Hydrothermal carbonization of anaerobically digested maize silage.

Area of Science:

• Biomass Conversion
• Materials Science
• Sustainable Energy

Background:

• Maize silage is an abundant agricultural residue with potential for valorization.
• Hydrothermal carbonization (HTC) is a thermochemical process for converting wet biomass into hydrochar.
• Previous solid-state treatment of silage may influence HTC outcomes.

Purpose of the Study:

• To investigate the production of hydrochars from pre-treated maize silage using HTC.
• To characterize the properties of the resulting hydrochars.
• To evaluate the potential applications of these hydrochars as alternative fuels or soil conditioners.

Main Methods:

• Maize silage was pre-treated at 55 °C in a two-stage solid-state reactor.
• Hydrothermal carbonization (HTC) was performed in a 1-L stirred pressure reactor at 190 °C for 2 hours.
• pH was regulated using citric acid during HTC.
• Hydrochar properties, including carbon content, higher heating value, and surface area (BET), were analyzed.

Main Results:

• Hydrochars exhibited amorphous macro-size features.
• Carbon content ranged from 59-79% (ash-free, dry).
• Higher heating values were between 25-36 MJ kg⁻¹.
• Brunauer-Emmett-Teller (BET) surface area reached a maximum of 12.3 m²/g at 190 °C.
• Temperature was identified as the primary factor influencing hydrochar properties.

Conclusions:

• Hydrochars derived from pre-treated maize silage possess favorable characteristics.
• The hydrochars demonstrate potential for use as alternative energy sources.
• These hydrochars could also serve as effective soil conditioners, contributing to sustainable agriculture.