How much CO2 emissions can you save with a 20 pounds investment?

Can you help save the planet with as little as  20 pounds in your pocket? Almost everyone of us has some degree of environmental consciousness. With the size of our planet, one can sometimes feel overwhelmed and even powerless about the prospect of individual effort towards environmental betterment.

To begin with, pupils at schools are taught to reduce, reuse and re-cycle. These steps themselves can go a long way in helping the environment. If however, one wants to do more and  wants to invest money into the environmental improvement, than it would be worthwhile exploring the best available options.

In this article  comparison will be made on how much benefit can be achieved by investing 20 pounds (28 USD) towards green devices/ environmental causes. The index by which the efficacy of these options will be gauged is the amount of CO2 savings.  It will also help us in putting in to perspective how our actions impact on the environment and which practices will benefit the planet most.

Note that all these options may not be available to every person. Our environmental impact  varies according to our location. Carbon dioxide emission saving is not the best gauge to measure the environmental impact, but because it is simple, universally understood, it is a good measure to begin with. A more holistic gauge is the environmental footprint which will be the subject of a later post.

Four different options have been examined.

1. Solar Battery Charger

Solar panels are available in the market range between 60-100 pounds (GBP). Although it is possible to fabricate a 100 Watt panel for less than 40 pounds, but it requires some effort and skill. Solar battery charger ( with a 12 Volt output)on the other hand is readily available in the market and is  used for  trickle charging car battery. It can also be used to charge devices such as cell phones.

A solar car battery charger has a 30 year shelf life. Mostly, it is made of amorphous silicone which doesn’t degrade much over time and performs well even when the sunlight turns mostly diffuse.

The maximum power output of the charger that can be bought for 20 pounds is 1.8  watt at peak sun (1000 W/m2) condition. If it is used in countries that lie between the tropic of cancer and tropic of Capricorn, than the output is considerably high. However, if it is used in countries of higher latitude, the output can be 5 times lower.

Consider that the device is used in Scotland where annual horizontal insolation is 800 Kilo Watt hour per meter square. The device will be able to produce 1.8 Watts * 8760/2*0.5 = 3.9 Kwh annually.

This means that through the life of the device, it can produce 3.9 *30 = 117 kWh

It should be noted that it is impractical to use the charge produced through PV charger continuously. Let’s assume that the solar panel replaces charging cell phones, than it replaces grid electricity.

If it is used only for charging car battery, than it replaces diesel. CO2 savings for both options have been calculated below:

As per DECC guidelines, if a unit of electricity is produced from a carbon free source than it offsets 0.542 kg CO2  that would have been produced if the electricity was taken from grid.

So the car battery charger can replace as much as 117 *0.542 =63.4 Kg if used to charge cell phones.

If is used to charge a cell phone that the diesel to kinetic efficiency is 33% for modern engines.

This means to produce 117 kWh of electricity, a car engine  would have to burn 354.5 Kwh of diesel. This equates to fuel of calorific value 354.5*1000* 60*60 = 1.276 Giga Joules

Given that one kg of diesel has 44800 kJ/kg = 28.4 kg of fuel needed to produce 117 kWh

Diesel CO2 emissions = 2614 gms/litre = 2.614 kg/litre

Given that Diesel density = 830 kg/m3 =0.830 kg/lt

Which equates to  2.614/0.830 = 3.14 kg of CO2 of emissions per kg of Diesel burned

So, total emissions will be 28.4*3.14 =89.17 kg of CO2

 Thus by purchasing a car battery charger and using it specifically for charging car battery, the amount of CO2 saved over the lifetime of the device will be  89.17 kg

2. Tree  Plantation

Trees can not only act as carbon sinks but can also provide priceless amount of  oxygen, the life and blood for all living species. A university study has shown that topical forest tropical forests absorb about 18% of all carbon dioxide added by fossil fuels.

For 20 pounds gift vouchers for planting tree from Trees for life, an organization that has reforested  large areas (Caledonian forest) in Scotland.   There are many other organizations in different countries performing similar work. In fact for 20 pounds, in many developing countries 2-4 sapling can be planted.

In a study it was again revealed that 1 tonnes of carbon stored in a tree is equivalent to 3.67 tonnes of atmospheric carbon.

Similarly another fact states that every year, approximately 2 kg of CO2 is locked by each tree.

If for the sake of specificity, it is assumed that Scottish pines are planted that has a life of up to 300 years than the total Carbon di oxide saving through this investment will be 600 kg.


3. Wind Farm

 In many countries a model of community ownership of a wind farm has been extremely successful. City dwellers often have the money but not the site suitable for large scale wind turbines. On the other hand rural communities have the land but not the capital. To synergize the two groups banks and investment agencies have crafted a model by which stocks can be purchased and ownership can be divided into affordable chunks.

Similarly there are utility companies (like Ecotricity)  through which only electricity  from a wind farm can be purchased without investing in the wind farm itself. The calculation for this investment is as follows:

The  cost of wind energy has dropped to 42 Euros /Megawatthours.

20 GBP = 25.8 Euros

So if 42 Euros equates to 1 Megawatt hours

25.8 Euros =0.61 Megawatthour

Total carbon saved = 0.61* 1000*0.542 = 332.9 kg of CO2

Thus by investing in a community owned wind farm,  a total of 332.9 kg of Carbon can be saved.

4. Bio-Diesel

Bio-Diesel that has been extracted waste vegetable oil  is now available in many cities thanks to our love of deep fried food. It is often 20% cheaper than the fuel at the pumps depending upon the surcharge by the government.  By using bio-diesel recovered through waste oil and not through plantation, not only one is helping the planet but also saving their pockets. It burns more cleanly compared to normal blended diesel. It should be noted that many modern diesel engines, particularly those manufactured after 2007 can not use bio-diesel.

The calculation for Bio-Diesel investment is as follows:

20 Pounds = 20.2 litres of Bio-Diesel  (99 pence a litre in UK)

Bi0-diesel has slightly lower calorific value.  90% of pump bended diesel

20.2 litres of Bio-diesel = 18.18 litres of normal diesel

Diesel CO2 emissions = 2614 gms/litre = 2.614 kg/litre

Total CO2 emissions are 2.164 *18.18 =39.34 kg

Thus by using 20 pounds worth of bio-diesel, almost 39.3 kg of CO2 emissions can be saved.


Four different options of 20 pounds investment in environmental cause  were examined. It was found that  investing that money in planting a tree is the most beneficial in terms of CO2   saving (600 kg).

CO2 saving for different investment options

Carbon Savings for 20 pounds of investment

It should be noted that if time scale is taken in to account than the saving done by tree plantation is not very favourable because it is over a period of 300 years. On the other hand 20.2 litres of bio-diesel can be consumed fairly quickly (in about 1 week).



Stiesdal, Henrik.$FILE/6_planting_more_trees.pdf

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