Sunday, November 15, 2009

Urban Gardening in Harare, Zimbabwe

This blog will analyze the relationship between agriculture, food supply, and wet waste disposal/reuse in subsistence urbanities.

Sub Saharan Africa has a population of approxinately 166 million people living in squalor and slums. These slums, despite any means of infrastructure that is commonly expected to exist in large cities, continue to grow and survive on very different means of organization from developed cities.
Harare, the capital of Zimbabwe, is one such example. In recent years it has suffered food shortages and severe hyperinflation. As a means to feed families and generate profit , the residents of Harare have turned to urban gardening. They grow produce just about anywhere they can such as backyards, vacant lots, even along the sides of the roads and on the rooftops. In 1991 approximately 8% of the land in Harare was covered in urban gardens, by 2001 this had grown to 25 %, and this percentage has steadily increased to the present day.1

This urban agriculture poses numerous benefits and surplus income to the inhabitants of the slums. It contributes to the households food needs, while any excess produce can be sold for much needed capital. In one such case, a man named Misheck Dando, who lost his job 5 years ago, turned to urban gardening as a means to feed his family. He started off growing tomatoes and onions in a small garden in his backyard. He sold the surplus to pay his childrens school fees, and despite lack of farming experience has prospered. His property now contains grains,vegetables, chickens, and rabbits and continues to provide both food and income for his family. 1

Another specific case is that of Grace Mambo, who as a result of being diagnosed with diabetes wished to eat healthier. However, healthy diets are out of normal budgetary constraints for most inhabitants of Harare. As a result, she began growing lettuce, beetroot and leaks in a neaby vacant lot.1 Recently she quit her job to sell excess produce to restaurants and grocery stores. She has gardens strewn throughout her neighbourhood, and access to a healthy diet.

However, the urban agriculture of Harae is threatened by water shortages and access to clean water. Nearly 2/3 of the city's population relies on urban agriculture.2 The primary source of water for Harare is Lake Chivero, which due to large deposits of residential and comercial waste has been declining in both water quality and quantity. This problem has led to increased costs of clean water, as well as water rationing; wherein some areas of the city do not have access to water for periods of 2 or more days per week.3 The extra cost coupled with the lack of this precious resource can put a serious hamper on urban agriculture.

In the city of Haroonabad, Pakistan, Urban waste water is a valuable resource for agriculture, and is used for approximately 80% of crop growing. This is due to the absence and high cost of clean water, as well as waste waters proximity reliabilty, and high nutrient value. The gross income of a wastewater farmer is significantly higher than that of a clean water farmer. The crops gorwn are mainly crops that are cooked before eating, such as cauliflower, cotton, spinach, wheat, and tomatoes, minimizing any health effects for consumers.4 Waste water agriculture is a more economical alternative to in developing countries, and is also ecologically responsible as well, since it cuts the quantity of municipal and industrial waste in lakes and streams.4

If the residents of Harare were to implement the use of greywater, or possibly (although more health risks are involved for the farmers) waste water, they could cut down on the need for wet waste disposal, and would see an incrrease in their agricultural production, income, and food surplus, due to reduced water costs and better access.

- Andrew Winters


1. Michelle Ajida, "Cultivating Food Security in the City," November 3, 2009, (accessed November 3, 2009).

2. Emaculate Madungwe, "Grey Water Use: A Strategy for Water Demand in Harare?", August 3, 2007, (accessed November 3, 2009).

3. "Reuse of Waste Water for Agriculture," (accessed November 3, 2009)

4. William Van der Hoake, "Waste Water Use In Pakistan: the Cases of Haroonabad and Faisalabad," (accessed November 3, 2009)

Wednesday, November 4, 2009

Types of Urban Composting

Composting is a method of turning wet, organic waste into nutrient-filled humus. It is used regularly on an industrial scale but the method is simple enough that anyone can do it in their own home or yard. These days, it is a fairly popular method of reducing household waste, helping the environment, and producing fertile soil.1

What some people don't realize though is that you don't need a lot of space or resources to compost. Even people living in very dense urban areas can benefit greatly from the goodness of compost; it does not require a very large investment.

The most basic necessity to compost is a bin with a lid, preferably plastic or stainless steel. If you can keep it on a balcony, outdoors, you should punch holes into the bottom and sides, and the container should be raised a few inches from the ground. If you lack a balcony, compost bins can also be kept indoors: under the sink, in a closet, near a window… almost anywhere. You still need the holes though, so if it the bin is indoors you will want a tray with to catch moisture or small particles.

To start composting, add a few inches of soil or shredded dry leaves to the bottom of your bin, and you can immediately start adding your organic waste (omitting things like meat and dairy products, which will generally become rancid before decomposing, and attract vermin). As you add wet waste, add an equal amount of dry bedding (straw, dead leaves, strips of newsprint, shredded cardboard, etc).

Bacteria will decompose your waste, turning it into soil. Agitate the contents of the bin every once in a while to aerate it. Once your bin has become close to full, remove the humus that has formed and continue.2

Vermicomposting is a method of compost that uses worms, in addition to the usual microbes and bacteria, to transform waste into humus.

The bin is the same as with regular composting, but the initial bedding should be thicker and damp (about as damp as a wrung sponge), so the worms don't dry out before you add your waste. Human effort required for vermicomposting is reduced because the worms can decompose the materials without the bin being turned. The most common type of worm to use are red wigglers (Eisenia foetida) because they are specially adapted to living in compost and manure.

The worms digest the organic material provided and produce "castings" (faeces), which contain nutrients and microbes that break down existing nutrients into plant-available forms.3 The mucous excreted from the bodies of the worms also help prevent nutrients from washing away when the compost is watered.4 Vermicompost is very rich-- richer than normal compost-- and should be mixed with less nutritive soil, so as not to overwhelm plants.5

Worms are most productive at or slightly below room temperature, and can survive at as low as 10 degrees and up to 30 degrees Celsius. They are quiet and do not "roam"; they are very easily kept indoors.6

Human faecal matter and urine contain many of the ingredients found in store-bought fertilizers. They also contain pathogens. Raw, untreated human waste ("nightsoil") can be, and is in some places, scattered on crops to help them grow. Unfortunately, this method can spread disease quite easily.

When composted, human waste has come to be known as "humanure". There are many acceptable methods to compost human waste relatively safely, such as composting toilets. These specialized toilets turn the waste that would normally flushed into humus with minimal effort on your part. Blackwater recycling systems take the waste from all drains in a house and convert it to the same.

A less expensive method to produce humanure is to make your own, relatively inexpensive, "sawdust toilet". Joseph Jenkins, who largely popularized the term humanure, explains how in his handbook.

Authorities in urban areas with sewage systems in place and running smoothly are generally hesitant to permit the production of humanure because of perceived potential health and sanitation issues.7 Theoretically, if humanure is produced correctly, with enough heat, pathogens shouldn't survive and the humus produced should be entirely safe, but there will likely be taboo surrounding the issue in the first world for some time.

Any of these composting methods will produce some incredibly nutritious soil. If the composting is done right, the methods will be neither unsanitary nor malodorous. A good way to put the humus to use if you do not have a garden is to grow plants indoors (see: container gardening). There are a number of useful, hardy, and low-maintenance plants that one can grow indoors. For example: various herbs, pole beans, carrots, lettuce, and aloe vera. Growing plants with your humus is economical and useful.

- Allison Suffel


1. Marion King, "Composting for Apartment Dwellers," The Peace and Environment Resource Centre, December 7, 2003, (accessed November 1, 2009).

2. Keith Addison, "Composting Indoors," Journey to Forever, June 13, 2009, (accessed November 2, 2009).

3. Collin Dunn, "Vermicomposting and Vermiculture: Worms, Bins and How To Get Started," Treehugger: A Discovery Company, February 8, 2007, (accessed November 1, 2009).

4. Avanish K. Panikkar, "Vermicompost," The Encyclopedia of Earth, August 25, 2008, (accessed November 1, 2009).

5. Dunn, "Vermicomposting".

6. Wikipedia contributors, "Vermicompost," Wikipedia, The Free Encyclopedia, October 27, 2009, (accessed November 1, 2009).

7. Envirolet, "FAQ", Composting Toilet World, November 2, 2009, (accessed November 2, 2009).

Biodigesters: Making Use Out Of Waste

A biodigester is a device that is able to convert manure and water into methane gas efficiently, cleanly, and cheaply. In order to effectively use a biodigester, manure and water is collected and mixed together. Allowing this solution to ferment, methane gas is produced, and it is then extracted from the biodigester and used for cooking. As fresh manure and water is added to the biodigester the used, fermented mixture is naturally released into an overflow tank and can then be used for fertilizer. This post will explore smaller biodigesters in developing nations which are used for individual homes and farms.

There are many different variations of biodigesters, depending on location, size, affordability, and demand of methane. However, all biodigesters have three main elements. The first piece is an inlet valve. This is where the manure is mixed with water, and fed into the main chamber. The manure to water ratio is about 1 Kg of manure to 15 L of water. Rainwater may be used in a biodigester as its main purpose is to simply liquify and quicken the fermentation process. After the mixture of manure and water, now known as slurry, has been created it then travels into the main chamber. The main chamber is usually around 1 cubic meter in size and it is where the fermentation process occurs. As slurry builds up in the main chamber, methane begins to separate out of the slurry. The methane collects at the top of the chamber, and is forced through a thin gas line which can power the stove of a household. As more slurry is added into the main chamber the methane depleted slurry is then pushed into an overflow tank where it may drain or be collected.

The cost of a household biodigester can vary depending on material. In more developed countries materials such as concrete, cement, and plastic layering can increase the efficiency, but it also increases the price. The most affordable unit is made from plastic, and costs roughly $40.00 american, as well as two days of labour to install. However, this investment can pay for its self in as little as four months. The general rule for the amount of manure needed states that four to five pigs can create enough manure to supply a biodigester for a family of four to five people.

This product allows wet waste (rain water) to be mixed with the waste of cattle and livestock to create a cheap way to cook food. The fermented slurry feeds nck to the system as it is a perfect fertilizer for crops. There is also no energy expended on transportation as all of the processes take place on individual farms. Biodigesters use less resources, not to mention significantly less man power, to create fuel for cooking and greatly decreases the amount of methane pollution.

Problems arise with biodigesters as they may be considered too expensive for some families. If the biodigester is not used regularly, solids can form inside the main chamber, which can result in significant decreases in efficiency. Improper installation can result in problems with the flow of the slurry and the amount of leakage in the system.

Overall the biodigester presents an interesting opportunity for both developing and developed nations to utilize waste to create a cheap green source of fuel.

This is a video demonstrating the use of a biodigester in a more developed country:

Biogas Digester for the Home

- Aidan Mitchelmore


Bui Xuan An, L. Rodriguez J. et. al., “Installation and Performance of Low-Cost Polyethylene Tube Biodigesters on Small-Scale Farms,” January 1997, (accessed November 4, 2009).

Big Gav, “Banana Methane Powerered Cars Pig Poo Power And Other Uses For Biogas,” September 1, 2009. (accessed November 4 2009).

Smart Innovations Canada, “Biogas Digestion,” Smart Innovations, (accessed November 3, 2009).

Renewable Energy and Environmental Information Network, “Biogas Uses For Cooking Purposes At Noakhali,” Biomass Program in Bangladesh, September 3, 2009, November 4, 2009).

Container Gardening: A Solution for Hunger in Mexico?

a Mexican slum

Mexico City is known as a victim of poverty, with nearly 15 million residents struggling to endure extreme living conditions. This accounts for nearly 20% of the total population. The amount of food is scarce which compelled a group known as ANADEGES, a collection of several non-profit organizations, to develop a plan to grow foods with the limited amount of space and materials available in Mexican slums. The proposal suggests using backyards, balconies, and rooftops as surfaces to cultivate small quantities of fruits and vegetable in order to compensate for the lack of food. This is known as "container gardening," which is commonly used in urban developments for herbs such as basil and parsley. Despite the confined space that the crops are grown in, they are capable of adapting to these restricting conditions. Moreover, the method is relatively inexpensive to operate and efficient in terms of production. Empty bags, bottle, and bins are all suitable containers that can be obtained cheaply or even for free and the seeds require minimal investment. In addition, vegetables that need little space such as carrots, radishes, or tomatoes make it easier to grow a greater span of products.

An example of a container grown herb

With the large quantity of waste water being produced in Mexico, it becomes increasingly harder to find ethical ways of disposing it. Only about 10% of water is treated for drinking purposes but the technique is costly. As a result, organizations invented multiple ways to make use of the wet waste, one being fertilization. This includes urine and rainwater which proves to be environmentally friendly solutions for growing foods.

Urine contains many traits that are ideal for fertilization. It is a good source of nutrients such as nitrogen, phosphorus, and potassium which are reoccurring ingredients in commercial fertilizers. When diluted with water, it can be directly applied to soil. Tests conducted show that plants grow faster, healthier, and larger, requiring less water to thrive. Instead of wasting water consumed by flushing toilets, the urine can be directly used without producing any harmful byproducts or pose any major risks to human health. Most importantly, it's extremely economical due to the fact that there is no cost and also reduces the amount of waste that pollutes our environment.

Rainwater harvesting is practice of gathering and preserving runoff agricultural purposes. This is a highly inexpensive process and can be executed with the same materials required for container gardening. Bins can be situated in large open areas to collect rainwater falling directly from the sky, or in places where they can catch the runoff from roofs and gutters. In the slums of Mexico, where rain isn't always frequent, it is best to capitalize on its useful applications.

Basic rainwater collection system

Mexico is a prime example of how wet waste is reused in fertilizing the crops that we eat, creating a cycle that maximizes the use of every available resource.

When relating to countries where poverty is prevalent, it is easier to understand how even minimal efforts can support agricultural practices.

- Lauren Tom


1. Michael Crown, "Desertification," February 16, 2008, (accessed October 30, 2009).

3. Van Cotthem, "Container Gardening," November 1, 2009, (accessed October 30, 2009).

4. "Wastewater Disposal and Reuse," December 13, 2004, (accessed October 30, 2009).

5. Julie Williams, "Ezine Articles," 2009, (accessed October 30, 2009).

Biosolids. Food Produced from Waste?

iosolids, also known as treated sludge, are the by-products of domestic and commercial sewage and wastewater treatment. Rich in minerals like organic nitrogen, and phosphorous and micronutrients such as zinc, magnesium and copper, biosolids are widely used in agriculture to benefit crops production and increase crop yield. When applied carefully, biosolids are able to improve soil fertility and add organic matter that enhance soil structure, moisture retention and permeability.

Biosolids have been use in various countries in North America and Europe for years and their application has been one of the most effective ways in recycling nutrients in the natural system. Although generated from sewage sludge, biosolids are treated to eliminate most complex organic molecules and pathogens.

In many developing countries, population growth is a major issue and the demand on food continues to grow over the years. However, water treatment plants are often considered a luxury in these countries and wet wastes are often just dumped into the river or land fills, putting toxics into the environment. Therefore, many developing countries especially those in south and south-eastern Asia are practicing wet waste agriculture, hoping to reuse and recycle wet waste for food production.

One example would be the East Kolkata Wetlands in West Bangel in India. It is a combination of natural and man-made wetlands and one special feature of this wetland is that it processes the city’s garbage and sewage. Since the mid-1800s people there have been dumping sewage and waste into the wetlands and slowly they realize the soil around the area becomes more fertile and the water more nutritious for pisciculture. Yet, hygienic problems started to rise as the system continues. Although they helped in production of food, these untreated sewage brings viruses and bacteria into the food, easily causing diseases.

Of course, without the proper water treatment facilities, it is also difficult for developing countries to produce safe biosolids similar to those used in developed countries. In developing countries, few cheaper methods are therefore used to produce biosolids such as lime stabilization and composting. In lime stabilization, sufficient lime is added to dewatered sludge to raise the pH, and depending on the time it maintains its pH value, different quality biosolids are produced. For composting, de-watered organic matter is biodegraded to carbon dioxide and water, producing compost, a material close to humus that can be used for agricultural fertilization.

Hydrated lime for lime stabilization


Lime Stabilization and composting may seem to be the easy and cheap method for producing biosolids for developing countries, but more improvement and studies must still be made on the matter, such as the acid treatment and anaerobic digestion. For making sustainable agriculture from wet waste in developing countries possible, much cooperation is needed from the developed countries, including funds and skills.

- Rachel Fung


1. Christine Furedy, Virginia Maclaren et Joseph Whitney, "Reuse of Waste for Food Production in Asian Cities: Health and Economic Perspectives," The International Research Centre, November 2004, (accessed November 1, 2009).

2. Amanda Suutari, "India – East Calcutta - Making the Most of It: Wastewater, Fishponds, and Agriculture," The Eco Tipping Points Project (accessed November 1, 2009).

3. The Government of Ontario,"Sewage Biosolids - Managing Urban Nutrients Responsibly for Crop Production," Ministry of Agriculture Food and Rural Affairs, October 6, 2009, (accessed November 1, 2009).

Monday, November 2, 2009

From Urban Agriculture to Art, Let's Beautify Our Cities

Lipsett, Owen. ""Puppy" by Jeff Koons." IgoUgo. Available from photos-p152389- Puppy_by_Jeff_Koons.html. Internet; accessed 2 November 2009.

The vertical gardens in Andjela's post reminded me of artist Jeff Koons' "Puppy" which is a massive sculptural topiary. Urban agriculture is not only showing up in architecture, it is also being used as an artistic expression. It has potential to extend its application beyond the immediate operations of daily life to becoming an outlet for creativity.

- Natalie Hui

Sunday, November 1, 2009

Urban Agriculture Innovation- CUBA

When you think about the minimum amount of calories an individual requires to stay healthy, and then about the amount of people on earth, it remains surprising that the whole infrastructure holding our food production and consumption together hasn’t fallen apart yet.

This type of situation is looming dangerously close however, and if we are to survive it, we must have a solution ready. I think urban agriculture is a viable one. It is the cultivation, processing, and distribution of food in or around the city (peri-urban).1

Although an old concept, its' most recent applications lend credence to its capability of providing more sustainable urban communities. In the near future sustainability is key, especially because unprecedented growth in urban populations world-wide will occur, and food shortages and other resource issues are expected.2 It is therefore of utmost importance that technologies such as urban agriculture be implemented into as many societies as soon as possible.

Luckily, some countries have already tackled the issue- although mostly out of necessity than want.

Cuba is a successful example of farming integrated into the heart of the city. In 1991 the fall of the Soviet Union caused drastic cut backs in fertilizer, fuel and food supplies shipped to Cuba. This led to a severe economic crisis, where food shortages were rampant.

A series of government initiatives led to a solution. Cuba managed to decentralize agricultural production from large state farms to municipal and individual levels. Planning laws prioritized land for food production, and urban gardens soon stood amidst city buildings. Called "agroponicos" or "organoponicos" they allow citizens to grow their own food, and raise livestock.

Hydroponics is one of a variety of techniques used to produce the food. Farms using this agricultural method are located in vacant lots in urban and peri-urban areas. Hydroponic gardening doesn't rely on soil, so it's particularly advantageous in urban settings where land may be scarce. Instead, plants grow in water and are watered by hand or through gravity-fed drip irrigation systems. The garden beds are made from any material blocking light penetration (to avoid algal growth) and are often lined with waterproof black plastic.3

Hydroponic agriculture recycles nutrients, therefore it uses less water than plants grown on soil, and fertilizers can be used from readily available materials such as composted chicken manure.

As well as the material sustainability of urban agriculture, its’ advantages include: the city location of the farms (therefore no transport of produce to consumers is needed), and efficient use of city space.4

By 1998, urban gardens produced more than 540, 000 tons of food for consumption in Havana alone. The year after, 4, 347 larger gardens existed. These were on the outskirts of cities and towns, and produced vegetables and herbs for the populace.5

Nowadays similar technology and concepts of urban agriculture are being applied in various developing countries to help solve food issues. The International Development Research Centre (IDRC) is an example of a corporation involved in these efforts.

Their projects of research include:
  • reuse of urban waste by urban agriculture
  • urban food insecurity
  • urban production and processing of food 6
- Andjela Tatarovic


1. Wikipedia contributors, “Urban Agriculture,” Wikipedia, The Free Encyclopedia, November 6, 2009, (accessed November 1, 2009).

2. Christine McGourty, “Global crisis ‘to strike by 2030’,” BBC News, March 19, 2009, (accessed November 4, 2009).

3. Treena Hein, “Hydroponics-a simple solution to limited land,” New Agriculturist, March, 2007, (accessed November 3, 2009).

4. Peggy Bradley, Wilfried O. Baudoin, C.V.Prakash, and B.S.Prabhakar, "Simplified Hydroponics to reduce hunger and poverty in India," Institute of Simplified Hydroponics, (accessed November 3, 2009).

5. Serge F. Kovaleski, "Cuba Goes Green: Government-Run Vegetable Gardens Sprout in Cities Across Island," Cuban Urban Agriculture, November 26, 1999, (accessed November 4, 2009).

6. "International Development Research Centre IDRC (Canada)," Cities Feeding People, October 1996, (accessed November 3, 2009).