Energy and carbon footprints of ethanol production using banana and cooking banana discard: A case study from Costa Rica and Ecuador

Banana and cooking banana (Musa spp.) production systems accumulate a considerable quantity of discard due to high quality demands of markets. Ripe fruits have high sugar contents, which can be easily processed to ethanol. The present study aimed to quantitatively assess the production potential of ethanol from Musa spp. discard and to analyze the energy and carbon (C) footprints of this production system using a life cycle approach. The study compared three case studies differing in management practices, which were (I) a coffee producer's cooperative in Costa Rica using Musa spp. as shade trees, (II) organic banana producers from Ecuador, and (III) conventional banana producers from Ecuador. It was found that banana and cooking banana discard accumulated at a rate of 1.4-3.4 t ha^-1, of which around 118-266 l ethanol could be produced on a yearly basis. The case study from Costa Rica yielded a net-energy balance (NEB) of 19.3 MJ l^-1 and avoided carbon emissions of 0.48 kg l^-1. It was closely followed by the organic banana producers from Ecuador with a NEB of 17.1 MJ l^-1 and avoided carbon emissions of 0.44 kg l^-1. NEB and avoided carbon emissions for the conventional banana farms in Ecuador were much lower (7.2 MJ l^-1 and 0.34 kg l^-1).Despite providing economic benefits to farmers through a biomass source that would have been otherwise lost, the study gave clear evidence that the ecological footprint of this ethanol production system is significantly influenced by the resource use during the production life cycle.