The collection features the work of people from various backgrounds, including members of the Arrels Fundació organisation, which encourages people who have lived on the streets to embrace their creative side.
Salvaged timber planks form the three legs supporting each of the chairs, while the seats and backrests are customised with techniques relevant to the usual jobs of each individual designer.
"The challenge was not really about trying to make them the way a cabinetmaker or craftsman would, but to try to make them exploring other techniques, like those used in the participants' daily occupations," Claret said.
Claret designed a horseshoe-shaped metal attachment that the participants could use to affix a backrest to the handmade chairs, which screws into a triple-pronged metal plate underneath the seat.
"The experiment explores how each of these people, with the help of their metal pieces, can make the chairs on their own as much as possible, giving shape and aesthetics in a very direct way, with his or her own identity," he said.
One of the chairs was designed by Careli, a cleaning woman by trade, who pieced together planks of recycled wood before burning them with an iron to create a darker pattern in the grain of the chair.
The skater chair was designed by a local skateboarder and features a splintered backrest and seat, made from a broken board.
One of the chairs is covered with fake designer handbags, found at street sellers' stalls in Barcelona. Another features a charred tree stump sat atop recycled planks, taken by a fireman from a burning forest he fought to save.
A car mechanic spilled oil onto the wood of one of the chairs before running over it with a car, while a sex worker wrapped her chair in pairs of sheer tights.
Cultural organisation Joana Barcala presented recycled furniture using an "urban knitting" technique, which involves stitching around objects like lampposts and statues.
In similar stories on Dezeen, Australian company DesignByThem previously designed a collection of recycled chairs repurposed from milk containers and factory waste while Studio Swine created a series of stools made from waste picked up by fishing trawlers.
Photography is by Juan Lemus.