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• Microwave and conventional pyrolysis of fuels with different geological age were compared. • Yield of solid pyrolysis products grows with increase in fuel geological age. • Conventional pyrolysis is preferable for producing high-calorie carbonaceous residues. • Microwave pyrolysis results in obtaining high-calorie gaseous products for all fuel types. • Gaseous products of microwave pyrolysis contains low CO 2 component (<10 %). The growth in anthropogenic impact on the environment caused mainly by energy activities and combustion of traditional fossil hydrocarbon sources necessitates the search for alternative energy generation technologies. Thermal processing of organic raw materials allows obtaining energy valuable products with less environmental impact. However, it strongly depends on the mechanism of thermal effect on the raw material and its characteristics. This paper compares two types of pyrolysis, including conventional one with heating of the entire reactor volume and microwave one with local impact of electromagnetic waves on the sample, for fuels with different degree of metamorphism. Comparative experiments indicate that the yield of high-calorie carbonaceous residue rises with an increase in geological age of fuels for both pyrolysis types, while the amount of solid products for conventional pyrolysis is 1.2–2.6 times higher than for microwave one. In its turn, regardless of the degree of metamorphism, microwave pyrolysis demonstrates advantages from the position of obtaining high-calorie gaseous products (from 18.6 to 28.0 MJ/m3) with low CO 2 component ballast (<10 %). Such fundamental differences are due to the nature and speed of ongoing thermal reactions. The presented results can serve as a basis for choosing the method of processing of organic raw materials depending on the intended purpose of the final products. [ABSTRACT FROM AUTHOR]

• Separation by sedimentation allows one to extract valuable fuel from high-ash biomass. • A peat fraction of less than 1800 kg m−3 is comparable with brown coals. • Mineral part of heavy peat fraction (over 1800 kg m−3) is connected with organic matter. • The addition of heavy peat fraction during the plant biomass combustion prevents slagging. Peat belongs to the slowly renewable biomass resources, therefore its use as an energy source helps to reduce the negative impact on the environment. However, its use in the energy sector is gradually decreasing due to high operating costs because of the characteristics of peat. The aim of this work is a comprehensive study of the peat characteristics and the development of recommendations for its effective use. In this paper, we consider the widespread methods for studying fuel (thermo-technical and fusibility characteristics determination, X-ray fluorescence and phase methods), as well as the original approach of separation by sedimentation in liquids of various densities. The peat separation by sedimentation in liquids of various densities made it possible to obtain a low-ash peat fraction comparable in characteristics to brown coals and a highly mineralized fraction (heavy fraction). On the example of grain processing waste, it is shown that the addition of a 5% of heavy peat fraction to bran prevents the formation of strong slag deposits and can be recommended for co-burning. This allows us to consider the separation by sedimentation in liquids of various densities as an effective tool for using highly mineralized types of biomass in energetic sector. [ABSTRACT FROM AUTHOR]

Involving biomass in the energy sector is a way to replace fossil fuels with renewable and CO 2 -neutral raw materials, reducing the negative impact on the environment. The energy application of agro-industrial waste is of particular interest, allowing one not only to obtain biofuel, but also to utilize by-products. The present work considers pine nut shells from a candy factory in relation to microwave processing into solid and gaseous fuels. The aim is to study the features of pine nut shells microwave pyrolysis, including the initiation mechanism and process behaviour, as well as the composition and characteristics of the resulting products. The study included experimentation in combination with application of high-speed video recording of the process and gas analysis, study of dielectric characteristics of raw materials, proximate and ultimate analysis of the obtained solid and gaseous products. At microwave pyrolysis, the conversion degree into liquid and gaseous products (76.9%) is much higher than, for example, at slow fixed bed pyrolysis (65.5%). The radiation absorption by the sample is nonlinear throughout the process and increases during the organic part degradation with the appearance of liquid and gaseous products. The gas obtained at microwave processing has a low ballast (share of CO 2 =3.5%) and a high hydrogen content (share of H 2 =19.3%) that results in a high heat of combustion (21.8 MJ·m−3), which is probably connected with interaction of pyrogenetic water and fuel carbon during plasma-chemical reactions. • Microwave pyrolysis of pine nut shells is caused by electric discharges. • Microwave radiation absorption by pine nut by shells is nonlinear over process time. • Microwave radiation absorption grows with increasing the yield of volatile products. • Interaction of pyrogenetic water and carbonaceous residue leads to high H 2 content. • Pyrolysis gas has a high heat of combustion (21.8 MJ·m–3) and low CO 2 content (< 3.5%). [ABSTRACT FROM AUTHOR]