2013 Annual Report
1a.Objectives (from AD-416):
1. Determine the physical and thermal characteristics of biomass from perennial warm-season grasses and annual crop residues; 2. Develop new protocols for assessing the size and particle size distribution of process biomass; and 3. Apply the new protocols in assessing the effect of size reduction on the densification and storage of biomass.
1b.Approach (from AD-416):
Herbaceous biomass of perennial warm-season grasses and annual crop residues will be harvested from ongoing ARS research at Mandan, ND and characterized for physical and thermal properties. Biomass will be analyzed for shear and tensile strength, thermal characteristics via thermal gravimetric analysis and differential thermal analysis, and storage hydration characteristics with a controlled environment chamber.
Mechanical properties such as tensile and shear stresses and specific tensile and shear energies of big bluestem, corn stalks, intermediate wheatgrass and switchgrass were determined with a high capacity MTI-100K universal testing machine equipped with adapted tensile clamps and a specially designed and fabricated double-shear device. Ultimate shear stresses of big bluestem (7.33 MPa), corn stalks (7.33 MPa), and intermediate wheatgrass (6.23 MPa) were significantly smaller (p < 0.05) than switchgrass (13.39 MPa). These results indicate shear-dominant size reduction devices (e.g. knife mills, chippers) would be more energy efficient. A manuscript reporting these results submitted to Transactions of the ASABE (Ref: FPE-10131-2013) is being revised based on review comments.
Standardization of biomass feedstocks by mixing for a desired gross calorific value (GCV) was tested using three biomass feedstocks, switchgrass, wheat straw, and field pea stalk. Equations were derived designing biomass proportions for a desired biomass mixture GCV. Two- and three-component biomass mixtures in simple equal and designed proportions were tested in the laboratory and analyzed using chi-square test. Results are currently being analyzed for publication.
Correlation of size reduction energy (SRE) with particle size distribution (PSD) parameters and also mechanical properties are continuing. Initial results indicate several PSD parameters correlate well (r > 0.9) with SRE and are also influenced by crop type (big bluestem, corn stalks, and switchgrass) and the size reduction device (knife mill and hammer mill). Correlation between the calorific value and thermogravimetric analysis (TGA) characteristics is underway.