LOW-TECH MAGAZINE

Urban Fish Ponds: Low-tech Sewage Treatment for Towns and Cities

In the mid 20th century, whole cities' sewage systems safely and successfully used fish to treat and purify their water. Waste-fed fish ponds are a low-tech, cheap, and sustainable alternative to deal with our own shit -- and to obtain high protein food in the process.

Could We Dredge the Netherlands Without Fossil Fuels?

The dredging industry has been the backbone of the Dutch economy for centuries. If canals, harbours and rivers would not be maintained for a few years, the whole country would literally grind to a halt.

Today, dredging happens with oil powered ships, which burn up to 3,000 litres of fuel per hour. However, in earlier times, the Dutch waterways were dredged mostly by hand, using simple but ingenious tools.

Manual dredging was heavy labour, especially when waterways became deeper. Therefore, it was supplemented by animal power, wind power and tidal power. However, in some parts of the Netherlands, people chose a different strategy: they designed a new type of cargo ship that could sail in shallow waterways. 

1699 scale model of a scratcher rigged with sails. Credit: Maritiem Digitaal

Heat Storage Hypocausts: Air Heating in the Middle Ages

Hot air vents in the floor of the Maulbronn monastery. Source: "Das Kloster Maulbronn. Geschichte und Baugeschichte.", Ulrick Knapp, 1997 / Via Spiegel 2016.

The Romans are credited with the invention of the first smoke-free heating system in Western Europe: the hypocaust. Until recently, historians had assumed that its technology was largely lost after the collapse of the Roman Empire. In fact, however, it lived on in large parts of Europe, and was further developed into the “heat storage hypocaust”, an underground furnace on top of which granite stones would be piled, to then release hot air through vents in the floor. By this means, a room could be kept warm for days with just one firing of the hypocaust's furnace.

Power Water Networks

During the second half of the nineteenth century, water motors were widely used in Europe and America. These small water turbines were connected to the tap and could power any machine that is now driven by electricity.

As we have seen in a previous article, operating motors with tap water was not very sustainable. Because of the low and irregular water pressure of the town mains, these motors used unacceptably high amounts of drinking water.

While the use of water motors in the US came to an end early in the twentieth century, the Europeans found a solution for the high water use of water motors and took hydraulic power transmission one step further.

They set up special "power water" networks, which distributed water under pressure for motive power purposes only, and switched to a much higher and more regular water pressure, made possible by the invention of the hydraulic accumulator.

Almost all these power water networks remained in service until the 1960s and 1970s. Hydraulic power transmission is very efficient compared to electricity when it is used to operate powerful but infrequently used machines, which can be distributed over a geographical area the size of a city.

Fruit Walls: Urban Farming in the 1600s

We are being told to eat local and seasonal food, either because other crops have been tranported over long distances, or because they are grown in energy-intensive greenhouses. But it wasn't always like that. From the sixteenth to the twentieth century, urban farmers grew Mediterranean fruits and vegetables as far north as England and the Netherlands, using only renewable energy.

These crops were grown surrounded by massive "fruit walls", which stored the heat from the sun and released it at night, creating a microclimate that could increase the temperature by more than 10°C (18°F). Later, greenhouses built against the fruit walls further improved yields from solar energy alone.

It was only at the very end of the nineteenth century that the greenhouse turned into a fully glazed and artificially heated building where heat is lost almost instantaneously -- the complete opposite of the technology it evolved from.

Power from the Tap: Water Motors

Few people in the western world realize that they have an extra power source available in their household, workshop or factory: tap water.

Just before the arrival of electricity at the end of the nineteenth century, water motors were widely used in Europe and America.

These miniature water turbines were connected to the tap and could power any machine that is now driven by electricity.