The utilization of traditional fossil fuels (oil, gas) as primary energy resources causes a destabilization of the eco-environmental situation in the world. Latvia has to significantly decrease energy imports from its neighbouring countries. This can be achieved by using high-quality local primary renewable energy sources. One of the solutions is to utilize anaerobic fermentation for biogas production. This process can be ensured by utilizing manure, food waste as well as energy biomass - wood, grass and maize. Biogas is utilized as a primary energy source in a cogeneration plant which is a combined cycle plant for electricity and heat power production. Microcogeneration plant for farming household needs would ensure an independent power supply, in case the overall electrical network is in a state of emergency. In order to ensure optimal biogas yield, which, in turn, would ensure a stable operation of the microcogeneration plant, it is important to know the parameters and quality of the biomass that have been filled in bioreactor. This research deals with the influence of the linkage biomass type on the qualitative and quantitative indicators of biogas. As a result, it has been found that biomass type affected the methane percentage in biogas greatly. The methane content of biogas independent with biomass type was diminished from 65% (galega) to 44.5% (fresh sawdust), but biogas yield decreased from 0.627 m**3 kgVSd E-1 (galega) to 0.185 m**3 kgVSd E-1 (fresh sawdust).

Biogas can be produced from industrial by-products, household waste and raw materials of agricultural origin. Agricultural resources can be agricultural by-products, for example, manure as well as biomass of energy crops. The objective of the trial was to evaluate the methane outcome from the winter wheat (Triticum aestivum L.) silage depending on the variety and the growth stage during the harvest. The trial was carried out in State Stende Cereals Breeding Institute in the autumn of 2009. The biomass of three varieties of winter wheat, harvested at three stages of maturity - at the beginning of flowering (GS 60-62), early milk ripeness (GS 70-72), and early yellow ripeness (GS 80-82) - was ensiled in laboratory conditions. The silage was analysed 180 days after it had been ensiled. The biogas and methane outcome in laboratory conditions (in Germany) was determined for samples of silage made from winter wheat variety ‘Skalmeje’ at all harvesting times according to VDI 4630 method. The theoretically obtainable methane outcome was calculated for silage samples of all varieties by using the results of chemical composition analysis (crude protein, crude fibre, crude fat, N-free-extracts). The highest methane outcome from one ton of winter wheat silage was acquired by harvesting and ensiling the biomass during the flowering stage. However, evaluating the methane yield from one hectare, the best results were obtained by harvesting and ensiling the biomass at the early milk stage of ripeness and at the stage of early yellow ripeness.

Methane is considered to be the main greenhouse gas (GHG) emitted by livestock. One method for reducing methane emissions from ruminants is to improve production efficiency, which reduces methane emissions per unit of product (FAO, 2010; Gworgwor, Mbahi, and Yakubu, 2006). There are many researches about prebiotics which can reduce methane production in livestock, for example, galacto-oligosaccharides reduced methane emission up to 11% (litres/day) (Zhou et al., 2004). There is almost no information about prebiotic inulin, so the aim of this research was to determine the impact of different dosages of inulin concentrate (50%) on the increase of calves’ body weight and its impact on methane emission, as well as to find out how the results change if it is added to barley flour not to milk as in our previous research. Approximately fifty days old, clinically healthy, different Holstein Friesian crossbreed calves kept in groups of 8, in a partly closed space with natural ventilation through windows were included in this research. Eight calves were in the control group (CoG) and sixteen received inulin (Pre12 (n = 8), Pre24 (n = 8)). At the beginning of the experiment – the 28th and 56th day - we determined each calf’s weight and measured the methane level in the rumen by using the PICARROG-2508 gas analyser (Fleck, 2013). We concluded that inulin supplement significantly (p ≤ 0.05) increased the live weight gain comparing Pre24 and CoG. The highest methane production on 1 kg of body weight at the end of the research was detected in Pre24 – 1.24 mg mE-3 and the lowest in CoG – 0.99 mg mE-3.

Ruminants produce a large amount of methane (CH4 ) and carbon dioxide (CO2 ) in their foregut. These gases cause greenhouse effect. There are a lot of studies about different feed additives which can reduce the production of greenhouse gases in ruminants. Prebiotics can also change the amount of bacteria in animal gastrointestinal tract and reduce the occurrence of diarrhoea. The aim of this study was to test whether the prebiotic inulin affects the production of CH4 and CO2 in calves’ rumen and whether it affects the bacteria count in the rumen fluid and bacterial overgrowth in intestines. We used the flour of Jerusalem artichoke (Helianthus tuberosus L.) containing 50% of inulin. Approximately fifty days old, Holstein Friesian crossbreed calves were used in this study. Eight were in the control group, 8 received 12 g of flour and 8 received 24 g per day. On the 28th and 56th day of the research, we measured the amount of CH4 and CO2 in calves’ rumen took rumen fluid samples for bacterial analysis and urine to measure the level of phenol and indican. We concluded that adding the flour of Jerusalem artichoke at doses 12 g and 24 g did not significantly impact the production of CH4 and CO2 in calves’ rumen, the prebiotic inulin may suppress the growth of anaerobic microorganisms in the rumen at concentration 12 g of inulin reaching 56th day of experiment. The amount of phenol and indican in calves’ morning urine did not correlate with the faecal consistency of calves.