ENGINEERING FOR RURAL DEVELOPMENT Jelgava, 29.-30.05.2008. 61 GALEGA BIOMASS FOR BIOGAS PRODUCTION Vilis Dubrovskis, Imants Plme 1 , Aleksandrs Adamovics, Valdis Auziš 2 , Indulis Straume 1 Latvia University of Agriculture, 1 Faculty of Engineering, 2 Faculty of Agriculture vilisd@inbox.lv, Imants.Plume@llu.lv, Aleksandrs.Adamovics@llu.lv, Indulis.Straume@llu.lv Abstract. There is need to find an acceptable energy crops for energy production for climatic and soil conditions in Latvian. The 35 mixed swards of fodder galega (Galega orientalis Lam.) were developed on Stagnic Luvisol and Gleyic Podzol soils. Swards were cut two to four times during the growing season. Green biomass yield of pure galega swards varies between 40 - 70 t ha -1 , obtained without application of pesticides or chemical fertilizers. Yield of dry matter (DM) for galega varies between 10.27- 14.23 t ha -1 DM, obtained by harvesting in early flower stage. Biogas from galega and cow manure (control) was investigated in laboratory scale digesters of volume 5 l. Methane yield in digesters was 384.2 l/kg VSd ; 309.2 l/kg VSd ; 244 l/kg VSd obtained from different mixtures of galega and cow manure, and was 218.6 l/kg VSd from cow manure. Estimated cumulative volume of biogas released from galega haylage, having volatile solids content 19.4 % or 11.1 %, was 116 lkg -1 VS or 244 lkg -1 VS respectively, or was 2 times higher in digester with lower content of volatile solids after 64-day fermentation period. Key words: energy crops, galega, anaerobic digestion, biogas, methane. Introduction Interest increases on obtaining of energy from biomass during last years in Latvia [1, 4]. Government of Latvia approved energy sector priorities in year 2006. The general goals foreseen the following:  Self-supply of electricity will be 100 % at year 2016, therefore more than 700 MWh of new power will be necessary to put in action.  Consuming of local energy resources will increase from 65 PJ up to 82 PJ at year 2016.  Electricity production from alternative energy recourses (AER) will increase up to 49.3 % at year 2010. Biogas production from energy crops is one of the most energy-efficient and environmental way for producing of biofuel in Latvia. Potential for biogas production is shown in Table 1. Table 1 Potential resources for biogas production Resource Dry biomass, t/year Biogas, milj.m 3 /year Energy, MWh/year Cow manure 107300 32.2 193300 Pig manure 44400 20.0 118830 Poultry manure 43160 21.6 129480 Food waste 57500 23.0 138000 Waste water treatment 23000 7.0 42000 Landfills 400000 23.0 138000 Crop remainder, grass 80000 (800000*) 20.0 (200.0*) 120000 (1200000*) Silage 20000 8.0 64000 Slaughterhouse wastes 3500 2.1 12600 *in case, if the grass will be raised for energy purposes. Galega (Galega orientalis Lam.) is introduced in Latvia due to its persistency and high yielding ability. Longlived legume survives in pure stands for 25 and more years and provides annual DM yields from 9.56 to 11.0 t ha -1 [1, 2]. Successful treatment of galega seeds with nodule bacteria results in fixation of atmospheric nitrogen from 200 to 453 kg ha -1 , thus can to decrease the need for commercial nitrogen fertilizers. Production of methane rich biogas through anaerobic digestion of organic materials can to provide clean form of energy, due to low emissions into environment from burning of biogas. Biogas can be used for heat and power generation or as a vehicle fuel, thus reducing the need for fossil fuels and slowing down the climate change. The traditional anaerobic digestion technologies are designed for wastes having high water content, e.g. sewage sludge or manure. Energy