Hello, bio: What’s the future of fuel? Can soy and sugar cane provide sustainable alternatives for transport?

When you think about the energy transition, what images come to mind? Wind turbines in the sea? Arrays of photovoltaic panels? Maybe a sleek electric car on your driveway? All these things will have a significant part to play in the world’s future energy systems. And all of them illustrate one of the defining characteristics of the change that is unfolding today: the central role of renewably sourced electricity as a cleaner, more efficient source of energy.

There is, however, a problem with this picture. Some of the ways we use energy are difficult or impossible with today’s electrical technologies. Many of those are applications that consume very large quantities of heat, such as primary steelmaking or cement production. Others are applications that require high-density energy storage, such as ocean shipping, air transport or long-distance road freight.

As the world moves away from the large-scale use of fossil fuels, we will need to find alternative sources of energy for these industries. In a new white paper, a team of Deutsche Post DHL Group specialists examines the options – available today and in development – that might allow that goal to be reached. Under its Mission 2050 initiative, the company is committed to the goal of achieving zero-emission logistics by the middle of this century, and, with its understanding of logistics and transport on a global scale, hopes to add a perspective that will contribute to a more structured approach to assessing and implementing these fuels.

Quiet and efficient, battery-electric solutions remain the preferred choice for many applications, especially lastmile deliveries in urban environments. Electric trains provide possibilities for some long-distance routes. Nevertheless, the overwhelming majority of modern freight transport – including all air and ocean cargo – cannot yet be electrified.

Attempts to address the challenges of fossil fuel-free, long-distance transport have encouraged significant research and industrialization efforts in recent years. The aim of many of these projects is to produce liquid and gaseous fuels with similar energy-carrying properties to conventional fossil fuels.

Much current work is focused on the production of fuels from biological materials. That isn’t a new idea: Oil, gas and coal all started out as animals and plants millions of years ago. Today’s biofuel technologies simply replace millennia of geological squeezing with faster chemical and biological reactions. Biofuel manufacturing can be used to make a wide range of products, from methane and ethanol to biological equivalents of diesel and aviation fuels.

Most biofuels have a significantly smaller carbon footprint than their fossil equivalents: The carbon in their structure is captured from the atmosphere by their vegetable (or animal) ingredients. From a broader sustainability perspective, however, the picture is more nuanced. When crops are grown specifically for biofuel production, agrochemicals, processing and transportation can all cause additional carbon emissions. Rising demand for biofuel crops could put increasing pressure on scarce land and water resources already needed for food production. Tearing down forests to make way for biofuel plantations is bad for the local ecosystems and wider atmosphere.

Those challenges have driven a lot of interest in the production of biofuels from materials that would otherwise go to waste. That could be residual materials from agriculture and food processing operations or municipal solid waste. According to the U.S. Environmental Protection Agency, biodiesel produced from soy generates 57% fewer greenhouse gas emissions than the fossil fuel equivalent. Using waste grease as feedstock pushes the reduction figure to 86%.

Projects to produce biofuels from waste are now springing up around the world. In the U.S., for example, a plant currently under construction in Nevada will produce 50 million liters of synthetic crude oil a year using waste from a huge landfill site next door. Despite these investments, however, biofuels are still mere drops in the ocean of oil today. Biofuels accounted for 2.7% of the world’s transport fuels in 2017, a number that is expected to rise to 3.4% by 2020.

Concerns about the availability and sustainability of biological fuel feedstocks are driving interest in an alternative set of fuel technologies known as “power fuels.” These approaches create fuels using entirely synthetic processes, building them up from their constituent molecules. The most basic power fuel is hydrogen. Generated by the electrolysis of water, hydrogen is a completely carbon-free energy source – provided the electricity used to make it comes from a zero-carbon source.

To make a power fuel that fits more easily into the existing energy supply chain, some power fuel approaches create synthetic hydrocarbons. They do this by combining hydrogen with a carbon source. Often this is carbon dioxide emitted as waste from another process, but the gas can also be drawn directly from the atmosphere. This technology is being used on a close-to-commercial scale to produce “e-methane,” which can be used directly in the many vehicles already converted to run on natural gas. Still at the pilot scale, “power-to-liquids” technologies combine electrically generated hydrogen and carbon to create heavier hydrocarbons that can be processed into gasoline, diesel or aviation fuels.

Clean fuel technologies are at very different stages of development today. Biofuels created from soy or sugar cane are already widely used and manufactured on an industrial scale. Full-sized, power-to-liquids plants, by contrast, may arrive any time between 2025 and 2050. And choosing the best approach won’t be easy. Hydrogen is potentially the cleanest of all the alternatives, for example, but it is difficult to store and to handle. E-methane and power-to-liquids approaches keep returning carbon to the atmosphere, and making these heavier fuels is more energy-intensive. They can, however, be used as drop-in replacements for fossil fuels, simplifying the transition process.

As it stands, the report’s authors say, zero-carbon logistics will most likely involve a combination of approaches, with four main components. First, electrification will be used wherever practicable. Second, the heavy work in ocean shipping and aviation will be achieved with drop-in power fuels. Third, transport assets in some sectors will be adapted to use new power fuels. This “non-drop-in” approach is likely to include the use of methane or hydrogen in long-distance trucking, for example. Finally, biofuels, especially those produced from waste, will have a niche role to play where they can be sourced and used sustainably.  — Jonathan Ward

Published: November 2019

Images: iStock; DHL