Abstract

To date, few studies on the potential utilization of agricultural residue torrefaction products have been performed. Thus, torrefaction product characterization aimed at its potential utilization was performed. Wheat-barley straw pellets and wheat-rye chaff were used in the study. The impact of the torrefaction temperature (280-320 °C) on polycyclic aromatic hydrocarbons (PAHs) content in the biochar and noncondensable gas (noncondensables) composition was investigated. The impact of the torrefaction time (30-75 min) on the composition of the condensable volatiles (condensables) and their toxicity were also studied. The torrefaction process was performed in a batch-scale reactor. The PAH contents were measured using HPLC, and the noncondensables composition was measured online using a gas analyzer and then GC-FID. The condensables composition and main compound quantification was determined and quantified using GC/MS. Three toxicity tests, for saltwater bacteria (Microtox® bioassay), freshwater crustaceans (Daphtoxkit F magna®) and vascular plants (Lemna sp. growth inhibition test), were performed for the condensables. The PAHs content in the biochar, regardless of the torrefaction temperature, allows them to be used in agriculture. The produced torgas shall be co-combusted with full-caloric fuel because of its low calorific value. Toxic compounds (furans and phenols) were identified in the condensable samples, and regardless of the process time, the condensables were classified as highly toxic. Therefore, they can be used either as pesticides or as an anaerobic digestion substrate after their detoxification.

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