Alternative Fuels from Forestry Biomass Residue: Torrefaction Process of Horse Chestnuts, Oak Acorns, and Spruce Cones

Abstract

The global energy system needs new, environmentally friendly, alternative fuels. Biomass is a good source of energy with global potential. Forestry biomass (especially wood, bark, or trees fruit) can be used in the energy process. However, the direct use of raw biomass in the combustion process (heating or electricity generation) is not recommended due to its unstable and low energetic properties. Raw biomass is characterized by high moisture content, low heating value, and hydrophilic propensities. The initial thermal processing and valorization of biomass improves its properties. One of these processes is torrefaction. In this study, forestry biomass residues such as horse chestnuts, oak acorns, and spruce cones were investigated. The torrefaction process was carried out in temperatures ranging from 200 °C to 320 °C in a non-oxidative atmosphere. The raw and torrefied materials were subjected to a wide range of tests including proximate analysis, fixed carbon content, hydrophobicity, density, and energy yield. The analyses indicated that the torrefaction process improves the fuel properties of horse chestnuts, oak acorns, and spruce cones. The properties of torrefied biomass at 320 °C were very similar to hard coal. In the case of horse chestnuts, an increase in fixed carbon content from 18.1% to 44.7%, and a decrease in volatiles from 82.9% to 59.8% were determined. Additionally, torrefied materials were characterized by their hydrophobic properties. In terms of energy yield, the highest value was achieved for oak acorns torrefied at 280 °C and amounted to 1.25. Moreover, higher heating value for the investigated forestry fruit residues ranged from 24.5 MJ·kg−1 to almost 27.0 MJ·kg−1 (at a torrefaction temperature of 320 °C).

Kinetic Parameters of Nut Shells Pyrolysis

“…The impact of thermal processing on the physicochemical properties of many popular types of biomass is known. The studies about biomass torrefaction and pyrolysis [10][11][12][13][14][15] showed that the higher temperature of the biomass processing improves its thermal properties. The biochar is characterized by higher heating value, lower moisture content, lower volatile matter content, and improved hydrophobicity.…”

“…The biochar is characterized by higher heating value, lower moisture content, lower volatile matter content, and improved hydrophobicity. The torrefied biomass is initially sterile and much more resistant to decay, and therefore it can be stored for a longer time [11]. As it is known, the first stage in thermal processes is dehydration.…”

Medical Peat Waste Upcycling to Carbonized Solid Fuel in the Torrefaction Process

“…It takes place at 200-320 • C in the absence of oxygen. Solids are the main process products [22]. The pyrolysis also takes place in the absence of oxygen but at temperatures over 320 • C. As a result, depending on pyrolysis conditions main products are liquid, gas, or solid; nevertheless, amounts of solids obtained from pyrolysis always are lower than from torrefaction.…”

Chestnut-Derived Activated Carbon as a Prospective Material for Energy Storage

“…Activated carbons derived from various types of chestnuts were also investigated for several other applications [ 9 , 10 , 39 , 40 , 41 , 42 , 43 ]. For instance, chestnut shells served as a raw material for the preparation of biochar with high calorific value as a potential fuel [ 39 ].…”

“…Chestnut cupulae was used by Kar et al for the preparation of bio-oil, serving as fuel or chemical feedstock [ 40 ]. Dyjakon et al studied forest biomass containing horse chestnuts as an alternative fuel [ 41 ]. Biochar from chestnut shells supported with carbon nanotubes was examined as an adsorbent for heavy metals contaminants by Yang et al [ 9 ].…”