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.
The pioneering developed simplified mathematical model can be used to determine the energy consumption of the torrefaction process. Specifically, the energy balance model was developed for torrefaction of municipal solid waste (MSW; a combustible fraction of common municipal waste). Municipalities are adopting waste separation and need tools for energy recovery options. This type of model is needed for initial decision-making, evaluation of cost estimates, life cycle analysis (LCA), and for optimizing the torrefaction of MSW. The MSW inputs are inherently variable and are site-, location-, and country-dependent. Thus, in this model, MSW inputs consist of eight types of common municipal waste components: chicken meat, diapers, gauze, eggs packaging, paper receipts, cotton, genuine leather, and polypropylene. The model uses simple experimental input consisting of thermogravimetric (TGA) and differential scanning calorimetry (DSC) analyses for each type of individual MSW material. The model was created in a Microsoft Office Excel spreadsheet and is available for download and use for site-specific waste mixes and properties. The model allows estimating the energy demand of the process depending on the percentage composition of the MSW and the final torrefaction temperature. The model enables initial optimization of the torrefaction process regarding its energy demand by changing the proportion of MSW mix and the final temperature.
Sewage sludge (SS) recycling is an important part of the proposed ‘circular economy’ concept. SS can be valorized via torrefaction (also known as ‘low-temperature pyrolysis’ or ‘roasting’). SS can, therefore, be considered a low-quality fuel or a source of nutrients essential for plant growth. Biochar produced by torrefaction of SS is a form of carbonized fuel or fertilizer. In this research, for the first time, we tested the feasibility of torrefaction of SS with high ash content for either fuel or organic fertilizer production. The research was conducted in 18 variants (six torrefaction temperatures between 200~300 °C, and three process residence times of 20, 40, 60 min) in 5 repetitions. Fuel and fertilizer properties and multiple regression analysis of produced biochar were conducted. The higher heating value (HHV) of raw SS was 21.2 MJ·kg−1. Produced biochar was characterized by HHV up to 12.85 MJ·kg−1 and lower H/C and O/C molar ratio. Therefore, torrefaction of SS with high ash content should not be considered as a method for improving the fuel properties. Instead, the production of fertilizer appears to be favorable. The torrefaction increased C, N, Mg, Ca, K, Na concentration in relation to raw SS. No significant (p < 0.05) influence of the increase of temperature and residence time on the increase of biogenic elements in biochar was found, however the highest biogenic element content, were found in biochar produced for 60 min, under the temperature ranging from 200 to 240 °C. Obtained biochars met the Polish regulatory criteria for mineral-organic fertilizer. Therefore SS torrefaction may be considered a feasible waste recycling technology. The calculation of torrefaction energy and the mass balance shows energy demand <2.5 GJ∙Mg−1 w.m., and the expected mass yield of the product, organic fertilizer, is ~178 kg∙Mg−1 w.m of SS. Further investigation should consider the scaling-up of the SS torrefaction process, with the application of other types of SSs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.