LOW←TECH MAGAZINE English

Could We Dredge the Netherlands Without Fossil Fuels?

Sun, 05 Aug 2018 00:00:00 +0000

1699 scale model of a scratcher rigged with sails. Image: [Maritiem Digitaal](http://www.maritiemdigitaal.nl/index.cfm?event=page.home)

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.

35 million m³ of mud

Siltation is a serious problem in the Netherlands, which lies in the delta area of various rivers that supply large amounts of silt and clay particles. At the same time, navigable waterways are essential to maintain transportation and trade — the country is home to the largest port in Europe, Rotterdam.

Each year, some 30 to 35 million m³ of mud are dredged out for the maintenance of the Dutch waterways. Approximately 75% comes from salty waters. In the port of Rotterdam alone, 20 million m³ of mud is collected each year.

The demand for dredging continues to increase. Both inland ships and seagoing vessels continue to get bigger, requiring ever deeper and wider waterways. A “modal shift” policy, in which cargo transport moves from the road to the water in order to improve sustainability and reduce congestion, also leads to more and larger ships, and thus to more dredging.

Dredging by hand in Delft, the Netherlands. Image: [Maritiem Digitaal](http://www.maritiemdigitaal.nl).

Although most of the mud is dumped into the sea, each year 3.5 to 5 million m³ of contaminated sediments must be landfilled. Then there is the dependency on fossil fuels. A typical suction hopper dredger has a pumping power of 2,500 kW and removes 100 m³ of sediments per minute. The largest dredgers have 30,000 kW engines and 6,000 kW of pumping power. At full power, these ships consume 3,000 litres of oil per hour.

Dredging a Country by Hand

Silting is a very old problem in the Netherlands, so how did this job happen before the arrival of fossil fuel powered dredging machines and boats?

For centuries, the Netherlands were mainly dredged by hand. Dredgers stood on a small boat and scraped mud from the bottom with their “dredge bag” (“baggerbeugel”). In an alternative configuration, the dredger stood on a wooden board that was supported by the river bank on one side, and by a floating container on the other side.

A dredging bag. Image: [Maritiem Digitaal](http://www.maritiemdigitaal.nl/index.cfm?event=page.home)

Dredging by hand, standing on a boat. [Image](https://www.yumpu.com/nl/document/view/18609381/pre-industrial-dredging-rosmolens-en-krabbelaars-baggeren-vssd/2).

Handling a dredge bag.

The dredge bag, a tool that was also used for peat cutting, was a long stick (up to 6 metres long) with an annular metal scraper and a net at the end. There were different types of nets and bags, depending on the composition of the sediment. Working with the dredge bag, the handle was rested against the shoulder, so that the net could be dragged over the bottom with two hands.

For large dredging works, thousands of workers with dredging bags were deployed.

The mud was pulled ashore or deposited in a flat barge. For large dredging works, such as the construction of the Northern Holland Canal in 1822-1825, thousands of workers with dredging bags were deployed. Until about 1960, contractors of dredging works employed men with dredging bags for the maintenance of shallow ditches and canals. The tool is still for sale.

Dredge Mills

Manual dredging is heavy and time-consuming work, so people designed technology that could ease and speed up the task. Furthermore, ships became ever larger. In the last quarter of the sixteenth century, the “dredge mill” was introduced, which worked up to a depth of two metres. It was still based on human power, but now people were merely the power source for a machine.

On a dredge mill, a group of people worked large treadmills or capstans, which drove a paddle wheel that scooped the mud from the bottom and threw it into a barge that was moored across. The dredge mill was usually made up of two flat barges with the rotating wheel in between. These machines were often operated by prisoners.

Dredge mill operated by prisoners. Image: [Beeldarchief Rijkswaterstaat](https://beeldbank.rws.nl/MediaObject/Details/331290).

However, one century later, the depth of a merchant ship had increased to between 3.5 and 5 metres — and this was too deep for the human powered dredge mill. In 1622, the first horse-powered dredge mill was built. Three to six horses ran a pivot which set in motion a bucket chain. The horses had to be changed every hour because of the heavy labour involved.

In 1829, horse powered dredge mills could be used to dredge up to a depth of 5-7 metres. If working at a depth of 3.2 metres, with three to six horses, approximately 20 m³ of mud could be collected each hour. By comparison, the average modern suction dredger — which removes 100 m³ of mud per minute — is as powerful as 300 horse powered dredge mills.

Mechanical dredge bags on a pontoon. [Image](https://www.yumpu.com/nl/document/view/18609381/pre-industrial-dredging-rosmolens-en-krabbelaars-baggeren-vssd/2).

The original dredging techniques were also improved. Mechanical dredge bags emerged in the sixteenth century, when someone got the idea to pull the dredging bag with a rope over a winch. Mechanical dredge bags could be mounted on ships, but several dredge bags and winches could also work side by side on a pontoon.

During the first half of the nineteenth century the valve barge was invented. The bottom of this small boat could be opened without causing it to sink. In this way, it took less time to remove the mud. The technique is still used in some modern dredgers.

Valve barge with dredge bag. Image: [Maritiem Digitaal](http://www.maritiemdigitaal.nl/index.cfm?event=page.home).

Scratchers

The Dutch also took advantage of renewable energy sources to lighten the work — in particular wind and tidal power. From the fifteenth century onwards, the “scratcher” (“krabbelaar”) was used, a scraper that could dredge gullies if there was enough current.

With a strong current, dredging becomes easier, because the mud only needs to be loosened. The tide ensures the discharge of the material to the sea.

Human powered scratcher. Source: [Maritiem Digitaal](http://www.maritiemdigitaal.nl/index.cfm?event=page.home).

Human powered scratcher. Source unknown.

Simple scratchers were a kind of large rakes that were dragged across the bed of the water body. These were pulled by horses or people — some were pulled by a rowing boat.

Wind Powered Dredgers

In harbours with strong winds and tides, scratchers were rigged with sails. These triangular sailing ships had a broad stern and a flat bottom. Attached to the bottom was a harrow with iron spikes. At mid tide, the scratcher was placed just before the lock gates of a scouring basin, which was filled during high tide.

At low tide, the sluice gates of the basin were opened and the scratcher was pushed through the harbour with great force as the iron teeth scraped across the bottom. The ship gathered extra speed through the wide stern and, if the wind was good, the use of sails. Horses could also be used, pulling the ship in the absence of good winds.

At low tide, the sluice gates of the basin were opened and the scratcher was pushed through the harbour with great force as the iron teeth scraped across the bottom.

Wind powered scratchers were in use at least since 1435 in the southeastern part of the Netherlands. The flat bottom of the scratcher hinged and could sink with the help of cables to improve the draft. Two revolving doors, which could make a sharp angle of about 45 degrees with the ship, increased the reach of the barge.

Backside of a wind powered scratcher.

Nevertheless, manpower was still needed. Five to six men kept the monster in the right lane, while two to three men kept the harrow at the desired depth through pulleys and hoist blocks.

Alternatives to Dredging

Dredging was not the only answer to the siltation of waterways. Until the nineteenth century, the choice was also made to increase the height of river banks and dikes, so that the water level was allowed to rise. This was especially true for large rivers.

In a report from 1825, the dredging of large rivers was not considered a possibility because they were too deep and too wide for the technology of those days. It was only with steam power that dredging was also done on major rivers.

A Frisian Skûtsje. Image: [Skûtsje Langwar](http://skutsjelangwar.nl)

The province of Friesland, in the north of the country, reveals yet another alternative to dredging. The Frisians never used dredge mills, horse mills or other tools than dredge bags. They continued to dredge by hand until the arrival of the steam engine.

However, they innovated in a different way: from 1889 to 1933, they built 1,200 large cargo ships with a very limited draft — the so-called “skûtjes”. Obviously, boats with a smaller draft meant less dredging. The strategy reminds of the medieval Chinese wheelbarrow, which allowed transportation to keep functioning at a time when the road infrastructure was crumbling.

How many people do we need?

In a more sustainable future, could we dredge the Netherlands without fossil fuels? Sustainability is all about cars and smart appliances, but what about large infrastructure and maintenance works? Powering today’s dredgers with solar or wind power sounds unrealistic: those ships would require enormous chemical batteries, which is not practical or sustainable.

Therefore, as part of the Human Power Plant, we investigated how many people would be needed if we were to dredge the Netherlands by hand again. To answer this question, we organised a workshop in which we dredged a piece of Frisian waterway by hand and measured how long it takes to collect 1 m³ of mud. The results are discussed in the video below.

For English substitles, click CC:

Sources:

Interviews and documentation Nationaal Baggermuseum, Sliedrecht, Rotterdam.

Canon van de geschiedenis van Smallingerland, Smelne’s Erfskip 2010; Drachtstervaart, Smelne’s Erfskip 2015, ISBN 978-94-90543-08-02.

Geschiedenis van de Techniek in Nederland. De wording van een moderne samenleving (1800-1890). H.W. Lintsen, 1992.

Rosmolens en krabbelaars: baggeren in pre-industriële tijd

Maritiem Digitaal.

Groot onderhoudsplan Baggeren 2015 tot 2020. Hoogheemraadschap de Stichtse Rijnlanden.

Uitvoeringsplan 2010 Meerjarenbaggerprogramma Waterschap Rivierenland

Scheepsmodel Krabbelaar, Katie Heyning, Zeeuwse Ankers, juli 2015.

Evaluatie van het Friese Merenproject, 2000-2010, Provincie Fryslân.

Baggeruitvoeringsplan 2007-2015. Wetterskip Fryslân

Baggerproblematiek in Nederland, Compendium voor de leefomgeving.

Meerjarenbaggerplan 2012-2018, Waterschap Hollandse Delta.

Baggerschepen: van baggermolen tot sleephopperzuiger Maritiem Nederland.

Could We Run Modern Society on Human Power Alone?

Sun, 28 May 2017 00:00:00 +0000

Image: [A human powered student room](http://www.humanpowerplant.be/2017/05/for-rent-750-human-powered-student-rooms.html), Golnar Abbasi.

Unlike solar and wind energy, human power is always available, no matter the season or time of day. Unlike fossil fuels, human power can be a clean energy source, and its potential increases as the human population grows. In the Human Power Plant, Low-tech Magazine and artist Melle Smets investigate the feasibility of human energy production in the 21st century.

To find out if human power can sustain a modern lifestyle, we are designing plans to convert a 22 floors vacant tower building on the campus of Utrecht University in the Netherlands into an entirely human powered student community for 750 people. We’re also constructing a working prototype of the human power plant that supplies the community with energy.

The Human Power Plant is both a technical and a social challenge. A technical challenge, because there’s a lack of scientific and technological research into human power production. A social challenge, because unlike a wind turbine, a solar panel or an oil barrel, a human needs to be motivated in order to produce energy.

The Rise and Fall of Human Power

Throughout most of history, humans have been the most important source of mechanical energy. Building cities, digging canals, producing food, washing clothes, communication and transportation: it all happened with human muscle power as the main source of energy. Human power was complemented with animal power, and windmills and watermills became increasingly important from the middle ages onwards. Most work, however, we carried out ourselves.

These days, human power plays virtually no role anymore. We have automated and motorised even the smallest physical efforts. Mechanical energy is now largely provided by fossil fuels, either as a primary fuel or converted to electricity. This ‘progress’ comes at a price. Industrial society is totally dependent on a steady supply of fossil fuels and electricity, which makes it very vulnerable to an interruption in this supply.

Digging the Panama Canal. Picture: [National Archives](https://www.neh.gov/humanities/2011/januaryfebruary/feature/digging-across-panama).

Furthermore, fossil fuels are not infinitely available and their large-scale use causes a host of other problems. On the other hand, renewable energy sources such as wind and solar power are not always available, and their manufacturing is also dependent on fossil fuels. Meanwhile, in order to keep in shape and stay healthy, people go to the gym to exercise, generating energy that’s wasted. The Human Power Plant wants to restore the connection between energy demand and energy supply.

Why Human Power?

Compared with fossil fuels and renewable energy sources, human power has a lot of advantages. A human can generate at least as much power as a 1 m2 solar PV panel on a sunny day — and as much as 10 m2 of solar PV panels on a heavy overcast day. Human power is a dispatchable energy source, just like fossil fuels. Its power output is not dependent on the season, the weather or the time of the day. In fact, humans can be considered renewable energy sources and batteries at the same time.

Unlike fossil fuels, human power can be a clean energy source, which produces little or no air pollution and soil contamination. Moreover, the potential of human power increases as the human population grows, while all other energy sources need to be shared among an ever-growing amount of people. Furthermore, unlike solar panels, wind turbines, and batteries, humans don’t need to be manufactured in a factory. In combination with the right diet, human power is carbon neutral.

The potential of human power increases as the human population grows, while all other energy sources need to be shared among an ever-growing amount of people.

Finally, humans are all-round power sources, just like fossil fuels. They not only supply muscle power that can be converted to mechanical energy or electricity, but also thermal energy, especially during exercise: a physically active human being can generate up to 500 watts of body heat. Furthermore, human waste can be converted to biogas and fertiliser. Arguably, human power is the most versatile and most sustainable power source on Earth.

Detail from the [communal shower and laundry floor](http://www.humanpowerplant.be/2017/05/communal-shower-laundry-floors.html), by Golnar Abbasi.

Modern technology has greatly improved the potential of human power production. On the one hand, many electric devices have become very energy efficient. For example, solid state lighting consumes roughly ten times less power than old-fashioned lightbulbs, so that a quick workout can supply many hours of light. On the other hand, we now have much better technology for human power production, ranging from sophisticated exercise machines to biogas power plants.

Lessons from the Gym

The power output of a human being is determined by three factors: the person, the duration of the effort, and the mechanical device that is used to convert human power into useful energy — human power generation is often a symbiosis between man and tool or machine. Our legs are roughly four times stronger than our arms, which means that a human on a stationary bicycle machine can produce more power (75 to 100 watts) than a human operating a small hand crank (10 to 30 watts).

During shorter efforts, the mechanical power output of a human being can increase substantially: up to 500 watts on a bicycle and up to 150 watts while operating a hand crank over a period of one minute. However, age, gender and fitness also play an important role. Athletes can generate more power for a longer period of time — up to 2,000 watts during three seconds, or up to 400 watts during one hour. So far the theory, which is far from complete.

Exercise machines for strength training are an interesting addition to stationary cycling machines for human power production.

During the research phase for the Human Power Plant, we followed a fitness programme to become better human power sources. This was a very instructive experience. One of the first things we learned is that there are important differences between individuals, even if they have similar age, gender and fitness.

Image: Kris and Melle at the gym.

Melle, the powerhouse in our team, could lift a heavier weight on almost any exercise machine. Kris, on the other hand, appeared to have better endurance, and could beat Melle with triceps and shoulder exercises. Such differences should be taken into account in order to achieve optimal energy production - there is no ready-made solution.

We also found out that exercise machines for strength training can produce a lot of power in a very short time, making them an interesting addition to stationary cycling machines for human power production. A five minute workout (including two breaks of one minute each) can supply more than 15 Wh of electricity, enough to charge a quarter of a laptop’s battery or to power a desk lamp for 3 hours.

Finally, we quickly discovered that gyms are pretty boring places. The exercise equipment is often positioned in such a way that people all look in the same direction, which excludes all but the most primitive communication. And, while a stationary bicycle is considered to be the most energy-efficient human power machine, we found out that stationary cycling is no fun at all.

How to Motivate Human Power?

The last point deserves extra attention. Unlike a windmill, a solar panel or an oil barrel, human power needs to be motivated in order to produce energy. If we make a switch to human power production, would everybody generate their own power for the sake of sustainability? Would people pay others to do it for them? Or, would people force others to do it for them?

Image: A bull's whip.

A financial reward won’t do the trick, because at the current energy prices in the Netherlands, a human generating electricity would earn only 0.015€ per hour. Consequently, unless environmental awareness increases dramatically, the use of human power could open the door to new forms of slavery. Is such slavery justified for a reduction in CO2-emissions? Could we force refugees or criminals to produce power?

At the current energy prices in the Netherlands, a human generating electricity would earn only 0.015€ per hour.

These are disturbing questions, because the history of human power is — broadly — also the history of slavery. These days we import oil, coal and uranium, in the past we imported slaves. There may be a third possibility. We can try and motivate people by making human energy production more fun, social, and exciting.

The few commercially available devices for human energy production are entirely focused on energy efficiency — there’s no attention to fun or motivation. They are also designed for emergency purposes, not for prolonged and daily use. For example, most hand cranks are made as compact as possible, while a larger device would be much more comfortable to use.

Designing the Prototype

For the design of our prototype human power plant, we wanted to address these issues. We teamed up with makers and sports coaches to develop fitness machines that are suited for different types of human power sources, are fun too use, and produce a maximum amount of power.

Various components of the prototype Human Power Plant. Illustration: Melle Smets.

To make power production more social, we decided that power producers should be able to talk to each other. They can even bring their pets to help with power production, creating a cosy and home-like atmosphere. This is not a new idea: dogs were commonly used as a source of mechanical power in pre-industrial times, and also provided their owners with a source of warmth.

Water Under Pressure

For extra motivation, all exercise machines in our prototype human power plant are facing a jacuzzi and shower where girls are invited to encourage the boys to flex their muscles and generate more power. Of course, the sex roles could be reversed, but during the first experiments we discovered that this is less energy-efficient. Girls don’t seem to get motivated by guys in jacuzzis, at least not to the extent that guys get motivated by girls in jacuzzis. ¹

The prototype Human Power Plant under construction.

The jacuzzi is not a gimmick, but an essential part of the prototype human power plant. That’s because we opted for water under pressure as the energy carrier. The kinetic energy produced by humans and their pets is pumped into a pressure vessel, which produces water under pressure that is led to water turbines which supply mechanical energy and electricity. The jacuzzi is the receiving reservoir of this closed system.

With the choice for water under pressure, we want to make energy more visible and audible. More importantly, however, it allows us to produce electricity without the use of batteries and electronics — which are not sustainable components. In our human power plant, the hydraulic accumulator takes the place of the battery and the voltage regulator. Small variations in human power production can be smoothed out, keeping the voltage constant. Longer term energy storage is provided by the humans themselves.

For Rent: 750 Human Powered Student Rooms

To find out if we could sustain a modern lifestyle with human power alone, we teamed up with architects to design plans for the conversion of a 22 floors tower building into an entirely human powered student community of 750 people.

The Willem C. Van Unnik building is the tallest building on the campus of Utrecht University. The concrete, steel and glass monolith, which occupies a central position on the campus, was built in the late 1960s and has been mostly empty for years. Maintaining it is an important cost for the university, who owns the building.

A time schedule tells the students when they have to produce elelectricity and heat, and when to perform other services for the community.

Because the university has the ambition to become carbon neutral in 2030, we propose to turn a problem into an opportunity. The ecological footprint of the human powered Van Unnik student community will be close to zero, and the building is already there.

The floor plan of the human powered student building. Illustration by Pietro Degli Esposti, Golnar Abbasi, Arvand Pourabbasi.

Each student in the human powered Van Unnik student building is responsible for generating the electricity that’s used in his or her individual room. The lower floors of the building are reserved for communal energy production, providing both electricity and warmth. This energy is used to heat the building, prepare food, wash clothes, take showers, and so on.

More energy is supplied by a biogas plant, which is operated by the students and runs on their food waste and excrements. A time schedule tells every student when he or she has to produce electricity and heat, and when to perform other services for the community.

Power Generation Schedule

According to our preliminary calculations, an entirely human powered student building is achievable. The students would maintain a modern lifestyle, including hot showers, computers, and washing machines. On the other hand, they would have to produce energy for 2 to 6 hours per day, depending on the season and their individual and communal preferences.

Image: Golnar Abbasi.

A human powered student community has enormous potential for a reduction in energy use. If students have to generate their own power, they are much less likely to waste it. How far would students go to reduce their efforts? Would hot showers go out of fashion? Would salads be the next culinary trend? Would typewriters make a comeback?

Energy use is also lowered by encouraging the communal organisation of daily household tasks, just like in the old days. Finally, the human powered student community applies low-tech solutions, such as fireless cookers, thermal underclothing, and heat exchange showers, which all maximize comfort in the context of a limited energy supply.

The design of the building and the construction of the prototype human power plant is documented on a separate blog: Human Power Plant. It’s a work-in-progress, and comments are welcome. Once the project is complete, we will post an update on Low-tech Magazine.

The Human Power Plant is part of the Zero Footprint Campus project, for which 12 artists examine sustainability.

Some readers were disturbed by this paragraph, calling it sexist, and asking we would delete or change it. We understand that people are upset. However, this art project describes an imaginary world that is very different from ours. In a world run by human power, sex differences matter again. In general, men are physically stronger than women, which makes them better power producers. In general, men are more obsessed by sex than women, which is another fact (at least partly rooted in biology) we take advantage of to increase human power production. Imagining a human powered world raises a lot of uneasy questions beyond slavery. For example, what happens to older people and people with disabilities? Should women bear 10 children again, like in the old days? Rather than sweeping these controversial issues under the carpet, an art project should deal with them. Fossil fuels did not only bring us material prosperity, comfort, and convenience. They also brought us social emancipation. We will continue to investigate these issues in future scenarios. See: www.humanpowerplant.com ↩︎