Carbon budgets of potential tropical perennial grass cropping scenarios for bioenergy feedstock production

Authors: PAWLOWSKI, MEGHAN - University Of Hawaii; MEKI, MANYOWA - Texas Agrilife Research; Kiniry, James; CROW, SUSAN - University Of Hawaii

Submitted to: Carbon Balance and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2018
Publication Date: 9/25/2018
Publication URL: http://handle.nal.usda.gov/10113/6142706
Citation: Pawlowski, M., Meki, M.N., Kiniry, J.R., Crow, S.E. 2018. Carbon budgets of potential tropical perennial grass cropping scenarios for bioenergy feedstock production. Carbon Balance and Management. 13:17. https://doi.org/10.1186/s13021-018-0102-8.
DOI: https://doi.org/10.1186/s13021-018-0102-8

Interpretive Summary: The impact on the environment of using fossil fuels is well recognized, leaving open many options for regional solutions for sustainable replacement fuels. The purpose of this study was to create a baseline carbon (C) budget for a conventionally managed sugarcane production system on Maui, Hawaii, and compare it to three different cropping scenarios for biofuel: (1) conventional sugarcane with a 50% deficit irrigation (sugarcane 50%), (2) ratoon harvested napiergrass with 100% irrigation (napier 100%), and (3) ratoon harvested napier grass with a 50% deficit irrigation (napier 50%). For each unit of biomass produced, the most greenhouse gas (GHG) intensive scenario was sugarcane 50% with a GHG Index (GHGI, a more negative value is better) of 0.11 and the least intensive was napiergrass 50% when a deep soil profile was considered in the net GWP calculation (GHGI=-0.77). Future scenarios for energy or fuel production on former sugarcane land across the Pacific Basin or other volcanic islands should concentrate on ratoon-harvested crops that maintain yields under zero-tillage management over long time periods between kill harvest and reduce costs of field operations and agricultural input requirements. For napiergrass on Maui and elsewhere, the further improvement in GHGI of the production system with deficit irrigation should be considered as an important aspect of planning a sustainable, diversified agricultural landscape.

Technical Abstract: The environmental costs associated with fossil fuel consumption are globally recognized, leaving open many options for regional portfolio solutions for sustainable replacement fuels. The purpose of this study was to create a baseline carbon (C) budget for a conventionally managed sugarcane production system on Maui, Hawaii, and compare it to three different future energy cropping scenarios: (1) conventional sugarcane with a 50% deficit irrigation (sugarcane 50%), (2) ratoon harvested napiergrass with 100% irrigation (napier 100%), and (3) ratoon harvested napier grass with a 50% deficit irrigation (napier 50%). Per unit of biomass yield, the most greenhouse gas (GHG) intensive scenario was sugarcane 50% with a GHG Index (GHGI, a more negative value is better) of 0.11 and the least intensive was napiergrass 50% when a deep soil profile was considered in the net GWP calculation (GHGI=-0.77). Future scenarios for energy or fuel production on former sugarcane land across the Pacific Basin or other volcanic islands should concentrate on ratoon-harvested crops that maintain yields under zero-tillage management for long intervals between kill harvest and reduce costs of field operations and agricultural input requirements. For napiergrass on Maui and elsewhere, the further improvement in GHGI of the production system with deficit irrigation should be considered as an important aspect of planning a sustainable, diversified agricultural landscape.