By B. Jackson, EL. Taylor, R. Schroeder, and S. Ashton
One recent innovation involves the compaction of logging residues into cylindrical bales called composite residue logs (CRL) or biomass bundles (Johansson et al, 2006). CRLs are approximately 24 inches in diameter (61cm) and 10 feet (3m) long. The John Deere 1490D Slash Bundler is currently being used in the Southeast United States. Retail price approximately $400,000.
One of the most appealing aspects of CRLS is, they can be handled similarly to round logs. Bundles are efficiently handled and transported with conventional equipment used for roundwood. Simple modification to the trailer may be required depending upon CRL length and makeup. The 1490D Slash Bundler can produce 18 to 26 bundles per hour. Cost to bundle at the logging deck is approximately $11 to $14 per green ton. Total cost of operations to gather, bundle and deliver is $21 to $25 per green ton. A blend of pine and hardwood offers best economic advantages due to the amount of available material on ground, relative ease of handling and energy content. The calorific heat content has been measured at 10 MJ per green kg (4300 Btu per green lb) and an energy density of 4.5 GJ per m3. By comparison, calorific heat content of oven dry bundles yield 19.7 MJ per ovendry kg (8500 Btu per lb).
Slash bundling offers superior storing characteristics. Private data shows that seasoning bundles (storing) for 11 months reduces moisture content to 25 percent to 30 percent and increase energy value to 17.2 MJ per kg (7400 Btu per pound). The post-seasoned delivered cost is $ 14.50 per ton. To date, approximately 67,280 m3 have been bundled from 15 sites in East Texas. The best comminution option appears to be horizontal grinders at a terminal. Grinders accept bundles easily and costs are minimized. Independent data show a 65-percent reduction in grinding costs, using a 1,500 horsepower electric motor from parasitic load of the electric power plant for which the bundles are serving.
- Johansson J, Liss J, Gullberg T, Bjorheden R. 2006. Transport and handling of forest energy bundles – advantages and problems. Biomass and Bioenergy 30:334-341.