1. Aboveground biomass C and N Belowground biomass C and N
CARBON LIFE CYCLE ANALYSIS APPROACH FOR BIOENERGY Plantation and alley cropping systems in Louisiana and Arkansas K.C. Dipesh1, Michael A. Blazier1, Hal O. Liechty2, Matthew H. Pelkki2, Montgomery W. Alison Louisiana State University AgCenter, 2Arkansas Forest Resources Center
ABSTRACT
The biofuel industry has received worldwide interest as biofuels offer several ecological and economic benefits. Bioenergy crops such as short-rotation woody crops and perennial grasses are high biomass-yielding crops that can provide ecosystem services such as carbon sequestration. Bioenergy crops can be grown on retired agricultural sites such as those in the Lower Mississippi Alluvial Valley (LMAV). The LMAV has high potential for bioenergy crop production because of its long growing season, well-developed infrastructure and moreover, LMAV has land removed from conventional agricultural crop production due to chronically suboptimal yields. An ecological justification for bioenergy crops is their production is carbon neutral relative to fossil fuels, so it is important to quantify the carbon efficiency of different potential biofuel cropping systems. Cradle-to-grave carbon Life Cycle Analysis (LCA) provides an excellent means to synthesize carbon influx and efflux within biofuel cropping systems. We plan to carry out an LCA on ‘Alamo’ switchgrass (Panicum virgatum L.), cottonwood (Populus deltoides Bartr.), switchgrass-cottonwood alley cropping compositions, and soybean-grain sorghum (Glycine max-Sorghum bicolor) rotations grown within the LMAV of Louisiana and Arkansas in a study started in The LCA will incorporate carbon data collected from biomass, soil, and biofuel conversion assays. Carbon equivalent emission data from the pre-establishment stage to the post-harvest stage will be included in the LCA. This approach will help us estimate the overall greenhouse gas emissions of each crop and cropping system, thereby allowing us to evaluate the production potential and ecological impacts of these biofuel production systems.
Data collection
Table 1 Table showing the months/years of field data collection from the study sites#
Biomass provides the benefits of sustainability, soil and water quality, and national security concerns (Albaugh et al. 2012). Biomass contribution is likely to increase as bioenergy crops are considered to be carbon neutral or carbon sequesters unlike fossil fuels. The Lower Mississippi Alluvial Valley (LMAV) has a high potential for cellulosic biomass production (Tripp et al. 2009). We aim to carry out a comparative carbon Life Cycle Analysis (LCA) study on the efficiency of growing switchgrass (Panicum virgatum L.), cottonwood (Populus deltoides Bartr.) ,and conventionally-grown row crop soybean-grain sorghum (Glycine max-Sorghum bicolor) rotation in the LMAV to ensure the optimum benefits of higher biomass production and lower greenhouse gases (GHGs) emission.
INTRODUCTION AND RATIONALE
Aboveground biomass C and N
Belowground biomass C and N
Soil C & N*
CO2 flux
N2O, CH4 AR PT RO
Cottonwood
2013
2011
2012, 2013,
2014 ( Jan-July)
Jun 2013 – Jun 2014
2012, 2013, 2014 ( Jan-July)
Mar 2013-Jul 2014
No data
Switchgrass
Soybean/Sorghum
*Data were collected only in April, July, and December from that year
# Sites include Archibald (AR), Pine Tree (PT), and Rohwer (RO)
Carry out carbon LCA study within each cropping system
Measure gaseous emissions of CO2, N2O, and CH4 gases
OBJECTIVES
Table 2 Table showing potential reference sources to be used during the study
Variables
Source
Vehicle, fuel type, and time data for the field operations
Self-collected and calculated
Carbon equivalent electricity required for irrigation, seed production, etc
West and Marland 2002, Lal 2004, Hill et al. 2006
Carbon equivalent emissions from fuel burns during crop establishment
West and Marland 2002, Lal 2004, Zielinska et al. 2004, Rounce et al. 2010
Emissions during herbicide and fertilizer production
West and Marland 2002, Lal 2004
Total biomass produced
CO2, N2O, and CH4 gases
Energy required during biomass conversion to drop-in biofuels (Facility energy use)
Hill et al. 2006
Emissions from drop-in biofuels usage
SCHEMATIC DIAGRAM OF LCA STUDY
Study sites and plot establishment
The study was established in 2009 and includes 2 study sites in Arkansas
and 1 in Louisiana along the LMAV (Fig. 1). Each block consists of five
treatments: 1) 100% cottonwood (W), 2) 100% switchgrass (S), 3) 67% cottonwood and 33% switchgrass (WS), 4) 33% cottonwood and 67% switchgrass (SW), and 5) a control consisting of a conventional soybean-grain sorghum rotation (C) (Figure 2). Cottonwood cuttings were planted at a density of 4495 per ha-1 in Similarly, seeds of ‘Alamo’ switchgrass seeds were drilled in the soil at 11.2 kg ha-1 in 2009 with replanting in 2010 where needed. The row crop plots consist of soybean plantation in 2009, 2011, 2012, and 2014, and sorghum in 2010 and 2013.
METHODS
Product I
-Biomass (+)
Establishment stage
-Site preparation (-)
-Plantation & seeding (-)
Mid-stage
-Competition control (-)
-Fertilzation (-)
Harvesting stage
-Biomass harvesting (-)
-Processing (-)
Pre-establishment stage
-Seed production (-)
-Cutting preparation (-)
Post-harvesting stage
-Transportation to the facility (-)
Product II
-Annual litterfall (+)
-Respiration (-)
Product III
-Emissions (-)
Inputs
- Gasoline, diesel, lubricants (-)
-electricity (-)
Final Output
-Drop-in biofuels (+)
Processing
-Conversion (-)
Usage
Outputs
Fig. 1. Study sites W S C
90 m
15 m
30 m
Fig 2(a). Schematic description of plots at each site. The smaller plot inside the W plot is a representation of a sub-plot (17X45 m) to monitor vegetation biomass.
Fig. 2(b). Study plots with treatments.
Albaugh JM, Sucre EB, Leggett ZH, Domec JC, King JS (2012) Evaluation of intercropped switchgrass establishment under a range of experimental site preparation treatments in a forested setting on the Lower Coastal Plain of North Carolina, USA. Biomass and Bioenergy, 46, 673–682
Tripp S, Powell SR, Nelson P (2009) Regional strategy for biobased products in the Mississippi Delta, Executive Summary. Battelle Technology Partnership Practice, pp 23.
REFERENCES
We would like to express sincere gratitude to Agriculture and Food Research Initiative of the National Institute of Food and Agriculture, Grant No We would also like to thank USDA Sustainable Agriculture and Research and Education program, Sun Grant, Arkansas Forest Resource Center, and Louisiana State University Agricultural Center.
ACKNOWLEDGMENT
We will be able to study the potential impacts on carbon cycle as a result of converting land for conventional cropping systems to biofuel feedstock system. In addition, emissions of greenhouse gases as a result of the conversion will also be estimated. We will also be able to tease out the total amount of energy used and emissions released by each system, which will probably work as a baseline for future energy budget studies in agroforest systems. Meanwhile, the yield potential of the LMAV as an agricultural industry will also be evaluated.
EXPECTED OUTCOMES AND FUTURE STUDIES
Fig 3. System boundary along with variables considered for the study. The -ve signs indicate carbon loss while +ve sign indicates carbon gain. See Table 2 for the reference sources.