The tipping point in transportation

By 2022, 100 percent of electric cars will have reached 10 per cent of global sales: the tipping point is passed, and the heat-powered car is heading into the sunset. Having reached the ripe old age of 140, it is ready to pass the buck despite merciless advisers refusing to give up. They have at their disposal not solid arguments but a large arsenal of slogans and buzzwords. Recently, a few have come back into vogue that invoke an idea of sustainability and feasibility, which is often anything but biofuels, synthetic fuels, and e-fuels. What are they all about?

Let's start with the key point of the issue. Today, we use about 4 billion tons of oil each year to fuel the transportation system. If we wanted to start with plant biomass, we would need at least 12 billion tons, 50 per cent of all the biomass we inject into the world economy annually through agricultural and forestry activities. One Earth would not be enough.

Why biofuels are not enough

Let's face it: the fossil transportation bunk (we burn about 500 years of Jurassic photosynthetic activity each year) is a one-time event in history that, in any case, it is foolish to perpetuate. As much as 3 billion tons of oil of the four we use does not go to move wheels, propellers or turbines but is dissipated as heat in engines. Thus, the real issue to be addressed is not the change of the fuel but the change of the engine

In the end, hanging fuels do not shift anything regarding - monstrous - energy waste and pollution: nitrogen oxides and ultrafine particulate matter do not decrease by putting the prefix "bio" to the noun fuel.

Petroleum is a fantastic liquid capable of sending any chemist into raptures: a kind of "semi-finished product" already available in nature, from which fuels for all means of transportation (gasoline, diesel, kerosene...) can be made through a relatively simple and standardized process, refining. The situation is quite different in the case of biofuels, where the raw materials are many and very varied: sugar cane or beet, corn, oil plants (such as rapeseed, sunflower or palm), waste biomass, used edible oils, animal fats... Each of these raw materials requires a specific process to then be converted into fuel for cars, trucks, planes, ships. All biofuels are "synthetic," meaning that they are produced in large industrial plants through various thermal, chemical, and biochemical processes. Moreover, they are generally used to "cut" fossil fuels: they can rarely be used exclusively. 

Hydrogen

A key ingredient in some biofuel production processes is hydrogen. The only sustainable hydrogen is "green" hydrogen, produced with electrolyzers from water and renewable electricity. One kilogram of green hydrogen requires nine liters of water and 55 kWh of electricity, which are very large quantities. Today, the cost of green hydrogen ranges between €10 and €20 per kilogram, values that are still too high for massive use in the biofuel industry. 

First- and second-generation biofuels

Biofuels are divided into two categories, whose boundaries are not always clear. "First generation" is defined as those obtained from dedicated crops, as with bioethanol and biodiesel. The former is similar to gasoline and made from products rich in sugars or starches (sugar cane, corn) that undergo fermentation. The second is obtained from vegetable oils (rapeseed, sunflower) subjected to a chemical process of "transesterification."

Decades of studies show that first-generation biofuels are a sustainable solution in limited geographical settings, such as where climatic and environmental conditions minimize the need to rinse or use fertilizers to grow the feedstock. This is the case, for example, with sugar cane in Brazil. However, they can never be a permanent solution. If Europe and the United States wanted to replace even 5 per cent of their fuel consumption with this option, they would have to dedicate about 20 per cent of their arable land for the purpose. In practice, the food vs. energy dilemma becomes an insurmountable obstacle.

The use of non-food biomass, i.e., organic waste or poor crops on marginal farmland, can overcome this hurdle: here are "second-generation" (or "advanced") biofuels. Unfortunately, after years of small-scale installations, progress in the field is limited and costs still high. Obtaining biofuels from plant waste requires complicated processing involving pre-treatment (such as pyrolysis or gasification) followed by further chemical processing (upgrading) from which the liquid fuel is derived. 

The e-fuels

Much emphasis is placed, finally, on so-called e-fuels, that is, fuels made from renewable electricity. The idea is to electrochemically break down simple molecules such as CO2 and H2O, to obtain mixtures of H2 and CO, which can then be converted into liquid fuels through appropriate treatments: typically the Fischer-Tropsch process, already used by Germany short of fuels in World War II. E-fuels are an exciting field of research, but their large-scale industrial production remains a distant goal. 

Where do we stand?

Biofuels currently meet less than 3 percent of the world's transportation fuel needs; more than 90 percent of these are first-generation. In Europe, about 50,000 km2 of arable land is devoted to the exclusive production of biofuels. Unchecked expansion of these activities globally may reduce the availability of food in markets, raising prices. This is a risk that must be averted in a world where tens of millions of people face severe food shortages on a daily basis.

Biofuels tend to promote intensive monoculture, which implies additional impacts and often generates leaky balances in climate emissions: reduced soil capacity to absorb carbon, disappearance of biodiversity, deforestation.

A diriment point is the overall energy balance of operations, which often remains ambiguous: the energy that moves a vehicle must discount all that expenditure in the fuel production chain. Numerous studies show, for example, that U.S. corn bioethanol, produced in huge quantities thanks to generous federal subsidies, turns out to be an expense (due to planting, irrigation, fertilizer, pesticides, harvesting, processing, transportation...) and not an energy source.

For some time now, the production of so-called HVO biodiesel, made by hydrogenating vegetable oil, has been in vogue. It is presented as a sustainable solution, but the reality is often quite different. For years, this product has been obtained almost exclusively from palm oil crops on deforested land in Southeast Asia.

Today, oil companies seeking a greener image promise to use only edible oils and waste animal fats. Numbers in hand, data from supply chain consortia indicate that about 40,000 tons per year of used edible oils are collected in Italy. Oil companies' plans are for ten times that volume, so the feedstock for HVO biodiesel will be imported from halfway around the world, opening up a serious issue of traceability, emission and energy balances.

I hope this cursory overview will help to understand the complexity of a subject that is too often told with a superficiality that sometimes borders on misleading advertising. Biofuel production is an interesting possibility, but one that needs to be carefully analyzed on a case-by-case basis, lest the best intentions be a nightmare. The most likely prospect is that the limited amounts of sustainable biofuels we will be able to produce will have to be directed almost exclusively to ships and airplanes, the most difficult vehicles to de-fossilize.

In the meantime, as we study and reflect, it may be useful to note that the 50,000 km2 of agricultural land used in Europe to produce biofuels for road transport would be reduced by 97.5 percent if it were covered by photovoltaic panels to power electric cars.

Perhaps there is no point in looking for solutions to problems we have already solved. Let's focus on the rest.