Food- and feed-based nutrient flows in two West African cities


Recent studies have examined the urban metabolism of cities using urban consumption as a proxy for food inflows but very few studies have aimed at quantifying the role of cities as trade hubs and nutrient sinks of their hinterlands. We therefore examined the linkages between food and animal feed supply, their places of production and nutrient flows through the urban system in the two West African cities of Tamale (Ghana) and Ouagadougou (Burkina Faso). Using primary data on food and feed flows, and secondary data to assess the transformation of these flows into nutrient terms, we show that, besides urban consumption, the function of the two study sites as trade hubs significantly determines nutrient flows. In Tamale, > 50% of the nutrient inflows was neither consumed nor was lost in situ but left that city again for other destinations. At least 30% of the incoming cereals was stored in the city for later consumption or export. Ouagadougou relied more on imported goods with 40% of N imported from foreign countries compared to Tamale where only 10% of the N was imported, thus contributing to heavier nutrient extraction in remote production areas.

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Fig. 1
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Source: Karg et al. (2016)

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  1. 1.

    The peak season was considered to be the main harvest period, November/December, and the lean season was defined as the end of the dry season, April/May.

  2. 2.

    Figures on solid waste generation and collection vary, depending on the source. A more recent news report referred to an amount of 300 t of solid waste generated per day and a collection rate of 82% (Daily Graphic 2015).


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This work was carried out as part of the UrbanFoodPlus project, jointly funded by the German Federal Ministry of Education and Research (BMBF) and the German Federal Ministry for Economic Cooperation and Development (BMZ) under the initiative GlobE – Research for the Global Food Supply, Grant Numbers 031A242-A and 031A242-D, with support from the CGIAR research programme on Water, Land and Ecosystems.

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Corresponding author

Correspondence to Hanna Karg.


Appendix 1

Form used to record food flows on the access road to Tamale (Ghana).


Appendix 2

Nutrient contents of food and feed items recorded in the survey of Tamale (Ghana) and Ouagadougou (Burkina Faso).

Category Commodity Nutrient content (kg t−1) Source Remarks
Cereals Maize 13 2.41 3.05 Stadlmayr et al. (2012)  
Rice 11.50 1.15 0.98 Stadlmayr et al. (2012)  
Millet 18.70 3.11 3.80 Stadlmayr et al. (2012)  
Fruits Watermelon 0.80 0.09 1.09 Stadlmayr et al. (2012)  
Orange 1.20 0.19 1.66 Stadlmayr et al. (2012)  
Banana 2.20 0.25 3.76 Stadlmayr et al. (2012)  
Mango 0.90 0.18 1.80 Stadlmayr et al. (2012)  
Livestock and fish Cattle 29.40 1.82 3.05 Stadlmayr et al. (2012)  
Fish 36.60 2.42 3.79 Stadlmayr et al. (2012)  
Goats 28.00 1.50 3.85 Stadlmayr et al. (2012)  
Sheep 26.30 1.49 2.50 Stadlmayr et al. (2012)  
Chickens 32.60 1.94 2.76 Stadlmayr et al. (2012)  
Roots, tubers and legumes Yam 3.10 0.53 8.16 Stadlmayr et al. (2012)  
Groundnut 41.00 3.94 7.20 Stadlmayr et al. (2012)  
Bean 5.00 0.56 2.42 Stadlmayr et al. (2012)  
Cassava 1.80 0.47 2.71 Stadlmayr et al. (2012)  
Plantain 1.90 0.34 5.00 Stadlmayr et al. (2012)  
Sweet potato 2.40 0.43 4.16 Stadlmayr et al. (2012)  
Vegetables Tomato 1.60 0.32 2.55 Stadlmayr et al. (2012)  
Onion 1.80 0.39 1.83 Stadlmayr et al. (2012)  
Hot pepper 3.00 0.43 3.31 Stadlmayr et al. (2012)  
Avocado 2.70 0.46 4.92 Stadlmayr et al. (2012)  
Cabbage 2.50 0.37 3.17 Stadlmayr et al. (2012)  
Animal feeda Cassava peel 7.38 2.10 6.40 Feedipedia (2018)  
Cowpea forage 27.85 2.40 19.10 Feedipedia (2018) Aerial part, fresh
Fresh grass 5.18 0.77 6.29 Feedipedia (2018) Fresh weight taken into account (i.e. nutrient contents reduced by 40.6% [feedipedia]); assumed type of grass: Andropogon (Andropogon canaliculatus)
Groundnut forage 24.15 2.00 18.90 Feedipedia (2018) Fresh
Maize bran 18.31 3.40 7.30 Feedipedia (2018)  
Fodder (not specified) 15.83 1.62 11.58 Calculated for Tamale (considering proportional nutrient contents by weight)  
Pigeon pea forage 29.23 1.80 14.70 Feedipedia (2018) Aerial part, fresh
Rice straw 6.46 0.90 18.00 Feedipedia (2018)  
Soybean forage 24.15 2.70 20.23 Feedipedia (2018) Aerial part, fresh
Bean forage 11.36 1.10 23.50 Feedipedia (2018) Common bean straw
Millet stalks 8.40 1.50 23.80 Feedipedia (2018) Pearl millet (Pennisetum glaucum), straw
Sorghum forage 5.92 0.70 12.90 Feedipedia (2018) Sorghum hay
Maize stalks 5.92 0.70 13.60 Feedipedia (2018) Maize stover, dried
Fodder (not specified) 13.85 2.40 10.37 Calculated for Ouagadougou (considering proportional nutrient contents by weight)  
Faecal sludge Dewatered faecal sludge (20% of raw sludge) 10.5 10.2 3.9 Cofie et al. (2009)  
Municipal waste HH organic waste 14.3 4.6 13.0 Cofie et al. (2009) Market and HH waste were merged for the nutrient contents of municipal waste
Market organic waste 12.5 4.5 9.4 Cofie et al. (2009) Market and HH waste were merged for the nutrient contents of municipal waste
  1. aFor animal feed, dry weight was assumed, apart from fresh gras
  2. HH household

Appendix 3

Quantification of faecal sludge and solid waste in Tamale (Ghana).

Sanitation % of urban households kg cap−1 day−1 Remark
Open defecation 25.6 1.45  
Private 19.6 1.8 Including 0.35 L for anal cleansing (wet)
Public 54 1.8 Including 0.35 L for anal cleansing (wet)
  Source: Ghana Statistical Service (2014) Source: Heinss et al. (1998)  
  Total waste generated (t day−1) Organic fraction (%) Total waste collected (t day−1)
Municipal solid waste (scenario 1) 250 60 115
Source: Pradhan et al. (2013) Source: Miezah et al. (2015) Source: Personal communication (Abudu Imoro, Deputy Regional Manager, Zoomlion Ghana Limited, 2014)
Municipal solid waste (scenario 2) 300 60 246
Source: Daily Graphic (2015) Source: Miezah et al. (2015) Source: Daily Graphic (2015)

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Karg, H., Akoto-Danso, E.K., Drechsel, P. et al. Food- and feed-based nutrient flows in two West African cities. Nutr Cycl Agroecosyst 115, 173–188 (2019).

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  • Food supply
  • Nutrient flows
  • Resource recovery
  • Urban metabolism
  • West Africa