Across much of sub-Saharan Africa, soil degradation is driving declines in agricultural productivity. After each harvest, crop residue is commonly burned to quickly clear fields and reduce pests; however, these fires release harmful gases and particulates—including black carbon, methane, and nitrous oxide—worsening air quality across the region. At the same time, residue burning, combined with excessive chemical inputs and poor waste management, has significantly reduced soil fertility and lowered crop yields. In Ghana, for example, more than 65 per cent of cultivated land now shows declining fertility. 

These practices also have a profound human cost: the World Health Organization estimates that household and ambient air pollution cause over 800,000 premature deaths each year in Africa, much of it linked to the burning of vegetation. At the same time, continuous fertilizer use without organic matter replenishment depletes soil structure, reducing water retention and nutrient balance. 

Despite the well-known risks, farmers have few viable alternatives. Composting is slow and labour-intensive; mechanized waste recycling is cost prohibitive, especially as the costs of agricultural inputs rise; and access to climate-smart technologies is limited. Policy measures discouraging open burning have had little effect without practical, profitable substitutes for farmers. As a result, open burning, declining soil fertility, and poverty reinforce one another in a cycle that threatens long-term food and climate security. These trends are only slated to intensify as population growth and food demand intensify.  

Turning crop residue into a soil-strengthening resource

Efforts to improve soil management and reduce agricultural emissions have often been fragmented or limited to short-term pilot projects. Many have focused narrowly on fertilizer efficiency or residue composting without integrating broader agroecological principles.  

The Agroecology and Circular Economy for Ecosystem Services in Sub-Saharan Africa (ACE4ES) Project decided to take a more systemic approach, combining agroecology, circular economy innovations, and SLCP mitigation. The project—coordinated by the Council for Scientific and Industrial Research – Crops Research Institute (CSIR-CRI)—introduced an integrated model that converts crop residues into biochar and compost. The process involves locally built low-oxygen pyrolysis chambers that transform crop residues into biochar; aerated composting sheds that accelerate decomposition; and mixing platforms that blend compost and biochar into high-carbon soil amendments. These methods replace burning with value creation—turning waste into a resource that restores degraded soil, reduces fertilizer dependence, and reduces black carbon and methane emissions.