The study aimed to obtain bioethanol from biomass using chemical treatment and enzymatic hydrolysis. Different concentrations of sodium hydroxide (5 and 10%) were used for the delignification process, and enzymatic hydrolysis was carried out using three commercial cellulolytic preparations (Cellic® CTec2, cellulase from Trichoderma reesei and cellulase from Aspergillus species). The final step involved an alcoholic fermentation process using Saccharomyces cerevisiae TYPE II yeast. After enzymatic hydrolysis, the content of reducing sugars was determined in the samples, and the fermentation yield was controlled by determining the ethanol content by pycnometry. Using chemical pretreatment increased the yield of the whole process by at least 50%. The content of reducing sugars after hydrolysis depended on the type of enzyme preparation used for hydrolysis and the use of NaOH in pretreatment. The highest reducing sugars content (45.8 g/dm3) was achieved in a sample of material purified with 5% NaOH, and enzymatic hydrolysis was carried out using Cellic® CTec2. It means the efficiency of the enzymatic hydrolysis process equals 94.69%. The concentration of bioethanol after alcoholic fermentation in this sample was 0.509 g/l.
The main objective of presented research work was the assessment of the impact of reduced straw content, as organic carbon source, on the course of sewage sludge composting process. During the research work performed in industrial conditions, the composting process going in periodically overturned windrows differing in proportion of dehydrated sludge, straw and structural material being 4:1:1 and 8:1:2 respectively, was observed. The consequence of increase of sludge concentration with relation to straw was decrease of C:N ratio in the input material from 11.5 to 8.5. The following parameters were analyzed as indicators for the assessment of the composting process: contents of fulvic acids (FA), humic acids (HA), lignin, cellulose and hemicellulose as well as absorbance in UV/VIS (λ=280, 465 and 665 nm) range. The results obtained have indicated that the increase of sludge content extends the elevated temperature (T>50°C) period from 42 days to approximately 65 days. Our tests did not confirm that limitation of straw content added to sewage sludge had any adverse effect on the course of composting. PI index (HA/FA), which qualifies the compost as mature in the first case – No 1, exceeds limit value of 3.6 on the 83rd day whereas, in the second case No 2, on the 48th day.
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