Carbon Neutral Fuels

Please note: The blog post works on the premise that you understand that carbon dioxide is a greenhouse gas and it is one of the molecules responsible for global warming.

‘Carbon neutral’ is a fairly common phrase we tend to see quite regularly today. I noticed that ‘Sky’ (the TV company) markets itself as a carbon neutral company. Another carbon related phrase is ‘offsetting carbon’ – so if you fly with BA you can pay extra and offset your carbon footprint…..

But what does all this mean?

Well, if something (a business for example) is carbon neutral, what they are really saying is that they produce no net increase in the amount of carbon dioxide released into the atmosphere. They are not responsible for (any more) global warming.

How can this be? If you work in an office, you will have lights. I’d bet that at least 99% of the lights out there run on electricity and the vast majority of electricity is produced by burning fossil fuels (which would release carbon dioxide in the atmosphere).

Admittedly, some electricity is produced from renewable sources (eg, solar) but (to my knowledge) it is not possible to purchase electricity that is made from renewable sources. So how can the company make such a claim?

The answer is in the detail – for every kilogram of carbon dioxide released, the company pays another company to plant trees. The idea is that the tree will absorb the same amount of carbon dioxide being produced.

As you can imagine, this must be very hard to (a) measure and (b) calculate but at least it is a start and the company is doing something about it.

Offsetting carbon is a similar idea – if you fly in an airplane, carbon dioxide (and nitrogen oxides) will be produced. The cost you pay goes towards covering the cost of planting trees to absorb this carbon dioxide. At least this must be easier to measure than a huge business.

It could be argued that using ethanol as a fuel is carbon neutral. Ethanol can be made by fermentation. Fermentation takes sugar and converts it into ethanol.

Fermentation makes sugar:

6CO2 + 6H2O –> C6H12O6 + 3O2

The sugar can be fermented into alcohol:

C6H12O6 –> 2C2H5OH + 2CO2

The ethanol can be combusted:

C2H5OH + 3O2 –> 2CO2 + 3H2O (x2 as there are two fermentation producing 2 molecules of ethanol)

This means that 6CO2 has been absorbed and 6CO2 is released – hence the idea that the fuel is carbon neutral.

That said, there are two main flaws with this method – the first one is land space, it is likely (unless you live in a large country such as Brazil) that there would not be enough land space to grow sugar beet for making ethanol and crops to feed people.

The second one is that carbon dioxide will be released through the transport or fuel, heating costs, etc.

What do you think? Is this a potential IA or EE? Please share your thoughts below.

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