Carbon footprint of primary production of cacao: a meta-analytical review

Cacao production occupies ≈120 000 km2 globally. Cacao beans are the most valuable agricultural export of four African countries and of importance in several other tropical countries. Greenhouse-gas emissions from cacao production are therefore of interest, as is the potential of the crop for mitigation of emissions by carbon sequestration. We present a global review of carbon footprints and CO2 removal rates in primary production of cacao. We aim to characterize typical overall values, identify determinants of footprints and removal rates, compare cropping systems, and suggest ways of reducing carbon footprints and increasing CO2 removal rates. The median ± interquartile range carbon footprints of cacao production, excluding any associated deforestation, were 732 ± 1 318.5 CO2e ha-1 (area carbon footprint, ACF) and 1.55 ± 2.703 kg CO2e kg-1 dry beans (product carbon footprint, PCF). The typical ranges of ACF and PCF, defined as those from the first to the eighth decile, were 26–1 691 CO2e ha-1 yr-1 and 0.05–3.74 kg CO2e kg-1 dry beans, respectively. Nitrogenous fertilizers and harvest residues were the most important emissions sources. The ACF and PCF of agroforestry production were than those of unshaded production n (p = 0.05, 0.09, respectively), as were yields (p = 0.04). The mean ACF and PCFs of organic production were significantly lower than those of non-organic production. CO2 removal rates were considerably larger than carbon emissions (ACF values), particularly for agroforestry production (median ± interquartile range of 3 445±1 952 kg CO2 ha-1 yr-1 and 10 237±4 178 CO2 kg ha-1 yr-1 for unshaded and agroforestry production, respectively). CO2 removal rates in organic and non-organic production did not differ significantly. We present a generalized approach for reducing the overall global-warming effect of cacao production, consisting of 12 specific intervention options within an overarching principle of zero deforestation. Improved management of harvest residues, wider use of agroforestry production, and use of organic nitrogen sources are central to enhancing the interventions. Implementation of interventions will also require the building of enabling frameworks that allow farmers to meet climate-change mitigation goals without sacrificing productivity or profitability.