Biofuels have long been touted as a carbon-neutral alternative to fossil fuels, doing for the world’s planes, ships and automobiles what windfarms and solar panels are doing for its electricity grids. Green biofuels could be an important ingredient of the zero emissions future envisioned by the Paris climate agreement. On paper, biofuels seem the ideal replacement for fossil fuels, which drive global warming by spewing tons of carbon dioxide into the atmosphere that would otherwise be locked away in geological deposits. With biofuels, the plants and algae used to produce the raw material inhale carbon as they grow, offsetting the carbon released when they are burned.
A recent Royal Academy of Engineering report says, however, that some biofuels, such as diesel made from food crops, have led to more emissions than those produced by the fossil fuels they were meant to replace. Instead, the report says, rising biofuel production should make more use of waste, such as used cooking oil and timber. The past decade has seen the biofuel industry face tough economic conditions and niggling questions over its green credentials. The fledgling industry is now turning to a raft of innovative crop and processing technologies to overcome its challenges. One of the biggest criticisms of the early generation of bioethanol crops, such as corn and sugarcane, was their propensity to mess with food markets and alter land use.
According to The Guardian, the report combines more than 250 analyses of the impact of biofuels around the world, including how demand for food-based biofuels drives the destruction of forests and peatlands when farmers expand into additional areas – the most contentious issue. It also warns that the promise of clean biofuels from algae remains far off, with current versions much worse than diesel. The researchers found that when land use changes were accounted for, all the significant types of biodiesel – palm oil, soybean, rapeseed and sunflowers – caused more carbon emissions than diesel itself. Bioethanol, which replaces petrol (gasoline) and is produced from corn, wheat, sugarcane and sugar beet, failed to meet the 50% reduction when land use change was included. Wheat-based bioethanol was the worst performer, actually producing more carbon emissions than petrol. The report advises the use of waste from farms and forestry, and from used cooking oil, to make biofuels, in order to cut emissions. In some cases, such as using waste stalks and cobs from corn, biofuels could have near-zero emissions overall.
Changes to processing technologies are also influencing the direction that the biofuel industry is taking. Traditional approaches use plant sugars for fermentation to bioethanol, or oils that can be chemically transesterified for biodiesel production. But the industry is also turning to methods that are less finicky about what plants are used. Progress towards producing better biofuels has been challenging. British Airways abandoned a £340m scheme to create jet fuel from London’s rubbish in January 2016, although in the same month the US navy launched its first aircraft carriers powered by biofuels. Despite the trend of electrification in public and private transport, the sustainable growth of biofuels production is a key part of tackling climate change, because no significant alternatives for liquid fuels are available for aircraft and ships for some years to come. So the difficult task of distinguishing good and bad biofuels remains essential, as does the research of even more promising technologies, such as algae and seaweed.
Once again, the use of the prefix “bio” for biofuels does not necessarily means that biofuels contribute to a more sustainable energy generation. The key-point, once more, is to consider the changes they bring in their whole life – cycle and interaction with the environment and not only during their use for energy generation. Instead of conclusions, this is one of the key-recommendations of the Royal Academy of Engineering report:
“It is also important to take into account that biofuels do not exist in isolation but are part of much wider systems, including energy, agriculture and forestry. Like other production systems with which they interact, biofuels impact on various ecosystem services, such as land, water and food. It is, therefore, essential to take an integrated, systems view to developing future policy to ensure that biofuels are not disadvantaged relative to other sectors or that progress made in this sector is not undone by unsustainable practices in others.”