Maize is increasingly used for energy production in agricultural biogas plants. The first biogas production project in agriculture is realized in the Research and Study Farm (RSF) Vecauce of the Latvia University of Agriculture in 2008 and animal manure together with plant biomass are planned to be used as substrate. The paper aimed to evaluate ten maize hybrids possibly suitable for biomass production at three different harvesting times. Field trial was carried out in Research and Study farm Vecauce of the Latvia University of Agriculture in 2008. Ten maize hybrids with different maturity rating according FAO numbers (FAO 180 - 270) were harvested at three different times beginning on 5 September at fourteen days intervals. Results showed that harvest time effect on maize yield was substantial (p is less than 0.05), but hybrid influence on the average yield per all harvest dates was not substantial (p is greater than 0.05). The highest organic dry matter yield was obtained harvesting maize on October 3. The Total N, crude ash, protein, fibre, cellulose, lignin, neutral detergent fibre (NDF) and acid detergent fibre (ADF) concentration decreased, but crude fat concentration increased during plant development. Relevance was not noticed between harvest dates and total carbon and hemi - cellulose content. The C : N ration rose from 34.76 at first, early harvest on 5 September to 37.97 at the last harvest on 3 October.

Maize (Zea mays L.) is one of the agricultural plants that is suitable substrate for biogas production. Fresh as well as ensiled maize can be used as biogas substrate. Practically, mainly maize silage is used because fresh maize is available only for short term during the vegetative period. The paper is aimed to determine the impact of ensiling on substrate composition of maize hybrids. A field trial was carried out in the Research and Study farm ''Vecauce'' of the Latvia University of Agriculture (LLU) in 2008 and 2009. Ten (in 2008) to eleven (2009) maize hybrids with different maturity rating according to FAO numbers (FAO 180 – 340) were harvested at three different times beginning on 5 September at fourteen-day intervals. Chopped maize samples of 1-3 kg were ensiled in plastic silos. Samples of fresh and ensiled (for at least 90 days) maize were analyzed detecting 14 parameters in the Scientific Laboratory of Agronomy Research of LLU using standard methods. Our results showed that ensilaging influence on organic dry matter and hemi-cellulose content was not substantial. High (p is less than 0.05) correlation between organic dry matter content of fresh and ensiled samples was noted. The crude protein, crude fibre, ash and cellulose concentration was greater in the ensiled samples if compared with fresh maize samples in 2008 and 2009. After ensilaging process neutral detergent fibre (NDF) concentration was higher compared with fresh samples in 2009 but lower in 2008.

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).

Jerusalem artichoke is suitable for use in biorefineries due to the very high biomass production and low soil, climate and cultivation requirements. Tubers of this species can be used for the production of methane fermentation or bioethanol. The aboveground part can be used for the production of biomethane, as well as in the direct combustion process or for the production of briquettes and pellets. Of the cultivars tested, Albik and Violet de Rennes proved to be the most useful for energy purposes. An important advantage of Jerusalem artichoke is its resistance to adverse climatic conditions (drought, frost), resistance to diseases and pests and the possibility of self-renewal.

Nowadays it is paramount to promote bioenergy for climate protection, energy security and creation of income/jobs. In this perspective, Anaerobic Digestion (AD) for biogas and digestate production seems to be a viable way to simultaneously improve waste management while producing Renewable Energy Sources (RES). The main objective of this work is to assess the environmental impact associated with biomethane and digestate production from an AD plant as Global Warming Potential, expressed in CO2 equivalents. Therefore, a LCA was carried out for the production of biomethane ready for the injection into the Italian distribution natural gas grid. A mix from different waste sources (cattle manure and slurry, pig slurry, Citrus industry by-product, chicken manure, manure from broilers, triticale silage and waste from vegetable cleaning) is considered for biogas and digestate production. Besides biomethane this plant will produce digestate, that is a biological and nutrient-rich fertiliser. Thus, the cycle of circular economy is closed, as the recovery of matter and energy is carried out from waste. The results clearly indicate the importance of the process steps transport of biomass to AD plant and, above all, methane upgrading (separation by membrane). Depending on the high amount of the substrate and long distance travelled, Citrus waste substrate transport accounts for the largest share in GHG emissions with 0.229 kg CO2-eq/Nm3 or 70.5 % of total transportation emission. Greenhouse gas emissions estimated for the various process stages for the Sclafani Bagni plant showed, that methane upgrading emits 1.95 kg CO2-eq/Nm3, while other processes totally emits 0.525 kg CO2-eq/Nm3. The LCIA results confirmed the negative total impact of the process with grid injection, in terms of kg of CO2 eq.: the LCA verified the carbon-negative-bio-energy concept of the project. Therefore, biomethane derived from biogas is an entirely renewable and readily available low carbon alternative fuel, that can be locally produced from organic waste and capable to replace the fossil natural gas in the near future.

The paper aims at analyzing agricultural production for energy generation purposes, including the production of agricultural biogas, as an opportunity for functional diversification of agriculture and for multifunctional rural development in Poland. There have been many changes observed in Polish agriculture. New directions of crop production and of the use of agricultural products have emerged. One of the changes is the increasing significance of the production of agricultural biogas and energy from biogas. There have been built both small-scale and large-scale biogas plants. Most of the agricultural biogas plants are located in northern, western and south-western Poland, i.e. in the areas where there are relatively large farms which can provide a supply of substrates necessary for the production of agricultural biogas. The formation of biogas plants and the use of agricultural production for generating energy are an eagerly anticipated trend contributing to the dissemination of renewable energy sources, the functional diversification of agriculture, the development of additional economic activities in rural areas, and the increase in the energy security of particular regions and the entire country.

One of the main objectives for the Baltic Sea regions is the harmonisation of the economic development and environmental sustainability. The identification of knowledge-intensive bioeconomy as one of the primary fields of the strategy for smart specialization (RIS3) in Latvia indicates the transition to sustainable and climate neutral approach for the development of Latvia. The strategy aims to promote a more sustainable and efficient use of natural resources, to create high added value, to promote coordination of export and economic interests with environmental protection. This is a multi-faceted and complex process. A scientifically sound approach is needed to develop the most appropriate solutions. The article examines algae biomass as a potential for renewable resources in the agriculture of Latvia in the context of sustainability. The research is aimed at exploring the potential of the Baltic Sea algae as a sustainable agricultural resource in Latvia, focusing on its impact on cultivated plants during the study. The potential is being assessed by conducting a practical study in two stages. The results of the study confirm the potential use of Baltic Sea algae as an agricultural resource in Latvia, which requires further evaluation of the effect of the liquid digestate fraction on crop green mass to determine its potential applicability in agriculture using algal biomass.