Pyrolysis of the food waste collected from catering and households under different temperatures: Assessing the evolution of char structure and bio-oil composition.

The accumulation of food waste brings several challenges to the economy and environment, its pyrolysis technology has received extensive attention. The present investigation mainly focused on the evolution of char structure and bio-oil composition during the pyrolysis process of the typical food waste, which was characterized by FT-IR, Raman, UV, and GC/MS. The experimental results show that the bio-oil has the highest yield at 400–600 ℃ and remains basically unchanged (around 40%), and decreases apparently at 700 ℃ due to the secondary thermal cracking and reforming. With the increase of temperature, the cracking of macromolecular organic matter in the food waste becomes more intense, resulting in the yield of bio-char gradually decreasing from 34.90% to 23.54% in the range of 400–700 ℃. The ratio of small aromatic ring systems to large aromatic systems (I (VR+VL+GR) /I D) in the bio-chars increases apparently with temperature, and the amounts of aromatic rings in bio-oil also increase gradually. The content and relative percentage of N-compounds are the largest in bio-oil, and the content of it reaches the maximum value at 500 ℃, while the changes in its relative percentage are slightly different, which decreases from 33.57% to 24.15% at 400–600 ℃, and then increases apparent to 40.63% at 700 ℃. Hydrocarbons are also one of the main components in bio-oil, their relative percentage decreases from 17.70% to 2.40% in the range of 400–700 ℃. In addition, Carboxylic acid, alcohols, esters, ketones, saccharides, phenols, and other substances are also contained in bio-oil, and its content has different changing trends with temperature. [Display omitted] • The maximum yields of bio-char and bio-oil are observed at 400 ℃. • The increase of temperature is beneficial to improve the aromatization degree of bio-oil. • The content of large aromatic ring system on the surface of char decreases with temperature. • N-compounds, hydrocarbons, and carboxylic acid are the main component in bio-oils. [ABSTRACT FROM AUTHOR]