TTC eBus Errata: Tonnes and Kilos Are Different

In a comment on my article TTC eBus Study: Final Results, an alert reader noted that the claimed GHG reduction from the new fleet was vastly out of proportion. Here is the TTC’s chart from that report and accompanying text (highlighing added).

The TTC’s first 60 eBuses were procured from BYD, NFI and Proterra. Prior to the delivery of these eBuses, three garages (Arrow Rd, Mt Dennis and Eglinton Garages) were retrofitted with depot charging systems to accommodate charging up to 25 eBuses per location. All 60 eBuses procured have now been in-service between one to 2.5 years at the TTC with more than 2.5 million kilometres driven, and have reduced GHG emissions by 3.3 million metric tonnes.

TTC Report at p. 14

The basic problem here is the claim that for every kilometre travelled by an eBus rather than by a diesel bus, the saving would be over 1 Tonne of GHG. In the paragraph above, the saving should be 3.3 thousand metric tonnes, not 3.3 million. Who knows how many times this erroneous number will be cited.

The basic numbers are summarized in one paragraph on page 97 of the report:

GHG Reduction

The greenhouse gases (GHG) reduction is primarily due to the avoidance of diesel fuel consumption. At an average fuel economy of 0.53 l/km, the TTC’s Nova clean diesel buses release 1.4 kg of CO2 per kilometre driven. The generation of electricity also creates emissions through many factors including direct emissions from fuel-fired power plants. For Ontario, the average CO2 emission for base load power is 32 g/kWh. The eBus fleet in 2021 averaged 1.62 kW/km (including all non-operating energy consumption sources), which equates to emissions of 0.05 kg CO2/km. Based on the fleet mileage of 1,555,174 km in 2021, emissions associated with the electricity supply are 80.8 Tons CO2. An equivalent clean diesel bus fleet would have emitted 2,177 Tons of CO2.

Note: The highlighted value should be 1.62 kWh/km. This is a typo in the TTC’s original text.

Running the Numbers

To save readers from working through these numbers, here they are consolidated as a spreadsheet.

The table below compares the TTC’s cited numbers with calculated values. Where a value is calculated, I have not rounded it as in the TTC’s descriptive text. For example, the GHG emissions per km for eBuses is shown as 0.05184 rather than 0.05 kg/km. Cells highlighted in yellow have the wrong units, but this is what the TTC specified in its chart.

The problem here is that the line “GHG Savings” claimed is erroneously stated in Tonnes (1,000 kg) rather than in kilos making the numbers 1,000 times bigger than they actually are.

This has the absurd effect of making the “saving” per kilometre over 1 tonne when the diesel fuel we start with weighs less than 1 kg.

I checked with the TTC, and, yes, the chart is wrong. It should specify savings in kilos, not in tonnes.

The calculated emission savings are obtained by multiplying the “delta” value (difference in emissions by fuel source) by the reported fleet mileages. The claimed values are taken from the TTC’s chart above.

There is a further problem that the ratio of claimed GHG savings to distance operated varies from one vendor to another. There is no explanation for this although the report does cite different fuel consumption rates for each manufacturer’s bus.

Although I have asked, the TTC has not explained why these values are different.

Clean Diesels vs Hybrids as a Reference

There is a further issue with the numbers published by the TTC. They are based on a comparison with “clean diesels” even though some of the vehicles to be replaced include the first generation of hybrids with have lower fuel consumption.

The TTC reports that the GHG saving between a first generation hybrid and an eBus is about 1.315kg CO2/km, as against 1.379 for clean diesels (from the table above). This suggests that the first generation hybrids are not saving much fuel compared to the diesels (less than 5%).

Getting It Right

The main report contains a more reasonable number:

When the entire fleet is zero-emissions, the following benefits are expected to be realized:

1. Greenhouse gas emissions will be reduced by approximately 250,000 tonnes of CO2 annually; […]

TTC Report at p. 3

In pre-covid times (2019), the TTC operated 145.1 million km with its bus fleet. At a saving of about 1.38 kg CO2/km, this translates to 200,000 tones of CO2, a somewhat lower figure than the TTC claims.

As Toronto launches into a new electric era, the TTC needs to clean up its statistics and calculations so that those trumpeting our efforts use the correct data.

Environmentalists, transit boosters, city planners, anyone who is touting electrification should be careful to cite correct figures for the expected benefit of eBuses.

I have no problem with “going green” and welcome the shift to electric vehicles. That said, it is important that the benefits be stated accurately and clearly so that “green” is not oversold. Toronto’s transit history is littered with hucksters.

8 thoughts on “TTC eBus Errata: Tonnes and Kilos Are Different

  1. I’ve recently seen confusion with both “mt” and “MT” being used to mean either “megatonnes” or “metric tonnes” of CO2eq emissions, which is of course a million-times difference. And there’s also the use of “M” to mean “thousands” and “MM” for “millions”, apparently derived from accounting and/or finance. That’s before getting into “ton”/”tonne” having at least three possible meanings.

    Given these, when creating analyses and calculations it really seems safer to use scientific notation and SI units like 3.3 x 10^9 g CO2eq and fully write out the units in final reporting: “3.3 thousand metric tonnes” or “3.3 million kilograms” (I suppose we’d get mocked for “3.3 billion grams”).

    Liked by 1 person

  2. Like, say – business cases for Suspect Subway Extensions – there’s a lot of potential for mathemagics and greenwishing in what is a very complex subject, especially as ‘we’ don’t really want to change course to sustainability, including here on the Torontic, where we don’t include even concrete in our civic GHG profile. (We’re so green, we don’t use any of that bad stuff eh? – and nope, no tiles, glass, metals etc.).

    My strong sense is that if ‘we’ – which absolutely includes the federal level – really felt there was a climate emergency finally, we’d be a lot more atop all of the Scope 2 and Scope 3, and a separate category, Scope 4, emissions, which maybe includes all the methane of permafrost and underseas about to pulse out, and the extra emissions of forest fires etc. and even maybe the pfcs of aluminum smeltings, though I’ve not checked in the last couple of decades to see if they’re curtailed vs. being ignored. So they may well be a coup de glace, or another one (ignoring international air travel is another one, with Pearson seeing c. population of Canada using it in more ‘normal’ times, with air freight another big ??)

    I’m very glad that someone’s been atop this ‘Oops’, (and likely a citizen vs. envirocrat at TAF or within the City/TTC, though Webster effect malingers), but there’s plenty of fuzzy thinking to rot around, more so under ‘carservative’ misrule. While cars can be marvellous technologies to use at some times and places, they’re even worse than transit is for uncounted and/or misrepresented impacts, and electric cars about that same ie. not real progress.

    Real, honest savings of both GHGs and billions would come from the federal level being far far stickier about what all they are poised to pour billions into boondougles like the SSE, the Richmond Hill Extension, the Eglinton W LRT and the Ontario Line as well, with a petition now online from the Save Jimmie Simpson folks.

    Steve: My gut feeling is that this is a matter of sloppiness, not of misrepresentation. My purpose in publishing the article was to alert others who might quote the wrong numbers.


  3. Same problem buying paint. In the 1950’s or 1960’s, we bought a gallon or quart of paint. It was the imperial gallon (4.54609 litres) or imperial quart (1.13652 litres).

    Then they switched to the metric system. We bought 4 litres or 1 litre. That was fine. At least we were told there was a difference.

    Then the paint companies switched to manufacture or sell in the USA. We now buy a US gallon (3.78541 litres) or a US quart (0.946353 litres). Surprise, don’t tell anyone.

    When we buy a gallon or quart of paint, we are NOT getting the proper amount. We should be getting an imperial gallon or an imperial quart, or at very least 4 litres or 1 litre. We’re are being short changed.


  4. kilowatts per kilometer??

    Another typo, surely (looks like you copy/pasted the quote, so TTC’s typo). Should be kWh per km.

    Steve: Yes that is a typo by the TTC. I will insert a note in the article pointing that out.

    Time of recharge is important — CIPK (CO2 intensity per kWh) of Ontario grid is generally much lower between 2300 and 0600 due to higher proportion of nuclear and hydro.

    Can’t tell if they included GHGs from the diesel heaters they have to bolt onto the buses because the batteries can’t handle the heat load (which begs why the hell even consider buses that can’t do that, which completes the loop back to “why not trolley”).

    Steve: Just after the typo you cite are the words “(including all non-operating energy consumption sources)” but this refers only to electricity use. Omission of the auxiliary diesel in the GHG figures is definitely an oversight, although it would not amount to as much as the propulsion load which takes more energy and is sporadic rather than steady.

    Great post Steve, thanks. I’m a latecomer to your blog, which is a true gem, ain’t no fugazi.


  5. Not sure if it happens here but the newer 4 stroke diesel engines do not have the same waste heat production as the old GM 2 strokes, so I think that the current buses also have diesel fuel heaters, but that fuel gets counted in the fuel used by the bus.


  6. Climate policy is really, or should be, energy policy, which really is, or should be, transport policy, which really is, or should be, transit policy (and bike policy too). Alas, in OntCARio we tend to have caronic denial, and I don’t think we’re all that serious about curtailing the climate emergency, as per a good cartoon via Stephen Wickens twitter feed:


  7. My investment banker friend told me that Russian-Jewish billionaire oligarch Roman Abramovich has an investment in Nova Bus Inc through a numbered company headquartered in Panama (a tax haven) as per the Panama Papers leak. If we are to be punishing Russian billionaire oligarchs, then may be we should avoid buying from Nova Bus Inc.

    Steve: I suspect that between various geopolitical considerations, we could find it difficult to buy anything from anyone. Frankly if there is info from the Panama Papers, or anywhere else, that should cause various companies who might bid on public works to be blacklisted, it should be released en masse, not dribbled out as rumours people have heard.

    In other news, a troll who comments regularly on this site (and whose posts I almost always delete), recently suggested that (a) I am pushing for Novabus (I’m not) and (b) that’s because I have shares in it (I don’t). This is the kind of crap I have to deal with here, but you gentle readers are spared the annoyance.


  8. Your mention of hucksters has me wanting to see some kind of history of them in regards to transit history in Toronto. I’m sure there have been PLENTY of them in transit history everywhere in the world.


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