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A 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 (I s = C O /C I , Where: C O is the sum of all outputs and C I 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 I s at 8·53. This was due to it having the least degradation of soil organic carbon (SOC) during land-use change (À730 kg ha À1 y À1 ) and second highest aboveground biomass production (9,881 kg ha À1 ). The highest aboveground biomass production occurred with NT (11,130 kg ha À1 ), although SOC losses were similar to DK-S, which on average was 2,899 kg ha À1 y À1 . The I s 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 À1 compared with NT with no grazing, although stocking density was low enough that I s 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 CO 2 3 years after establishment in reclaimed mine land, because of high biomass yields compensating for SOC losses from land-use change.

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