Technological solutions for the use of biomass with evaluation of cost effectiveness

Increasing attention in the European Union is paid towards broader use of various renewable energy sources. High amounts of grass biomass being wasted on a field has a potential to be used in many alternative ways, including production of biofuel, biogas or pellets for further energy generation or other purposes.

Increasing attention in the European Union is paid towards broader use of various renewable energy sources. High amounts of grass biomass being wasted on a field has a potential to be used in many alternative ways, including production of biofuel, biogas or pellets for further energy generation or other purposes.
Within the frame of the LIFE+ project “Alternative use of biomass for maintenance of grassland biodiversity and ecosystem services” research on possible solutions for use of grass biomass has been carried out. The aim of this study has been to test various technical and technological options for processing of biomass for production of biobutanol and biogas. The research included field works – collection of biomass samples from different habitats in Sigulda and Ludza Municipalities (Latvia) and in different times of the year during the vegetation season in 2014, 2015 and 2016. During the laboratory tests the collected biomass has been exposed to various physical and chemical conditions, microorganisms in order to find out the optimum combination of these variables for pre-treatment of grass biomass. The obtained results will serve as the bases for specification of technical parameters for pilot facilities and highlight possible synergies in a process of production of biogas and biobutanol.
Second generation biofuel - biobutanol produced from lignocellulosic biomass is regarded as a good alternative to cellulosic ethanol. However, its fermentation is closely linked to effective pre-treatment and hydrolysis of the biomass. Application of complicated techniques limits the introduction of the technology to a wider scale, thus, options for a simple pre-treatment/hydrolysis must be introduced. The aim of this study was to test various simple biomass conversion techniques for biobutanol production to demonstrate an efficient technology. The report describes the research performed to identify and describe several critical points in technology development. As a result a method of mechanical grinding, followed by boiling and enzymatic hydrolysis at low temperature (30°C) for 24 hours is defined and applied for natural biomass sample analysis collected over 3 months period 2014 –2016 in Sigulda and Ludza Municipalities.
Besides traditional substrates – maize, manure also different grass biomass – green grass, hay, silage and digestate (waste product from anaerobic fermentation) can be used for production of biogas. The report presents laboratory tests and the research carried out for obtaining biogas from grass biomass and digestate. Laboratory tests show that pre-treatment of biomass e.g., by steam explosion ensures essential disintegration of fibrous structures. Results show that it is possible to produce 70 m3 biogas per 1 ton of grass biomass (methane concentration < 52%). Green grass gives the best indication on maximum biogas production volumes. In parallel laboratory tests of biogas production from digestate have been performed. Based on the research results, it can be calculated that about 60 m3 of biogas per 1 ton of digestate can be produced (methane concentration ca. 53%). Laboratory tests on optimum conditions and proportions of different grass substances and pre-treatment conditions for digestate are being continued.
Based on research results the cost effectiveness assessment of the proposed technological solutions for production of biogas and biobutanol will be performed. The report includes methodology for cost effectiveness assessment to be followed when the laboratory investigations are finalised. The project envisages testing possibilities of production of pellets from grass biomass obtained during restoration activities of grasslands in Sigulda and Ludza Municipalities. Cost effectiveness of production of grass pellets will be evaluated, too.

Read article