Central Control for Optimized Herbaceous Feedstock Delivery to a Biorefinery from Satellite Storage Locations

Abstract

The delivery of herbaceous feedstock from satellite storage locations (SSLs) to a biorefinery or preprocessing depot is a logistics problem that must be optimized before a new bioenergy industry can be realized. Both load-out productivity, defined as the loading of 5 × 4 round bales into a 20-bale rack at the SSL, and truck productivity, defined as the hauling of bales from the SSLs to the biorefinery, must be maximized. Productivity (Mg/d) is maximized and cost (USD/Mg) is minimized when approximately the same number the loads is received each day. To achieve this, a central control model is proposed, where a feedstock manager at the biorefinery can dispatch a truck to any SSL where a load will be available when the truck arrives. Simulations of this central control model for different numbers of simultaneous load-out operations were performed using a database of potential production fields within a 50 km radius of a theoretical biorefinery in Gretna, VA. The minimum delivered cost (i.e., load-out plus truck) was achieved with nine load-outs and a fleet of eight trucks. The estimated cost was 11.24 and 11.62 USD/Mg of annual biorefinery capacity (assuming 24/7 operation over 48 wk/y for a total of approximately 150,000 Mg/y) for the load-out and truck, respectively. The two costs were approximately equal, reinforcing the desirability of a central control to maximize the productivity of these two key operations simultaneously.

Optimization of herbaceous feedstock delivery to a network of supply depots for a biorefinery in the Piedmont, USA

“…The depot sites were chosen from 34 potential biorefinery locations, defined as multi‐county production zones, in the Piedmont province 5 . The study area was chosen to encompass a region that has already undergone extensive research into the logistics for delivery of herbaceous feedstock from SSLs to a potential biorefinery centered in Gretna, Virginia 11,16 . Three zones were selected from the south central Virginia Piedmont (VA5, VA6, VA7) and two zones were selected from the north central North Carolina Piedmont (NC2, NC3) 5 (Fig.…”

“…Resop et al 16 . analyzed a set of 199 SSLs within a 48 km radius of the potential biorefinery and estimated the feedstock delivered to the biorefinery for each week in a 49 week annual operation.…”

“…It was assumed that the hauling for load‐out operations would consist of two 20‐bale handling units per truck 15 . Modern balers can produce 5 × 4 round bales of switchgrass, which weigh about 0.4 Mg, resulting in about 16 Mg per truckload 16 …”

“…To obtain an estimate of the minimum number of load‐out operations required to supply each depot, the following design constraints were used. The average expected load‐out productivity was assumed to be 60 Mg day − 1 , based on a previous study of load‐out operations for the Gretna database 16 . However, it is expected that the achieved productivity will vary from depot to depot depending on the number of load‐out operations and the amount of feedstock in storage.…”

“…The method for scheduling moves between SSLs in the load‐out sequence was described by Resop et al 16 . The time allowed for moves between SSLs was assumed to be constant (0.5 day per move).…”