Dorothy Kimakia a retired stock broker admires lush vegetation on a plot of land the size of a basketball pitch adjacent to her dwelling in Rongai. Talking over car horns and city bus engines, she shows off bumper lettuce, aloe vera, and spider plant produce that has transformed the once rocky land to an oasis.

Dorothy is among hundreds of city dwellers who have set up urban gardens to shield themselves from runaway food prices. But these urban gardens are now assuming a new role of cleaning the city’s polluted environment at a time when studies show that contamination scale of air inhaled by Nairobi city residents is five times higher than the recommended international levels.

Nairobi’s air quality has had an impacting health. Particle counts that run at 10.7 in Kenyan rural areas were recorded at 128.7 in central Nairobi in 2009. According to experts the alarming toxic levels are attributable to extreme concentration of diesel-consuming vehicles and high-rise buildings that hold the polluted air while blocking out cleaner air. The situation is too dire that a World Health Organization study of 2012 indicated an ordinary person in Nairobi lives ten years lesser than their rural counterparts due to the air conditions. These toxins have been associated with a growing list of health conditions including cancer and asthma.

But a group of vanguard city dwellers are now reversing the sorry state of affairs with their miniature gardens. From planting trees and plants that gobble up toxins, to recycling waste ventures, the modern urban farmer is emerging heroic in rescuing Nairobi from the twin woes of toxic ridden city and the most expensive city to live in which studies have shown that upto a fifth of Nairobi residents are “ultra-hungry”.

The spider plant and aloe vera that Dorothy grows to sell have been identified by scientists as among plants that takes in the harmful gases like carbon monoxide while giving off health-giving oxygen and water vapour as part of the photosynthesis process.

But it's not only carbon dioxide they take in. These plants have a proven record of absorbing impressive amounts of other toxins and pollutants like formaldehyde which comes from carpets, plywood, furniture and insulation materials and benzene from paints.

The other biggest eyesore for Nairobi is the unused tyres that litter the city. The toxins released by the burning tyres have carcinogens, cancer causing elements, and anyone who inhales the smoke is 60 percent more likely to be exposed to cancer according to Environmental Protection Agency of US. The tyres are particularly harmful to kids and can cause deformity and asthma due to the tremendous number of small particles that settle deep in the lungs.

Bereta Wahinya is taking the health menace out of the streets. In a model that has turned her into an award winning urban farmer, Bereta buys old tyres from mechanics which she turns into gardens.  It is estimated that over 7,000 tyres are discarded a day in Kenya after being worn out beyond repair. Bereta who resides in Kawangware buys the tyres at Sh20 each.

“I have a small compound outside my house, the only thing I associated the compound with was misery from my boys who would play football and smash my windows. I had to look for a way to keep them doing homework after school while saving my windows. In one year I had almost  replaced the windows about six times. I couldnt take it more,” she said.

But what started as a simple idea to keep her from breaking the windows has now transformed into a thriving business having started with two tyres and now owning over 100 tyres which occupy a space of two conventional tables. “I struggled at first with how I could arrange the tyres together, but with time I learnt how to position them to form a ring and therefore create more space. Of course there are some tyres I have placed in the roof of my house,”she added.

In creating the tyre garden she first lays the tyres at the spot where she wants it to be and then proceed to cut the sidewall of the upperside completely. This she says help in doubling the planting area available.
She then prepares the compost from well decomposed materials, and spread a plastic bag at the base of the tyre ensuring the bag is strong enough because it forms the foundation of the tyre-vegetable-garden. She grows Kales, tomatoes, and cucumbers from the garden.

It is a discovery she has shared with fellow women in their self help group, chamaa, which has transformed into feeding homes and even selling the extra. “When we heard of her venture we took time to study it, and besides the income that it provides for her, it has managed to get rid of discarded tyres that are usually burnt and which we know as the leading cause of respiratory diseases in Nairobi. That is why we are collaborating with other institutions to support her cause,” said Dr. Ken Muheria an environmental scientist working with Clean Cities a not for profit organization supporting clean Sub Saharan cities.

Behind rows of succulent tomatoes and towering onions planted in plastics a few kilometres from where Beretta lives, is another story of one woman’s resolve to rid Mathare slums off the plastic eyesore that has not only solved the environmental menace in the area but saving her from from erratic commodity prices.  On average it is estimated that 25percent of the 1500 tonnes of solid waste collected in Nairobi alone is plastic.

The idea was conceptualized by Elizabeth Nyaberi, a self-confessed queen of urban farming in 2007. Due to poor garbage disposal in the informal settlement, locals have now turned her small garden into a dumping site, more so: plastic materials hence hindering crop production. To mitigate this, the self proclaimed queen of urban farming has resorted to 'plastic farming' where she collect and plant onions, coriander and even flowers an aspect that she says offers a double solution to food security and environmental degradation.

''I got tired of complaining about waste disposal in my garden. These people surely lack garbage site so I had to think and do it fast,'' explained the mother of two who has over 100 plastic gardens that she has hanged around her room and those of her neighbours. Elizabeth has made it a habit to pick plastic containers thrown anyhow by residents especially those with wider volumes like old basins and buckets which she fills with soil and plant crops of her choice especially vegetables. But this labour of love has birthed a commercial venture which is now seeing her sell the extra and supplementing her family’s income.

This form of farming has been adopted by many residents within informal settlements in Nairobi and Elizabeth is always available to help new farmers launch their own plastic gardens. Besides Nairobi, Nyaberi occasionally travel to his rural home in Kisii County to educate people on this new found farming. She has already trained 50 people who have set up more than 500 plastic gardens. '' I have given them a supplement to their small farms and can now get extra produce,'' she explained happily.

The transformative role that city farms are playing in cleaning the city’s environment while fighting hunger, couldn’t have happened at a better time. Numerous reports hail them as a potentially viable policy response to the complex challenge of striking the balance between maintaining a clean environment while feeding a burgeoning mass of urban residents amid decline in food production in rural areas. A joint report by the United Nations Habitat and The African Capacity Building Foundation for example says the biggest threat of the 21st century is the escalating level of environmental pollution in urban cities like Nairobi which has cut life expectancy for thousands.

But for Berreta, Dorcas and thousands of farmers providing their families with daily bread through the miniature gardens, their resolves are riding the city from toxins and saving lives a garden at a time.