Pruning residues belong to the agricultural wastes generated in the agro-food processing sector, whose energetic potential can have a significant influence on the local energy market. This study is focused on the assessment of the feasibility of using apple tree pruning residues in the form of bales for energetic purposes. The research was performed in a commercial apple orchard located in the central-western part of Poland, an area characterized by the largest concentration of apple orchard in Europe. The biomass yield, pruned bales quality, energy input and output flow, as well as the economic sustainability of the pruning-to-energy strategy were evaluated. The results indicated the available collected biomass potential in an amount of 0.69 t DM ·ha −1 per year. Pruned biomass analysis showed a moisture content of 45.1% in the fresh material, the ash content was 0.8% dry mass, and the lower heating value was 18.05 MJ·kg −1 dry mass. Total production cost, including all steps and avoided cost of mulching, was 74.7 €·t −1 dry mass. Moreover, the net energy balance of this value chain was very positive, giving a value of ca. 12,000 MJ·ha −1 per year. As a result, the yearly harvested pruned biomass may be considered a good energy source for local heating systems.

The annual potential of waste biomass production from food processing in Europe is 16.9 million tonnes. Unfortunately, most of these organic wastes are utilized without the energy gain, mainly due to the high moisture content and the ability to the fast rotting and decomposition. One of the options to increase its value in terms of energy applications is to valorize its properties. Torrefaction process is one of the pre-treatment technology of raw biomass that increases the quality of the fuel, especially in the context of resistance to moisture absorption. However, little is known about the influence of torrefaction temperature on the degree of valorization of some specific waste biomass. The aim of this paper was to analyze the influence of the temperature of the torrefaction on the hydrophobic properties of waste biomass, such as black currant pomace, apple pomace, orange peels, walnut shells, and pumpkin seeds. The torrefaction process was carried out at temperatures of 200 °C, 220 °C, 240 °C, 260 °C, 280 °C, and 300 °C. The hydrophobic properties were analyzed using the water drop penetration time (WDPT) test. The torrefied waste biomass was compared with the raw material dried at 105 °C. The obtained results revealed that subjecting the biomass to the torrefaction process improved its hydrophobic properties. Biomass samples changed their hydrophobic properties from hydrophilic to extremely hydrophobic depending on the temperature of the process. Apple pomace was the most hydrophilic sample; its water drop penetration was under 60 s. Black currant and apple pomaces reached extremely hydrophobic properties at a temperature of 300 °C, only. In the case of orange peels, walnut shells, and pumpkin seeds, already at the temperature of 220 °C, the samples were characterized by severely hydrophobic properties with a penetration time over 1000 s. At the temperature of 260 °C, orange peels, walnut shells, and pumpkin seeds reached extremely hydrophobic properties. Furthermore, in most cases, the increase of torrefaction temperature improved the resistance to moisture absorption, which is probably related to the removal of hydroxyl groups and structural changes occurring during this thermal process.

This paper presents a series of economic efficiency studies comparing three different investment variants: without energy storage, with energy stored in batteries and hydrogen installation with a PEM fuel cell stack for a location in Poland. To reach a target, the current solar potential in Poland, the photovoltaic (PV) productivity, the capacity of the energy storage in batteries as well as the size of the hydrogen production system were calculated. The solar potential was determined using archival meteorological data and the Krieg estimation method. A laboratory scale PV system (1 kW) was used to estimate the decrease in real solar installation power during the last 10 years of operation. All analyses were made for a 100 kW photovoltaic array located in Poland using static and dynamic methods of investment project assessment, such as Simply Bay Back Period (SPBP) or Net Present Value (NPV). The results showed that the SPBP amounted to 8.8 years and NPV 54,896 € for non-storage systems. Whereas, for systems with energy stored the economic indexes were, as follow: SPBP = never, NPV = 183,428 € for batteries and SPBP = 14.74 years, NPV = 22,639 € for hydrogen/fuel cell installation. Storage in hydrogen is more advantageous than batteries due to the smaller investment outlays.

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).

Sustainable development is one of the fundamental and most important objectives of the worldwide policy. The conducted research shows that sustainable development (SD) is increasingly important in the consciousness of the EU countries, which can be viewed through a prism of the undertaken projects. This paper raises the issue of clusters and their significance in the development of a sustainable economy. The article explores trends in the European Union policy related to sustainable development and clusters. The purpose of this study is to find an answer to the following questions: How can clusters contribute to sustainable development and what are the key factors that ensure this process? To achieve the goal of the article a systematic study of the literature and reports was carried out. Moreover, the analysis of the activity of European clusters in the context of sustainable development was performed. Next, the examples of cluster projects focused on sustainable development were presented. It was shown that the clusters contribute a smarter and sustainable development by succeeding in technological and scientific results, developing new technologies for emerging industries, creating new business activities, enticing major technology companies, and connecting local firms into world-class value systems. Furthermore, the clusters participate actively in sustainable development as they promote knowledge creation, joint learning, technology transfer, as well as collaboration, and sustainable innovations. Finally, clusters facilitate the sustainable upgrading of small and medium enterprises and encourage the participation of stakeholders in the process of sustainable development.