LAUSR

Abstract The application of sewage sludge as fertilizer in the production of non-food crops is an environmentally sustainable approach to sewage sludge management. This article presents the results of a multidirectional analysis (agronomic and energy efficiency analysis) evaluating the effects of sewage sludge applied at rates equivalent to 100 and 160 kg N ha−1 on the production of giant miscanthus (Miscanthus × giganteus Greef and Deuter) in north-eastern Poland in 2013–2018. The optimal fertilizer rate was 160 kg N ha−1 regardless of nitrogen source (mineral fertilizers, sewage sludge), and it contributed to the achievement of the highest biomass yield (19.8 Mg ha−1 dry matter - DM) and the highest energy output (272–275 GJ ha−1). Energy demand was highest (19–24 GJ ha−1) in production technologies involving mineral fertilizers. The replacement of mineral fertilizers with sewage sludge decreased energy inputs in the production of giant miscanthus biomass by 32–34%. Energy gain was highest (259 GJ ha−1) when M. giganteus was supplied with sewage sludge at a rate equivalent to 160 kg N ha−1. The energy efficiency ratio peaked (24.7) in the production technology without fertilization. Energy efficiency was 43–52% higher when giant miscanthus plants were supplied with sewage sludge rather than mineral fertilizers.