Estonian researchers have created a low-cost and environmentally friendly building material out of rice hulls, a byproduct of rice processing. The new material is currently being tested in Kenya, where small-scale residential houses for a new capital city are built from it.
About ten percent of worldwide carbon emissions are caused by the production of building materials.
"The carbon footprint of concrete is the highest of any material. Despite the continued popularity of this material, it is critical to plan ahead of time and look for alternatives," Jüri Liiv, a researcher in colloidal and environmental chemistry at the University of Tartu, said.
In developing nations, a variety of ashes with distinct properties, such as rice straw ash, are easily available. The latter is the foundation of a new carbon-negative construction material developed by Estonian researches and already utilized for building the first houses in Kenya.
"According to our research, rice husk contains up to 98 percent silica, and when blended with wood ash, which is high in calcium oxide or lime, the two react to produce a cement that is suitable for home construction as it holds heat," Ergo Rikmann, a research associate in environmental materials chemistry at the University of Tartu, said.
Liiv added that the material is lightweight and extremely durable and it is impervious to termites and mold.
"Additionally, it requires no additional processing and can be simply torn up in pieces and scattered in fields when no longer in use. Moreover, it is free to obtain, as it is not edible."
The researchers add that the construction material they have developed is appropriate for any climate where it is necessary to maintain a difference in temperature between the interior and exterior. Therefore, it could also be useful in tropics.
"Our material minimizes greenhouse gas emissions and saves energy in tropical climates where cooling would otherwise be necessary," Rikmann explained.
The researchers are collaborating with the Institute of Civil Engineering at Kenyatta University (KU) in Nairobi, with whom they are partnering to identify environmentally sustainable and cost-effective ways to construct houses in Kenya.
"Kenya is building a new capital city; our material may be ideal for constructing small residential houses there," Liiv said.
Estonians have built a machine for industrial production of building blocks that combines raw elements on-site.
"Our tests have been completed, and the machine has been delivered to the site. Now we must wait for the final results to see how well the house holds up and how the interior environment is. However, Kenyan partners are in charge of this," Liiv said.
Upon completion of the test houses, the internal climate, sink marks and other data will be measured.
"The material is brand-new, and there is no existing equivalent. If the outcome in practice resembles what we achieved in the lab, everything should go smoothly," Rikmann said.
A successful industrial trial is usually necessary to generate widespread production interest, but this type of pilot project is difficult to finance wuthin academia, the researcher said.
"No one is eager to pay for the phase between laboratory tests and industrial production during which initial samples must be produced," Liiv said.
In the past, the team has produced peat material that has garnered curiosity but has not been picked up industrially.
"Even if a new material is far more environmentally friendly, it is still easier for a builder to use conventional materials instead of switching to a completely new one," Liiv added.
Editor: Kristina Kersa