Potencjał energetyczny substratów roślinnych pochodzących z nieużytków drogowych

Uzyskane wyniki wielkości produkcji oraz składu biogazu, powstającego podczas fermentacji metanowej substratu roślinnego pochodzącego z nieużytków przydrożnych wskazują na potencjalna możliwość wykorzystania tego źródła biomasy. Średnio uzyskiwano biogaz w ilości 0,354 l/gs.m. (354 m3/t) przy zawartości metanu około 56,5%. Biorąc pod uwagę iż w większości miast w naszym kraju prowadzi się regularne okresowe koszenie terenów zielonych w miastach można wykorzystywać pozyskiwany materiał jako wsad do lokalnych biogazowni. Koszona trawa jest zbierana i wywożona, koszt związany z tą operacją jest więc ponoszony niezależnie od tego, czy substrat zostanie wykorzystany czy nie.

The paper presents the results of research on the quantity and quality of biogas produced in the process of methane fermentation of vegetable substrates from road barrens. The study used a mixture of waste collected along one of the streets in Olsztyn. The waste included in its composition the fallen leaves of roadside trees, especially poplar italian (Populus nigra) and linden (Tilia europaea) and roadside grasses. In order to efficiently process the collected material it was grinded to particle size of 2 mm using Robot Coupe Blixer. Then for each sample the analysis of solids was performed six times and waste were treated in anaerobic digestion process in the dynamic sets using a respirometric Oxi-Top Control WTW. They were equipped with a reaction chamber with a volume of 1 liter tightly coupled with the device - measuring unit. This method allows to determine the activity of anaerobic sludge, the susceptibility of organic substrates, in this case roadside waste, to biodegradability and it was possible to estimate the quantity and composition of gaseous products of metabolism. The process was carried out by microorganisms under anaerobic conditions and the production of biogas was determined by the changes of partial pressure in the measuring chamber recorded and analyzed by measuring devices. Applied load in the chamber was 1 kg of fermentation d.m./m3.day. For substrate collected in each of five sites the analysis of quality and quantity of biogas produced was performed. The values of mean and standard deviation of the error and the quantity of biogas and the contents of basic components: methane and carbon dioxide were determined. Normality of distribution was confirmed by a test of the Shapiro-Wilk, while the hypothesis of homogeneity of variance in the groups was verified on the basis of Leveney test. Tests of differences between the averages of each group were performed using Tukey test RIR (reasonably significant difference). The amount of biogas in the conditions of the experiment ranged from 0.29 l/g d.m. for samples taken from 3, to 0.38 l/g d.m. in the case of the sample taken from 5 (Figure 2). At the same time there was no statistically significant differences in the amount of biogas formed between the substrate of fermentation attempts of successive research points. Average for all points was 56.5% methane, and carbon dioxide 43.5%. The highest percentage of methane was found in biogas plants originating from point 4, in this case, methane was up 63% of the resulting biogas. Significantly lower was the participation of methane in the biogas obtained from the substrate from the point 2 and 4. In this case, methane accounted for about 50.5%. The possibility of using energy crops as a substrate for biogas process is the subject of numerous scientific reports that confirm the effective use of different kinds of biomass fermentation processes. Often, the biomass materials are mainly from agricultural waste or specially geared towards the production of energy crops. The obtained results of volumes and composition of biogas produced during anaerobic digestion plant substrate from roadside wasteland indicate the potential use of this source of biomass.