Extrusion pretreatment of maize straw - case study for a Polish biogas plants

One of the most commonly used substrates in biogas plants is maize silage, however, the application of monofermentation technology under Polish economic conditions has a tendency to rapidly bankrupt the investor. The lack of profitability of investments based on this material has encouraged investors to search for other, more economically favourable biomass sources i.e. maize straw. The aim of the research was to compare the energetic potential of untreated maize straw and extruded maize straw used for biogas production and furthermore, to determine the amount of electricity and heat generated as well as the amount of heat produced from direct combustion. The results obtained confirmed the substantial energy potential of maize straw. It has been proven that using the extrusion method as a pretreatment before the fermentation process, enables the producer to increase biogas and methane production respectively by 7.50 and 8.51%. However, the use of an extruder machine in biogas plants in Poland is economically unjustified due to its high energy consumption. Moreover, it has been shown, that the use of maize straw in the methane fermentation process enables it to generate (in Poland) a higher income than is the case of using this material in a direct combustion process.