The EU has prioritized electric vehicles as a way to develop carbon-free mobility. This is understandable, as the population density in other parts of Europe is much higher than in the Nordic countries. The government has included in its program the promotion of biogas.

While working on the carbon balance of Ekokympi transportation, I have become familiar with the fuel options used in transportation and made some amazing discoveries in my calculations.

The most crucial factor in reducing emissions is the fuel used and how it is produced.

Based on the comparison, diesel vehicles have the most favorable opportunities to transition to carbon-free mobility. Carbon dioxide emissions from diesel vehicles can be reduced by a tenth by switching to renewable diesel.

That remaining tenth is less than the entire life cycle carbon dioxide emissions of electric and biogas vehicles. The fuel is somewhat more expensive, but significantly cheaper than buying a newer gas or electric car.

The downside of diesel engines is particulate emissions, which are harmful, especially in cities. In such cases, gas or electricity are a better option.

For climate action, we need all power sources with a lifecycle CO2e emission factor of less than one kilogram. At that time, fossil diesel, natural gas or “dirty electricity” will be out of the game.

Car propulsion comparison

Electric energy

For now, an electric car is a year-round option for those whose journeys are less than a hundred kilometers. There is room for improvement in the current ecology of electricity production. Unfortunately, the electricity used in cars is not yet green enough. Motiva gives the carbon dioxide emissions of electricity used in Finland as an average of 0,131 kg CO2/kWh (131 kg CO2/MWh) over the past three years. (https://www.motiva.fi/ratkaisut/energiankaytto_suomessa/co2-paastokertoimet).

Biogas energy

Biogas is also not the cleanest option when it comes to CO2e emissions over its entire life cycle. Although the use of biogas is not counted as carbon dioxide emissions, its production generates emissions of 1,21 kg CO2e/kg, according to SYKE's Y-Coal emission calculator. (https://www.syke.fi/fi-FI/Tutkimus__kehittaminen/Kulutus_ja_tuotanto/Laskurit/YHiilari emission factors tab). According to information received from Gasum Oy, the entire life cycle carbon footprint of the gas produced at their Oulu biogas plant is 0,819 kg CO2e/kg.

The availability of biogas will have to be replaced with fossil natural gas, which has a CO2 emission value of 3,07 kg CO2e/kg.

Diesel energy

Fossil diesel has an emission value of 3,6 kg CO2e/kg. Oil companies have developed and introduced renewable diesel, the entire life cycle of which is 0,4 kg CO2e/kg, which is only one tenth of that of fossil fuel. The fuel has a filterability of -32 °C and can be used as is in all diesel engines.

See for example: https://www.neste.fi/artikkeli/neste-my-uusiutuva-dieseltm-sinun-panoksesi-ilmastotalkoisiin

https://www.teboil.fi/yhtio/tiedotearkisto/2018/teboil-green-uusiutuva-diesel-jakeluun-paakaupunkiseudulla/

https://www.st1.fi/yrityksille/tuotteet-ja-palvelut/polttonesteet/dieselit-ja-adblue/hvodiesel?gclid=Cj0KCQiAkZKNBhDiARIsAPsk0Wi16We7qZNVdmErF_l28TfOkE9oMYQAzQyYKyyqWSof7Vmkg8wZpPwaAlqLEALw_wcB

Comparison of car fuel options

Let's take a few examples. The Skoda Octavia is available in petrol, diesel and gas-powered models. Skoda doesn't yet have any electric cars, so I'll use the average consumption of electric cars in the same size class. I'll write the equations out so that everyone can adjust the coefficients, for example, to adjust the consumption amounts if they don't correspond to reality.

Electric car consumes an average of 15–30 kWh/100 km of electricity in year-round use, of which the average is 22,5 kWh/100 km. Multiplying that figure by the rolling average of the carbon dioxide emissions of electricity used in Finland over the last three years, 0,131 kg CO2e/kWh, provided by Motiva, gives the carbon footprint of using an electric car 2,95 kg CO2/kgUsing an electric car is emission-free only when powered by renewable energy (e.g. wind power, hydropower, solar energy and wood).

In cold winter conditions, the consumption of an electric car can double the values given by the manufacturer due to the increased need for heating the interior air, while in traditional combustion engines, heating is mostly done with waste heat.

Petrol-powered Skoda consumes 4,9 liters of gasoline per hundred kilometers. SYKE's Y-Hiilari emissions calculator reports the carbon dioxide coefficient of gasoline as 2,88 kg CO2e/kg. With the specific gravity of gasoline of 0,745 kg/liter, the consumption can be converted to a weight-based consumption of 3,65 kg/100 km. Multiplying by that number, the gasoline emission coefficient is 2,88 kg CO2e/kg, which gives the Skoda emission amount 10,51 kg CO2e a hundred kilometers.

Gas-powered Skoda consumes 3,104 kg/100 km of biogas. Multiplying this by the SYKE Y-Hiilar emission factor of 1,12 kg CO2e/kg, which takes into account the production of biogas, gives an emission value of 3,52 kg CO2e per hundred kilometres. The value is a third of the petrol car in the previous example. With the biogas produced by Gasum, the Skoda's emissions are 2,54 kg CO2e/100 km.

Diesel-powered Skoda consume fossil diesel 4,7 liters per hundred kilometers. With a specific gravity coefficient of diesel of 0,806 kg/liter, the consumption is 3,79 kg/100 km. The CO2e emission value of fossil diesel is 3,6 kg CO2e/kg. Therefore, the product of the last two figures is the emission value 13,64 kg CO2e/kg per hundred kilometers.

Let's refuel. diesel for Skoda renewable diesel. The specific gravity of renewable diesel is 0,78 kg/liter lighter than fossil diesel, which is why the liter consumption increases slightly to 4,86 liters per hundred kilometers. We use the same weight-based value of 3,79 kg/100 km as the consumption value. By multiplying that value by the renewable diesel value of 0,4 kg CO2e/kg, the emission remains 1,52 kg CO2e/100 km.

Table 1. Comparison of emissions by vehicle propulsion system

Based on these benchmarks, renewable diesel produces 52% lower carbon dioxide emissions than driving an electric car.

Diesel cars account for 28% of the total number of passenger cars in Finland. The heavy vehicle fleet is almost entirely diesel-powered. The share of those powered by gas and electricity is still marginal. What would be the impact, for example, if municipalities switched to using renewable diesel in public transport and street maintenance? Similarly, in other logistics and waste management?

In Kajaani on November 29.11.2021, XNUMX

Esa Kumpulainen

Cycle Low Carbon Expert Student

esa.kumpulainen@ekoykymppi.fi