Could diesel be replaced by biogas in city trucks?

We calculated the life cycle costs of fuel for existing diesel trucks by comparing diesel and biogas. Biogas is more attractive as the more a car consumes, the more kilometres it drives per year. A low-emission solution can also be the most economically sustainable. Espoo’s goal is to be carbon neutral by 2030.

The city of Espoo has 42 trucks with diesel engines. In a city aiming for carbon neutrality by 2030, fewer low-emission alternatives to diesel are being sought. Already, more than 60% of the fuel used is low-emission biodiesel.

We are evaluating how our trucks could run on biogas instead of diesel in an economically sensible way. We made the calculation based on the calculator provided by Gasum, where we entered the data and assumptions for our own user cases. Using the calculator, we calculated the total cost of ownership of the biogas car for fuel. The calculations are based on estimates and assumptions about the cost of acquiring, maintaining and operating cars. Changes in the input data, such as fuel prices or car diesel consumption, have a big impact on the results, so it is good to always check and update the input data when calculating profitability calculations for own use.

The picture below shows a summary of the calculations made with the trucks used by the City of Espoo and the actual consumption data. Based on the calculations, biogas is cheaper to use in the maintenance of the city’s roads during the car’s life cycle compared to diesel. The savings depend on the way of use and area. For example, for longer journeys in northern Espoo (30,000 km/year, consumption 50 l/km), Scania would save up to EUR 52,000 in 10 years. At the same time, almost 350 tCO2e of CO2 emissions would be reduced, calculated using the EU RED II (Renewable Energy Directive II calculation method). The Mercedes-Benz Atego drives 20,000 km/year in the example in the picture and has a consumption of 40 l/km.

Read below more detailed information about making the calculation and other things to consider.

The maintenance of a gas truck costs on average the same as a similar diesel truck, so the cost analysis was limited to acquisition and operating costs. Operating costs, on the other hand, can be expected to depend very directly on fuel costs.

Based on the information retrieved from the fuel price monitoring service Polttoaine.net(external link, opens in a new window) diesel paid an average of EUR 2.16/l on 8 March 2022 in Espoo. According to the gas company Gasum(external link, opens in a new window), fuelling biogas at stations in Espoo cost EUR 1.70/kg. The prices quoted include VAT, which the city does not have to pay. The prices will therefore be tax-free, resulting in EUR 1.74/l for diesel and EUR 1.37/kg for biogas.

So according to our simple calculation, running on gas is currently more than 20% cheaper than running on diesel!

Almost all the trucks used by the City of Espoo belong to the City Technology Centre, which uses them especially for street care and maintenance. There must be space under the car chassis for various maintenance equipment, such as de-icing blades when plowing roads. In order to have space for gas tanks in addition to the accessories, the wheelbase of the car must be quite long. Therefore, it is not currently possible to use biogas in all cars, but the intended use must always be considered first.

It is assumed that some of the city’s maintenance tasks could also be done with gas trucks. Maintenance tasks consume a lot of fuel, up to 35–50 litres of diesel per 100 kilometres. The annual number of trips depends a lot on where in the city the car is used. We talk up to 30,000 kilometres a year at highest. There is a difference between working in the longer-distance area of northern Espoo or in the more urban environment of southern Espoo.

Some caution should be exercised when assessing financial viability. It is assumed that 20,000 km would be driven per year, which would burn 8,000 litres of diesel. It costs the city almost EUR 14,000. If a diesel car were replaced with gas, the cost of fuel would fall to EUR 11,000 a year when calculation with the prices in March.

The city typically uses one truck for ten years before it is replaced with a new one. The savings in future years must be discounted in order to estimate how much savings will be achieved over its lifetime. Discounting means calculating the present value of future cash flows. The higher the current value relative to the future, the higher the discount rate used. For example, choose an interest rate of 3% and add up the savings of EUR 3,000 each year. The savings from switching to biogas can be estimated at around EUR 26,000.

Is this a lot or a little? Depends on the price of the gas truck. To put it simply, if a gas truck is no more than EUR 26,000 more expensive than a similar diesel truck, it pays to replace it. When, on average, a gas truck is about EUR 16,000 more expensive, the savings in this example would be EUR 10,000.

It is possible for private operators to receive support for the purchase of a gas car, and the utilisation rate of cars is often higher than that of a municipal operator. Therefore, the savings for a private operator may be even greater.

Reducing emissions is important primarily for the environment and human health. The value of biogas is also increased by its domestic and renewable nature. Biogas improves Finland’s security of supply. At present, biogas is also an excellent option in economic terms.

Useful links (some in Finnish):

You can read up-to-date information on the topic from the compilation of the Future of Biogas Webinar  we organized on 22 April 2022.

More information on acquisition subsidies can be found on Traficom’s website(external link, opens in a new window).

There are various car calculators, for example, at Gasum (external link, opens in a new window)and the Finnish Climate Panel(external link, opens in a new window).

Did you know? 

Diesel is bought in litres and gas in kilograms

• A gas engine consumes about 25 percent more energy than a diesel engine. Since diesel is sold per litre and gas per gram, some simple calculations need to be made to estimate gas consumption. 
• Let’s picture a situation where it would be desirable to start using gas in a truck that has consumed 20 litres of diesel over a hundred kilometres. The density of diesel can vary between 0.82 and 0.845 kg/l, so 20 litres weighs about 16 to 17 kg. A kilogram of diesel produces 42 to 46 megajoules of energy, so driving a hundred kilometres consumes 690 to 780 megajoules (or about 190 to 220 kilowatt hours).
• The energy consumption of a similar gas truck would therefore be 860-970 megajoules, or 240-270 kilowatt hours. One kilogram of gas produces 13.7 kilowatt hours of energy, so 17–20 kg of gas would be needed to drive one hundred kilometres.
• According to the results, the consumption of a diesel truck in litres is approximately the same as the consumption of a gas truck in kilograms. The costs can thus be conveniently estimated by looking at the prices of diesel and gas as well as the lengths of the journeys made by car.

Sustainable growth is promoted in Espoo’s sustainable development projects

The TCO calculation was implemented in the RAKKE project. The City of Espoo’s Solution path to sustainable growth ecosystems (RAKKE) project is funded by the Uusimaa sustainable growth and vitality support (UKKE) funding.