Analysing the potential for CAM-fed bio-economic uses in sub-Saharan Africa

Abstract

Crassulacean Acid Metabolism (CAM) plants have the potential to provide future-proof biomass growth under increasingly stressed climatic conditions. Using active cultivation and anaerobic digestion, CAM plants can be grown and fermented to produce biogas or hydrolysed to extract valuable volatile fatty acids (VFAs) which can be applied to a range of uses: energy provision, protein and bioplastic production, carbon sequestration. However, an understanding of the spatial potential for CAM plants to be actively grown and harvested for bio-economic uses across Africa is unknown. A combined conservative assessment which incorporates three key dimensions is lacking from the literature: i) where can CAM plants physiologically grow? ii) where can CAM plants be cultivated without competing with existing land use? and iii) where lies the greatest energy demand? Answering these three questions and mapping the spatial variability between these aspects is essential to the future bioplastics/protein sector and opportunity to capitalise on generating sustainable energy which can connect off-grid rural and peri-urban communities whilst also achieving climate change mitigation targets. Using Opuntia ficus-indica as an example, this study compares two measures of land suitability estimation based on ecophysiological requirements and social, environmental and land-use masks. Focusing on abandoned land, conservative baseline estimates suggest that c.28–55 million hectares of land may be suitable for active CAM cultivation, with the potential to repurpose degraded lands and provide alternative bio-economic livelihoods to communities across semi-arid regions of Africa.