Life Cycle Assessment of Select Agricultural Practices: Assessing the Potential for Climate Mitigation

Author

Mukesh Dev Bhattarai, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2016

Degree Name

Doctor of Philosophy

Department

Environmental Resources & Policy

First Advisor

Secchi, Silvia

Abstract

Climate change may have detrimental effects on agriculture productivity (Challinor et al., 2009). At the same time, agriculture also plays a role in contributing to the causes of global warming (IPCC, 2009). The present research examined current agro-management practices of select agriculture management practices and products with a threefold objective, namely i) to understand the possible impact of climate change on crop yields, ii) to examine the carbon sequestration potential of select agricultural crops and management practices, and iii) to conduct a thorough life cycle assessment to estimate the carbon footprint of select agriculture crops and management practices, so as to help policy makers, planners and business managers in devising appropriate mitigation and adaptation policy frameworks and make sensible management decisions in the context of climate change. The research was conducted in a series of three studies. The first study investigated future corn and soybean yields in the Raccoon watershed in the US Corn Belt using projected climate data. This study used the Environment Policy Integrated Climate (EPIC) model to estimate the impact of climate change for 2015-2099 with data downscaled from eight atmosphere-ocean general circulation models (AOGCMs) with three emissions pathways reflecting low, medium and high greenhouse gas scenarios. Soil properties were gathered from the Soil Survey Geographic Database and data on crop rotation was derived from CropScape, a geospatial cropland data layer product of the US National Agricultural Statistics Service. Our findings show that 5-year averages of both corn and soybean yields for 2095-2099 depicted by all eight AOGCMs under low and medium carbon scenarios will increase in comparison to the 5-year average yields for 2015-2019. However, under the high carbon scenario, 5-year averages of both corn and soybean yields for 2095-2099 will decline in comparison to the 5-year average yields for 2015-2019 pointing to the effects of climate change. The study also examined the possible impact of carbon fertilization on yields. The results show that carbon fertilization of soybean, a C3 plant, may contribute to an increase in yield of 3% to 22% while its contribution to the growth of corn, a C4 plant, will be much lower. The second study focused on land-based carbon sequestration possibilities. Land-based carbon sequestration constitutes a major low cost and immediately viable option in climate change mitigation. Using downscaled data from eight atmosphere-ocean general circulation models for a simulation period between 2015 and 2099, the study examined the carbon sequestration potential of alternative agricultural land uses in an intensively farmed Corn Belt watershed and the impact of climate change on crop yields including impact on switchgrass. The results of the study show that switching from conventional tillage and continuous corn to no-till corn-soybean can sequester the equivalent of 192.1 MtCO2 eq of soil organic carbon per hectare with a sequestration rate of 2.26 MtCO2 eq ha-1 yr-1. The results also indicate that switchgrass can sequester the equivalent of 310.7 MtCO2 eq of soil organic carbon per hectare with a sequestration rate of 3.65 MtCO2 eq ha-1 yr-1. The findings of this research suggest that climate change does not have a significant effect on switchgrass yields, unlike on corn and soybean yields, possibly due to the carbon fertilization effect. As mentioned, agriculture can contribute to climate change mitigation efforts by providing low–land-based options through changes in agricultural management practices. A thorough life cycle assessment is necessary to compare various opportunities provided by a variety of agricultural approaches. The last study is a cradle-to-farm gate life cycle assessment of the contributions of select agricultural practices to mitigate global warming. The study focused on land-based practices including crop rotations instead of just individual crops. In the assessment, the study also included examinations of below-the-ground soil to determine the organic carbon sequestration potential of such practices, which most of the time is ignored in life cycle assessments due to lack of data. Specifically, the study examined three farming practices in the intensively farmed Raccoon watershed: continuous corn rotation with conventional tillage, corn-soybean rotation with no-till, and switchgrass. The assessment was conducted based on land units (hectares), instead of utilizing the usual practice of reporting life cycle assessment in product units, such as kilograms. The results of the life cycle assessment reveal that among the three agricultural practices, switchgrass has the lowest carbon footprint overall, and continuous corn rotation has the highest. Switching from continuous corn to switchgrass would reduce the overall greenhouse gases the most, by 6.30 Mg CO2eq/ha/yr, or by 62% compared to the emissions generated by the continuous corn rotation. Similarly, planting switchgrass instead of a corn-soybean rotation would reduce the overall emissions of greenhouse gases by 1.84 Mg CO2eq/ha/yr, or by 32% compared to the corn-soybean rotation. Finally, switching from continuous corn to the corn-soybean rotation would reduce overall greenhouse gases emissions by 4.46 Mg CO2eq/ha/yr or by 44% of the emissions generated by continuous corn. These findings can inform policy discussions on the potential of agriculture’s role in climate change mitigation.