The product of thermochemical processing of lignocellulosic biomass is biochar. It has a range of properties that make it suitable for a variety of economic applications. However, during pyrolysis and torrefaction, volatile organic compounds (VOCs) are released and may redeposit on the surface of the biochar. Some of these compounds may be harmful to the environment and humans. Bibliometric study shows that, to date, studies on the release of VOCs from biochar have been of an inventory nature and concerned with specific case studies of the specific types of biomass. To date, there has been no comprehensive and systematic analysis of the influence of lignocellulosic biomass properties and pyrolysis/torrefaction process parameters on VOC formation and redeposition on biochar. In this paper, the analysis is presented of the potential harmfulness of VOCs released during the thermochemical processing of lignocellulosic biomass components, based on cellulose, hemicellulose, and lignin pyrolysis/torrefaction chemistry data. 10 volatile organic compounds from cellulose, hemicellulose, and lignin pyrolysis were identified as potentially harmful due to the following properties: carcinogenicity, toxicity, flammability, skin corrosion/irritation, eye irritation, and mutagenicity, with different degrees of harmfulness. Additionally, the VOCs identified on biochar samples show a potential hazard. Among 140 identified compounds, 33 of them had harmful properties. Therefore, the redeposition on biochar of ketones, aldehydes, cyclic and aromatic hydrocarbons including polyaromatic hydrocarbons, and their derivatives, esters, and furans may lead to environmental contamination due to their release from biochar. A new niche for systematic research on the development of new knowledge regarding the biochars produced from biomass as a source of pollutant emission has been identified.

The use of residual forms of biomass, resulting from processes of transformation of the agri-food and/or forest industries, presents itself as an alternative with high potential for energy recovery, given the existing availability, both from the perspective of quantities, but also from the perspective of geographic distribution. In this work, samples of four by-products originating from the agri-food industry were collected, namely coconut shells, sugarcane bagasse, cashew nutshells, and palm kernel shells, which were characterized in the laboratory by determining their Thermogravimetric and Elemental analysis, subsequently calculating the High Heating Value, Low Heating Value, Hardgrove Grindability Index, Mass Yield, Energy Yield, and Energy Densification Ratio. The values obtained show the potential to optimize logistical operations related to transportation, demonstrating that energy densification operations, especially if associated with physical densification processes, enable the use of these residual forms of biomass in the replacement of fossil fuels, such as coal.

Torrefaction is known to reduce the logistical costs of biomass. Torrefied biomass’ prospects as feedstock for fermentation to liquid biofuel are largely unknown. This study investigated the interactions of torrefaction and alkaline pretreatment of wheat straw on glucose yields from enzymatic hydrolysis, including treatment order and the potential for pH to play a role in the process. Across a range of torrefaction severities with temperatures of 200 °C, 220 °C, and 240 °C and durations of 20, 40, and 60 min, torrefaction had a negative impact on glucose yield of wheat straw with or without alkaline pretreatment and regardless of the order of alkaline pretreatment. Alkaline pretreatment after torrefaction results in higher glucose yield than alkaline pretreatment before torrefaction, or by torrefaction alone. Hence, there is the prospect for adding logistical benefits of torrefaction to the bioethanol system if alkaline pretreatment is coupled with torrefaction. Decreasing trend in pH with increase in torrefaction severities was observed for trials without buffer, indicating chemical changes causing the decrease in pH might be associated with the reduction in yield.

Two dedicated biomass crops, shrub willow (Salix sp.) and miscanthus (Miscanthus giganteus), were evaluated for their ability to remove lead from contaminated water, both in raw ground form and after pretreatment by torrefaction or alkaline treatment. Sorption capacity experiments were conducted using a contaminant concentration that ranged from 1 mg to 15 mg per L and a biomass loading rate of 0.05 g biomass per mL. The results indicated that sorption capacities for the two feedstocks ranged from 0.15 mg to 0.26 mg of lead removed per gram of biomass, and the percentage of removal ranged from 54.3% to 93.6%. The sorption capacity of willow tended to decrease as particle size increased. Increasing torrefaction severity increased the sorption capacity of miscanthus, and alkaline treatment also increased the sorption capacity of miscanthus. The Langmuir isotherm, when fitted to measured data, characterized the samples’ sorption performance with a Mean Absolute Error (MAE) of 0.0014 mmol g-1.