Anaerobic digestion residue represents a nutrient rich resource which, if applied back on land, can reduce the use of mineral fertilizers and improve soil fertility. However, dewatering and further thermal processing of digestate may be recommended in certain situations. Limited applicability of digestate as fertilizer may appear, especially in winter, during the vegetation period or in areas where advanced eutrophication of arable land and water bodies is developing. The use of digestate may be also governed by different laws depending on whether it is treated as fertilizer, sewage sludge or waste. The aim of this paper is to present the effects of thermal treatment of solid fraction of digestate by drying followed by pyrolysis and gasification. Pyrolysis was carried out at the temperature of about 500°C. During this process the composition of flammable gases was checked and their calorific value was assessed. Then, a comparative analysis of energy parameters of the digestate and the carbonizate was performed. Gasification of digestate was carried out at the temperature of about 850°C with use of CO2 as the gasifi cation agent. Gasification produced gas with higher calorific value than pyrolysis, but carbonizate from pyrolysis had good properties to be used as a solid fuel

The influence of sewage sludge torrefaction temperature on fuel properties was investigated. Non-lignocellulosic waste thermal treatment experiment was conducted within 1 h residence time, under the following temperatures: 200, 220, 240, 260, 280 and 300°C. Sawdust was used as lignocellulosic reference material. The following parameters of biochar have been measured: moisture, higher heating value, ash content, volatile compounds and sulfur content. Sawdust biochar has been confirmed to be a good quality solid fuel. High ash and sulfur content may be an obstacle for biochar energy reuse. The best temperature profile for sawdust torrefaction and fuel production for 1 h residence time was 220°C. At this temperature the product contained 84% of initial energy while decreased the mass by 25%. The best temperature profile for sewage sludge was 240°C. The energy residue was 91% and the mass residue was 85%. Higher temperatures in both cases caused excessive mass and energy losses.

The investigations of energetic piles on the landfill in Zakurzewo near Grudziądz were done. The study provided answers to the following questions: I - are the piles worth digging up, li - what kind of material may be recovered after that, and Ill - what kind of process dominates currently in piles? It has been found out that plastic. mineral fraction and fraction of waste with the particles at the diameter below 10 mm made up about 75-90% of the total mass of waste in piles. Therefore. in the future these groups should be selected from the whole mass. Small fractions - I fraction of waste (with the particles of the diameter below 10 mm) and li fraction (with the particles of the diameter between 10-40 mm) made up significant share (50-93%) of the total mass of waste in piles. Organic matter content in dry mass of I fraction was high ranging from 71.6-86.8% of d.rn. This fraction can be used as a biological layer on the landfill. but should not be treated as a neutral waste for the sake of lcachuig of high pollutants concentration. fur the sake of low reduction of organic matter further fermentation of waste from piles W I - W6 with biogas recovery is advisable. In order to improve structural and odor features of waste. before sorting on the secondary materials. three weeks of air drying is advisable.

jakość wód podziemnych. W badaniach zastosowano trzy gatunki roślin, jako możliwe kierunki stosowania osadów ściekowych: trawa - rekultywacja gleb zdegradowanych, kukurydza - produkcja pasz, wierzba- wykorzystanie energetyczne biomasy. Jako kontrolę zastosowano lizymetry pozbawione roślinności. Przyjęto nastepujące dawki osadów ściekowych: O. IO, 50. 110,225 i 450 Mg s.m./ha. Statystycznie istotna. liniowa zależność pomiędzy dawką osadów a wielkością przewodności elektrolitycznej właściwej (EC), ChZT oraz azotanów wskazuje na potencjalne zagrożenie zanieczyszczenia wód podziemnych przy przyrodniczym wykorzystaniu osadów ściekowych, szczególnie w przypadku wysokich dawek osadów przekraczających 50 Mg s.m./ha. Zależności te oraz ryzyko zanieczyszczenia wód podziemnych obserwowano przez trzy lata doświadczenia dla wskaźników zanieczyszczenia EC i ChZT. W przypadku azotanów, zagrożenie ich migracji stwierdzono jedynie w pierwszym roku badań. Dodatkowo stężenia metali ciężkich oraz obecność patogenów w wodach gruntowych była na niskim poziomic. Stwierdzono, że zastosowane rośliny nie zmniejszyły negatywnego wpływu osadów ściekowych na jakość wód podziemnych.

The paper presents the results of anaerobic digestion and co-digestion under mesophilic conditions in the OxiTop system and in lab-scale fermentors. The goal of the study was to determine the effect of reaction-based oil waste on biogas production in co-fermentation with sewage sludge (mixture of thickened primary and excess sludge). The average water content in sewage sludge was 97 %, with 70 % of total volatile solids concentration (TVS) in total solids. Weight content of oil waste in the mixture of sewage sludge ranged from 15 to 45 % (w/w) and the increase in TVS to 83.7 % was observed. The primary investigations of gas productivity by manometrie method (OxiTop) showed that biogas production increased with increasing content of oil waste in the mixture with sewage sludge. The rate constant of the first-order kinetics for biogas production was determined. To determine the yield parameters of cofermentation, the experiment was performed in four continuously stirred anaerobic reactors with a working volume of IO drrr'. Organic loading rate (OLR) changed from 0.9 to 3.1 kg TVS/m3•d. High correlation between biogas flow rate and OLR was observed. Volumetric biogas production rate and the average methane content in the biogas increased from 0.79 to 1.98 m3/m3-d and from 52.3 to 62.3 %, respectively, as OLR increased. The results obtained in lab-scale fermentors are promising and open the possibilities of the implementation of co-fermentation of sewage sludge and oil waste.

The impact of mechanical pre-treatment of municipal solid waste (MSW) on its biogas production potential was examined. Mechanical separation allowed the following size-fractions to be obtained: fine fraction - mineral fraction of municipal solid waste (MFMSW) (cf> < 20 mm), middle fraction - organic fraction of municipal solid waste (OFMSW) (20 mm< cf>< 80 mm), and coarse fraction (cf>> 80 mm). The most suitable fraction for biological treatment was OFMSW, containing about 76 % of high rate biodegradable organic fraction (HRBOF). The rate constant of degradation for organic compounds in OFMSW was 0.23 d·1• It was shown that total gas production (TGP) during 10 years may achieve 550 m3/Mg OFMSW. Mechanical pre-treatment may allow an 45 % decrease of the amount of landfilled MSW resulting in a reduction of greenhouse gas emissions of up to 70 m3/Mg over 10 years of landfilling (in contrast to MSW landfilling - 213 m3/Mg). The experimental results revealed that gas production potential should be determined on the basis of HRBOF content and measurements of the biogas production.