In this paper, the differences in mechanical strength tested during the static tensile and compression test of Scots pine (Pinus sylvestris L.), European larch (Larix decidua) and Norway spruce (Picea abies) wood exposed to continuous soaking in water with a salinity of 7‰ were determined. The value of salinity corresponded to the average salinity on the Polish Baltic coast. This paper also aimed to examine the content of mineral compounds absorbed during four cycles of two weeks each. The essence of the statistical research was to identify the effect of the mineral range compounds and salts depending on the mechanical strength of the wood. Based on the results of the experiments, it can be concluded that the medium used has a specific effect on the wood species’ structure. The effects of soaking on the wood parameters depend obviously on the type of wood. A tensile strength test of pine, as well as the tensile strength other species, was enhanced by incubating it in seawater. A native sample’s initial mean tensile strength was 82.5 MPa, which increased to 94.8 MPa in the last cycle. It was found that the larch wood had the lowest tensile strength difference (9 MPa) of the woods studied in the current study. Four to six weeks of soaking was necessary to notice an increase in tensile strength.

The aim of this article is to show how the situation of domestic biofuels in Poland and the alternative fuels sector is changing. On the basis of our own research and the available literature, changes in the production potential of Poland in the field of alternative fuels/biofuels are examined. Moreover, the reasons for changes in the production structure are analyzed. The flexibility of production potential to changes in legal conditions is assessed, and the value of sectors and their future are determined. This paper discusses legal and market aspects related to selected renewable energy sources used in Polish transport. Based on a review of literature and statistical data, the production and use of methyl esters and bioethanol are characterized in detail. Analysis of legal regulations enables the presentation of targets regarding renewable energy source (RES) use in transport by 2030. The results of studies conducted in 2020 are discussed with regard to the value (attractiveness) of methyl esters, bioethanol, electromobility and liquid bio-hydrocarbons, and these are compared and contrasted with the result from earlier years since 2010.

The paper discusses issues related to the sectors of biofuels for transport. Development directions of those sectors and factors limiting the growth rate thereof are analysed. At present, researchers’ attention is increasingly focused on development of the alternative fuels sector. Moreover, issues related to waste used in the sector of alternative fuels are now among the leading undertakings of environmental engineering. The authors have analysed the potential of biofuels sectors in Poland taking into account the EU’s legislative requirements. The paper contains a discussion of the sector of esters, liquid biofuels, sector of lignocellulose, sector of liquid bio-hydrocarbons and, additionally, pays attention to the sector of electromobility as one of the most attractive and prospective sectors in terms of emission reduction.

Convective drying is the most common drying method, and mathematical modelling of the dewatering process is an essential part of it, playing an important role in the development and optimization of drying devices. Modelling of the leek drying process can be difficult as the specific structure of this vegetable, in which the slices of leek are delaminated into uneven single rings at different times during drying and the material surface changes more than in other vegetables. This study aimed at proposing a theoretical model for leek convective drying, based on the theoretical laws of heat and mass exchange, which should take into account the observed random process disturbances in the form of random coefficients of this model. The paper presents a non-linear model of water content changes with a random coefficient n. Values of the coefficient n, which were considered to be a random variable, were obtained using the Monte Carlo method, using the inversed distribution function as a probabilistic method. The non-linear model of water content changes when a random n coefficient gives a good approximation of the measurements of water content changes to approximately 1–2 kg H₂O/kg d.m.

The objective of this paper was to create a mathematical model of vacuum drops in a form that enables the testing of the impact of design parameters of a milking cluster on the values of vacuum drops in the claw. Simulation tests of the milking cluster were conducted, with the use of a simplified model of vacuum drops in the form of a fourth-degree polynomial. Sensitivity analysis and a simulation of a model with a simplified structure of vacuum drops in the claw were carried out. As a result, the impact of the milking machine’s design parameters on the milking process could be analysed. The results showed that a change in the local loss and linear drag coefficient in the long milk duct will have a lower impact on vacuum drops if a smaller flux of inlet air, a higher head of the air/liquid mix, and a higher diameter of the long milk tube are used.

Ze względu na rosnące zapotrzebowanie na energię elektryczną celowe wydaje się poszukiwanie i wykorzystanie nowych źródeł energii odnawialnej. Biomasa jest najszerzej