Organic waste: a source of minerals to combat malnutrition

Key points

Malnutrition can take several forms, one of which is micronutrient deficiencies, particularly in iron, zinc and vitamin A. Currently, more than two billion people worldwide suffer from these deficiencies, with major impacts for healthcare systems.

In low-income countries, deficiencies in zinc, iron and vitamin A are among the top ten causes of illness. A person with iron deficiency will become anaemic, leading to reduced physical and intellectual abilities and lower resistance to infection. Zinc deficiency weakens the immune system and causes chronic inflammation. In children, growth delays are frequently observed, especially if mothers are also deficient, along with higher neonatal mortality rates.

These health impacts spill over into education and the economy. In 2014, the African Union Commission estimated that the negative impact of these micronutrient deficiencies was, on average, 11% of the GDP of African countries.

Biofortification: improving nutritional quality in the field

To address this challenge, the goal of the OR4FOOD project is to improve the micronutrient content of several widely consumed agricultural products in Africa through “agronomic biofortification”. This practice is aimed at improving the nutritional quality of food during cultivation, directly in the field. The project was funded by the African Union and the European Union and lasted four years, from 2018 to 2022.

The OR4FOOD project team adopted a two-pronged approach:

• Selecting existing varieties of millet, teff, cowpea and sweet potato that are naturally rich in micronutrients
• and fertilising them with organic waste combined with effective microorganisms produced on the farm.

According to Jean-Michel Médoc, an agronomist at CIRAD and coordinator of the project, the results are promising: “for cowpea, we have managed to increase the iron content by around 20% in just under two years”.

Using organic waste to increase the mineral content of crops

OR4FOOD focuses on agroecology. After selecting several naturally nutrient-rich varieties, the team tested different types of organic fertilisers using residues from human activities: manure, poultry litter and sewage sludge from urban wastewater treatment plants. These organic materials were combined with effective microorganisms (such as beneficial indigenous microorganisms, or BIM, and mycorrhizae) with the aim of improving the availability of micronutrients in the soil.

“There are several types of effective microorganisms”, says Jean-Michel Médoc. “For OR4FOOD, we used fermentation to multiply natural microorganisms collected from local forest litter. This is known as a biostimulation technology, which helps to produce beneficial indigenous microorganisms. The whole process takes place directly on the farm”.

These tests were carried out over two years on several crops: cowpea, millet and sweet potato. By the end of the project, the team observed an increase in the concentration of iron, zinc and provitamin A in all three test crops. Most importantly, these gains are maintained during processing, including extrusion cooking, a common food processing technique. “The micronutrient gains can still be absorbed by the stomach”, says the researcher.

In Senegal, for example, the Thieye and Thissine cowpea varieties showed higher yields and higher concentrations of iron and zinc compared to traditional varieties. When these naturally micronutrient-rich varieties were treated with a combination of poultry litter and microorganisms, the iron gains were +25% and the zinc gains were +33% compared to the same varieties grown conventionally. Similarly, the orange-fleshed sweet potato varieties Apomudem and Kandee showed gains of +69% for iron and +39% for zinc compared to conventionally grown varieties.

Another advantage of these agroecological practices is that they have no negative impact on yields. However, farmwork needs to be reorganised around these new resources: the organic matter chosen needs to be accessible and easy to transport to the field, and the effective microorganisms need to be produced on the farm. “The practices implemented are not actually new to these communities”, says Jean-Michel Médoc. “What OR4FOOD has done is simply revive cropping systems based on organic residue recycling. The main innovation lies in combining these residues with effective microorganisms”.

A short-term solution and a first step towards food diversification

The results obtained by OR4FOOD show that agronomic biofortification through agroecology can provide a quick solution to certain nutritional problems in the Sahel. Three growing cycles were enough to observe an increase in micronutrients, or from one and a half to three years depending on the crop and access to water. Further to the project, the World Bank is currently funding a postdoctoral project in Senegal to scale up these practices.

However, agronomic biofortification will not solve everything, as Jean-Michel Médoc points out: “deficiencies are mainly due to monotonous diets and limited access to sufficient quantities of nutrient-rich foods. The long-term solution is food diversification”. For many rural populations in the Sahel, diets mainly consist of cereals and a few vegetables. Meat and fish remain scarce, due to limited physical or economic access. Improving diets is a complex, long-term process, and is dependent on factors such as increasing income, improving access to diverse foods, and providing better health and nutrition services.

Legumes can boost food and nutrition security in Africa

Beans, lentils, soybeans, groundnut and others… legumes include a vast diversity of crop species. In several African countries, they form the basis of many traditional dishes. They have both agronomic and nutritional advantages, and could be used more. The levers for boosting their consumption including raising awareness of the range of products and improving processing techniques.

According to Jean-Michel Médoc, developing biofortified agronomic systems is the first step towards food diversification, which depends on crop diversification. In this respect, agroecology not only provides suitable agronomic solutions for low-income countries, but also fosters a fairer and more sustainable social and economic restructuring of agricultural labour. Since it requires the participation and engagement of all food system stakeholders, the agroecological transition can, for example, empower women, who have primary responsibility for nutritional issues as they are in charge of food processing and meal preparation. In OR4FOOD, the voices of women were particularly important when selecting varieties, as this choice directly impacts the types of foods subsequently available to households.