Biomass yield and chemical composition of perennial grasses for energy production.

The increase in energy consumption and the security of global energy marketmake renewable energy a topical issue, for example, the use of biomass for bioenergy, which influences directly the generation of wood ashand digestate – residues of biogas production. These products have high value of plant nutrients, therefore it is important to study their effectiveness. Reed canary grass(RCG) and festulolium fertilisationtrials were arranged in 2012. In all fertilisertreatments ( wood ash, digestate once per season; digestate twice per season and mineral fertilisers) the same amount of main plant nutrients (N, P, K) was provided; and the missing quantities of elements in ash and digestate were compensated by mineral fertilisers. The dry matter yield (DMY) and chemical composition of biomass in two cutting regimes (one-cut and two-cut harvest system) were assessed. All fertilisersprovided a significant increase of DMY; however, better results for both species were ensured by the usage of mineral fertilisersand wood ash. Lower ash content (4.0-5.4 %) and hence more appropriate raw material for combustion can be obtained by mowing RCG once per season late in the autumn. The chemical composition of grass biomass was mostly influenced by the cutting regime and fraction.