Elsevier

Industrial Crops and Products

Volume 95, January 2017, Pages 27-32
Industrial Crops and Products

Elephant grass ecotypes for bioenergy production via direct combustion of biomass

https://doi.org/10.1016/j.indcrop.2016.10.014Get rights and content

Highlights

  • Cameroon group showed more aptitude for biomass combustion than Napier group.

  • In a genetic breeding program should be given priority to Cameroon group.

  • There are association between calorific value and morpho-agronomic traits.

  • It’s possible to increase calorific value by selection via morpho-agronomic traits.

Abstract

Several perennial grasses have been studied as energetic feedstock due to high lignocellulosic production, making it an alternative bioenergy source. This is the first study to investigate the aptitude of elephant grass (Pennisetum purpureum Schum.), aiming to breed it for bioenergy production via direct combustion of biomass. The evaluation of the aptitude and the estimates of the genotypic values were carried out using the mixed models methodology. The canonical correlation analyses were carried out among morpho-agronomic and biomass quality traits for the groups Napier and Cameroon. Complementarily, it was used path analysis with calorific value as the principle variable. Elephant grass presented 22.59 Mg ha−1 mean biomass production. Cameroon group presents the greatest aptitude to be used as bioenergetic raw material via direct combustion of biomass, with 24.13 Mg ha−1 total dry biomass, and 18.16 MJ kg−1 calorific value. The ash content has high correlation and high direct effect on the calorific value. Genetic breeding for morpho-agronomic traits within the Cameroon group is recommended. The canonical correlation analyses and path analyses indicate that in the initial stages of elephant grass breeding program, there is a possibility of indirect selection via morpho-agronomic traits to obtain genetic gain in calorific value. In this sense, tandem selection within the Cameroon group could be a good option, in which the genotypes with the tallest and the thickest stalk diameter should be selected among the genotypes with the greatest dry matter content.

Introduction

Plant biomass for energetic feedstock has gained importance in the development of alternative energy for an environmentally renewable and sustainable energy matrix (Nass et al., 2007, Samson et al., 2005), since it can be converted into chemical products, thermal/electrical energy, biofuels, among other essential materials (Fontoura et al., 2015, McKendry, 2002).

The biomass of crops intended to be used for combustion should have low proportion reproductive structures in the biomass, as well as phenology that allows long growing season, associated with high biomass production (Porter et al., 2007). Aside from morpho-agronomic traits, some authors indicate that biomass quality properties (moisture content, calorific value, ash content, and cellulose, lignin, and nitrogen levels) are fundamental for its utilization, since they are able to influence the entire conversion process and thermal utilization (Dorez et al., 2014, Gani and Naruse, 2007, Jaradat, 2010, Karp and Shield, 2008, McKendry, 2002, Obernberger et al., 2006, Prochnow et al., 2009).

Several crops have been quoted as candidates for biomass energy generation (Boehmel et al., 2008, David and Ragauskas, 2010, Ra et al., 2012, Sanderson and Adler, 2008). Some authors (Fontoura et al., 2015, Morais et al., 2009, Ra et al., 2012, Strezov et al., 2008) have highlighted elephant grass (Pennisetum purpureum Schum.), mainly for gathering appropriate biomass quality traits and high biomass production.

However, the quantification of the biomass quality is costly and time-consuming. Thus, selection based on morpho-agronomic traits in order to obtain indirect gains in biomass quality is a promising strategy at the initial stages of an elephant grass breeding program for bioenergy. In this sense, the canonical correlation analysis is noteworthy, since it maximizes the estimate of the correlation between two sets of variables (Rajasundaram et al., 2014).

Furthermore, the understanding of the association between calorific value released by biomass combustion and its main morpho-agronomic and biomass quality traits contribute for the selection of genotypes with greater calorific value and biomass production. However, according to Silveira et al. (2015), the simple correlation among traits does not represent the cause-effect measurement, and its direct interpretation may result in mistakes in the selection strategy. In this context, the path analysis is noteworthy since it decomposes the simple correlation coefficient into direct effects and indirect effects in relation to a variable of interest (Tyagi and Lal, 2007).

Morphological variability in elephant grass germplasm can be divided into four groups of standard ecotypes: Cameroon – presents erect genotypes with thick stalks, broad leaves, upright clumps and late flowering; Napier – presents genotypes with thick/intermediate stalks, broad leaves, open clumps and intermediate flowering; Mecker – presents reduced height genotypes with thin stalks, thin and more numerous leaves, and early flowering; and Dwarf – presents lower height genotypes (up to 1.5 m high), and high leaf/stalk ratio (Lira et al., 2010). However, there were no reports on the interrelations between biomass quality and morpho-agronomic traits in these groups, which could determine their potential in the production of bioenergy via direct combustion.

Thus, the objective of this study was to evaluate the aptitude of the groups Cameroon and Napier, aiming at the breeding of elephant grass for the bioenergy production via direct combustion.

Section snippets

Genetic material and experimental conduction

A total of 100 accessions of the Active Elephant Grass Germplasm Bank of Embrapa (BAGCE) were used, of which 18 were classified in the Cameroon group, 44 in the Napier group, four in the Mercker group, and the other accessions were classified as intermediate to the aforementioned groups. However, only the data of the groups Cameroon and Napier were used to compare the aptitude, due to the small number of genotypes in the Mercker group, and to the non-existence of genotypes of the dwarf group in

Napier vs. Cameroon comparison

Table 1, Table 2 show the genotypic values of the morpho-agronomic and biomass quality traits of the groups Napier (44 accessions) and Cameroon (18 accessions). There was significant variability for all of the morpho-agronomic traits for both the Napier and Cameroon groups. The same was observed for biomass quality traits, except for HCEL, which did not present variability in either of the groups.

Considering the F test to contrast the treatment effect – Napier vs. Cameroon – for the 17 traits

Conclusions

In general, the present results suggest that the Cameroon group presents the greatest aptitude when compared with the Napier group for the generation of bioenergy from biomass combustion. The ASH level is highly correlated with and has direct effect on CAV. Genetic breeding from the morpho-agronomic traits within the Cameroon group is recommended; therefore, among the genotypes with higher total dry biomass, it should be selected those with greater height and stalk diameter, in order to obtain

Conflict of interest

The authors declare no conflict of interest.

Acknowledgments

The authors thank the agencies CAPES, FAPEMIG and UNIPASTO for the financial support to this research.

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