Biomass and potential energy yield of perennial woody energy crops under reduced planting spacing

doi:10.1016/j.renene.2020.02.074

Renewable Energy

Volume 153, June 2020, Pages 1238-1250

https://doi.org/10.1016/j.renene.2020.02.074 Get rights and content

Highlights

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Woody energy crops plantations in Southern Brazil has been studied.
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Planting spacing influenced woody biomass yield, partitioning and growth traits.
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The highest biomass and energy yield was observed for Eucalyptus grown in 2.0 × 1.5 m.
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Residual woody biomass can contribute with 22.8% in the potential energy yield.
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Helpful information for producers interested in energy generation from woody biomass.

Abstract

Woody biomass can be used for supplying energy as a strategy to mitigate climate change and increase energy security by reducing the dependency on fossil fuels. The aims of this study were: (i) to evaluate the biomass production for energy generation; and (ii) to determine the leaf area index, solar radiation interception and mean annual increment of three perennial woody crops Eucalyptus grandis, Mimosa scabrella and Ateleia glazioviana, grown under four planting spacings in Southern Brazil. A field experiment was conducted from September 2008 to September 2018 in Frederico Westphalen, Brazil. The above-belowground woody biomass was determined by the destructive method. Also, the solar radiation interception, leaf area index, potential energy yield, biomass yield and partitioning were evaluated. Findings have shown that the highest biomass yield and potential energy yield were obtained in the planting spacing (2.0 × 1.5 m) for the Eucalyptus grandis. Among the woody species studied, the Eucalyptus grandis was the one that presented the largest potential to produce biomass for energy, followed by Mimosa scabrella and Ateleia glazioviana. Therefore, reduced planting spacings should be recommended for woody energy crops plantations, changing the planting spacing pattern (3.0 × 1.5 m) used by the majority of the forest producers.

Introduction

The use of renewable energy sources is becoming increasingly necessary if we are to achieve the changes required to address the impacts of global change and increase the environment protection. Of the renewable energy sources, woody biomass appears to be the most important in terms of technical and economic feasibility in the coming decades [ [[1], [2], [3], [4], [5]]]. The production of renewable energy from woody biomass is an alternative for the diversification of the Brazilian energy chain [6].

Woody biomass is one of the most promising strategies for the generation of renewable energy in Brazil [ [[7], [8], [9], [10]]]. In this context, new studies involving woody crops that present an energetic potential are needed, such as the species Eucalyptus grandis, Mimosa scabrella and Ateleia glazioviana, which are important for the Brazilian energy chain. Currently, much attention has been focused on identifying and characterizing suitable woody species and its essential characteristics, regarding ecological and silvicultural factors, and those related to the energy potential of woody biomass in order to provide high-energy outputs, to replace conventional fossil fuel energy sources.

In this context, an important question arises: When fossil fuels are depleted, will woody biomass converted to energy-fuel for several needs be enough to provide the energy needs of future generations? Certainly, woody biomass alone will not meet all the energy demand, however, together with different kinds of bioenergy [ [[11], [12], [13], [14], [15]]] that have been deeply investigated, produced and used in the last years, it can provide a large amount of energy-fuel worldwide. Studies show that bioenergy will provide 30% of the world’s energy demand by 2050 [16]. Considering the Brazilian energy chain, there is a great contribution of renewable resources that account for 43.5% of total energy demands in 2016 [17]. Brazil has been conducting research for large-scale production of energy derived from wood, investing in fast-growing woody crops plantations dedicated to the production of wood for energy (short-rotation woody crop).

The concept of short-rotation woody crops plantations (SRWC) was introduced in the 1980s to define woody crop plantations with a large number of trees per hectare in a short-rotation cycle, whose purpose is to produce the largest volume of biomass per unit area and time [18,19]. Moreover, woody biomass for energy generation is considered nearly carbon-neutral [20,21] because the amount of CO₂ released during combustion is nearly the same as taken up by the tree during growth.

In order to meet global energy demand, new research is needed to study woody crops energy plantations, considering different woody crops growing under different planting spacings in order to evaluate the potential for woody biomass production. According to Couto and Müller [18] and Welfle et al. [4], the woody crop management aimed at the production of biomass for energy basically consists of choosing the appropriate species, managing the tree density and planting spacing, and the rotation time of the perennial woody plantations.

The planting spacing is a key factor in the management of woody crops plantations that aimed biomass production. The most used spacings for biomass production for energy are those that provide a useful area varying from 3 m² to 9 m² [22]. The use of reduced planting spacing is being extensively studied and disseminated due to the benefits provided [23,24]. The tendency of reducing the planting spacings for biomass production is highlighted by the need to reduce the crop cycle, resulting in gains in productivity, time and cost with woody crop management [25,26]. However, there is a lack of studies that evaluate in the field the response of different woody crops when grown under reduced planting spacing.

Woody crop management for biomass production is carried out mainly by companies and forest producers. The basic management regime adopted by them is planting with a spacing of 3.0 × 1.5 m and shallow-cut between the 6th and 8th year [ [20,27,28]]. In this context, the authors proposed in this study to evaluate the feasibility of the use of reduced planting spacings, whereas trees grown in these spacings can maximize the solar radiation interception, and increase the biomass production for energy.

Climatic conditions have a great influence on tree growth and yield. Among meteorological variables, solar radiation is one of the most relevant, especially when woody crops plantations are conducted under reduced planting spacings. Wider planting spacings result in less competition for solar radiation while closer spacings can increase tree interaction, resulting in variations on tree growth and yield. Moreover, closer spacing promotes faster development of the leaf area index, which increases light interception and photosynthesis [28].

Woody energy crops have been deeply studied in the last years in the Brazilian forestry chain [ [6,7,19]]. We intend with this study to evaluate the use of reduced planting spacings and study the feasibility of different woody crops in addition to Eucalyptus species. Also, it is important to quantify the potential use of residual woody biomass (including branches, leaves and roots) to generate energy.

We hypothesized that woody crop managers can accelerate growth and increase the production of woody biomass by manipulating available natural resources, especially solar radiation, using the most appropriate planting spacing. Therefore, the aims of this study were: (i) to evaluate the biomass production for energy generation; and (ii) to determine the leaf area index, solar radiation interception and mean annual increment of three perennial woody crops Eucalyptus grandis, Mimosa scabrella and Ateleia glazioviana, grown under four planting spacings in Southern Brazil.

Section snippets

Study area and experimental design

The study was conducted from September 2008 to September 2018 in the city of Frederico Westphalen in the state of Rio Grande do Sul, Brazil, at the coordinates 27º22′S, 53º25′W and an altitude of 480 m. The climate is characterized as Cfa, i.e., humid subtropical with mean annual temperatures of 19.1 °C, varying from 0 to 38 °C, according to Köppen’s climates classification [29]. The soil was classified as Oxisol typical, clayey texture, deep and well-drained. Fertilization was performed before

Biomass yield and partitioning

The biomass yield for the three short-rotation woody species studied grown under four planting spacings is shown in Fig. 3. We observed a significant difference in the biomass yield. The woody crop Eucalyptus grandis presented the higher biomass yield when cultivated under the 2.0 × 1.5 m spacing, which was 21.6, 19.2 and 36.6% higher than 2.0 × 1.0, 3.0 × 1.0, and 3.0 × 1.5 m spacing, respectively. Moreover, the widest planting spacing was responsible for the lower production of biomass for

Discussion

This study demonstrated that planting spacing has a significant influence on woody energy crop plantations. Our results showed that reduced planting spacing promotes higher values of biomass yield, potential energy yield and growth traits according to the woody species studied. Also, we observed a significant difference in the potential to produce woody biomass among species. This may be related to the ability of each species to acquire available resources, especially solar radiation, the

Conclusion

The biomass yield and potential energy yield of the woody species studied were affected by the planting spacings. The highest biomass production and potential energy yield were observed for the Eucalyptus grandis grown under the 2.0 × 1.5 m spacing. Among the woody species studied, the Eucalyptus grandis presented the largest potential to produce biomass for energy, followed by Mimosa scabrella and Ateleia glazioviana.

The hypothesis of this study was confirmed since forest managers can

CRediT authorship contribution statement

Felipe Schwerz: Conceptualization, Formal analysis, Investigation, Writing - original draft, Funding acquisition, Project administration. Durval Dourado Neto: Formal analysis, Writing - review & editing, Supervision. Braulio Otomar Caron: Conceptualization, Resources, Writing - review & editing, Funding acquisition. Claiton Nardini: Methodology, Writing - review & editing. Jaqueline Sgarbossa: Methodology, Writing - review & editing. Elder Eloy: Conceptualization, Methodology, Writing - review

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The authors are grateful to the National Council for Scientific and Technological Development (Grant No. 142261/2017-3) and São Paulo Research Foundation (FAPESP) (Grant No. 2018/06023-6) for the financial support of the author Felipe Schwerz. Also, I would like to thank the members of the Agrometeorology laboratory for the help in this project.

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Biomass and potential energy yield of perennial woody energy crops under reduced planting spacing

Highlights

Abstract

Introduction

Section snippets

Study area and experimental design

Biomass yield and partitioning

Discussion

Conclusion

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgments

Biomass Bioenergy

Energy Pol.

Biomass Bioenergy

Biomass Bioenergy

Renew. Sustain. Energy Rev.

Energy Build.

Energy

Renew. Sustain. Energy Rev.

Renew. Sustain. Energy Rev.

Biomass Bioenergy

Appl. Energy

Biomass Bioenergy

For. Ecol. Manage.

For. Ecol. Manage.

Biomass Bioenergy

Renew. Sustain. Energy Rev.

Biomass Bioenergy

For. Ecol. Manage.

For. Ecol. Manage.

J. Hydrol.

Biomass Bioenergy

Biomass Bioenergy

For. Ecol. Manage.

Ind. Crop. Prod.

For. Ecol. Manage.

Renew. Sustain. Energy Rev.

For. Ecol. Manage.

For. Ecol. Manage.

Generating low-carbon heat from biomass: life cycle assessment of bioenergy scenarios

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