If there is one abiding image from my time in Sri Lanka, it’s the weird odds and ends that wound up in the fridge, covered by cling film.

It didn’t matter how little milo was left in my glass. The tiniest drop was whisked away to the fridge, expected to be finished later.

This is just a small example of something much larger. Nothing is wasted in Sri Lanka. Cars, computers, cans – everything can be put to another use. Anything can be mended or broken down, given away or put to some other purpose.

In the West this behaviour is, unfortunately, met with something akin to derision. Recycling, upcycling and zero waste are part of a subculture. I often visit my local tip or re-use and repair centre to find perfectly serviceable furniture and gadgets. Disposability and planned obsolescence are accepted norms.

We’ve come a long way from considering waste an input, consumption as a chain.

But this is a recent phenomena. Recycling and upcycling played a pivotal role in humanity’s rise. Many parts of the world have just gotten so wealthy they’ve forgotten about it. From The Ghost Map by Steven Johnson:

Waste recycling is usually assumed to be an invention of the environmental movement, as modern as the blue plastic bags we now fill with detergent bottles and soda cans. But it is an ancient art. Composting pits were used by the citizens of Knossos in Crete four thousand years ago.

So we’ve been doing this a while. It wasn’t invented by the gluten intolerant.

But Johnson keeps going, and starts making interesting allusions to the natural world.

We value tropical rain forests because they squander so little of the energy supplied by the sun, thanks to their vast, interlocked system of organisms exploiting every tiny niche of the nutrient cycle. The diversity of the system is precisely why rain forests do such a brilliant job of capturing the energy that flows through them: one organism captures a certain amount of energy, but in processing that energy, it generates waste. In an efficient system, that waste becomes a new source of energy for another creature in the chain.

Here’s the magic – our cities were once ecosystems like this. Before we went to extraordinary lengths to haul stuff out of sight and mind, we had to do something with it. We, too, created energy and input loops. And they helped build our modern world.

Waste recycling — in the form of composting and manure spreading — played a crucial role in the explosive growth of medieval European towns. High-density collections of human beings, by definition, require significant energy inputs to be sustainable, starting with reliable supplies of food.

The towns of the Middle Ages lacked highways and container ships to bring them sustenance, and so their population sizes were limited by the fecundity of the land around them. If the land could grow only enough food to sustain five thousand people, then five thousand people became the ceiling. But by plowing their organic waste back into the earth, the early medieval towns increased the productivity of the soil, thus raising the population ceiling, thereby creating more waste—and increasingly fertile soil.

The collecting of human excrement was a venerable occupation; in medieval times they were called “rakers” and “gong-fermors,” and they played an indispensable role in the waste-recycling system that helped London grow into a true metropolis, by selling the waste to farmers outside the city walls.

Of course, there’s an obvious reason Sri Lankans and eighteen century Londoners are careful with waste. And despite the veneration, I doubt anyone really chose to be an 18th century "raker".

That’s not what I’m advocating. But the mindset is. Let’s go back to thinking of waste as an input. Just think of all the potential we are squandering.