While cost-effective biomass feedstock supply chain systems often focus on maximizing crop yields, there is another way to amplify efficiencies in the supply chain. By increasing the bulk density of the feedstock in the transportation and packing process, it will result in additional cost savings.
Bulk density is a term used to describe the amount of a given material that will fit inside a cubic foot of space. Essentially, the greater the amount of a harvested crop in a cubic foot, the less space you need to transport it. Materials with higher density are more effective to transport, as more weight can be placed on each truck. Higher density materials require fewer trucks, reducing your transportation fuel and maintenance expenses.
Every energy crop has a different density which leads to a number of different handling and packaging options. For example, switchgrass can be square baled, round baled, or chopped in the field. Each of these processes affects the number of trucks and truck loads needed to move that material around. The bulk density of a square bale or large round bale is around 10 to 12 lbs per cubic foot.
However, chopped switchgrass is a light, loose material that does not pack well (even under its own weight). Traditionally, it is blown into a tip wagon, but when using this technique bulk densities of only 6 lbs per cubic foot have been shown. Until recently, chopped switchgrass, while an easier method than baling, has not been very cost effective to transport.
To address this challenge, Genera Energy Inc., partnered with the University of Tennessee to develop a unique system that compresses field-chopped material using a hydraulic ram. Using this prototype system, bulk densities of 11 to 12 lbs per cubic foot have been achieved with chopped switchgrass. These numbers are very comparable to baled material and have the added advantage of not having to be staged in the field like baled material. This new bulk-format system offers feedstock growers a better way to harvest, handle, store, and deliver high-tonnage feedstocks like switchgrass.
By Marshall Hauser, Feedstock Information Systems Developer