Because of the lack of large commercial utilization of lignocellulosic biomass for liquid fuel production, very little commercial know-how and experience are available to learn from. Therefore, we will examine the inbound logistics of grain and corn cobs in a grain elevator and a dry-grind corn ethanol plant (biorefinery) in order to have an insight of the inbound logistical operations that take place at the plant gate during the delivery of feedstocks for further shipment or the production of bioproducts and biofuels. The brief description of these handling operations is taken from Mukunda (2007) and the material flowchart presented in Figure 7.8.

Grain Handling in a County Elevator

A brief overview of the grain handling in an elevator is presented. There are a number of layouts for inbound receipts of grain trucks, but the one described is from Berruto and Maier (2001). Grain is delivered to a county elevator with hopper bottom trucks with a capacity to carry about 25,500kg (1000bushel) grain. The first stop of the grain delivery truck at the elevator is the sampling station where samples of grain are pulled from the truck load using automatic telescopic probes. The pulled samples are graded to determine U. S. grades for grain quality by which the price to be paid is set. The variables tested to determine U. S. grade for corn include the moisture content, test weight (bulk density), broken kernel and foreign mate­rial (BCFM) and damaged kernels total (DKT), and heat-damaged kernels (Stored Product Management, E-912 1995). While the samples are being graded, the trucks drive up to an unloading station where it is weighed for gross weight, unloaded in a dump pit, and then weighed again for tare weight to determine the weight of the grain delivered. A ticket is made out for the delivery after this process. The moisture content of the grain determines if the grain is directly sent to one of the many storage silos or if it is first cleaned and dried to a safe moisture level before storage. A discount to the price is estimated for every percent point of moisture removed in drying.

The design layout of an elevator facility is very important and determines the efficiency at which inbound grain trucks flow through the facility, especially when delivering identity — preserved grain or different grain types during peak harvest season. Coordination of the opera­tions in delivering the grain from sampling to exit of the truck using a queue management system is vital to reducing the time it takes to service customers delivering grain to the facility. A goal is to minimize the average waiting time per truck so that the maximum designed capac­ity for the facility can be obtained for most of its service period. The cost of shipping grain is also reduced if trucks spend a minimal time waiting to receive their cargo. The inbound logistics of grain at an elevator does give us a glimpse of the challenges that would be faced processing large volumes of inbound trucks with plant biomass through a biorefinery.