ARS | Publication request: Production and analysis of fast pyrolysis oils from proteinaceous biomass

Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 14, 2011
Publication Date: June 7, 2011
Citation: Mullen, C.A., Boateng, A.A. 2011. Production and analysis of fast pyrolysis oils from proteinaceous biomass. BioEnergy Research. 4;303-311.

Interpretive Summary: In order to meet the renewable fuels standards set by the US government, 21 billion gallons of advanced bio-fuels will need to be produced by 2022. Accomplishing this will require the use of several different types of feedstocks including crop residuals, forest residuals and purpose grown energy crops and also the use of many different technologies to convert these feedstocks to liquid fuel. One promising process is fast pyrolysis which can convert biomass to a liquid called pyrolysis oil which could be refined to "green" gasoline and diesel fuels that are indistinguishable from those produced from petroleum. Fast pyrolysis is done by rapidly heating the biomass in the absence of air and then quickly cooling the vapors. Most of these biomass feedstocks consist mostly of carbohydrates (cellulose and hemicellulose) and lignin, a polymer which gives structural stability to plants. Both carbohydrates and lignin consist of carbon, hydrogen and oxygen; however some feedstocks have higher levels of other substances including proteins. Protein contains significant amounts of nitrogen in addition to carbon, oxygen and hydrogen, and therefore its presence can alter the chemistry of the fast pyrolysis process and the properties of the pyrolysis oil. In this paper, the effect of varying amounts of protein in biomass on the fast pyrolysis process and the makeup of the pyrolysis oil was studied. While the presence of the protein did not seem to significantly alter the overall yield, it was learned that nitrogen from biomass with high protein content can drive out oxygen during the pyrolysis process, making a pyrolysis oil product which is less acidic, contains more energy and in some cases is more stable than in cases where protein content is low. This information will be useful to help select feedstocks for those producing or considering producing bio-fuels via a fast pyrolysis process and those considering producing energy crops.

Technical Abstract: Fast pyrolysis of lignocellulosic biomass is a facile method for producing high yields of liquid fuel intermediates. However, because most fast pyrolysis oils are highly oxygenated, acidic and unstable identification of feedstocks that produce higher quality pyrolysis liquids is desirable. Therefore, the effect of feedstock protein content was studied by performing fast pyrolysis experiments on biomass with varying protein content. The feedstocks ranged from low protein content, ~5 percent up to feedstocks with >40 wt percent protein content. Protein content was not a major factor in the yield of pyrolysis oil or the distribution of biomass carbon into the pyrolysis products. However, elevated levels of protein did cause a deoxygenation effect in the pyrolysis process with more of the oxygen rejected from the biomass as water. The deoxygenation caused the pyrolysis oil from the higher protein containing biomass to have higher energy content. Furthermore, the concentration of basic nitrogen groups caused the pyrolysis oil from the higher protein biomass to shift to a more neutral pH and lower TAN than has been measured typically for lignocelluloic biomass pyrolysis oils. Some of the pyrolysis oils, particularly those from the mustard seed family presscakes exhibited better thermal stability than low protein pyrolysis oils.