a corpse has a lot of choices these days. And, if you’ve tried to live your life in an environmentally sustainable way, you can extend that priority through your death, if that’s your jam.

Thank you for watching this particularly morbid Infusion, shot in the Keith Chiem Studio, and thank you to all of you Subbable subscribers for your continuing support of SciShow. You can find us on Facebook and Twitter, and if you want to keep getting smarter with us here at SciShow, you can go to youtube.com/scishow and subscribe.