Editor’s note: For the past two weeks, experts have focused on urban food systems and the importance of urban production, city-regional planning, and the connections beyond city limits. Today, Mary Njenga and Nancy Karanja bring this discussion to the specific case of Nairobi, Kenya, where urban agricultural production is contributing to food security and livelihoods in the poorest areas of the city. But even beyond the actual growing of food, there is concerted effort to take a systems approach, tapping into waste management and energy production. We may look and see efficiency by reaching across sectors, but for many this is simply essential to survival.

Since world food prices shot up during 2008, food insecurity in Africa has been a fact of life for low-income urban and rural dwellers alike. Set back in the 1980s during the structural adjustments programme of the World Bank, this problem is not due to lack of food but rather that the high prices caused by the inequitable distribution of wealth across many African cities make it unattainable. Although rural agriculture has a major role to play in meeting urban food needs, urban agriculture has great potential to help fill the gap during the food shortages that are a common occurrence for African people. Urban agriculture’s advantages over rural farming include proximity to the major demand centers, resulting in low transportation cost and low postharvest losses. Moreover, it provides benefits to the economy in terms of employment and income, particularly for women and other disadvantaged groups among the poor. Studies in nine African cities reveal that on average 35% of households engage in agriculture, but this rises to over 70% depending on their location along the peri-urban to urban transect.

In Nairobi, Kenya, urban agriculture is practiced in backyard farms, open spaces under power lines, along roadsides, railway lines and river banks, as well as on institutional land. In Nairobi’s informal settlements, where space is limited, communities practice low or zero space agriculture by growing vegetables in a recycled sack. The most interesting part of urban farming is its linkage with waste reuse, either as source of plant nutrients or, in the case of inorganics (such as sacks, plastic bags, etc.), as growing containers for establishment of bag gardens. Exploitation of urban wastewater is also a very exciting innovation for adaptation to climate change in agriculture as explained here below.

Waste recycling for urban agriculture and environmental management

Farmers in cities use wastewater to irrigate crops and harvest plant nutrients to substitute for chemical fertilizer. It is estimated that more than 2,200 hectares (5,436 acres) within a 20 km radius of Nairobi are irrigated with water from streams (upstream) and indirect or direct reuse of untreated urban wastewater. The farmers have small sizes of land of about 0.5 acres and mainly grow exotic vegetables, such as kale (Brassica oleracea), spinach (Spinacia oleracea), and traditional vegetables such as amaranth (Amaranthus spp.) and African nightshade (Solanum villosum). Some of the produce is sold to neighbours and the income is used for health care, animal protein food types such as milk, school fees and rent. These farmers have also sustained their links with the rural friends and relatives, through exchange of produce, seeds, and seedlings. This exchange is especially clear after dry seasons, since city-dwellers are able to multiply germplasm using wastewater that is accessible all the year round.

Solid waste management is also an enormous challenge in sub-Saharan Africa, and garbage heaps, pollution, and health problems are widespread. Nairobi generates approximately 2,500 metric tonnes of solid waste daily, of which 70 percent is organic and has the potential for reuse as livestock feed or organic fertilizer. Njenga et al. found that only 2,500 tonnes (equivalent to 0.6 percent) of the total organic waste produced in the city annually was used for compost-making by 11 community based organizations in Nairobi. These groups then sold the compost to urban plant nurseries, urban and rural farmers, and landscapers. In sub-Saharan Africa, millions of tonnes of waste are produced annually, for example 646,780 tonnes in Dar es Salaam, 313,900 tonnes (domestic) in Kumasi, and 765,040 tonnes in Accra. Processing of this waste into fertilizer would go a long way in improving the regional impoverished soils, which are one of the underlying causes of food insecurity.

Finally, there is the issue of cooking and fuel. Poor urban households are opting to use unhealthy sources of fuel, such as tires, old shoes, and plastics, while simultaneously many families are shifting from traditional meals of beans that require long cooking times, compromising dietary diversity and nutrition as a result. Poor urban households are starting to turn to briquette, which is made by compressing charcoal dust bound with either bioderadable waste paper, soil, or cow dung, or sawdust bound with gum arabica resin, into a solid unit. Briquettes have good heating value, produce low emissions, provides income, and create employment opportunities, all while cleaning urban neighbourhoods. In Kibera slums households that produced charcoal briquettes for personal use and those that bought them saved 70% and 30% (respectively) of money normally spent on cooking energy. Cooking a traditional meal with charcoal briquettes costs 3 ksh (US$0.04), with charcoal costs 26 ksh (US$0.35), and with kerosene costs 45 ksh (US$0.6).

Urban agriculture contributes to the well-being of urban dwellers through supplying food, generating income and creating employment opportunities. It also has supporting and regulating roles to the ecosystem through supplying nutrients, absorbing organic waste, and cleaning the neighbourhoods. Urban food security among the very poor would not be achieved without people having access to clean and affordable cooking energy and reutilizing the resources at hand. City dwellers continue to innovate to meet these needs, and recycling organic by-products for fuel briquettes is one that could go a long way toward improving people’s lives.

Please contact Mary Njenga or Nancy Karanja for more information on this work.

Mary Njenga is a researcher in urban agriculture at the University of Nairobi and also works on biomass cooking energy at the World Agroforestry Centre in Nairobi. Nancy Karanja is a professor in soil ecology at the Department of Land Resource Management and Agricultural Technology (LARMAT) at the University of Nairobi.