Researchers from the UNAM have developed technosoils , a mixture of organic and inorganic waste in order to create urban “milpas”, a Pre-Hispanic crop-growing system , gardens, and green roofs to revegetate Mexico City and avoid its flooding.
Experts from the Geology Institute have been producing the artificial soils for five years. Currently, they are testing seven types of soils, which were created using organic waste, such as compost from one of the city's plants.
They also use vermicompost, produced by the California worm ( Eisenia foetida) ; Sawdust , that favors the radical growth of plants; and biochar , obtained by the thermal decomposition, pyrolysis , of any organic waste and is used to improve the soil 's properties.
On the other hand, they also use inorganic waste from excavations, constructions, and demolitions, such as bricks, concrete and walls, which are crushed and mixed with the wastes.
In a statement, the UNAM emphasized that they created an inventory of organic and inorganic waste in Mexico City , before experimenting with artificial soils to grow corn, beans, and squash in an urban milpa .
Blanca Lucía Prado Pano
, in collaboration with Lucy Mora Palomino , and Víctor Manuel Peña Ramírez , have grown ornamental plants like cempasúchil, cactus, and evergreens, and have also grown chili and tomato, and now they know in which soils does the fruit of the tomato plants are best produced.
Last year, the experts' urban milpa completed a full cycle, and now it will reach its second cycle. During the first trial, mixtures of compost with pieces of wood, and vermicompost with pieces of wood were the ones that showed the best performance.
However, their organic composition causes them to generate significant amounts of carbon dioxide. Therefore, in the second cycle, they added biochar which has great stability over time. An artificial soil with vermicompost , biochar , demolition waste , and wood chips would be very competitive.
"Preparing soils to grow edible plants is the hardest part. If we can obtain an important amount, we can grow any plant we want”, said Peña Ramírez.
Therefore, the group is working to develop artificial soils not only to promote urban agriculture , but to regenerate gardens and build new parks, and to rehabilitate polluted areas. "Our goal is to develop technosoils with many uses," said Mora Palomino , head of Soil Analysis Laboratory.
In major cities, most soils are compacted, as if they were made of concrete; here, the artificial ones can be used to plant native trees and recover some ecological functions, besides creating green roofs and greening gray areas, he explained.
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