Green fuel for MSW Collection

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The project will demonstrate conversion of excess renewable energy into liquid fuel to power Adelaide’s garbage collection, net free of CO2 emissions.

How this will impact Adelaide's carbon emissions

A challenge for regions that are well endowed with renewable energy is to determine how to efficiently store the excess supply that is produced when the sun is shining (or the wind is blowing, etc) so that it can be conveniently used, on demand, when the renewable energy source is unavailable. Chemical storage, in this case a substance which is also a liquid fuel, is a very efficient way to achieve this.

This project will demonstrate the use of excess renewable energy to produce liquid fuel for vehicular use, by municipal garbage trucks (or other fleet vehicles). The only materials consumed will be water and carbon dioxide. Hydrogen (H2) will be produced by electrolysis from water and carbon dioxide (CO2) will be captured from the air. Hydrogen and carbon dioxide will then be combined in a catalytic reaction to give methanol and/or dimethylether. Methanol can be used in petrol engines. Dimethylether (DME) is produced from methanol and is an excellent diesel substitute (with much lower NOx and particulates). Unlike agriculturally-based biofuels, no precious arable land is required for the production of this renewable fuel.

The key to this idea is the ability to produce H2 and CO2 using electricity based from renewable energy. Both H2 production by electrolysis and CO2 adsorption from air can operate in a dynamic mode to utilise the energy when it is available. This is achieved in the case of H2 by operating a large number of electrolysis cells, which switch on/off as the electricity becomes available. Similarly the adsorption of CO2 from air requires very little electricity and the adsorbent can hold the CO2 until electricity becomes available for desorption. The methanol reaction (CO2 + 3H2 → CH3OH + H2O) occurs at high pressure which facilitates the storage of H2 and CO2 in a compressed form. It is envisaged that the methanol production would be continuous whereas the raw materials would be produced dynamically.

Whilst the ‘Transport’ category has been selected for this idea, we note the project also aligns significantly with the ‘Energy’ and Waste’ categories.

Voting has now closed for the Wildcard prize. Stay tuned to find out which project will be the 11th finalist.

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