Green additive to upgrade biochar from spent coffee grounds by torrefaction for pollution mitigation

Kuan-Ting Lee; Jyun-Ting Du; Wei-Hsin Chen; Aristotle T Ubando; Keat Teong Lee

doi:10.1016/j.envpol.2021.117244

Green additive to upgrade biochar from spent coffee grounds by torrefaction for pollution mitigation

Environ Pollut. 2021 Sep 15:285:117244. doi: 10.1016/j.envpol.2021.117244. Epub 2021 Apr 28.

Authors

Kuan-Ting Lee¹, Jyun-Ting Du², Wei-Hsin Chen³, Aristotle T Ubando⁴, Keat Teong Lee⁵

Affiliations

¹ College of Engineering, Tunghai University, Taichung, 407, Taiwan; Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan, 701, Taiwan.
² Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan, 701, Taiwan.
³ Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan, 701, Taiwan; Research Center for Smart Sustainable Circular Economy, Tunghai University, Taichung, 407, Taiwan; Department of Mechanical Engineering, National Chin-Yi University of Technology, Taichung, 411, Taiwan. Electronic address: weihsinchen@gmail.com.
⁴ Mechanical Engineering Department, De La Salle University, 2401 Taft Avenue, 0922, Manila, Philippines; Center for Engineering and Sustainable Development Research, De La Salle University, 2401 Taft Avenue, 0922, Manila, Philippines.
⁵ School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, Nibong Tebal, 14300, Pulau Pinang, Malaysia.

PMID: 33965857
DOI: 10.1016/j.envpol.2021.117244

Abstract

A green approach using hydrogen peroxide (H₂O₂) to intensify the fuel properties of spent coffee grounds (SCGs) through torrefaction is developed in this study to minimize environmental pollution. Meanwhile, a neural network (NN) is used to minimize bulk density at different combinations of operating conditions to show the accurate and reliable model of NN (R² = 0.9994). The biochar produced from SCGs torrefied at temperatures of 200-300 °C, duration of 30-60 min, and H₂O₂ concentrations of 0-100 wt% is examined. The results reveal that the higher heating value (HHV) of biochar increases with rising temperature, duration, or H₂O₂ concentration, whereas the bulk density has an opposite trend. The HHV, ignition temperature, and bulk density of biochar from torrefaction at 230 °C for 30 min with a 100 wt% H₂O₂ solution (230-100%-TSCG) are 27.00 MJ∙kg^-1, 292 °C, and 120 kg∙m^-3, respectively. This HHV accounts for a 29% improvement compared to that of untorrefied SCG. The contact angle (126°), water activity (0.51 a_w), and moisture content (7.69%) of the optimized biochar indicate that it has higher resistance against biodegradation, and thereby can be stored longer. Overall, H₂O₂ is a green treatment additive for SCGs solid fuel. This study has successfully produced biochar with greater HHV and low bulk density at low temperatures. The green additive development can effectively reduce environmental pollutants and upgrade wastes into resources, and achieve "3E", namely, environmental (non-polluting green additives), energy (biofuel), and circular economy (waste upgrade). In addition, the produced biochar has great potential in the fields of bioadsorbents and soil amendments.

Keywords: Biochar; Environmental pollutants; Neural network; Spent coffee grounds; Torrefaction; Waste reuse.

MeSH terms

Charcoal
Coffee*
Environmental Pollution
Hydrogen Peroxide*

Substances

Coffee
biochar
Charcoal
Hydrogen Peroxide