Olive Pomace-Derived Carbon Materials-Effect of Carbonization Pressure under CO2 Atmosphere.

Howaniec Howaniec

doi:10.3390/ma12182872

Abstract

The valorization of waste and by-products from various industrial activities is a must in our world of depleting natural resources and increasing volume of environmentally negative waste materials. The economic utilization of solid biowaste involves predominantly its use as a carbon-neutral energy resource or a precursor of porous carbon materials, with a potential application range including sorption processes, energy storage, and electric engineering. With the considerable number of lignocellulosic residues tested and applied as the most suitable porous material precursors, such as woods, shells, stones, peels, husks, and stalks of various crop plants, there is still space and need for further developments in the valorization of high amounts of other types of biowaste. Here, the olive pomace was considered because of both the vast volume and the environmentally undesired (when stored) phytotoxic effect of its components. While the literature on chemical (acidic and alkali treatment) and physical activation (temperature, carbon dioxide, and/or steam) of various biowaste precursors is considerable, the effects of pressure in the carbonization step are reported rarely, although the results observed are promising. The same applies to reports on the application of olive pomace for porous materials production, which indicate that olive pomace currently seems to be underestimated as a carbon materials precursor. In the study presented, the combined effects of pressure (0.1–3 MPa), temperature (800 °C), and carbon dioxide atmosphere in the carbonization of olive pomace were assessed on the basis of qualitative and quantitative data on micro- and mesoporosity of the carbon materials produced. The results showed the positive effect of increasing the process pressure on the development of a porous structure, and particularly, on the development of supermicropores and ultramicropores under the carbonization conditions applied. Carbon material with the most developed porous structure and the highest share of micropores was obtained under the maximum pressure tested.

Highlights

In the world of depleting natural resources, waste biomass is considered to be a valuable, carbon-neutral resource for various industrial applications, covering predominantly energy systems where waste biomass is applied in the production of energy and hydrogen in gasification and co-gasification [1,2,3,4] or methane-rich gas in anaerobic digestion [5]
On the use of pressure as an activation agent in tailoring the porous structure of carbon materials, and these works are mainly related to bituminous coal or lignite as precursors [34,35,36,37,38], with a few works devoted to biomass treatment under elevated pressure and temperature for the development of carbon materials of increased porosity [18,39,40]
The olive pomace-derived carbon materials resulting from the carbonization process performed at 800 ◦ C under the pressure of 0.1–3 MPa and carbon dioxide atmosphere demonstrated a micro-mesoporous structure

Summary

Introduction

In the world of depleting natural resources, waste biomass is considered to be a valuable, carbon-neutral resource for various industrial applications, covering predominantly energy systems where waste biomass is applied in the production of energy and hydrogen in gasification and co-gasification [1,2,3,4] or methane-rich gas (biogas) in anaerobic digestion [5]. The economic utilization of waste in energy production is placed alongside the incorporation of carbon dioxide and excess industrial heat in the low carbon-footprint valorization cycles of sustainable economic systems [6,7,8] Another important method of waste biomass valorization is the production of carbon materials with enhanced sorption properties for environmental applications, including removal of contaminants from gaseous and liquid phases. The potential of olive pomace in environment-friendly valorization cycles, together with the scarce data on the role of carbonization pressure alone and in combination with other parameters in tailoring the porous structure properties of waste-derived carbon materials were the main reasons prompting the study presented in his paper. Experimental data on olive pomace-derived carbon materials preparation are limited and practically missing when activation with pressure and carbon dioxide under elevated temperature is considered These are, the main rationales of the study presented. A wide range of porous structure parameters of the resulting chars were determined, providing qualitative and quantitative data on their micro- and mesoporosity, which are important for their potential application as prospective porous materials

Materials and Methods

Results and Discussion

Conclusions