Evaluation of two round baling systems for harvesting understory biomass

The objective of this study was to evaluate the performance and to estimate costs of two round baling systems for harvesting understory biomass. One system was a cutter-shredder-baler prototype (Bio-baler). The other system required two successive operations. The first operation was cutting and shredding with a Supertrak tractor equipped with a Fecon mulcher head. The second operation was baling with a Claas baler. The machines were evaluated in three different pine stands on the Osceola National Forest in Florida, United States. Data collection included time study, fuel consumption and bale measurements. Material was collected from a sample of bales for heat and moisture content determination. On the most representative site (Site 2), the Bio-baler recovered 8.05 green t ha−1 while the mulcher and the Claas baler recovered 9.75 green t ha−1 (43 and 52 percent of original understory biomass, respectively). Productivity was 0.30 ha h−1 for the Bio-baler and 0.51 ha h−1 for the Claas baler. Density of the bales was 321 green kg m−3 for the Bio-baler and 373 green kg m−3 for the Claas baler. Average net heat content was 6263 MJ bale−1 for the Bio-baler and 6695 MJ bale−1 for the Claas baler with biomass containing 38 percent of moisture content on a wet basis. Cost per unit area was less with the Bio-baler (US$320.91 ha−1) than with the mulcher-baler system (US$336.62–US$596.77 ha−1).

► Two prototype forest understory harvesting machines were tested and collected 8 to 10 green t ha−1.
► Biomass collected was slightly less than half of the total understory biomass available.
► Cutting and baling forest understory cost approximately $40 t−1 when the production rate was 2.3 green t hr−1.