Next Article in Journal
Potential of Sentinel-1 Surface Soil Moisture Product for Detecting Heavy Rainfall in the South of France
Previous Article in Journal
The Progress of Glucose Monitoring—A Review of Invasive to Minimally and Non-Invasive Techniques, Devices and Sensors
Previous Article in Special Issue
Improvement of Sensing Performance of Impedancemetric C2H2 Sensor Using SmFeO3 Thin-Films Prepared by a Polymer Precursor Method
Open AccessArticle

Waste Coffee Ground Biochar: A Material for Humidity Sensors

Center for Sustainable Future Technologies, Italian Institute of Technology (IIT), Via Livorno 60, 10144 Torino, Italy
Department of Applied Science and Technology (DISAT), Politecnico di Torino, Corso Duca degli Abruzzi, 24, 10129 Torino, Italy
INSTM R.U PoliTO-LINCE Laboratory, Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi, 24, 10129 Torino, Italy
Faculty of Science, University of Ontario Institute of Technology, Oshawa, ON L1H7K4, Canada
Author to whom correspondence should be addressed.
Sensors 2019, 19(4), 801;
Received: 20 December 2018 / Revised: 11 February 2019 / Accepted: 12 February 2019 / Published: 15 February 2019
(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)
Worldwide consumption of coffee exceeds 11 billion tons/year. Used coffee grounds end up as landfill. However, the unique structural properties of its porous surface make coffee grounds popular for the adsorption of gaseous molecules. In the present work, we demonstrate the use of coffee grounds as a potential and cheap source for biochar carbon. The produced coffee ground biochar (CGB) was investigated as a sensing material for developing humidity sensors. CGB was fully characterized by using laser granulometry, X-ray diffraction (XRD), Raman spectroscopy, field emission-scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and the Brunnauer Emmett Teller (BET) technique in order to acquire a complete understanding of its structural and surface properties and composition. Subsequently humidity sensors were screen printed using an ink-containing CGB with polyvinyl butyral (PVB) acting as a temporary binder and ethylene glycol monobutyral ether, Emflow, as an organic vehicle so that the proper rheological characteristics were achieved. Screen-printed films were the heated at 300 °C in air. Humidity tests were performed under a flow of 1.7 L/min in the relative humidity range 0–100% at room temperature. The initial impedance of the film was 25.2 ± 0.15 MΩ which changes to 12.3 MΩ under 98% humidity exposure. A sensor response was observed above 20% relative humidity (RH). Both the response and recovery times were reasonably fast (less than 2 min). View Full-Text
Keywords: waste coffee ground; biochar; humidity sensor; pyrolysis; impedance waste coffee ground; biochar; humidity sensor; pyrolysis; impedance
Show Figures

Graphical abstract

MDPI and ACS Style

Jagdale, P.; Ziegler, D.; Rovere, M.; Tulliani, J.M.; Tagliaferro, A. Waste Coffee Ground Biochar: A Material for Humidity Sensors. Sensors 2019, 19, 801.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

Back to TopTop