We Should Have An Air
Cleaning Levy On Fuel
By MUNGAI KIHANYA
The Sunday Nation
Nairobi,
18 December 2005
Trees “breath” in carbon dioxide and release oxygen
into the air. A car engine on the other hand, burns petrol with oxygen
and produces carbon dioxide (and steam). So the question arises, how
many trees would be required to clean up the carbon dioxide released
into the atmosphere by a car?
A welltuned car will produce about 2.4kg of carbon
dioxide from every litre of petrol consumed. The fuel consumption rate
(litres per kilometre) depends on many factors but on average, a family
saloon will do about 10km per litre in urban driving and about 15km/L on
the highway.
The average motorist covers about 20,000km in a year
– mainly urban driving during the weekdays and highway trips only on
weekends. Thus we can assume that five out of every seven kilometres are
done in town and the remaining are on highways.
That is, about 14,000km are done on urban roads and
6,000km are on highways. 14,000km at 10km per litre works out to 1,400
litres of petrol. 6,000km at 15km/L gives 400 litres. Therefore, the
average motorist consumes about 1,800L very year. Since each litre
produces about 2.4kg of carbon dioxide, the total annual production of
the gas from each car is 4,320kg.
Now, on average, one tree “breaths in” about three
kilograms of carbon dioxide in one year. That may sound little about it
is about 1,500 litres or four litres per day at normal atmospheric
temperature and pressure. Therefore, it turns out that we need 1,440
trees to remove all the carbon dioxide produced by one car.
The next question is, how much would it cost to plant
these trees? The cost of buying one seedling is about sh10. But the
young tree has to be delivered from the nursery and planted in the right
place. This can raise the
cost to, say, sh50.
Thus the total cost for one car comes to sh72,000. If
this is spread over the life of the tree, say 20 years, then the cost is
about sh3,600 per car per year. This is money that can be collected as
part of the annual road license.
Alternatively, the money can be collected as an
additional levy on fuel. Every year we consume 460 million litres of
petrol in Kenya, from which we produce 1.1 million tonnes of carbon
dioxide. To clean this up will require 368 million trees.
The total cost of planting these trees would be
sh18.4 billion. Dividing this figure over the average life of 20 years
gives about sh920 million per year. This total sum is then collected
from the 460 million litres that we consume per year. The result is sh2
per litre.
But can’t our natural trees doing the job? Kenya has
about 3.5 million hectares of forest. The average tropical forest has
about 250 trees per hectare, therefore we have about 875 million trees.
That is over 40 per cent of the national stock of natural forest!
Clearly, we must plant more trees. And a twoshilling
per litre “air cleaning” levy on petrol can do the job.
