Grasslands can produce biomass to be used in pyrolisis, a technology that rapidly heats biomass in the absence of oxygen to create a liquid fuel intermediate known as bio-oil. Through catalytic upgrading, bio-oil can be transformed into hydrocarbon fuels like gasoline, diesel or jet fuel. Though fast pyrolysis and catalytic upgrading can convert a wide variety of plant species into fuels, certain feedstocks may have advantages for this strategy on the basis of feedstock composition. As many different plant species can serve as bioenergy feedstocks, compositional variability should be exploited to select those that are most readily converted into products with desirable qualities.

Video explanation on fast pyrolisis of biomass:

This is contrary to those who claim their processes are “feedstock agnostic,” as clearly the composition of the reactants affects the quality of the products. In this study, the magnitude and origins of compositional variability were investigated for eight grass species in order to improve species selection for bioenergy production.

biodiversity bioenergy crops

Grasslands can be sustainably managed with one or more harvests per year without affecting environment and producing renewable energies that could replace up to 80% of emissions when producing power.

One such technology, fast pyrolysis, is a thermochemical approach for converting biomass into a liquid product known as bio-oil, a hydrocarbon fuel intermediate. In this research, the eight aforementioned grass varieties were characterized by fiber and metal analyses as well as calorimetry and thermal gravimetry. Conversion by analytical pyrolysis showed that although variability exists, all eight grasses produced a similar spectrum of chemical compounds. Principal component analysis of pyrolysis-GC/MS data detected statistically significant differences amongst the grass varieties on the basis of six key chemical markers: glycolaldehyde, acetic acid, acetol, methyl glyoxal, 4-vinylphenol and levoglucosan. Though taxonomic classification was not found to affect product composition, correlation analysis verified that biomass composition and thermal properties might be responsible for the differences in pyrolysis products.

In this study 8 C4 grasses were demonstrated. As for selecting amongst grass species to identify future candidates for bioenergy production by pyrolysis, composition analysis of the eight grass species suggests that coastal panicgrass, with the highest HHV, lowest ash and low Ho:L ratio may be suitable for pyrolysis applications. Sideoats grama and deertongue, with the lowest HHV, highest ash and Ho:L ratio may be better suited for fermentation based processes. Switchgrass, indiangrass and big bluestem cluster together on the PCA plot and showed less tendency to produce small carbonyl and carboxylate compounds, which implies that the pyrolysis products may be less chemically reactive, less corrosive to metal surfaces and more stable during storage. Conversely, sideoats grama and prairie sandreed, produced higher levels of acetic acid and acetol, which may be unsuitable for producing stable bio-oil that can readily be transported and stored for further chemical upgrading. 

Get the article here