|DADSON, ROBERT - University Of Maryland Eastern Shore (UMES)|
|HASHEM, FAWZY - University Of Maryland Eastern Shore (UMES)|
Submitted to: Energy and Fuels
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2014
Publication Date: 11/26/2015
Citation: Mullen, C.A., Boateng, A.A., Dadson, R.B., Hashem, F.M. 2015. Biological mineral range effects on biomass conversion to aromatic hydrocarbons via catalytic fast pyrolysis over HZSM-5. Energy and Fuels. 28:7014-7024.
Interpretive Summary: The Delmarva Peninsula is home to a large portion of the United States poultry industry. The raising of nearly 570 million birds has led to a large environmental problem for the Chesapeake Bay. The leaching of nutrients (e.g. phosphorus, potassium and nitrogen) into the watershed from poultry manure left on the ground or used as fertilizer has led to levels of nutrients in the bay that have detrimental effects on native ecosystems. A potential mitigation strategy for this problem is to grow crops that accumulate these nutrients from the soil into their plant material, and then harvest these crops for removal from the watershed. Crops that accumulate minerals include switchgrass, sorghum and miscanthus and one use for these crops could be as a feedstock for biofuels. Pyrolysis (heating in the absence of air) based methods of biomass conversion would be especially attractive for this application because the accumulated nutrients would be concentrated into a bio-char product that could be economically shipped out of the watershed area. At the same time a liquid product called bio-oil that can be refined into fuels would be produced. Especially of interest is a process called catalytic fast pyrolysis (CFP) that can produce a liquid rich in aromatic hydrocarbons, chemicals which are found in gasoline and diesel fuels. However, the effects of the levels of nutrients and minerals on the CFP process are not completely understood. We studied the CFP of a set of 20 switchgrass, sorghum and miscanthus samples that were grown on poultry manure treated soils resulting in a sample set that had a wide, but biologically relevant, range of these mineral components. We found that the level of some components, specifically potassium and iron, correlated with the yield and composition of the CFP products. Higher potassium levels negatively affected the yields of aromatic hydrocarbons, but iron had a positive effect on those yields. This information is important to those designing CFP systems and those evaluating various biomasses for biofuels production via pyrolysis based processes.
Technical Abstract: A set of 20 biomass samples, comprising 10 genotypes of switchgrass, sorghum and miscanthus grown in two different soils with high and low poultry manure input conditions, and having a wide biological range of mineral content, were subjected to catalytic fast pyrolysis (CFP) over HZMS-5 using py-GC/MS. The resulting products including BTEX (benzene, toluene, ethyl benzene and xylenes), naphthalenes and gases including carbon oxides, methane and olefins were quantified in terms of product carbon yield and chemical selectivity. The effects of total ash content as well as the individual mineral components were compared to evaluate the effect of the natural range of these components on the product distribution. While there was considerable variation in the data due to the biological influence, a positive correlation was found between ash content and carbon conversion to aromatic hydrocarbons, which was particularly strong when considering only the switchgrass samples. This large degree of variation may be characteristic only of this sample set. Among individual mineral elements in the biomass, potassium, an essential mineral for plant growth, was found to have a strong negative influence on the carbon conversion to aromatic hydrocarbons, but iron was found to have a positive influence on the conversion to aromatics. Correlations between mineral content, the chemical intermediates from the incipient pyrolysis process and the final CFP products suggest that potassium’s main influence is on the initial pyrolysis reactions while iron may affect the catalytic reactions over HZSM-5.