Calorific Value and Ash Content of Extracted Birch Bark

Abstract

Wood bark is one of the main residues in the forest industry worldwide. Currently, the bark is used to produce process heat and energy. A major amount of this is mainly used in power and heating plants. Due to the fact that the demand for heating energy is seasonal, the storage of bark is necessary. The storage process of bark and therefore related problems (like biomass loss, increase of ash content etc.) were discussed in previous studies. Different approaches to increase the economic and ecologic value of wood bark through gaining extractives from the bark were investigated in order to revalue this by-product as well. This study shows the change in calorific value and ash content of birch bark based on results of ultrasound-assisted extraction (UAE). Regarding the energy content (gross calorific value), a comparison was made that showed that due to the extraction process, the energy content of the birch bark is decreased. The extraction yield of the methanol extracts results as 17.74%. The total phenolic content (TPC) of this extract was 447.75 mg GAE/g of oven-dried bark extracts. The amount of ash increased by 23.74% after the extraction. The gross calorific value of the birch bark decreased by 6.98%. The calculated energy content decreased from 2.48 MWh/m3 before extraction to 1.61 MWh/m3 after extraction, which is a loss of 35.08%. The obtained results show that through the extraction of birch bark via ultrasound-assisted extraction, valuable substances can be produced. At the same time, the ash content of extracted birch bark increased whereas the energy content decreased.

Assessment of Bark Properties from Various Tree Species in Terms of Its Hydrophobicity and Energy Suitability

“…Among the obtained results, the most calorific material was Silver Birch bark. A similar higher heating value content for this species was obtained in other studies (HHV = 22.21 MJ•kg −1 ) [75]. Similarly, the value of the higher heating value of Scots Pine bark is comparable to other data available in the literature (HHV= 19.70 MJ•kg −1 [30], HHV= 19.94 MJ•kg −1 [73]).…”

“…Among the examined species of deciduous trees, the lowest ash content was found in Silver Birch bark. A similar relationship was also observed in other studies [75], where a deficient level of ash content distinguished the species compared to other deciduous species.…”

“…As stated by Hosseinpour et al [100], HHV is an essential indicator of the quality of biomass fuels because it shows their thermochemical properties, and knowledge of this value is necessary for the proper design and operation of effective biomass thermal conversion systems. Gruber [75], based on his own and others' research [30,101], indicated that significant differences in the structure and chemical composition of bark relative to wood make it a much more calorific material (e.g., due to a higher content of fatty acid esters and lignin). Its higher heating value may be in the range of 21-24 MJ•kg −1 .…”

The Use of Black Pine Bark for Improving the Properties of Wood Pellets

“…Szyszlak-Bargłowicz et al [31] reported the low calorific value of bark pellets due to the high ash content and loss of volatiles during drying, while other researchers [10,[32][33][34][35] reported higher calorific values for bark than for wood. Generally, the calorific value of dry bark amounts to 17,000-22,000 kJ kg −1 (4.7-6.1 kWhkg −1 ) and is comparable to that of dry wood [36]. Kamperidou et al [35] reported that the incorporation of bark of some fast-growing hardwood species (pseudoacacia, poplar, ailanthus, and paulownia) to the feedstock of the same species of wood material significantly increased the calorific value of the produced biofuels and that optimized wood-bark ratios could result in biofuels of low ash content and adequate quality for both commercial (residential and industrial) applications.…”

A Qualitative Assessment of the Specific Woody Biomass of Fruit Trees

“…Reis Portilho et al [11] investigated the potential of briquette produced by torrefying agroforestry biomass to generate energy, reporting that torrefaction and briquetting increased the energy potential of the biomasses. Gruber et al [12] established the calorific value and ash content of extracted birch bark, concluding that the higher the ash content of extracted birch bark, the lower the energy content.…”