By Gina Baldivieso
La Paz, Aug 13 (EFE).- Bricks and concrete or cement blocks that are disposed of by the ton every day on river banks and in Pura Pura, an urban park that is this Bolivian metropolis’s green lung, are being put back into circulation thanks to a municipal initiative to recycle used construction material.
Construction and demolition waste (CDW) is a major problem in a city like La Paz, which lies in a narrow valley surrounded by mountains, has a complex topography and unstable geological conditions and is criss-crossed by at least 300 surface and subterranean rivers.
“This is a city that grows upward more than expanding horizontally and extending its borders … This results in a large supply of construction and demolition waste being generated,” La Paz’s environmental management secretary, Jose Carlos Campero, told Efe.
La Paz’s skyline has filled up with high rises in recent decades, a construction boom that has required the constant demolishing of houses and has led to building rubble ending up on river beds.
These practices are not illegal but they are improper and harmful due to their environmental impact, Campero said.
The city was generating an estimated 1,400 tons of CDW per day prior to the Covid-19 pandemic, prompting city officials to install a pilot plant to treat 60 tons of that waste per day.
The project was carried out with assistance from the Italian Agency for Development Cooperation and Cooperazione Internazionale, an Italian non-governmental organization with a mission to fight poverty and promote long-term community development.
Although that plant processes less than 10 percent of the metropolis’s total construction waste, the initiative has given the local government a better understanding of what CDW processing entails, Campero said.
That facility has been in operation since March and is located inside the municipal nursery in Aranjuez, a residential area on La Paz’s south side.
Construction companies or individual builders provide the plant with bricks, plain and reinforced concrete and cement, but no metals or wood, since the process essentially involves converting these materials into aggregates, the plant’s supervisor, Ivan Vildoso, told Efe.
Once it arrives at the plant, the CDW is meticulously classified to remove any material that is not building debris and then is put through a grinding mill, he said.
The material then is placed on a conveyor belt with a system of magnets to remove the tiniest of metallic residue and later goes through further screening and milling.
The end result is separated into three byproducts based on their diameter. The largest are returned to the plant, while the other two need no further processing prior to reuse.
Campero said the aggregates are used as base and subbase in road construction projects, as material for making sidewalks or plastering walls and as an ingredient in concrete mixtures.
“It’s a material highly coveted by the private construction sector due to its characteristics. And since they’re concrete residues they’re of higher quality than natural aggregates (like pebbles and sand) that are (found) in rivers,” Campero said.
The current city administration plans to use the mechanism of a public-private partnership for a larger production facility that will be capable of processing at least half of all the CDW generated daily in La Paz and contain space to store all of that debris, Campero said.
“This is extremely important because in this way we avoid the degradation and harmful and negative environmental impact we have today,” he said, adding that the industry that generates DCW also benefits by having a place to properly dispose of that waste. EFE