Chemical Composition and Energy Yield of Elephant-Grass Biomass as Function of Five Different Production Ages

Rafael Souza Freitas,Ana Kesia Faria Vidal,Bruna Rafaela Da Silva Menezes,Wanessa Francesconi Stida,Antônio Vander Pereira,Rogério Figueiredo Daher,Tatiane Da Costa Barbé,Verônica Brito Da Silva

doi:10.5539/jas.v10n1p343

Abstract

Elephant grass has high biomass production, with qualities suitable for conversion into bioenergy, but has long been used exclusively for animal feed and only in recent years has it become an energetic alternative. Therefore, it is necessary to select genotypes with potential for energy production. This study evaluated the effect of five harvest times (8, 12, 16, 20, and 24 weeks) on the yield and chemical composition related to biomass quality through combined polynomial regression analyses of the following elephant grass genotypes: Cubano Pinda, Mercker 86-México, Pusa Napier n°1, Mole de Volta Grande, P-241-Piracicaba, and King Grass. A completely randomized design with three replicates, in a split-plot arrangement, was adopted, including two factors (plots = genotypes, subplots = harvest times). The evaluated variables were whole-plant dry matter yield, in t ha-1 (DMY), percentage of neutral detergent fiber (%NDF), and percentage of acid detergent fiber (%ADF). The elephant-grass genotypes Cubano de Pinda, Mercker 86-México, and P-241-Piracicaba showed a linear first-degree effect as a function of the harvest intervals, indicating that they did not reach their maximum production potential. Genotypes Pusa Napier n°1, Mole de Volta Grande, and King Grass, in turn, had a linear second-degree effect. For the NDF variable, all genotypes showed a significant linear second-degree effect as a function of the harvest intervals, except P-241-Piracicaba, for which no regression was observed. For this genotype, there was a significant linear first-degree effect on the %ADF variable.

Highlights

As a consequence of the oil crisis, the energy system had to be reorganized into more solid and sustainable bases, which is one of the great challenges of research, since, in addition to being finite, the energy derived from oil contributes to the greenhouse gas effect, which threatens the earth’s climate balance (Scarlat et al, 2011).The biomass is a prominent alternative renewable-energy source
The aim of the present study was to evaluate the effect of five harvest times (8, 12, 16, 20 and 24 weeks) on the yield and chemical composition related to the biomass quality of six genotypes of elephant grass through combined polynomial regression analyses so that one can determine the ideal age of cutting the elephant grass for energetic purposes
The soil of the experimental area is classified as a Typic Dystrophic Yellow Latosol (EMBRAPA, 2006) with the following chemical composition: pH – 6.3, phosphorus – 5.0 mg dm-3, potassium – 176 mg dm-3, calcium – 2.6 cmolc dm-3, magnesium – 1.4 cmolc dm-3, aluminum – 0.1 cmolc dm-3, hydrogen + aluminum – 0.0 cmolc dm-3, and carbon – 1.26%

Summary

Introduction

The biomass is a prominent alternative renewable-energy source. Because its production recycles the atmospheric CO2 through photosynthetic processes, it is one of the safest energy alternatives (Schemer et al, 2008). This scenario indicates a need for the development of technologies able to convert the biomass of plants into chemical products, energy, and other materials that may be fundamental to move the world economy towards a renewable and sustainable energy matrix (Fontoura et al, 2015). This figure may jump to 34%, reaching 60% in Africa (IPCC, 2011), suggesting that, in the long term, biomass will be one of the most efficient energy alternatives (Kalt & Kranzl, 2011)

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