Characteristics of Hydrochar and Liquid Products Obtained by Hydrothermal Carbonization and Wet Torrefaction of Poultry Litter in Mixture with Wood Sawdust

Abstract

Poultry farms with floor-standing poultry generate large amounts of poultry litter waste. The direct application of this waste as an organic fertilizer does not ensure sustainable and cost-efficient utilization of all waste fractions, and can also be linked to environmental hazards. Therefore, the development of new technologies is required for processing poultry litter into a safe product with higher added value. In this work, the characteristics of activated carbon derived from hydrochar, along with the liquid products obtained from hydrothermal carbonization (HTC) and the wet torrefaction (WT) of poultry litter, were investigated. Poultry litter (PL) was applied in a mixture with sawdust (SD) in the following ratios: 1:0 (PL/SD 1:0), 1:1 (PL/SD 1:1), 1:2 (PL/SD 1:2), and 2:1 (PL/SD 2:1). WT processing took place in an innovative fluidized bed system in a superheated steam medium with low overpressure (less than 0.07 MPa) at 300 °C and 350 °C for 30–45 min. Conventional HTC processing was performed in a water medium at 220 °C for 1–4 h. The hydrochar produced in the experiments was activated with steam for 1 h at 450–750 °C. The porosity characteristics of activated hydrochar were measured, including pore size, pore volume, and specific surface area, in view of potential industrial applications as an adsorbent. Additionally, the contents of 5-hydroxymethylfurfural (HMF), as high-value product, were determined in the liquid products obtained from HTC processing, as well as in the condensate obtained after WT processing. Specific surface areas of the activated hydrochars may still be too low for application as adsorbent material. Hence, its use as a biofertilizer and soil improver should be preferred. Interestingly, the liquid fraction obtained from the innovative WT process displayed a significantly higher 5-HMF content compared to the conventional HTC process.

Management of Agri-Food Waste Based on Thermochemical Processes towards a Circular Bioeconomy Concept: The Case Study of the Portuguese Industry

“…In addition to affecting yield, higher temperatures can lead to higher surface areas [4]. The degree of aromatisation of hydrochars is also affected by the HTC temperature [4] because the hydrochars produced contain higher amounts of oxygen functional groups and lower levels of aromatisation, which enables further chemical activation [107]. HTC is a relatively slow process, as the residence time varies from a few hours to several days.…”

Superheated Steam Torrefaction of Biomass Residues with Valorisation of Platform Chemicals—Part 1: Ecological Assessment

“…Beside water, the condensable volatile fraction contains valuable chemical substances (e.g., furfural, acetic acid, methanol, formic acid) that can be used as platform chemicals [19]. In this regard, the use of superheated steam as torrefaction agent is very interesting because it allows for a fast and uniform process and an easy recovery of volatiles [20][21][22]. In addition, the condensation heat can be recovered in order to make the whole process more energy efficient.…”

Study on the Effect of Hydrothermal Carbonization Parameters on Fuel Properties of Chicken Manure Hydrochar

“…Ways of chicken waste disposal or management include: a) anaerobic digestion, for the management of chicken manure (CM), offers advantages including odor removal, carbon neutral biofuel, production of organic fertilizer in the form of liquid digestate byproduct that contributes to tackling global warming and climate change; b) composting: as an alternative way of CM management to serve as organic fertilizer for crops, of which the content of pure nitrogen (N), potassium (K2O) and phosphorus (P2O5) are about 1.63, 0.085, and 1.54%, respectively; c) combustion: as a process to offer an energy recovery from CM, combustion is often used to power incineration facilities; d) direct land spreading: the application of CM in the form of direct spread on land as a fertilizer for crops [10,11].…”