Renewable and Sustainable Energy Reviews 117 (2020) 109477 Available online 16 October 2019 1364-0321/© 2019 Elsevier Ltd. All rights reserved. Characterization of Ugandan biomass wastes as the potential candidates towards bioenergy production Abdulfatah Abdu Yusuf a, b, * , Freddie L. Inambao a a Green Energy Solution, Discipline of Mechanical Engineering, University of KwaZulu-Natal, Durban, South Africa b Department of Mechanical Engineering, Kampala International University, P. O. Box 20000, Uganda A R T I C L E INFO Keywords: Biomass waste Bio-energy Functional groups Heavy metals SEM-EDS ABSTRACT Biomass waste can be characterized to identify its use in bio-energy production. This study aimed to characterize Mbwazirume peel (MP) and Nakyinyika peel (NP) biomass using various analyses such as proximate and ultimate, TGA, FT-IR, AAS, and SEM-EDS. This was in order to assess their suitability for bio-energy application in Uganda. Results indicate that MP biomass shows higher VM 69.988%, FC 13.582%, ash content 5.825%, and HHV 18.28 MJ-kg 1 , and shows lower moisture content 10.605%, nitrogen (N) 5.78%, oxygen (O) 46.74% and sulfur 0.30%. The decomposition of hemicellulose mainly takes place at 100–250 C, cellulose at 300–500 C, and lignin at 500 C and above. The spectrometer results exhibit various functional groups which are related to C– – C, OH, C– – O, and C–O–C. The heavy metals (HMs) results for both samples indicate that Cu, Cd and Pb were low, and Zn was high. These toxics may not affect the environment due to their low amount of eco-toxicity and bioavailability. The SEM images show the presence of starch granules and irregular particles with heterogeneous morphology. This might justify the occurrence of high cellulose content due to additional restrictions on mo- lecular motion. During the EDS analysis, the elements found in both ash residues were ordered as follows: O > K > C > Cl > Mg > P for MP, and K > Cl > Mg > P > Al for NP. All these properties proved that MP biomass is more suitable as a potential application for bio-energy. 1. Introduction Banana is among of the most consumed fruits in the world, yet there is little industrial use for its peel, which constitutes 30%–40% of the weight of the fruit [1]. Uganda is ranked the second largest producer of bananas at 11.1 m tons per year, after India with 29.7 m tons of bananas produced per year [2]. Uganda is the number one consumer of bananas at 240 kg per capita per annum [2]. This means that bananas are key part of many families’ everyday diet, which in return generates considerable quantities of banana peels each day all year round [3]. There are different types of bananas grown in Uganda for food consumption. These have been classified as green bananas (Matooke), plantain, and yellow or sweet bananas [1]. Matooke (Musa-AAA-EA) is a variety of banana indigenous to Uganda, which is the most essential staple food crop for human consumption. It comes from the family of bananas known as East African highland bananas. It appears to be green in color and thick at the midsection [4], and cannot be peeled in the same way as yellow bananas. These peels are used as animal feed or as local briquettes. Despite the usage, about 61.8 kg per capital per annum of Matooke peels produced in Uganda become waste, due to the lack of sufficient structure and indiscriminate dumping. This huge amount of waste leads Abbreviations: AAS, Atomic absorption spectroscopy; ASTM, American society for testing and materials; CO 2 , Carbon dioxide; Cu, Copper; Cd, Cadmium; CF Z , Content of HMs found in the residue; DTG, Derivative thermogravimetry; DIN, Deutsches institute für normung; EDS, Energy dispersive X-ray spectrometer; FC, Fixed carbon; FT-IR, Fourier-transform infrared spectroscopy; LCB, Lignocelluloses biomass; GHG, Greenhouse gas; H 2 O, water; HMs, Heavy metals; MC, Moisture content; MP, Mbwazirume peel; NP, Nakyinyika peel; HHV, Higher heating value; M f , After heat treatment; M i , Before heat treatment; N, Nitrogen; NEMP, National envi- ronment management policy; NEP, National energy policy; NO x , Nitrogen oxides; NOGP, National oil and gas policy; O, Oxygen; Pb, Lead; RETs, Renewable energy technologies; REP, Renewable energy policy; SEM, Scanning electron microscopy; SO 2 , Sulfur dioxide; TGA, Thermogravimetric analysis; T idt , initial decomposition temperature; TC Z , Total content of HMs in the residues; UIRI, Uganda industrial research institute; UNBS, Uganda national bureau of standards; VM, Volatile matter; Zn, Zinc. * Corresponding author. Green Energy Solution, Discipline of Mechanical Engineering, University of KwaZulu-Natal, Durban, South Africa E-mail addresses: abdulfatahabduyusuf@gmail.com, yusuf.abdulfatah@kiu.ac.ug (A.A. Yusuf). Contents lists available at ScienceDirect Renewable and Sustainable Energy Reviews journal homepage: http://www.elsevier.com/locate/rser https://doi.org/10.1016/j.rser.2019.109477 Received 30 April 2019; Received in revised form 29 September 2019; Accepted 7 October 2019