Energy cane: a new biomass with potential for bioenergy production
Traditionally, sugarcane breeding programs have always prioritized selecting sugarcane genotypes with high sugar content; consequently, a considerable part of the genes contributing to increase fiber content were gradually eliminated from commercial varieties (Creste et al. 2014). Moreover, there was never any interest in selecting sugarcane varieties with high fiber content, since it would hinder industrial extraction of the juice.
More recently, due to the industrial sector’s increased interest in genetic materials with higher fiber concentration for bioelectricity and cellulosic ethanol production, energy cane production has begun to be studied and encouraged in Brazil. Energy cane is considered a good alternative for the production of biomass, since, like sugarcane, the Brazilian climatic conditions should favor its production performance, while the sugarcane mills can be adapted for processing this new raw material.
In the last decade, breeding companies have started to select energy cane genotypes and have begun to commercialize these materials to bioenergy producing companies in Brazil. The advantage of producing more fiber instead of sugar is that the plants tend to be more vigorous and rustic, which generates economic and environmental benefits. Despite the lack of information about the crop, energy cane is believed to have greater vigor than sugarcane because it has a greater number of alleles originating from the species Saccharum spontaneum compared to Saccharum officinarum, which is used as a source of genes for disease resistance and sprouting vigor of the ratoons (Bischoff et al. 2008).
Energy cane genotypes tend to adapt better to low fertility soils, as they are less demanding in water and nutrients, more resistant to pests and diseases, and have greater competitive ability against invasive plants, resulting in greater efficiency in their cultivation (Carvalho-Netto et al. 2014). According to Matsuoka et al. (2012), energy cane, when compared to sugarcane, presents even greater longevity, and maintains more stable productivity throughout the crop cycles, due to the great vigor of the ratoon of this type of plant. However, despite these several reported benefits, energy cane genotypes are still recent in the market and consequently, there are few studies proving the pros and cons of energy cane cultivation in Brazil.
In the last decade, the sugar-energy sector made the first tests with energy cane cultivation in Brazil and showed promising results, but also encountered the absence of a technological package for the cultivation and industrial use of this biomass. It is understood that energy cane, despite having a genetic similarity to sugarcane, must have its own technological package for its production and processing, which will involve the main agricultural practices and also the most appropriate industrial settings for the transformation of this biomass into bioenergy.
Besides the biomass production capacity, the potential use of energy cane for the production of bioenergy and biofuels depends on the composition of the raw material. The mineral and structural composition and moisture level of plant biomass influence energy production by increasing or reducing the efficiency of biomass conversion plants (Tanger et al. 2013). High levels of lignin are desirable for biofuel production, however high concentrations of N, alkali metals and alkaline earth metals and/or ashes in biomass can reduce the efficiency of the thermochemical conversion of the fuel by causing fouling, slagging and corrosion during its combustion (Shahandeh et al. 2011; Tröger et al. 2013). Similarly, high moisture contents can cause incomplete combustion of the material, reducing the efficiency of the process (Tanger et al. 2013). Thus, the chemical characterization of the feedstock, energy cane, is of fundamental importance.
Although the potential use of energy cane depends on the composition of the raw material and the extraction of nutrients, there are still few studies in the literature evaluating such parameters in energy cane clones, especially in Brazil, because the selection of energy cane genotypes by improvement programs in the country is relatively recent. These responses will be important not only for energy conversion processes (Sami et al. 2001), but also for the long-term sustainability of cropping systems (Somerville et al. 2010). In view of this, the objective of energy cane studies focusses on the characterization of biomass partitioning (dry leafs, shoot and stem), biomass mineral composition and nutrients removal for energy cane genotypes in order to highlight promising genotypes as a source of plant biomass.
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Fundamental Bibliographical References