Muhaimin Iqbal
Author

Two Sides of the Same Coin of CO2

Advanced Renewable

Wed , 28 Feb 2024 17:20 WIB

Like two sides of the same coin, so far we tend to see carbon in the form of CO2 from only one side - namely as a form of emissions that pollute the earth's atmosphere, causing global warming, climate change, extreme weather and all the consequences it causes.

We have not yet seen the other side which is full of potential, including being the biggest new energy source that is before our eyes. This new energy, which we call Regenerative Energy (RE), can come in various forms, in the form of power/electricity or liquid and gas fuels, from oxygenates, hydrocarbons or carbon-free energy such as hydrogen.

By looking at these two sides as a whole, we will also be able to justify a more appropriate CO2 handling pattern. Because when CO2 is only seen as a source of emissions, the handling pattern will tend to become a cost center only. Likewise, when we only look at CO2 as a new energy source, we tend to compare it with other energy sources that could be cheaper, such as hydropower, wind and solar.

If hydroelectric, wind and solar electricity existed together with electricity from coal and diesel, for example, then it is true that the first three do not add CO2 to the air, but the last two will require large costs to reduce CO2. Imagine if RE is present along with diesel and coal-powered electricity, the presence of RE not only adds a new source of energy that is emission-free, but also absorbs CO2 from power plants that use diesel and coal that exist with it.

The illustration below is that if we put side by side diesel power as an example with RE, all the CO2 will be absorbed through two reactions, Boudouard (CO2+C==>2CO) which is the left side of the coin, and Water Gas Shift or WGS (CO+ H2O==>H2+CO2) is the right side of the coin. The CO2 that emerges from the WGS is then re-captured again to enter the next cycle.

The increase in energy efficiency will be very significant, because the energy that was originally only produced by burning diesel (45 MJ/kg), through the thermomechanics process - namely the heat that drives the diesel engine - generally only has an efficiency of under 30%, with RE the energy will be added by thermochemicals energy - namely when CO2 changes to CO in the OCCYRE reactor, then CO changes to H2 in WGS, and finally when H2 reacts with O2 to form water by releasing 120 MJ/kg of heat.

Of course, to be able to process CO2 into CO and then also H2, you need energy, namely heat. But this heat energy can be obtained cheaply from burning carbon or biomass - which is not as expensive and scarce as diesel. Then from CO2 to H2 with an energy content of 120 MJ/kg, only around 22.5 MJ of heat energy is needed, or only around 18.75% of energy is used for process.

With a configuration like this, energy efficiency which was originally below 30% jumps to around 57% and is now emission free!