The aim of the conducted research was to obtain information on the main components of ashes from 35 biomass species used in combustion processes to obtain reference data for the development of utility possibilities for these ashes, with particular emphasis on agricultural use. The examined biomass samples were divided into groups depending on origin: woody biomass and energetic woody plants I-WWB, herbaceous and grassy energy plants II-EC, agricultural waste III-AR, forest waste IV-FR and waste from the agri-food industry V-AFIW. The analysis of the studied elements contents was carried out in the designated groups. The chemical composition of ash was dominated by the macroelements Ca, K, P and S, which suggests the possibility of their agricultural use. At the same time, the low content of toxic elements such as As and Pb should not be a limiting feature in their use, with the exception of wood biomass. In addition, ashes obtained from the biomass combustion were enriched with microelements such as Zn, Cu and Mn, which further increases their possibilities of fertilizer use. The potential use of ash from each type of biomass in the aspect of its chemical composition should be considered individually, regardless of the division into groups depending on the origin of biomass.

Aquaculture wastewater contains a huge amount of substances that can cause environmental pollution. However, microalgae can absorb these compounds and convert them into useful biomass. In this study, Chlorella minutissima was grown in the wastewater resulting from saline aquaculture. The microalgae were found to effectively utilize nitrogen and phosphorus in the wastewater for its growth. During wastewater treatment, the cell density increased almost fivefold compared to the initial value (OD₆₈₀ 0.502). Moreover, batch culture resulted in the maximum biomass concentration and productivity of 4.77 g/L and 0.55 g/L/day, respectively. The contents of total nitrogen and total phosphorus in wastewater decreased by 88% and over 99%, respectively. In addition, the content of N-NO₃ was reduced by 88.6%, N-NO₂ by 74.3%, and dissolved orthophosphates (V) by 99%. At the beginning and throughout the experiment, the content of N-NH₄ in wastewater remained below 0.05 mg/L. Furthermore, a high lipid content of 46.4% (w/w) was also obtained from the studied microalgae.

Taking into consideration the fact that used oils are considered hazardous and extremely toxic, their subsequent use creates a real threat to the environment. The only effective measure for protecting the natural environment from used oil contamination is collection and controlled utilization. Only appropriate used oil management can guarantee minimal environmental contamination and prevent its irreversible degradation. The aim of our study was to determine the content of select heavy metal elements in used engine oils originating from agricultural tractors and agricultural machines of varying mileage. The tests were carried out by using the HD XRF method. The researched samples showed a high content of zinc remaining at 726- 1,389 mg·kg^-1. The contents of molybdenum, iron, and copper also were high, at Mo 360-689 mg·kg^-1, Fe 16.5- 267 mg·kg^-1, and Cu 4.63-76.87 mg·kg^-1. Low nickel, manganese, chromium, and lead contents were found in the ranges: Ni 0.14-0.75 mg·kg^-1, Mn 0.41-4.27 mg·kg^-1, Cr 0.36-10.66 mg·kg^-1, and Pb 0.9-13.71 mg·kg^-1. Mercury and cadmium were not found in the tested oils.

This paper presents the results of the evaluation of the energy potential of waste from the process of drying corn grain in the form of corn cobs, damaged grains, corn grain husks, and mixtures of starting materials. A technical and elementary analysis was performed for the biomass under investigation. The elemental composition of ash and the tendencies for slagging and boiler slagging were determined, and the emission factors were estimated based on the elemental analysis performed. The tests showed the highest calorific value among the starting materials for corn cobs (CCs) (14.94 MJ·kg⁻¹) and for the mixture of corn cobs with corn husk (CC–CH) (13.70 MJ·kg⁻¹). The estimated emission factors were within ranges of 38.26–63.26 kg·Mg⁻¹ for CO, 936–1549 kg·Mg⁻¹ for CO₂, 0.85–4.32 kg·Mg⁻¹ for NO_x, 0.91–1.03 kg·Mg⁻¹ for SO₂, and 3.88–54.31 kg·Mg⁻¹ for dust. The research showed that the creation of mixtures from starting materials leads to materials with lower potential for negative environmental impact as well as a reduced risk of slagging and fouling of biomass boilers. However, taking into account all the parameters determined for the biomass under study, the highest energy potential was characteristic for corn cobs and the mixture of corn cobs with corn husk.

This article presents the influence of ash-forming temperature on ash content and the content of selected heavy metals. The biomasses most commonly used in low-power heating boilers, such as miscant, oak, pine, sunflower husk, wheat straw and willow, were selected for the research. The biomass was incinerated at temperatures of 600 °C, 700 °C, 800 °C, 900 °C and 1000 °C, using the X-ray Fluorescence Spectrometer (XRF) for the measurement of element content. The results show that the content of heavy metals in the examined ash was not excessive and could not be considered as potentially dangerous. As the ash-forming temperature increased, the content of Zn, Cd, Cu and Pb decreased, which indicates that, at higher temperatures, they went into the gas phase. Cr, Ni and Fe were thermally stable and less volatile, thus the ashes were enriched with them as the ash-forming temperature increased.

Energy biomass characteristics of chosen plants: The chosen energy plants species: willow, mallow andMiscanthusare presented. Result of analysis of combustion heat and heating value of these species biomass indicate on possibility of their utilization as fuel for combustion and energy and heat production.