Carbon Life Cycle Assessment for Prairie as a Crop in Reclaimed Mine Land

Abstract

ABSTRACTA life cycle assessment with carbon (C) as the reference unit was used to balance the benefits of land preparation practices of establishing tall‐grass prairies as a crop for reclaimed mine land with reduced environmental damage. Land preparation and management practices included disking with sub‐soiling (DK‐S), disking only (DK), no tillage (NT), and no tillage with grazing (NT‐G). To evaluate the C balance and energy use of each of the land preparations, an index of sustainability (Is = CO/CI, Where: CO is the sum of all outputs and CI is the sum of all inputs) was used to assess temporal changes in C.Of the four land preparation and management practices, DK had the highest Is at 8·53. This was due to it having the least degradation of soil organic carbon (SOC) during land‐use change (−730 kg ha−1 y−1) and second highest aboveground biomass production (9,881 kg ha−1). The highest aboveground biomass production occurred with NT (11,130 kg ha−1), although SOC losses were similar to DK‐S, which on average was 2,899 kg ha−1 y−1. The Is values for NT and DK‐S were 2·50 and 1·44, respectively. Grazing from bison reduced the aboveground biomass to 8,971 kg ha−1 compared with NT with no grazing, although stocking density was low enough that Is was still 1·94. This study has shown that converting from cool‐season forage grasses to tall‐grass prairie results in a significant net sink for atmospheric CO2 3 years after establishment in reclaimed mine land, because of high biomass yields compensating for SOC losses from land‐use change. Copyright © 2014 John Wiley & Sons, Ltd.