Proof-of-Concept of Spent Mushrooms Compost Torrefaction—Studying the Process Kinetics and the Influence of Temperature and Duration on the Calorific Value of the Produced Biocoal

Abstract

Poland, being the 3rd largest and growing producer of mushrooms in the world, generates almost 25% of the total European production. The generation rate of waste mushroom spent compost (MSC) amounts to 5 kg per 1 kg of mushrooms produced. We proposed the MSC treatment via torrefaction for the production of solid fuel—biocoal. In this research, we examined the MSC torrefaction kinetics using thermogravimetric analyses (TGA) and we tested the influence of torrefaction temperature within the range from 200 to 300 °C and treatment time lasting from 20 to 60 min on the resulting biocoal’s (fuel) properties. The estimated value of the torrefaction activation energy of MSC was 22.3 kJ mol−1. The highest calorific value = 17.9 MJ kg−1 d.m. was found for 280 °C (60 min torrefaction time). A significant (p < 0.05) influence of torrefaction temperature on HHV increase within the same group of torrefaction duration, i.e., 20, 40, or 60 min, was observed. The torrefaction duration significantly (p < 0.05) increased the HHV for 220 °C and decreased HHV for 300 °C. The highest mass yield (98.5%) was found for 220 °C (60 min), while the highest energy yield was found for 280 °C (60 min). In addition, estimations of the biocoal recirculation rate to maintain the heat self-sufficiency of MSC torrefaction were made. The net quantity of biocoal (torrefied MSC; 65.3% moisture content) and the 280 °C (60 min) torrefaction variant was used. The initial mass and energy balance showed that MSC torrefaction might be feasible and self-sufficient for heat when ~43.6% of produced biocoal is recirculated to supply the heat for torrefaction. Thus, we have shown a concept for an alternative utilization of abundant biowaste (MSC). This research provides a basis for alternative use of an abundant biowaste and can help charting improved, sustainable mushroom production.

Torrefaction of Straw from Oats and Maize for Use as a Fuel and Additive to Organic Fertilizers—TGA Analysis, Kinetics as Products for Agricultural Purposes

“…It should be borne in mind that the calculated kinetic triplet is only the optimal mathematical fit of the equation to the experimental data and has no strict physical significance (reaction order) in this case. The activation energy calculated in this way is apparent: it only serves to correlate the model with the experimental data and has no meaning as in the definition [32]. It was also concluded that the methods of kinetic analysis using various heating rate results were more efficient than the method involving a single heating rate [2].…”

A Review of Biochar Properties and Their Utilization in Crop Agriculture and Livestock Production

“…Syguła et al [20] used mushroom spent compost as a feedstock material subject to torrefaction at a similar temperature and time range (200 to 300 • C, 20-60 min). The research was focused mainly on the evaluation of torrefaction kinetics, but it is another example of "waste-to-carbon" strategy, showing that wastes of different origin can be successfully turned into a valuable resource.…”

Waste to Carbon: Biocoal from Elephant Dung as New Cooking Fuel

“…In this work, the E a and the reaction rate constants were determined in isothermal conditions and a temperature range of 200-300 • C. The same conditions and temperatures were used previously by Pulka et al [56], who tested sewage sludge (SS) with high ash content, and Syguła et al [57] who tested spent mushroom compost (MSC). The E a for torrefaction process of elephant dung was 18 kJ•mol −1 , and k values were increasing with process temperature from 1.16 × 10 −5 •s −1 to 2.73 × 10 −5 •s −1 (from 200 to 300 • C), respectively.…”