Bulk compressibility behavior for select crops

Authors: TURNER, AARON - Clemson University; MONTROSS, MICHAEL - University Of Kentucky; MCNEILL, SAMUEL - University Of Kentucky; Casada, Mark; PETINGCO, MARVIN - Kansas State University; MAGHIRANG, RONALDO - University Of Illinois; THOMPSON, SIDNEY - University Of Illinois

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2023
Publication Date: 10/1/2023
Citation: Turner, A.P., Montross, M.D., McNeill, S.G., Casada, M.E., Petingco, M.C., Maghirang, R.G., Thompson, S.A. 2023. Bulk compressibility behavior for select crops. Applied Engineering in Agriculture. 39(5):509-518. https://doi.org/10.13031/aea.15593.
DOI: https://doi.org/10.13031/aea.15593

Interpretive Summary: Bulk-density is an important metric for stored grains and oil seeds for calculating compressibility, which is critical for generating accurate estimates of grain inventory and calculating wall loads inside grain bins. Accurate equations require the ability to account for different densities at different depths in a bin. This study established pressure-density equations for nine common grains and oilseeds (barley, canola, corn, oats, rice, sorghum, soybeans, hard red winter wheat, and soft red winter wheat) based on new data for seven of the crops that was combined with other datasets from previous work. Two of the tested equations performed especially well for characterizing the compressibility relationship and were further evaluated by incorporating each into a model for estimating bin inventory. Both equations performed well in this application, with margins of errors of less than 2.5% except with oats. This new expanded compressibility data set produces equations that are more robust than the previous data alone and should lead to improved predictions of compaction and wall loads in grain bins, particularly with larger bins with higher internal pressure, providing more accurate bin design and grain inventory calculations.

Technical Abstract: Knowledge of the pressure-dependent bulk density increase observed in stored grains and oil seeds, commonly referred to as packing or compressibility, is important for maintaining accurate grain inventory, evaluating wall loads, and other applications that require estimating density at specific depths in a bin. This study presents compressibility equation parameters determined utilizing a compilation of the best data available, including previously published and new datasets. In all, confined uniaxial compression tests for nine crops (barley, canola, corn, oats, rice, sorghum, soybeans, hard red winter wheat, and soft red winter wheat) were included. The data was fit using two candidate compressibility equations, both of which generally fit well and resulted in root mean squared errors ranging from 1.7 to 7.1 kg/m^3, depending on the model and crop. For crops with full scale bin data available from previous research, the resulting equations were applied to estimate inventory and were compared with the measured mass of grain in the bin. Results from both equations were similar, and apart from oats, median errors were less than 2.5%.