Biofuels - for example from corn, grain or rapeseed - are considered a climate-neutral alternative to fossil fuels such as petrol and diesel. But this calculation does not work out in the long term, as researchers have now found out. Since forest areas have to be cleared to grow enough energy crops, biofuel ultimately harms the climate more than it benefits it. It even goes so far that biofuel could be more harmful to the climate than fossil fuels in 30 years - provided its production remains unregulated worldwide.
The concept of biofuels sounds promising: Starch, sugar and oil from plants such as corn, grain, beet or sugar cane are turned into sustainable fuel. Although the combustion of biodiesel and bioethanol also releases CO2, unlike fossil fuels, the plants have already drawn CO2 from the atmosphere during their growth. Due to this zero-sum game, biofuel is in theory climate-neutral, which is why enormous demand for it can be expected in the future.
Biofuel in three scenarios
The more demand there is for biofuel, the more energy crops have to be grown to produce it. But where? Most agricultural land is already being used to grow food and animal feed. Experts assume, however, that biofuel suppliers such as corn, beets and the like will spread to these areas if the demand for biofuels increases and will displace the crops previously grown there. Their cultivation would then have to switch to other, as yet undeveloped areas. For example, forest areas come into question, which would then have to be cleared for this purpose, which would lead to considerable CO2 emissions.
"If the cultivation of bioenergy grasses is not strictly limited to marginal or fallow land, food production could shift and agricultural areas could expand at the expense of natural areas," explains Leon Merfort from the Potsdam Institute for Climate Impact Research (PIK). Together with colleagues, he has now examined and quantified the consequences of this ring exchange of landscape uses in more detail. With the help of special computer programs, the researchers also ran through various future scenarios and their consequences for the climate.
In one scenario, for example, Merfort and his colleagues assumed that the cultivation of biofuel crops would not be regulated in any way. Another scenario priced the CO2 released in the process at a sum that was 20 percent of the current emission prices for the energy sector. Other scenarios are based on the assumption that measures are taken to protect the forests, i.e. that 90 percent of the forest areas worldwide are placed under protection.
Biofuel is more harmful in the long term than diesel and petrol
"Our work shows that without additional land use policies, the emissions from deforestation for the production of modern biofuels can be even higher over a period of 30 years than from the combustion of fossil diesel," reports co-author Florian Humpenöder. So simply letting the producers of biofuel do their thing unregulated will, in the long term, mean that the actually climate-neutral effects of biodiesel and bioethanol will turn into the opposite. But how can land use be regulated in such a way that this scenario does not occur? Surprisingly, putting a large part of all forest areas under protection does not lead to the goal, as the research team reports. According to the researchers, even if 90 percent of all forest areas worldwide were protected, the remaining ten percent would still offer too large a loophole.
In addition to protecting the forests, another measure is therefore needed: CO2 pricing of the emissions caused by the cultivation of biofuel crops, similar to what is currently the case in the energy sector. Even prices of 20 percent of the usual level there would make a big difference, explains co-author Nico Bauer. This would make biofuel more expensive and less attractive for the consumer, which would cause general demand to fall. However, it is unlikely that all of these political regulations will actually occur globally and uniformly, given the general disunity of the world community. However, this also means: "If the regulatory gap remains so wide open, bioenergy will not be part of the solution on the way to climate neutrality, but part of the problem," says Bauer.
Source: Potsdam Institute for Climate Impact Research; Specialist article: Nature Climate Change, doi: 10.1038/s41558-023-01697-2