Process optimization of biogas production at Nemščak biogas plant by pre-treatment of the substrate and combining with waste sludge

摘要

The purpose of this thesis is to increase the amount of biogas produced by pre-treatment of the substrate and combining with waste sludge. For anaerobic digestion of different substrates, we used a pilot reactor to determine the biogas potential at Nemščak biogas plant. The pilot reactor was built in 2009 for the purpose of testing new substrates in the process of biogas production. The pilot reactor has a working volume of 2000 litres; there is a gas tank above it with the volume of 500 litres. The reactor is heated to a mesophilic temperature range. It is controlled through a computer program that continuously records the amount of the resulting biogas. The composition of the biogas was measured with a handheld gas composition analyser. First we tested the unchanged silage in the reactor and determined her dry matter, organic matter, biogas yield and methane yield. Then we tested the silage in the reactor, which was ground with a hand mincer prior to dosing. Ground silage was also determined with biogas and methane yield. As a third substrate we tested waste sludge from Murska Sobota municipal wastewater treatment plant. Waste sludge generated there is destined for disposal; therefore, we found this substrate suitable for anaerobic digestion. All three substrates were testedudusing the same method and the same boundary conditions. For the purpose of this thesis we monitored Nemščak biogas plant for a period of one month.