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More lettuce thanks to biochar

More lettuce thanks to biochar

Urban agriculture in West Africa

by Julia Weiler  

October 15, 2015


In West Africa, many farmers move to the cities, where they cultivate fallow land or dried river beds for agricultural purposes. The soils are often not very fertile, cultivating those lands is sometimes illegal and harmful to the environment. An interdisciplinary research team is striving to find a remedy.

Volker Häring spent nine months in total in Burkina Faso and Ghana, in order to research urban agriculture.In the lab, the concentration of dissolved carbon and nitrogen is determined.Charred biomass, also called biochar, can be manufactured from harvest residues and it renders the soil more fertile. In the lab, Volker Häring identifies the cation exchange capacity of soil samples; it indicates how many nutrients the soil can adsorb.Volker Häring and Kofi Atiah in the RUB labThe researchers from Bochum use these tin capsules for identifying carbon and nitrogen volumes. They are prepared for many tests.In order to determine how much carbon and nitrogen is contained in the biochar, a sample is filled into a tin capsule.Volker Häring and Kofi Atiah take soil samples and identify the clay content.

West Africa boasts one of the highest urbanisation rates worldwide. The people who leave the rural areas are, for the largest part, farmers whose existence depends on agriculture. They try to use every free square metre in the city for that purpose. In the course of the project UrbanFoodPlus, researchers are attempting to find ways of rendering urban agriculture more productive, sustainable and climate-friendly. The RUB Chair of Soil Science and Soil Ecology, headed by Prof Dr Bernd Marschner, coordinates the project, together with colleagues from Kassel University. One of the numerous subprojects aims at boosting crop yields on urban soils. In order to compile the necessary data, Dr Volker Häring had temporarily relocated his workplace from Bochum to West Africa (fig. 1). He spent nine months in total in Burkina Faso and Ghana, in order to conduct field experiments together with colleagues from a wide range of different disciplines and to talk to the farmers in the area. "The intercultural adventures appealed to me," says Häring. But not only that. The soil ecologists believe that the strong RUB-internal collaboration under the umbrella of Urban FoodPlus offers huge opportunities.

Fig. 1© Christoph Steiner

Volker Häring discusses soil fertility with farmers in Tamale, Ghana.

Thanks to a long and proven track record of development programmes, death of starvation hardly ever occurs in those countries these days, especially not in Ghana. However, droughts or other natural disasters may still jeopardise food security, and health problems due to malnutrition are a common phenomenon. "It is virtually impossible to insure oneself for harvest failure," says Volker Häring. "People depend on their families and cultivated crops." This is why it is vital for them to be able to rely on successful and ample harvest.

In order to get an overview of the situation, the researchers interviewed 270 farmers from Tamale, Ghana, as well as 246 from Ouagadougou, Burkina Faso, in an initial study and analysed the soils used by them. In a first step, they had to find suitable areas and participants. "I bought a motor scooter. It makes life considerably easier," tells us Häring. "We could not afford a massive 4x4, like other projects do. Still, I believe a vehicle like that would not be suitable for driving out to poor farmers anyway."

Fig. 2© Volker Häring

Field experiment in Tamale, Ghana

The study provided a good overall image regarding soil quality, the use of fertilisers and pesticides and usual crop yields. The subsequent task was to find means of boosting the yields. For the team from Bochum, biochar is the magic word. It describes charred biomass which is gained by burning plant material in low-oxygen atmosphere. Applied to the soil, it improves the water balance and facilitates better adsorption of nutrients. "In West Africa, water is the number one limiting factor for agriculture," says Häring. The second-largest is soil fertility; the sandy soils do not store nutrients well. Biochar could solve both problems at once. "It’s made a massive splash in the research community," tells us the RUB scientist. "The hype it has generated must, of course, be regarded critically. Suddenly, do-gooders have crawled out of the woodwork, who wanted to solve all problems using biochar but who didn't think the issue through sufficiently." In their defence, field experiments have admittedly verified the yield-increasing effect of biochar (fig. 2). The experiments in West Africa revealed the significant potential of the substance.

Fig. 3© RUBIN, graphics: Weiler

When lettuce grows on soils that are enriched with biochar, the heads reach a greater size than those on untreated soils. The data for this diagram was supplied by PhD student Edmund Akoto-Danso.

In the first step, the "UrbanFoodPlus" team conducted studies under controlled conditions. The lettuce heads grown in the test fields that the researchers had treated with biochar were indeed larger than those grown in untreated fields (fig. 3). A promising result. But would the farmers be able to handle biochar in their everyday life? Another question that arises immediately is where the soil conditioner is supposed to be coming from – and at what price. The idea: generating biochar from harvest residues. Remains of corncobs or the husks of rice grains would be fit for this purpose. Not only is such plant waste free, converting it to biochar offers yet another advantage. Typically, crop residues are burnt or they decay naturally over time. In the process, most of the carbon from the organic material escapes into the atmosphere, is lost as a resource to the soil and has a harmful impact on the climate in the form of CO2 (fig. 4). Conversely, in the manufacture of biochar, at least fifty per cent of the carbon is stored in a stable manner.

Fig. 4© RUBIN, photo: Gorczany

Kofi Atiah fills a sample dish. The concentration of carbon contained in a soil sample is about to be identified.

"All citizens of Ghana are familiar with coal production, because they use charcoal for cooking," relates Häring. "There are people in every village who have specialised in its production." Using the same process, biochar could be manufactured too. Special furnaces required for its production can be built easily and at low cost. Together with his colleagues, Häring distributed twelve such furnaces among farmers who were willing to take part in an experiment. The researchers demonstrated briefly how the devices work and then withdrew to assume the perspective of neutral observers. The farmers manufactured biochar without any help, applied it to fields and planted lettuce. Volker Häring is now eagerly awaiting the results. "In such projects, there's always the danger that something unexpected might happen," he says. "For example that the plants will be eaten by wildlife."

Other problems cropped up that had not been on the researchers' radar at first. In order to supply small fields with a sufficient amount of biochar, considerable biomass volumes are necessary: two kilogrammes per square metres, to be precise. "First, the farmers have to have such quantities of plant waste at their disposal," points out Häring. "And they have to have it transported and be able to pay for the transport." More often than not, the researchers learn about such obstacles only when talking with the people involved. To this end, the UrbanFoodPlus team regularly meets with the farmers to hold group discussions. Communication usually works quite well: in Burkina Faso in French, in Ghana in English. "The people of Ghana are language wizards", as Volker Häring soon realised. "Many are illiterate, but they are fluent in four or five languages, because they often have close ties to neighbouring ethnic groups."

Fig. 5© Volker Häring

Traditional agriculture: soil is being piled up. Thus, root space is expanded, the fertile topsoil is collected in one location and the water balance is improved.

Those group discussions have proved to the researchers that the farmers are well informed. Häring: "They actually know all there is to know, for example how the water balance of soil can be improved. They simply cannot explain the processes in chemical or physical terms." (fig. 5) The research team is surprised that, despite their expertise, the farmers often do not implement useful measures. The reasons become apparent during the group discussions. "They are usually utterly banal; for example, the farmers don't even have a bike to transport something from A to B," elaborates the researcher from Bochum. "Or the additional effort required to implement the soil protection techniques is not considered profitable. Often, the land is not private property, and the farmers don't know if they will be permitted to still cultivate it in five years' time. Consequently, the motivation to improve soil fertility by implementing any sustainable measures is rather low. A complex issue."

The project UrbanFoodPlus will not be able to eliminate those obstacle. But that is not the goal, either. Even though the team is testing techniques that would benefit the people of the region, their implementation in everyday life is the task of development cooperation. Volker Häring is happy about the good collaboration with the farmers as well as the project partners in Germany and West Africa. Without the support of the latter, the research undertaking would not have been possible. "It is a genuine cooperation among equal partners. That's really important to us; without it the entire project would be unthinkable," he says. "For my part, I like spending time in West Africa."

More information about the project:

Project Urban Food Plus

The research activities outlined in the article reflect only a small fraction of the project UrbanFoodPlus, which is funded by the German Federal Ministry of Education and Research. The researchers from Bochum, Kassel, Göttingen and Freiburg, together with 14 African partner institutions and two international agricultural research institutes, constitute an interdisciplinary research association. Engineers and scientists develop techniques for improving soil fertility and water balance, while economists evaluate the processes from the economic point of view. Ethnologists investigate possible implementation problems in everyday practice. In addition to the Chair of Soil Science and Soil Ecology, other RUB departments involved in the project include the Chair of Development Research headed by Prof Dr Wilhelm Löwenstein as well as the team at the Department of Sanitary Engineering and Environmental Engineering headed by Prof Dr Marc Wichern and Dr Manfred Lübken.

Contact faculty

Prof Dr Bernd Marschner and Dr Volker Häring
Soil Science and Soil Ecology
Faculty of Geosciences
Ruhr-Universität Bochum
44780 Bochum, Germany
Phone: +49/234/32-22108 and -23439
Email: and

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