Biogas Production Potential of Mixed Banana and Pineapple Waste as Assessed by Long-Term Laboratory-Scale Anaerobic Digestion

Biogas is a renewable energy source generated through the anaerobic digestion (AD) of organic feedstocks. This study aims to quantify the biogas production potential (BPP) of fruit wastes via semi-continuous lab-scale mesophilic AD over a total of 100 days. The feed was composed of 80% banana peelings and 20% pineapple residues, mimicking the waste composition of a Costa Rican fruit processing facility used as a test case. The average loading rate of volatile suspended solids (VSS) corresponded to 3.6 kg VSS·m−3·d−1. Biogas yield and composition were monitored, along with the concentration of ammonium, volatile fatty acids, and pH. Discounting the start-up phase, the BPP averaged to 526 LN (kg VSS)−1 with a methane concentration of around 54%, suggesting suitability of the substrate for AD. We calculated that if upscaled to the Costa Rican test case facility, these values translate into a gross average heat and electricity production via AD of around 5100 MWhel·a−1 and 5100 MWhth·a−1, respectively. Deducting self-consumption of the AD treatment, this is equivalent to 73% of the facility’s electricity demand, and could save about 450,000 L of heavy oil per year for heat generation. To circumvent nitrogen shortage, the addition of a co-substrate such as dry manure seems advisable.