Benjamin Wirth

Hydrothermal carbonization (HTC) of wheat straw: influence of feedwater pH prepared by acetic acid and potassium hydroxide.

In this study, influence of feedwater pH (2-12) was studied for hydrothermal carbonization (HTC) of wheat straw at 200 and 260°C. Acetic acid and KOH were used as acidic and basic medium, respectively. Hydrochars were characterized by elemental and fiber analyses, SEM, surface area, pore volume and size, and ATR-FTIR, while HTC process liquids were analyzed by HPLC and GC. Both hydrochar and HTC process liquid qualities vary with feedwater pH. At acidic pH, cellulose and elemental carbon increase in hydrochar, while hemicellulose and pseudo-lignin decrease. Hydrochars produced at pH 2 feedwater has 2.7 times larger surface area than that produced at pH 12. It also has the largest pore volume (1.1 × 10(-1) ml g(-1)) and pore size (20.2 nm). Organic acids were increasing, while sugars were decreasing in case of basic feedwater, however, phenolic compounds were present only at 260°C and their concentrations were increasing in basic feedwater.

Behavior of selected hydrolyzed and dehydrated products during hydrothermal carbonization of biomass.

In this study, effects of reaction temperature and reaction time on both solid hydrochar and HTC process liquid products were studied for hydrothermal carbonization (HTC) of cellulose, wheat straw, and poplar. A novel slurry sampling system was designed and used with an 18.6L Parr reactor for 0-480 min in 200, 230, and 260 °C. Sugars (sucrose, glucose, and fructose), HMF, and furfural were found maximum in lower HTC temperature and time. However, they degrade following first order degradation kinetics. Activation energies of total sugars (glucose, fructose, sucrose, and xylose), furfural, and HMF for straw and poplar were 95-127, 130-135, and 74-90 kJ mol(-1), respectively and individuals were lower for HTC of cellulose than others. Organic acids (acetic acid, formic acid, and lactic acid) and phenolic compounds (phenol, catechol, and guaiacol) were increasing with higher HTC severity.

Pyrolysis of hydrochar from digestate: Effect of hydrothermal carbonization and pyrolysis temperatures on pyrochar formation.

Digestate from anaerobic digestion of biomass often contains more than 90% of water, which is economically unfavorable for pyrolysis. Hydrothermal carbonization (HTC) has potential to treat very wet biomass, however, the hydrochar may be acidic, contains polycyclic aromatic hydrocarbons (PAH) and toxic organic substances (e.g., phenolic compounds), and has very low Brunauer-Emmett-Teller (BET) surface area. In this study, pyrolysis of digestate derived hydrochar is performed at various pyrolysis and HTC temperatures. Solid chars were characterized for elemental analysis, pH, PAH, BET, pore size and volume, and phenolic substances, while HTC process liquids were characterized for pH, organic acids, furfural derivatives, and phenolic substances. Physicochemical characteristics of pyro-HTC char were compared with corresponding pyrochar and hydrochar. Pyro-HTC chars produced at higher HTC (i.e., 260°C) and pyrolysis temperatures (i.e., 800°C) showed highest BET surface area (63.5m(2)g(-1)), no PAH, relatively mild basic pH (9.34), and no phenolic compounds.

Upflow anaerobic solid-state (UASS) digestion of horse manure: Thermophilic vs. mesophilic performance

Energetic use of complex lignocellulosic wastes has gained global interest. Thermophilic digestion of horse manure based on straw was investigated using the upflow anaerobic solid-state (UASS) process. Increasing the organic loading rate from 2.5 to 5.5gvsL(-)(1)d(-)(1) enhanced the average methane production rate from 0.387 to 0.687LCH4L(-)(1)d(-)(1), whereas the yield decreased from 154.8 to 124.8LCH4kgvs(-)(1). A single-stage and two-stage process design showed almost the same performance. Compared to prior experiments at mesophilic conditions, thermophilic conditions showed a significantly higher efficiency with an increase of 59.8% in methane yield and 58.1% in methane production rate. Additional biochemical methane potential (BMP) tests with two types of horse manure and four different bedding materials showed that wheat straw obtained the highest BMP. The results show that the thermophilic UASS process can be the key to an efficient energy recovery from straw-based manures.

Anaerobic digestion of horse dung mixed with different bedding materials in an upflow solid-state (UASS) reactor at mesophilic conditions.

Aim of this study was to investigate the use of upflow anaerobic solid-state (UASS) digestion for treating horse manure. Biochemical methane potential (BMP) tests conducted for varying mixtures of dung (hay and silage feed) and bedding material (wheat straw, flax, hemp, wood chips) showed that straw mixed with hay horse dung has the highest potential of [Formula: see text] . Continuous mesophilic digestion was conducted for 238 days using a single-stage UASS reactor (27 L) and a two-stage UASS system with an anaerobic filter (AF, 21 L). Increasing the organic loading rate (OLR) from 2.5 to 4.5 g vs L(-1)d(-1) enhanced the methane rate of the single-stage reactor from 0.262 to 0.391 LL(-1)d(-1) while the methane yield declined from 104.8 to 86.9 L kg vs(-1). The two-stage system showed similar yields. Thus, for solid-state digestion of horse manure a single-stage UASS reactor appears sufficient.