Investigation of Pressed Solid Biofuel Produced from Multi-Crop Biomass

The paper presents the preparation and use of pressed solid biofuel of multi-crop plants (fibrous hemp (Cannabis sativa L.), maize (Zea mays L.) and faba bean (Vicia faba L.)) as mono, binary and trinomial crops. The results of the investigation show that three main chemical elements (carbon, oxygen and hydrogen) accounted for 93.1 to 94.9% of the biomass pellet content. The moisture content varied from 3.9 to 8.8%, ash content from 4.5 to 6.8% and calorific value from 16.8 to 17.1 MJ·kg−1. It was found that the density (DM) of all variants of pellets was very similar; the faba bean biomass pellets had the highest density of 1195.8 kg·m−3 DM. The initial ash deformation temperature (DT) of burning biomass pellets was detected, which varied from 976 to 1322 °C. High potassium (K), calcium (Ca) and phosphorus (P) concentrations were found in all types of biomass ash. The quantities of heavy metals in pellet ash were not large and did not exceed the permissible values according to Lithuanian legislation. These chemical properties of multi-crop biomass ash allow them to be used in agriculture for plant fertilization.

Development of double screw press and method of controlling the parameters of the briquetting process

Paper is focused on development of new patented construction of screw briquetting machine for compacting biomass into the solid biofuel. Developed machine design is based on achieved results of comprehensive research of the complicated process of biomass densification. Patented construction provides two main goals: the elimination of axial forces, which causes increasing of bearings lifetime, and a new modular design of pressing chamber and tools with geometry based on application of the mathematical model. Research of the biomass densification pointed to the need for modular design of densification machine, where it is possible to control all significant parameters of the densification process. The goal of this paper is to present a new patented design of screw press, which satisfies all requirements for modularity and control of the parameters. It allows optimizing this process for different types of raw materials and achieving high quality production. Results of experimental research of densification process then allow the engineering design of the production machine tailor-made to the customer, while being able to minimize investment, energy and operating costs. The developed design of screw press is unique in its modularity and high reliability.

Productivity of switchgrass (Panicum virgatum L.) agrophytocenoses for long-term use

Purpose. To determene the productivity of switchgrass (Panicum virgatum L.) agrophytocenoses under the long-term use. Methods. Field, statistical, calculation and comparative. Results. During long-term switchgrass cultivation, the lowest yield was obtained in the first vegetation year: 19.7 t/ha in the control treatment, 25.3 and 17.5 t/ha in the experimental treatments. The average raw biomass yield was as following: 30.3 t/ha in the control (variety ‘Cave-in-Rock’), 32.6 t/ha and 26.5 t/ha in the experimental treatments (varieties ‘Kanlow’ and ‘Morozko’, respectively). The yield of solid biofuel (17.3 t/ha) indicates the advantage of ‘Kanlow’ over the control (11.7 t/ha). The lowest yield (15.7 t/ha) was obtained from ‘Morozko’ variety. The energy yield over the treatments: 312.8 GJ/ha in the control, 397.5 and 367.2 GJ/ha in the experimental treatments, respectively. The cost of the grown production was as following: 416.03 UAH/t in the control (‘Cave-in-Rock’), 312.01 UAH/t in ‘Kanlow’, and 366.42 UAH/t in ‘Morozko’. The profitability of the control (‘Cave-in-Rock’) was 69.5%, ‘Kanlow’ – 101.4%, ‘Morozko’ – 66.8%. Economic evaluation of the productivity of switchgrass agrophytocenoses resulted in the following ranking: ‘Kanlow’, ‘Cave-in-Rock’, ‘Morozko’. When analyzing the energy equivalent of switchgrass biomass production and energy consumption, it was found that ‘Kanlow’ yielded 588.8 GJ/ha and the control – 468.3 GJ/ha, which is lower by 120.5 GJ/ha. Conclusions. The yield of switchgrass agrophytocenoses on average over the years of research (2014–2019) was 30.3 t/ha in ‘Cave-in-Rock’ (the control), 32.6 t/ha in ‘Kanlow’, and 26.5 t/ha in ‘Morozko’. The energy equivalent of the obtained yield was 468.3 GJ/ha in ‘Cave-in-Rock’ and 588.8 GJ/ha in ‘Kanlow’, which is by 120.5 GJ/ha higher than in the control.

Pine Wood and Sewage Sludge Torrefaction Process for Production Renewable Solid Biofuels and Biochar as Carbon Carrier for Fertilizers

This work presents the results of research on the thermo-chemical conversion of woody biomass–pine wood coming from lodzkie voivodship forests and sewage sludge from the Group Sewage Treatment Plant of the Łódź Urban Agglomeration. Laboratory scale analyses of the carbonization process were carried out, initially using the TGA technique (to assess activation energy (EA)), followed by a flow reactor operating at temperature levels of 280–525 °C. Both the parameters of carbonized solid biofuel and biochar as a carrier for fertilizer (proximate and ultimate analysis) and the quality of the torgas (VOC) were analyzed. Analysis of the pine wood and sewage sludge torrefaction process shows clearly that the optimum process temperature would be around 325–350 °C from a mass loss ratio and economical perspective. This paper shows clearly that woody biomass, such as pine wood and sewage sludge, is a very interesting material both for biofuel production and in further processing for biochar production, used not only as an energy carrier but also as a new type of carbon source in fertilizer mixtures.

Valorization of winery and distillery by-products by hydrothermal carbonization

This work aims at finding an alternative strategy to manage the waste generated by the winemaking industry to obtain a solid biofuel and phenolic compounds. The effect of temperature (180–260 °C), residence time (1–7 h), and biomass-to-liquid ratio (0.05–0.25) on the co-hydrothermal carbonization of vine pruning and exhausted grape pomace, by using vinasse as moisture source, is studied. The effect of the variables is investigated and optimized using the Box–Behnken design of response surface methodology to maximize mass yield, fuel ratio, energy densification yield and phenols extraction yield and to minimize energy consumption. The statistical analysis shows that the carbonization temperature is a crucial parameter of the process, decreasing the product yield on one hand and improving the quality of hydrochar on the other. At the optimal conditions (246.3 °C, 1.6 h, 0.066), an hydrochar yield of 52.64% and a calorific value of 24.1 MJ/kg were obtained. Moreover, the analysis of the H/C and O/C ratios of hydrochars demonstrates that carbonisation significantly improves the fuel properties of solid biofuel. Liquid by-products obtained from the HTC process are found to contain high concentrations of organic matter but the BOD/COD ratios suggest their potential valorization by biological methods.

Valorization of Hemp Stalk Waste Through Thermochemical Conversion for Energy and Electrical Applications

The presented research aimed at finding new ways to value hemp by-products (stalks) from the cannabidiol industry through thermochemical conversion. Chemical and elemental composition of hemp biomass was investigated by successive chemical extractions and Scanning Electron Microscopy along with Energy-dispersive X-ray Spectroscopy. Proximate and elemental analyses completed the chemical characterization of the hemp biomass and its biochar. Thermogravimetric analysis of the hemp biomass allowed to understand its kinetic of decomposition during thermal conversion. The carbon structure and porosity of the biochar were assessed by Raman spectroscopy and CO2 gas adsorption. Properties of interest were the energy production measured through calorific values, and the electrical conductivity. Two ways of valorisation of the hemp biomass were clearly identified, depending mainly on the chosen pyrolysis temperature. Hemp biochar carbonized at 400–600°C were classified as lignocellulosic materials with a good potential for solid biofuel applications. Specifically, the resulting carbonized biochar presented low moisture content (below 2.50%) favourable for high fuel quality, low volatile matter (27.1–10.4%) likely to show lower particle matter emissions, limited ash content (6.8–9.8%) resulting in low risk of fouling issues during the combustion, high carbon content (73.8–86.8%) suggesting strong energy density, associated with high higher heating values (28.45–30.95 MJ kg−1). Hemp biochar carbonized at 800–1000 °C displayed interesting electrical conductivity, opening opportunities for its use in electrical purposes. The electrical conductivity was related to the evolution of the biochar microstructure (development of graphite-like structure and changes in microporosity) in regard with the thermochemical conversion process parameters. Graphical abstract