Mud houses can cope with water much better thanks to cow manure. A Delft University of Technology (TU Delft, the Netherlands) researcher hopes to contribute to the improvement of these ‘earthen’ houses through scientific research. This offers perspectives, particularly in poorer countries. There, this type of housing is losing popularity due to its image, even though it is cheap and environmentally friendly.
PhD candidate Yask Kulshreshtha will be discussing this during the opening of the academic year today at TU Delft. As a speaker, the engineer from the Faculty of Civil Engineering and Geosciences will be given the opportunity to talk about his dream of making a global impact. His work has been made possible by the TU Delft Global Initiative, which aims to come up with concrete solutions to worldwide problems in cooperation with local partners.
There is a lot of interest in earthen houses that are made from soil, which are particularly common in poorer countries. They are cheap, produce fewer CO2 emissions than cement houses and can regulate the temperature effectively by retaining and releasing moisture in an optimal way. But they score less well on water resistance and sturdiness factors.
Earth houses in India
Kulshreshtha focuses on improving the material for earthen houses by adding a ‘stabiliser’, something that makes houses tougher and longer lasting. His Indian background means that he is well acquainted with the issues.
“Residents in rural India live in mud houses made from a mixture of clay, sand and silt. The material is not waterproof. Rain crumbles the walls. After each rainy season, the walls have to be replastered.”
“Bricks are not always a good alternative. This is mainly because transporting stones and cement makes construction more expensive, while earth or soil is abundantly available everywhere locally. Moreover, cement production releases a lot of CO2.”
Opting for cow manure
The low level of water resistance that mud houses have is often solved by the addition of chemical stabilisers, such as Portland cement and hydraulic lime. But this raises costs, requires energy and degrades the beneficial properties of the soil.
Cow manure (for example) is already being used, but without a proper understanding of how it works. Kulshreshtha wants to reinvent the use of this natural stabiliser with the help of scientific research. He leaves other biological stabilisers (such as seaweed or starch from bio-waste) out of the equation, as they are too expensive and not widely available.
Corona has made it more difficult to work in his native country. “Because of the pandemic, it is difficult to conduct research and build structures in India. So, I decided to build a demonstration model in the Netherlands to see how it performs. The aim is to apply the revised knowledge gained from cow manure blocks to the construction of low-cost housing in India.”
“It involves mixing a thousand kilos of fresh cow manure and six thousand kilos of mud, earth. The mixture is compressed using a dedicated machine. We now know that this kind of mixture is at least twenty times more water resistant than one without cow manure.”
The Delft engineer goes on to explain the process. “Compression was done with an electric limestone engine in Emmen in the Netherlands. That is also where the soil was, which is why it was easier to bring the manure from an organic farm near Delft to Emmen instead of the other way around.”
A different type of machine
The manure-mix blocks now made signify a step towards Kulshreshtha’s dream of cheaper and more sustainable construction, especially in his native country. The blocks are drying out at the moment.
The Delft resident can joke about his product: “It literally is the ‘shit that matters‘.”
However, things will be different when it comes to using it in India. “There are manual, cheap machines available of good quality for compressing mixtures, but the production speed is low. In the Netherlands they are (semi-)automatic and faster, but too expensive for use by a family or a small community in India.”
Reinforcing materials with ‘biowaste’ is fairly well known in science, but the discussion on waterproofing is limited. It is also for this reason that Kulshreshtha is now focusing on cow manure as a stabiliser.
Which is why the Delft engineer conducted experiments with different components of manure, different in size, Such as fibers and bacterial biomass made up of medium and small pieces of material. It turned out that the small pieces of cow manure were almost exclusively responsible for the water resistance of the soil that was pressed into blocks.
Design as well
Not only the quality, but also its image plays a role in the waning popularity of mud houses. “That’s why I also want a nicer design. With a flat roof, while an earthen house traditionally has a pointed roof. Especially in India, there is a high demand for new construction within the short term. So if we can contribute to a better image with improvements to the traditional model, that would be great.”
For the Netherlands, one constraint is being able to meet the strict building standards. Because even an improved form of ‘mud houses’, more water-resistant and stronger, will not be readily approved. “Something like that takes time. In general, building this kind of house has to take into account local conditions because the ground needed for it can vary quite a bit.”
He hopes that the Netherlands can also benefit from the insight he has gained. Especially as a country with a manure surplus where this poses a major problem due to unwanted emissions.
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