Does nitrogen application improve elephant grass yield and energetic characteristics of biofuels?

Abstract

This study aimed to evaluate the effect of nitrogen (N) application in the biomass yield and energetic characteristics of biofuels (fresh and briquettes) of elephant grass grown in tropical conditions. The experiment was carried out during two consecutive harvests, and the following nitrogen fertilizer doses were evaluated: 0, 50, 100, 150, and 200 kg of N ha−1 year−1. Biometric variables, biomass yield, total accumulated nitrogen, and C:N ratio and biomass energetic characterization were carried out. Briquettes were produced for the evaluation of the energetic, physical, and mechanical characteristics. Nitrogen application influenced the elephant grass yield growing in tropical conditions. The biomass yield reached 43 Mg ha−1 in the second harvest. The application of 100 kg ha−1 N promoted greater efficiency in the use of N and biomass yield. Thus, this is the recommended dose for cultivation of elephant grass for energy purposes in the edaphoclimatic conditions of the Cerrado biome (Brazilian Savannah). Elephant grass presented high heating value (17,196 kJ kg−1), ash content (4.77%), and bulk and energy density (206.00 kg m−3 and 0.84 Gcal m−3) that make it suitable for use as an energy resource in the fresh form. However, the production of briquettes improved its energetic characteristics. The application of N did not change the high heating value of biomass and the characteristics of briquettes.