The city startup building trade from broken glass

Bottles ready for recycling at the 23 Glass Studio workshop. [Maryann Muganda, Standard]

Zimmerman is a hive of activity, with traders, boda boda riders and waste pickers going about their business.

Nearby, workers at a scrap collection centre sort piles of discarded plastic. A few metres away, the 23 Glass Studio is quietly giving waste a new lease of life.

From outside, the studio could easily be mistaken for a carpentry shop. Inside is a colourful collection of art made from discarded materials.

Recycled metal has been turned into sculptures and toy vehicles, while an old deodorant container has been transformed into a butterfly. Beads and other discarded materials add colour to the creations.

But glass is at the heart of the studio. A 2025 assessment by the Centre for Science and Environment estimates that Kenya generates about 204,000 tonnes of glass waste annually, with only about 30 per cent recovered for recycling and reuse.

Globally, about 130 million tonnes of glass is produced each year, of which roughly 27 million tonnes is recycled, according to the report.

Unlike organic waste, glass does not biodegrade and can persist in the environment for extremely long periods. Yet it can also be recycled repeatedly without losing its basic quality.

It is this contradiction that 28-year-old Charles Muturi, founder of 23 Glass Studio, is trying to exploit.

Muturi started the studio in 2021, initially working alone. His idea was born during the Covid-19 period when he and his friends, most of them fresh from university and without jobs, were looking for something to do.

“We looked for something that was less expensive to start and required less capital,” Muturi says.

They soon noticed an overlooked resource in their neighbourhood: discarded glass bottles.

Unlike plastic, which waste collectors could sell for a better price, glass had little commercial value. Muturi says a kilo of glass could fetch as little as Sh3, making it unattractive to many waste pickers.

Yet in Zimmerman, where bars, wines and spirits shops generate large amounts of discarded bottles, Muturi saw an opportunity. “I already have a raw material here,” he says.

Together with three friends, he began collecting bottles from dumpsites and around the neighbourhood. They sorted them, cleaned them and initially sold the glass to recycling companies.

But the returns were small, and the amount of work involved in collecting tonnes of glass made the business difficult to sustain.

Muturi decided they needed to do more than simply collect and sell waste.

Charles Muturi, founder of 23 Glass Studio, at work at Zimmerman in Nairobi. Bottles ready for recycling at the workshop. [Maryann Muganda, Standard]

With a background in art and design, he began experimenting with ways to turn the bottles into useful, decorative products. The studio started cutting bottles into drinking glasses, with the first order coming from a nearby pub.

The owner asked the young team to make 24 glasses from recycled bottles.

They sold each for Sh100, earning Sh2,400 from their first order.

“It felt nice just getting the first money,” Muturi recalls.

That was only the beginning. As production grew, Muturi noticed another problem. Cutting a bottle into a drinking glass left behind the top section, creating another pile of waste.

Muturi realised that recycling one form of waste while creating another defeated the purpose. “I need to have zero waste from my recycling,” he says.

That became the next challenge for the young entrepreneur: finding a use for every part of the bottle.

The leftover glass, particularly the bottle tops, was sold to Ardagh Glass Packaging Kenya (formerly Consol Glass), a glass manufacturing  company, where it could be used to make new bottles.

“But not every bottle could be turned into a drinking glass,” he says.

Muturi says there are differences in the quality of glass bottles, with some unsuitable for cutting into drinking glasses. Such bottles are mixed with other discarded glass and sent for recycling.

“Maybe like you see these small normal quarters bottles. These cannot make nice glasses for drinking water, so we mix them with this other waste bottle,” he explains.

The young business received another boost later in 2021 when a client placed an order for 600 drinking glasses and supplied the bottles.

The order was far bigger than the first 24 glasses, and it convinced Muturi that there was a viable business in turning discarded bottles into products.

“It was a very busy time,” he says.

By then, however, the realities of running a business were beginning to emerge.

Starting the business required about Sh100,000, according to Muturi, although much of the money went into preparing the workshop rather than buying raw materials.

“The workshop itself, where it is, we had to build it. So, the finishing and stuff,” he says.

They fenced the premises and invested in setting up the workshop before buying machinery.

At the beginning, the machines they used were later sold, forcing Muturi to rethink how he could continue production and improve the equipment needed for glass recycling.

Rather than buy new equipment, Muturi and his team decided to build their own machines.

The first machines they used had been donated by another small-scale glass-recycling studio in Naivasha. But the equipment had limitations, particularly the noise it produced.

“We didn't buy any machines. We made our own machines, which we are using to this day,” Muturi says.

Commercial glass-recycling machines are available, he says, but can cost between Sh100,000 and Sh150,000, an amount that can be difficult for a young entrepreneur starting with limited capital.

Muturi eventually sold the first machines to someone who wanted to start a glass-recycling workshop in Kitusuru. The machines fetched Sh50,000 and helped another budding recycler get started.

For Muturi, however, selling the machines was also an opportunity to rethink how they could be improved.

The original machines were noisy, a problem in a residential neighbourhood such as Zimmerman. The team began experimenting with motors and built quieter machines suited to their surroundings.

The innovation did not stop there. Glass sent to a manufacturing company for recycling cannot simply be delivered as whole bottles. It first has to be crushed.

“After making the machines, you have to break the glass at least once before taking it to the glass manufacturing company,” Muturi explains.

The process involves crushing the bottles into glass fragments, commonly referred to by recyclers as cullet.

Muturi describes it as larger pieces of crushed glass that can be used in the manufacture of new bottles.

“Its value varies depending on the volume and consistency of supply,” Muturi says.

Recyclers can initially receive about Sh5 per kilo, with the price rising to as much as Sh10 for those who consistently supply larger quantities.

At Ardagh Glass Packaging Africa's Nairobi facility, about 15,000 tonnes of waste glass is received annually, according to the Centre for Science and Environment. The facility uses sorted clear, amber and green glass alongside other raw materials to manufacture new glass packaging.

When they started, Muturi and his four friends crushed the bottles by hand.

They would measure the glass into 50kg bags, working until they had about 20 bags, equivalent to one tonne. A vehicle would then collect the cullet and deliver it to the manufacturing company.

The more regularly they supplied, Muturi says, the better the price.

But the manual process was slow and physically demanding. It also presented another opportunity for innovation.

“I figured, 'why are we crushing them manually? We could as well build a machine to crush them'” Muturi recalls thinking.

The team went ahead and built their own glass-bottle-crushing machine.

Similar machines are commercially available and widely used by businesses such as restaurants and golf courses seeking to recycle their glass waste. But Muturi says the machines can be expensive, with some costing about Sh500,000.

For a small recycling enterprise operating on limited capital, such a price is difficult to absorb.

Instead of simply crushing bottles into cullet, Muturi wanted to crush them further into sand for use in construction and other industries.

“The glass bottles, which had once been a problem in Zimmerman, could now return to the community in an entirely different form,” he says.

The crushed glass yields different particle sizes, which Muturi separates using sieves. At 23 Glass Studio, the material is currently graded into three main categories.

“The finest grade resembles flour and is processed into glass powder. The second is closer to ordinary sand, while the third consists of larger pieces resembling small pebbles. Each grade has a different use.”

The larger pieces can be mixed with cement for flooring, including terrazzo. Muturi says the glass gives the finished floor a distinctive shine when light hits it.

“The same material can also be used in landscaping as glass mulch, where its different colours can be used to decorate gardens and other spaces.”

Green, blue, brown and clear glass can be separated to create different finishes.

The second grade has opened another market for the studio: sandblasting.

“Sandblasting uses abrasive material propelled at high pressure to remove rust and paint from metal surfaces.”

Muturi says the glass-based material can be used in automotive applications and other industries, including aerospace, where it can help restore worn parts.

Then there is the finest glass powder. Muturi says it can be used as a partial replacement for cement in construction, with the powder replacing up to 30 per cent of cement in some applications.

The three grades can also be combined to produce another product: glass-based water filter media.

“The material is sold to pool shops and used in swimming pool filtration systems.”

Muturi says glass filter media has an advantage over traditional sand because it does not hold water in the same way, allowing water to pass through while filtering it.

For Muturi, this is where the economics of recycling begin to change.

The National Environment Management Authority estimates that recycling one tonne of waste glass saves about 315kg of carbon dioxide emissions associated with manufacturing new glass. NEMA also identifies recycled glass as a material that can be used in concrete, landscaping, water filtration, fibreglass insulation, ceramic products and abrasives.

Recycling also reduces the need for virgin raw materials.

The European glass industry estimates that every tonne of recycled glass can replace about 1.2 tonnes of virgin raw materials, while increasing the amount of recycled glass in the furnace reduces the energy required to melt the material.

A kilo of discarded glass may fetch only a few shillings when sold as raw waste. Process it into a specialised product, however, and its value rises sharply.

Muturi says the studio has sold some glass sand for as much as Sh1,000 per kilo, particularly when it is sold as sandblasting media in small quantities.