Contamination of soil by toxic elements is a global issue of growing importance due to the increased anthropogenic impact on the natural environment. Conventional methods of soil decontamination possess disadvantages in forms of environmental and financial burdens. This fact leads to the search for alternative approaches of remediation of contaminated sites. One such approach includes phytoremediation. Phytoremediation advantages consist of low costs and small environmental impact. Several fast-growing energy plant species are suitable for phytoremediation purposes. Our article focuses on the phytoremediation potential of energy woody crops of Salix and Populus, and energy grasses Miscanthus and Arundo, which are grown primarily for biomass production. This approach links the environmentally friendly and economically less demanding remediation approach with the production of the local sustainable form of energy that decreases dependency on external energy supplies. Energy plants are able to provide high biomass yields in a short period of time, they are resistant against abiotic stress conditions and have the ability to accumulate toxic substances, thus helping to restore the desirable soil properties. The phytoremediation research is very interdisciplinary in its nature. In order to implement phytoremediation practices together with bioenergy successfully, it is crucial to involve site owners, local people, farmers, technology providers and consultants, remediation experts, sustainability assessors, regulatory agencies and certification bodies, biorefineries, financial sponsors, NGOs and other voluntary organizations. Some disadvantages and challenges of phytoremediation are also indicated.

In Slovakia, maize silage is preferred as the input material for biogas production whereas it should be used primarily as feed for cattle. The purpose of this paper is to point out the possibilities of using the fast-growing giant reed Arundo donax L. that is not used as fodder and can be grown on low-quality agricultural land. The experimental stand of A. donax L. used in the study provided a yield of 60.8 t ha -1 of fresh biomass in the third year of cultivation. Part of the biomass produced was ensiled as maize and later the silage was co-fermented with cattle excrements and pig slurry. The resulting biogas can be used as fuel for internal combustion engines. The average content of CH 4 and CO 2 is 52% and 44%, respectively. These values are very similar to the composition of maize silage biogas. The average hydrogen sulphide content in the biogas from A. donax L. was 730 ppm. The disadvantage is that the biogas production is 46% lower compared to maize silage.

Although the effects of climate change across the world and regions are different, its adverse effects on socioeconomic systems and landscapes are increasingly important and require an active solution. There is a gradual change of the main features of the territory, which also changes the possibility and the method of its use, as well as the structure of the population itself. Renewable energy plays a key role in the longterm strategy of the European Commission (a secure, competitive and decarbonized energy system in 2050), as outlined in its Energy Roadmap 2050 [1].

The energy-efficient low-carbon EU economy (known as the 20-20-20) sets fundamental objectives in reducing greenhouse gas emissions (20%), increasing the share of renewable energy sources (20%) and saving primary energy consumption (20%). The objectives are incorporated in the National Renewable Energy Action Plans (NREAPs). Slovakia has to increase the share of renewable energy sources (RES) by 14% in its energy mix by 2020. Currently, the most widely used RES are water and solar energy, biomass and biogas. Our country has suitable ecological conditions for growing the so called energy crops in lowland and upland areas. So far, however, there is a lack of science-based information on the potential production of biomass in different soil-ecological and climatic conditions of the Slovak Republic. Our experimental research is focused on quantification of biomass production of various willow (genus Salix), poplar (genus Populus) and silvergrass (Miscanthus sinensis) varieties grown in ecological conditions of southern Slovakia. We evaluated the biomass production of the studied crops. The results were evaluated in terms of the EU call (2013): to obtain more energy while reducing inputs and negative environmental impacts.

In this paper, we present the results of research of phytomass production allocated to aboveground organs, leaves and stalks, after the third growing year. The research was conducted in the field experiment conditions of Farm holding in Kolíňany. The results of the aboveground dry matter production are expressed in tonnes of dry weight produced on the area of one hectare (t.ha-1). The total dry weight of the aboveground biomass was 6.89 t.ha-1 at the end of the first growing year 2010. In the growing year 2011, it reached 15.21 t.ha-1 (an increase by 121 %.) The total dry weight of the aboveground phytomass increased by 37% compared to 2011, and it reached 20.82 t.ha-1 in the third growing year (2012). The increase of phytomass is directly proportional to off shoot circle. Average off shoot circle of individuals in the first growing year was 300 mm and the average number of stems produced in a clump was 37.60. In 2011, the average off shoot circle of individuals was 502 mm and there were 43.73 stems created in a clump. In the third growing period of 2013, the extension of the off shoot circle by 113.7% (641 mm) was registered in comparison with 2010 and the amount of 80.19 stems per clump was recorded.