Effects of wood ash on physicochemical and morphological characteristics of sludge-derived hydrochar pellets relevant to soil and energy applications

• Hydrochar is produced through a process called hydrothermal carbonization (HTC) and constitutes a carbon-rich solid material with different remarkable applications. This study investigated the effects of wood ash on the physicochemical and morphological properties of biosludge-derived hydrochar in pelleted form relevant to the use of the pellets as a soil nutritional and liming agent and as a biofuel source. The hydrochar was mechanically compressed into uniformly-sized pellets under applied pressures of 4 and 8 kN after blending with varying percentages of wood ash in the order 0, 20 and 50%. The pure and blended pellets were characterized to determine the impact of wood ash on key properties, correlated to the two applications mentioned above. Results demonstrated a strong relationship between key features of the pellets and ash proportion. The wood ash-blended hydrochar pellets showed good hydrophobicity as a consequence of increased contents of alkali and alkaline earth metals, but were low in aromatic functional groups compared to the pure hydrochar pellet. Furthermore, the heating value of the pure hydrochar pellet was about 4% higher than that of its parent material and indicates that this pellet has the capacity to serve as a source of energy. The study generally reveals that blending hydrochar produced from biosludge under HTC conditions with up to 20%–50% of wood ash and mechanically compressing into homogeneous pellets has promising potential for a nutrient-rich material that can enhance soil fertility.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Naturresursteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Environmental Engineering (hsv//eng)

Nyckelord

Scanning electron microscopic analysis

Elemental composition

Enrichment

Soil amendment

Heating value

Biokemisk processteknik

Biochemical Process Engineering

Miljö- och energisystem

Publikations- och innehållstyp

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