Electric cars powered by battery or fuel cell hydrogen, natural gas, ethanol and other biofuels: the consultancy firm Carbone 4 compared the emissions over the life cycle of vehicles to determine the best solutions to fight against global warming due to transport.
Evolution between 2020 and 2030
To carry out its simulations, the independent consultancy firm specializing in low carbon strategy and adaptation to climate change has integrated technological advances that will change the situation on several levels. First of all in order to have cleaner energy.
Thus by incorporating more biofuels in gasoline (SPE20, exploitation of wheat straw) and diesel (B10, arrival of waste-residues), by benefiting from a greener energy mix for recharging the batteries of electric vehicles and the electrolysis of hydrogen, by diversifying the products to be methanized in order to obtain biogas and add a growing share of it to CNG.
Carbone 4 also assumes that hybridization will become widespread, including on city cars running on natural gas. This will result in significantly lower consumption for all thermal engines.
1 – The bioNGV
For both B-segment city cars and D-class sedans, bioNGV appears to be the energy most likely to reduce greenhouse gases.
Now 96% of the anaerobic digestion of agricultural and livestock waste, it will gradually rely on a growing share of sludge from sewage treatment plants (15% in 2050) and other bio-waste (Also 15%). Although it is already possible in a good number of dedicated stations to obtain bioNGV, it is still conventional CNG that is used the most by motorists today. However, the latter already contains a small proportion of biogas, with an increasingly higher incorporation projection.
In the most virtuous situation, emissions could drop from 225 gCO2e / kWh (NGV) to 40 g (pure bioNGV).
On city cars …
Thanks to hybridization, the consumption of city cars would drop from 4.4 to 3.3 kg of natural gas per 100 km, and that of sedans from 5.8 to 4.3 kg.
Currently, the carbon footprint of B-segment passenger cars running on bioNGV is the lowest: 71 gCO2e / km, against 81 g for electric with the energy mix of the network, however advantageous in France (112 g depending on the mix European, 150 g in Poland), 170 g for CNG, 172 g for ethanol, 180 g for plug-in hybrids, and 222 g for gasoline engines. No value for diesel, which is far behind this category of passenger cars, nor for hydrogen, which is not yet interested in it.
The projection towards 2030 shows that the gap would widen between models powered by bioNGV, whose carbon footprint would improve, and electric ones whose technological progress would be erased by higher capacity batteries with a heavier CO2 impact.
… as on sedans
Sedans powered by biogas also stand out as the least emitting (76 gCO2e / km), although followed by battery electrics (80 g) and those carrying a heat pump and receiving exclusively green hydrogen (86 g). Otherwise, the carbon footprint of the latter would climb to 112 g.
At the bottom of the table, diesel (271 g), plug-in hybrids (216 g) and CNG (210 g) are much more emissive.
Ten years later, bioNGV would remain the best solution to minimize the carbon weight of its trips in a sedan, without however widening the gap with green hydrogen, which would be placed as a more than satisfactory alternative.
2 and 3 – Electric batteries and fuel cells
Thanks to a low-carbon energy mix in France, battery-powered or hydrogen-powered city cars and sedans also emerge from Carbon 4 calculations as excellent solutions for reducing greenhouse gases emitted when traveling with private cars.
For other European countries, the situation is different. Conventional electric vehicles continue to rank higher than gasoline or diesel models, even when the latter are equipped with a plug-in hybridization system.
This is no longer the case with versions operating with a fuel cell. Unless you supply them with energy in a station supplying green hydrogen, their CO2 impact is deplorable, much higher than that of diesel units. The latter is credited with 271 gCO2e / km, against 312 g on average for hydrogen in Europe, and 426 g in Germany.
In addition, the consulting firm dissuades from exploiting biogas to create hydrogen, thus thwarting some projects of this type. The reason ? A significant increase in CO2 emissions for France: 109 gCO2e / km for hydrogen obtained from biogas to feed a D-segment sedan, compared to 86 g for green hydrogen by electrolysis, and 76 g when driving to bioNGV. You might as well run the vehicles directly with this product!
Betting everything on bioNGV?
Reading the first few pages of this study, it would be tempting to consider bioNGV as the sole or majority alternative energy with passenger cars. A projection that Carbon 4 certainly does not do.
Referring to the national low carbon strategy, the 40 TWh of renewable gas for transport would be consumed by 12% of heavy goods vehicles converted to natural gas, ie 130,000 trucks, coaches and buses. By aligning the figures with European ambitions, 25% of these vehicles could work with this product.
In the end, the consulting firm seems to agree in substance on the other studies: favoring bioNGV for heavy vehicles, decarbonizing passenger cars with electric models, and, if we want to make hydrogen an efficient solution , it is imperative to combine it with electrolysis using renewable sources.
What about biofuels?
Carbone 4 believes that the incorporation of biofuels in gasoline and diesel only allows an anecdotal reduction in the carbon footprint. Even in pure use, for example with HVO100 or bioethanol, the gain would be only 20-25% including the change in use of agricultural land.
Faced with these products, the choice of bioNGV, electricity and hydrogen has other benefits: positive outsourcing thanks to the emissions avoided in agricultural sectors and the treatment of waste for biogas, assistance in the management of electricity networks (V2G) favored by the development of battery-powered electric mobility, and management of the intermittence of renewable energies with hydrogen. These last 2 solutions also make it possible to effectively combat air pollution and noise.
Without forcing too much on this exercise, the study opens the way to the search for a certain sobriety (reduction of the weight of vehicles, longer duration of use, less bulky batteries, etc.). The projections appear promising.
Source: Carbon 4 study
Although the work carried out by Carbone 4 is very substantial and just as interesting, some comparisons are sometimes questionable.
So when bioNGV and green hydrogen are opposed to electricity from the grid. With an electric car, it is also possible to drive with energy obtained from renewable sources. Of course, the difference in gCO2e / km will not be huge. But when there is only 4 grams of difference between biogas and electricity, one inevitably wonders if the EV would not ultimately win over the models powered by biogas or, if quite simply, we would not be in. situation of equality.
When making comparisons at European level, it is important to keep in mind that green hydrogen is also a reality outside France.
In addition, some studies point to the distribution of natural gas for a carbon footprint that would be heavier due to leaks at different levels of the chain. Hence a certain reserve on my part when the ranking is played at a handful of grams of CO2 equivalent per kilometer.
Emissions from plug-in hybrids appear to be high. They are, it is true, difficult to fix, so much they depend on the use of these vehicles. What the authors report elsewhere.
What is interesting in the Carbone 4 study is to distinguish not one, but several energies to fight against climate change. The future is indeed plurality in the field.
Another thing too, the projection work clearly shows that the ambitions of zero-carbon transport cannot ignore a certain sobriety. In this regard, the study authors were very cautious. Which is understandable very well. You should probably imagine pushing the cursor much more.
The study also presents the situation of utility vehicles, buses and 40-ton tractor units. To find in the document whose link appears at the end of the article.