Abstract
The paper presents, for the first time, the results of fuel characteristics of biochars from torrefaction (a.k.a., roasting or low-temperature pyrolysis) of elephant dung (manure). Elephant dung could be processed and valorized by torrefaction to produce fuel with improved qualities for cooking. The work aimed to examine the possibility of using torrefaction to (1) valorize elephant waste and to (2) determine the impact of technological parameters (temperature and duration of the torrefaction process) on the waste conversion rate and fuel properties of resulting biochar (biocoal). In addition, the influence of temperature on the kinetics of the torrefaction and its energy consumption was examined. The lab-scale experiment was based on the production of biocoals at six temperatures (200–300 °C; 20 °C interval) and three process durations of the torrefaction (20, 40, 60 min). The generated biocoals were characterized in terms of moisture content, organic matter, ash, and higher heating values. In addition, thermogravimetric and differential scanning calorimetry analyses were also used for process kinetics assessment. The results show that torrefaction is a feasible method for elephant dung valorization and it could be used as fuel. The process temperature ranging from 200 to 260 °C did not affect the key fuel properties (high heating value, HHV, HHVdaf, regardless of the process duration), i.e., important practical information for proposed low-tech applications. However, the higher heating values of the biocoal decreased above 260 °C. Further research is needed regarding the torrefaction of elephant dung focused on scaling up, techno-economic analyses, and the possibility of improving access to reliable energy sources in rural areas.
Highlights
It is estimated that there are around~450,000 elephants today, of which 400,000 are in Africa and50,000 in Asia
The ash content was inversely proportional to the organic matter (OM) content and increased to over 71% in comparison to 50.81% for raw dung (Table A1) in biocoal produced at 280 and 300 ◦ C at 60 min (Figure 7)
Endothermal reactions are related to depolymerization and volatilization process, whereas exothermic transformations are due to the charring process [59] phenomenon, the Differential Scanning Calorimetry (DSC) plot shows that the elephant dung torrefaction is an endothermic process and it requires energy delivery
Summary
It is estimated that there are around~450,000 elephants today, of which 400,000 are in Africa and. It is important to consider managing the residues (e.g., raw dung and sludge), which may require specialized collection, storage, treatment, and disposal It has not been described yet how existing or developing technologies (anaerobic digestion, biohydrogen production) could be used for waste management, especially in rural regions in which elephant dung is available in large quantities. Jia et al [16] described the possibility of using a co-gasification of woody biomass and animal manure as a useful technology to utilize organic waste, which could be practical in the case of elephant dung as well. Whether the duration of the torrefaction process at a given temperature affects the dung conversion gasification of mass woody biomass animal manure as a useful to utilize organic waste, rate (e.g., loss, energyand densification, and improved fueltechnology properties); which could be practical in the case of elephant dung as well.
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