Biogas production possibilities
This action aims to encourage regular grassland management by offering the alternative for use of grassland biomass. Biogas made of biomass may largely be used by various customers and also provide socioeconomic benefits for local community and invest sustainable development.
Implementation: October 2013 – December 2017
Implemented by: LTD “Bio Re”
During the time period 2013-2016 LTD “Bio RE” performed the laboratory tests and the research for obtaining biogas from grass biomass and digestate. Various technological processes and solutions had been used for optimization of this process. The obtained results were used for construction the pilot facility of biogas production.
Firstly, the laboratory analyses were done to evaluate the total solid and volatile solid in the grass biomass samples (about 20 – 30g each) collected from the sampling plots in Sigulda and Ludza areas in 2014 and in 2015. In addition, one large biomass sample (about 100 kg) collected in in More parish, Sigulda district in 2013 was analysed.
Laboratory tests were carried out in order to find the optimal processing regime and parameters for production of biogas from different types of grass biomass. For this purpose, grass, hay and silage samples (average sample from grass biomass samples collected in different habitats) in and two 50 litre large bio- working in parallel were used.
Results of experiments show that for preparation of grass samples for biogas production, cutting of grass in smaller pieces is recommendable. This enlarges the external surface of the material and intensifies production of biogas. The destruction of grass structure to smaller pieces can be realized industrially by the steam explosion equipment. Grass is placed in a chamber and exposed to a water steam (temp. 145-170oC) for ca. 10 minutes. When the chamber is opened, steam inside grass structure destroys (explodes) grass in small pieces needed for better biogas production. Here volatile substances left after the explosion can be measured and tested, too. The obtained results give a possibility to evaluate limitations and applicability of this technology for industrial production of biogas.
The obtained results provide bases for elaboration of technological solution for the pilot facility. Results show that anaerobic fermentation process has to be optimised by adding up microelements in bioreactors at low levels of volatile solids. This can be reached by separating stages of anaerobic fermentation (e.g., hydrolyses). Such solution would allow creating a synergy for simultaneous production of biogas and biobutanol as envisaged in the project.
Another series of laboratory tests were done in order to identify the optimal treatment regime to obtain biogas from digestate samples. Thermal treatment of digestate (70o C temperature for 24 hours) has been carried out. Biogas production volume (ml) and the speed (ml/day) from untreated digestate and digestate who had experienced thermal treatment have been measured. The results of laboratory tests show that biogas production outcome from thermally treated digestate and untreated digestate is similar.
Pilot facility for biogas production was designed and relevant technical parameters calculated by “Bio RE”. Based on hydraulic retention time and organic loading rate, the total volume of the reactor, its modules and a separated hydrolysis module has been calculated. Technical solutions for biomass movement in the reactor and mixing substrate have been developed, and engineering preconditions for installing the facility (needed capacity of water and electricity networks etc.) have been defined. The design for methane separation device (water scrubber), gasholder and biogas burner has been developed. The optimal level of automated control system for the biogas reactor has been calculated. The pilot facility serves for combined heat-power production, which requires a system for removal of nitrogen oxides.