The possibility of using plants from hybrid constructed wetland wastewater treatment plant for energy purposes

•Constructed wetland systems can be used to wastewater treatment and to produce biomass for energy purposes.•High Heating Value was the highest for willow than for common reed.•Biomethane production during anaerobic fermentation was the highest for common reed and the lowest for Jerusalem artichoke.•The methane concentration in biogas was rather low, comparing to other typical substrate for biogas production. In recent years, constructed wetland systems are used widely for the purification of small amounts of wastewater because they provide very high effects of removing impurities. The existing research results show that constructed wetland systems can be used not only for highly efficient wastewater treatment, but at the same time in order to produce biomass for energy purposes. The aim of this paper was to determine the possibilities of energy use of the plants: common reed, willow, Jerusalem artichoke, giant miscanthus, obtained from constructed wetland system. The yield of common reed was the highest compared to the other plant species used in analyzed object and amounted to 13.6MgDMha−1 and then 8.7MgDMha−1 for willow. The lowest dry matter yield was 5.9MgDMha−1 in the case of Jerusalem artichoke. High Heating Value was similar in all analyzed plants (17.9–19.2MJkg−1), the highest results were obtained from willow. Biomethane production during anaerobic digestion was the highest from common reed (108m3Mg−1 FM) and the lowest from Jerusalem artichoke (66m3Mg−1 FM). The methane concentration in biogas was rather low (50.9–54.9) comparing to other typical substrates for biogas production.