Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Information on the performance of fast pyrolysis tests

Pyrolysis tests were performed with all four perennial grasses at a lab-scale pyrolyser such as those studied in this project have the potential to be converted into a useful bio-oil energy product.

The result from the test show that these crops have alkali metals contents sufficiently high that pyrolysis yields would be much lower than for most low ash wood feedstocks.

Crops with low alkali metal content (perhaps less than about 0.3wt% d.b.) will provide pyrolysis yields similar to those obtained from clean wood feedstock i.e. an organic liquid yield of over 60% and a total liquid yield of over 70% of the dry ash fee mass of the feedstock. The oils produced from such feedstocks appear very similar
to oils produced from woods such as beech and poplar, but further work needs to be done to understand their physical and chemical properties in more detail. In particular, their ability to dissolve small amounts of pure hydrocarbons may enable quality improvements to be made through the use of additives.

To obtain low alkali metal content with reliability would probably require a pre-treatment such as cold-water washing since natural rain leaching (as experienced by some of the project crops) cannot be relied upon.

The work has shown that the washing process could be fairly simple given the availability of sufficient clean water. However there is much work to be done to determine the technical feasibility and costs of such a system.

It will be important to establish the relationships between increase in oil yield and improvement in quality and the incremental cost of washing.

Even without washing, and with low pyrolysis liquid yields of 40 to 50% (d.b.) there may be some applications for which poorer quality bio oil could be suitable, for instance it may have value as an industrial fuel oil for process or space heating applications provided that its storage stability could be managed, for instance by blending with other biofuels such as biodiesel and /or bioethanol.

At the moment the cost of fast pyrolysis for producing high-grade energy such as electricity is very high (even assuming high pyrolysis efficiency and without the cost of pre-treatment of the feedstock) and would require substantial subsidy to be economic.

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Reported by

ASTON University, School of Engineering and Applied Science, Chemical Engineering and Applied Chemistry
Aston Triangle
B4 7ET Birmingham
United Kingdom