At the time the plant operator was paying closer to $20 a ton for the coal - and the plant did not factor in some of the combustion issues, or some of the costs in growing the grass, since EPA mandated that the field could only contain permitted species and thus it had to be treated with some weed killers to remove unwanted species. (This is from a paper that was given at Dubuque last year, and which I wrote about at the time .) Going back to check the reference I see I got some of the numbers wrong

Three test burns have been made, addressing such issues as boiler corrosion.

They harvest the grass after a killing frost, so that virtually all the nutrients have left the plant body which is harvested, and are left in the root bit which is left on site. The grass is bundled into special bales 3 x 4 x 8 ft, and hauled to storage. You can’t leave it in the field as it wicks water, and it must be stored on gravel in a barn (same reason). Bale integrity controls energy availability. The bales weigh 1,000 lb and when reground for combustion they prove to be abrasive, and moisture content helps with this (12% moisture at the boiler if kept well, which matches the harvested value). The third test burn used 25,000 tons of grass over the 90-day test period. It cost $61 per ton for haulage, and $26 per ton for re-processing the grass at the power plant into small fragments (< ¾ inch) that could be blown into the furnace. The plant was paying about $20 a ton for the coal, and in the above you will note that the farmer did not get paid for the grass. Like the coal, the grass had to be totally consumed by the fireball within 3 seconds of being fed into the boiler fireball.

They displaced 2% of the coal in these tests, and are now permitted to burn the switchgrass.