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.
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.
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Interesting read. I am not an expert at all in this field, but had the pleasure of being involved as a (potential) financier of such projects and I have seen several hiccups in the process. I wonder what is a more viable technology for this biomass, pyrolysis or torrefaction. Sofar I have seen only success with the latter technology and only one example really getting the technology up and running. Pyrolysis has many promesses, I have seen so many pilots, but no commercial scale yet.
There are few commercial pyrolisis, but they exist already. Not only for large scale projects but also for smaller scales. Biochar can be exported at 250$/ton and heat and power make these projects to have very high potential in countries with expensive and imported energy like small islands or even developed countries as we see in Spain. Of course you’re right, there are very few that became commercial. Torrefaction is an alternative we support very much, however there are several context in which briquettes, pellets, bales or even wood chips are low cost feedstock alternatives to consider.
Price indication best done in $/GJ, not in tons. On average, for renewables like wood pellets, torrefaction pellets are in the range of $ 8 / GJ to $ 10 /GJ. Mild torrefacted products with 22 MJ/kg should therefore be around a $220 / ton and wood at 17 MJ/kg at a $ 170 / ton. Above that you pay a ‘bonus’ on the energy value for perhaps the way less volume to be transported (if product densified to 650 to 800 kg per m3), the easier to handle material (hydrophobic) and easier to grind. Like wise with pellets graded I1: you pay for the extra ‘benefits’ as low ash, easy to handle format (15~40 kg/bags, jumbo bags) and a lot of jumbo-mumbo.
Torrefaction is a form of (mild) pyrolysis. The low temperature form (making either bio-oil or charcoal)
The potential is huge, the combination or herbaceus biomass and pyrolysis is probably the best answer for small scales cogeneration and distributed energy generation.
http://www.biogreen-energy.com/
This is a very good example of commercial success of pyrolisis in small scales. There is much more commercial success in medium scales in gasification such as http://www.prmenergy.com.
Thin-tech widely deployed is the fast path forward to making use of thinly distributed, currently “stranded” energy. Karl Frogner chapter 18 of “The Biochar Revolution” relays the promise about as concisely as anyone. Thin tech is not attractive to investors, so it is up to individual efforts to implement the great change to clean, local energy from naturally stored solar.
The change is happening, because pyrolysis works extraordinarily well at the hyperlocal level. Raising awareness and training techs are the remaining hurdles.
http://www.ithaka-journal.net/55-anwendungen-von-pflanzenkohle?lang=en
There are 55 identified possible uses of biochar, including charcoal, organic cement, activated carbon, animal food and soil remediation.
Besides charcoal all of the other markets are incipient. Biochar as soil remediation is growing at more than 100% per year although it will probably take time to establish a market, as composting did. The good thing is you can remediate poor soils with biochar plus other composting methods to activate the carbon. By doing this you can grow on marginal lands bioenergy crops, and using pyrolysis low scale, you can produce and sell locally locally. With a cost of 4 usd per GJ you can achieve a cost for biochar of 6 usd per GJ and a cost of heat of 6 GJ too (add 2 Usd for capital costs). You can sell the heat under a PPA to a local retail costumer and use biochar to create more soils and land or export it to being used in any of the 55 forms. That is a cost of 150 usd per ton and could be sold as charcoal at 250 Usd per ton or 10 usd per MMBTU.