Bromopsis inermis and Phalaroides arundinacea are increasingly grown not only for feed but also for other purposes, such as obtaining energy. Composting sewage sludge and using such compost to fertilize various plants is also becoming more popular. Therefore, the aim of our study was to investigate how the fertilization of the mentioned plants with sewage sludge compost (SSC) affects the biomass yield and biomass quality of these plants. It was also important to determine whether fertilization with SSC is possible in low-yielding soils of light texture without harming these soils There are no similar studies in Lithuania, and there are very few in Europe and the world. It was found that investigated grasses formed a small biomass DM yield (6.6 t/ha within three years). The biomass of B. inermis and Ph. arundinacea had a very high ash content and concentrations of nitrogen and potassium. This greatly reduced the quality of the biomass of these grasses as a solid biofuel. SSC performed poorly as a fertilizer. Fertilization with 125 t/ha SSC significantly increased the total biomass yield of Ph. arundinacea only. At the same time, using SSC as a fertilizer significantly increased the concentration of Cu, Zn, and Cd in the soil.
Keywords: biomass; energy crops; heavy metals; sewage sludge compost; soil.