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The purpose of this work was to determine the effect of initial pH on the production of volatile fatty acids (VFA) and hydrogen (H2) in the dark fermentation processes of kitchen waste. The study was conducted in batch bioreactors of working volume 1 L for different initial pH in the range from 5.5 to 9.0. The dark fermentation processes were carried out for 4 days at 37°C. Initial organic load of the kitchen waste in all bioreactors amounted to 25.5 gVS/L. Buffering of pH during the fermentation process was carried out with the use of ammonia contained mainly in digested sludge. The optimal conditions for the production of VFA and H2 were achieved at the initial pH of 8. Production of VFA and H2 in these conditions was, respectively, 13.9 g/L and 72.4 mL/gVS. The main produced components of VFA were acetic and butyric acids. The production of ethanol and lactic acid was at very low levels due to the high ratio of the volatile fatty acids to total organic content of 0.86. With the optimal initial pH of 8 the yield of CO2 production was 0.30 gC/gC. High initial pH value (above 8) extended the lag phase duration in the course of H2 production. The dominant groups of micro-organisms at the most favourable initial pH of 8 for the production of VFA and H2 were Bacteroidetes, Firmicutes, Spirochaetes and Waste Water of Evry 1 (WWE1) at the phylum level. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effect of different inoculum ratio on the dark fermentation of kitchen waste in terms of volatile fatty acids (VFAs) and H2 production. The experiments were performed in batch bioreactors of effective volume 1 L without pH regulation. The ratio between the DS and KW was being increased from 0.11 to 0.51 on a volatile solids (VS) basis, while the initial content of KW was equal to 34.1 g VS/L. Increase of the DS/KW ratio from 0.11 to 0.28 resulted in the rise of VFAs and H2 production. Further increase in the amount of added DS did not cause a significant change in the production of VFAs and H2. In the bioreactor with the DS/KW ratio of 0.28, the production of VFAs and H2 was equal to 16.0 g/L and 68.1 mL/g VS, respectively. Acetic and butyric acids were produced in the largest amount and their content, for DS/KW ratio of 0.28, were equal 37% and 43%, respectively. At the ratio of DS/KW above 0.4, the caproic acid content attained the level of 25%. Based on the DS and KW microbiological analysis, it was observed that dominant bacteria were Bacteroidetes, Firmicutes, Proteobacteria, Spirochaetes and WWE1 at the phylum level. [ABSTRACT FROM AUTHOR]

The aim of this work was to investigate the process of biodrying of municipal solid waste from the old landfill to preparing it for pyrolysis or gasification. New aspect of this research is biodrying of waste from old landfill. Biodrying of wastes was carried out at different aeration rates (7, 35, and 175 dm3/kg dry matter/d) at two temperatures (23 and 50 °C). The research was carried out in the laboratory bioreactors of special design (lysimeters), which simulated the conditions prevailing in the landfill. The optimal conditions for reduction of moisture in waste (63.2%) has been attained for the highest aeration rate (175 dm3/kg dry matter/d) and temperature equal to 50 °C. The final moisture content of the obtained biodried product was 23% w/w. In the bioreactor, in which the greatest reduction of moisture was obtained, the total amount of produced CO2 was 44.9 gC/kg dry matter, and the biodrying efficiency was equal to 0.89. During biodrying of wastes in optimal conditions, higher heating value of waste increased from 4.3 to 11.0 MJ/kg. As a result of the performed pyrolysis of biodried waste at 900 °C, char, oil, and gas were obtained the respective yields of 47, 32, and 21% w/w. The gas emerging in the gasification process was characterized by higher heating value equal to 11.3 MJ/m3. [ABSTRACT FROM AUTHOR]

The effect of air flow rate on the change of biomass (organic waste material) temperature and moisture content during an autothermal drying process is discussed. The laboratory-scale experiments were performed using a 240-dm3 horizontal composting reactor equipped with an air supply system, biomass temperature measuring system, and air humidity and temperature sensors. An organic fraction of municipal solid waste with the addition of a structural material was used as a substrate in this process. As a result of the autothermal biodrying process, the initial moisture content of organic waste ranging from 0.8 to 0.9 kgH2O/kg of raw waste mass decreased by 50%. Water balances were calculated before and after biodrying, and the difference was less than 10%. The heat of combustion and the calorific value of dried wastes ranged respectively from 6,750 to 12,280 kJ/kg and from 8,050 to 10,980 kJ/kg. The biodrying efficiency varied from 0.73 to 0.97, depending on process conditions. Energy balances showed that average biological energy production rates varied between 1.66 and 6.90 W/kg of raw waste mass. [ABSTRACT FROM AUTHOR]