Investigations of biogas production potential from grass hay pellets
2018
Dubrovskis, V., Latvia Univ. of Life Sciences and Technologies, Jelgava (Latvia) | Plume, I., Latvia Univ. of Life Sciences and Technologies, Jelgava (Latvia) | Straume, I., Latvia Univ. of Life Sciences and Technologies, Jelgava (Latvia)
There are large agricultural land areas overgrown with grasses and not used for agricultural production or having protective environmental status in Latvia. Grass biomass from those areas can be utilised for biogas production, however, the most of abandoned lands are located far from the existing biogas plants and high transportation expenses is often the limiting factor for usage of the grass biomass for biogas production. This problem can be solved by production of grass pellets, having low moisture content (8−12 %), high density and high dry organic matter (DOM) content. Such grass pellets production can be provided on relatively small equipment with the size adapted to the local grass biomass resources. After production, grass pellets can be transported to biogas plants with minimal transport expenses, so providing additional supply of valuable biomass to biogas plants for stable round year biogas production. Investigation of biogas potential from grass hay pellets was carried out using the laboratory facilities. The grass hay pellets were fermented anaerobically in 16 bioreactors operating in batch mode at temperature 38 ºC. On average, 0.666 l·gE-1 DOM biogas (0.355 l·gE-1 DOM methane) was obtained during 46 days of the anaerobic digestion period. Investigations show that high specific methane yield can be obtained from the grass hay pellets, and its utilisation in biogas plants can be useful taking in account the high content of dry organic matter in the initial biomass. The second study deals with investigation of the methane yield obtainable from co-digestion of the grass hay pellets with sunflower oil and molasses. Addition of sunflower oil increases the methane yield by 28.8 % and addition of molasses increases the methane yield by 8.8 %.
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