By Don Hewison (ScEdD, ChEdD)
My wife and I play a little game which we call – spot one of the ghostbuses.
The name comes from the movie ‘Ghostbusters’.
In our game, a Ghostbus is one that appears to go around in circles as a bus should do, but a Ghostbus doesn’t have passengers on board, nor does it seem to stop for anyone to let on or off. We play it when we are out walking, or perhaps when we see a bus drive past our house. The number of Ghostbuses we see suggests a large percentage of the buses in our street are Ghostbuses – especially between the busy ‘going to’ and ‘going home’ to/from school times.
This raised the question – how much CO2 emissions are produced for no apparent purpose. More so is the question, “How many trees are required to negate the production of these emissions”.
The street we live on is part of the Rototuna Circular route and is approx. 1.2 km long (according to Google Maps). It is on this street where we count our Ghostbuses – at home or out walking.
The Rototuna Circular (RC) route timetable reveals the number of buses as:
Fuel used during one year alone for this part of the circular route can be estimated using fuel consumption values. It is considered that a diesel bus normally consumes 19-27 L per 100km.
“On average, Christchurch’s standard-sized Red Buses consume a bit over 35 litres of fuel per 100 kilometres. This may seem high but buses are heavy and they have to stop and start often.”
Simon Kemp, Do buses reduce greenhouse gas emissions?, Stuff NZ, 2020
Given that the buses we are considering don’t seem to stop often, and are often empty, let us assume a figure of 20litres/100km. The bus kilometers per year for our street is 7341.6km, giving a fuel consumption of 1468.32 litres per year.
According to Michelin’s “How to Calculate Your Fleet’s Carbon Footprint”, one litre of diesel creates 2.54kg of CO2.
For 1468 litres of diesel per year, the CO2 emissions would be approx. 3730kg (or 3.73 tonne) – for our street, each year.
The question that must be asked would be ‘how many trees would need to be planted to offset these carbon emissions?’
A visit to the Christchurch Botanical Gardens will give people the opportunity to appreciate with wonder the magnificence of this tree.
At the base of the tree is a sign which states…
“This One Tree (in Christchurch Botanical Gardens) Contributes to Life:
Atmospheric carbon dioxide reduction per year: 804 kilograms
(the average car generates about 800kg each year)
Carbon dioxide trapped per year: 120 kilograms
(one direct flight from Dunedin to Auckland adds 180kg per passenger)
Oxygen produced per year: 310 kilograms
(a person consumes about 740 kg per year)
Height (in 2020) 37 metres
Trunk girth at human height 7.27 metres
Crown width 32 metres
Approximate area of canopy 9300 sq metres”
Using this information, the trees required to offset the pollution from buses travelling down the length of our street, as part of scheduled timetable, over the time of one year, often carrying no passengers is approx. 31 of these large trees.
If the whole Rototuna Circular Bus route is considered, at a distance of 21 km, the number of trees needed to offset the carbon emissions is at least 540 of these large trees. Even to plant trees now, we need to realise that this tree in Christchurch is 100 years old.
Admittedly, buses need to run regularly, but where are the trees required to reduce/cancel out carbon emissions?
[The content of any Opinion pieces represents the views of the author and the accuracy of any content in a post labelled Opinion is the responsibility of the author. Posting of this Opinion content on the CityWatch NZ website does not necessarily constitute endorsement of those views by CityWatch NZ or its editors. CityWatch NZ functions to provide information and a range of different perspectives on New Zealand’s cities and local councils. If you disagree with or dispute the content, CityWatch NZ can pass that feedback on to the author. Send an email to feedback@citywatchnz.org and clearly identify the content and the issue.]
