Recycling Humans?

Chemistry as it applies to the human population.

Recent bush fires in Australia have had me thinking down some very black roads.  Some related to politics, capitalism and how the world could have been better if we had taken advantage of different “sliding door” moments.

I have reflected on climate change, sustainability, the death of native animals, destruction of houses and communities. I thought about the moments in history which have led us here to this time and place.

…And then I got to thinking about thermodynamics. About available energy and matter.  The fact that there is a finite number of atoms on this Earth.

The big question in my mind then became “How many people could live on this planet without ruining it?”

As a chemist, I have studied closed system reactions. Our earth is essentially a closed system.  A closed system only has a certain number of atoms available so once you use them up the reactions have to stop. Rearranging atoms usually uses up energy. Energy is also limited.

These limited atoms are used to make up all the things on Earth including humans. There are an estimated 7,656 million people on the planet. Let’s say the average mass of a human is around 80kg. That’s 612,480 million kilograms of humans. (1 kilo = 2.2 lbs)

If we wind back the clock just 300 years to the 1700s, the estimated upper limit[1] of the human population was 680 million. That means there is an extra 558,080 million (558,080,000,000) kg of human flesh on the planet now compared to then.

Most of those extra kilograms have come from other living things in our closed system because we eat them.  There has to be a time when we simply run out of atoms and energy to keep making more humans. The majority of the energy we are using now has come from the stored energy of ancient living things – a.k.a fossil fuel.

While some of the atoms in current humans may have come from recycled humans (i.e. the return of nutrients to the soil through decomposition) most of the time we don’t generally “recycle” humans. We put them in sealed boxes in burial grounds off-limits to agriculture where the nutrients can not be returned to the system. Cremation adds to the carbon in the air.

We waste and misuse so many resources. As consumers, we salve our conscious with the catch-cry,  reduce-reuse-recycle, but that is unlikely to be enough to stop or reverse climate change.

Is it time to stop being humans who recycle to humans who are recycled?

Is it time to start thinking about burial practices so the nutrients in humans are available for other uses? I’m of course not the only one thinking about this sort of thing; burial trees pods have been mooted for a while.

It’s all sounding like Soylent Green may not be such a bad idea after all! By the way, that movie, where people were recycled to make food for other humans was set in 2022.

I also believe that those of us in developed economies, who use a lot of resources, have a moral imperative to reduce the number of children we have. We need to seriously consider limiting our population through natural attrition so that some of the atoms can be returned to make other things.

Instead of “one [child] for mum, one for dad and one for the country” how about just one for the planet?


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