The ancient Romans got the hang of how to use volcanic ash. They used it as an ingredient in their concrete, and the result was buildings like Colosseum in Rome, still standing there today.
Now scientists have proved the worth of volcanic ashes from Mount Etna in Sicily as a soil fertilizer. They have thoroughly tested the ashes and found that it has a potential to support plant growth and soil health. The study was recently published in the journal Chemical Engineering Transactions. The researchers behind the study are part of the EU-funded LANDFEED project.
Giuseppe Mancini is one of the researchers behind this project. He is a professor of chemical engineering at the department of electric, electronic and information technology at the University of Catania in Sicily. He has personal knowledge of living close to Etna, in Catania.
He says that they had fifty-seven ashfalls in 2021 alone, sometimes with more than one event in the same day. One ashfall on February 16, 2021, caused centimetre-sized lapilli (stone-like volcanic fragments) to fall on Catania.
“It covered everything; cars, gardens, roads, and caused a lot of work when large amounts of ashes had to be taken care of in a short time,” he said.
People have tried to use ashes as an ingredient in bricks and construction materials before, but the problem is the irregular access to the ashes and that the content differs from eruption to eruption.
That triggered Giuseppe and the paper’s co-authors to find other ways of using the ashes instead of regarding it as waste.
“We already knew that the best wine is produced close to volcanoes because of the climate but also because of the soil. Ashes can also improve the structure of ‘clayly’ soil,” he said.
There were only two questions left to be answered. Are the ashes from Etna safe to use as a fertilizer, and what can make the authorities reclassify the ashes from a waste material to a useful, sustainable, and traceable resource?
The ashes examined in the study came from eruptions in 2021. The researchers collected ash samples from multiple sites around Etna and ran it through different tests, checking its content.
The tests showed no harmful hydrocarbons or persistent organic pollutants, and heavy metals were found to be at least 70 percent below legal limits.
Leaching tests revealed that the ash releases beneficial nutrients such as sodium, calcium, magnesium, potassium, phosphorus and nitrates, all well-known to gardeners.
The tests also revealed that three out of the seven samples fully complied with the regulatory thresholds for waste recovery. The remaining four samples exceeded limits in only a single parameter each, mainly fluoride or copper.
Washing reduced fluoride to acceptable levels in two of the problematic samples, although it is yet another concern handling the wash water sustainably.
The conclusion of the study is that volcanic ash from Mount Etna has a potential to support plant growth and soil health, especially when used with conventional fertilizers.
The research team then developed a management protocol for volcanic ashes. The protocol is based on the current regulatory framework and potential applications of volcanic ashes. It describes the critical steps like checks, alternative actions, challenges and possible solutions, to maximise volcanic ashes as a multipurpose raw material.
Today, as volcanic ash fallout primarily affects urban areas, the municipalities act as the waste holders and are responsible for classifying the ashes. That would enable the ashes to be introduced into a production cycle at an authorized facility, where an internal verification will confirm whether the conditions for the material’s recovery exist.
“There has to be a control system where you can certify that the ashes don´t have a negative impact on the environment. The process of using the ashes must also be well defined,” Giuseppe Mancini said. “But this is absolutely not impossible to solve.”
“With this study we captured a lot of problems and gave it a solution. When there is an ashfall we need to quickly collect the ashes, and with a facility for controlling the ashes, as well as a network of local farmers, we could turn a waste problem into a useful resource,” Giuseppe Mancini says.
“It is a system that provides us with the required flexibility and sustainability. Since it is more expensive to deal with ashes as a waste, it is also sustainable in an economic perspective. And I really want people to know there are so many good things happening in our scientific research,” he concludes.