Methods of characterization of pyrolytic products.

In the context of an energy transition, the pyrolysis of biomass is increasingly regarded as a promising solution for recovering agro-waste. This thermochemical process, which depends on operating conditions such as temperature, residence time, and heating rate, generates three distinct products: biochar (a carbon-rich solid residue), bio-oil (a complex condensable liquid), and non-condensable gas. To ensure their efficiency and integration into industrial value chains, these products must be rigorously characterized and evaluated. This article explores characterization methods and practical industrial applications for these bioproducts.

1. Methods of characterization of biochar

Biochar is a porous material with a high carbon content, primarily used to enhance soil fertility and increase water retention. Additionally, it is utilized as an adsorbent material for wastewater treatment and as a precursor for active materials in batteries. The characterization of biochar is based on several properties, including:

• Physico-chemical properties: analysis of fixed carbon content, volatile matter, ash, pH,
  specific surface area (BET).
• Structural properties: analysis by scanning electron microscope (SEM) and X-ray diffraction
  (XRD).
• Functional properties: assessment of adsorption capacity, fertilizing power, and soil stability.

2. Methods of characterization of bio-oil

Bio-oil is a brown, viscous liquid composed of water and hundreds of organic compounds derived mainly from the dehydration and depolymerization of biomass macromolecules (hemicellulose, cellulose, and lignin). Bio-oil can be used as a substitute fuel in industrial boilers or upgraded into biofuels through processes such as hydrodeoxygenation or emulsification, for instance. It is also a potential source of platform chemicals (e.g., phenols and organic acids). Various analyses can be conducted to characterize its properties, including:

• Physical properties: density, viscosity, flash point, pH, water content, solid content.
• Chemical properties: ultimate analysis (CHNOS), calorific value, chemical
  composition by using GC-MS.

3. Methods of characterization of synthesis gas.

Synthesis gas, or syngas, is a gaseous mixture primarily containing carbon monoxide (CO),hydrogen (H₂), carbon dioxide (CO₂), methane (CH₄), and other light hydrocarbons. This gaseous product can be utilized as a heat source in industrial furnaces or as a feedstock for producing hydrogen, methanol, or synthetic fuels through catalytic processes. Characterization of syngas can be performed through the following analyses:

• Composition analysis using Gas chromatography, mass spectrometry, thermal
  conductivity detector, and flame ionization detection (GC-MS/TCD/FID).
• Calorific value calculated from chemical composition using the modified Dulong
  formula.
• H2/CO ratio: an essential criterion for applications in chemical synthesis.

In conclusion, pyrolysis technology offers a sustainable solution for converting biomass waste into energy and valuable chemical resources. With rigorous characterization of the products—biochar, bio-oil, and syngas—it is possible to assign them concrete and optimized industrial uses. However, despite its many advantages, the valorization of pyrolysis products faces challenges, including:

• The variability of biomasses, leading to heterogeneous composition that affects product
  quality.
• The instability of bio-oils, which often necessitates post-pyrolysis treatment.
• Integration into existing industrial infrastructures, which may be challenged by a lack of
  standardization or the need for process adaptation.

As technologies evolve and biorefineries emerge, these obstacles are being addressed, paving the way for broader and more sustainable exploitation of pyrolysis products.