Leftover Magic: Powering Planes With Chinese Hot Pot

The aviation industry is under pressure to find greener alternatives to power its jet engines, with several major airlines pledging to replace about 10% of their jet fuel with a sustainable alternative by 2030. Waste oil from kitchens has emerged as a major source of sustainable jet fuel, and China, with its love for greasy hot pots, is the largest exporter. In 2016, a startup in Chengdu began exporting leftover restaurant grease to Europe and Singapore, where it gets recycled into fuel pure enough to power aeroplanes.

The process of creating Sichuan hot pot

The process of creating a Sichuan hot pot is a fun and interactive meal, perfect for a cosy night in or when hosting guests. The first step is to prepare the equipment, which includes a pot and a heater. For convenience, an electric cooker with a pot is recommended. A wide pot is preferable so that all participants can cook their ingredients simultaneously.

The next step is to prepare the soup base. This can be done by making a clear broth and adding spices like chilli pepper, doubanjiang, and Sichuan peppercorn. Alternatively, a store-bought soup base can be used. There are two common types of soup bases for Sichuan hot pot: a spiced version and a mild version.

Once the soup base is ready, it's time to prepare the ingredients. Common ingredients for Sichuan hot pot include thinly sliced meat, such as beef or lamb, assorted vegetables, mushrooms, noodles, and tofu. It is important to cut the ingredients into thin slices so that they cook quickly and evenly in the broth.

To create a more personalised hot pot experience, each person can make their own dipping sauce. Common ingredients for the dipping sauce include Chinese black vinegar, sesame paste, peanut butter, soy sauce, and chopped scallions.

Finally, it's time to assemble the hot pot. Place the prepared pot of broth on a hot plate and bring it to a low boil or simmer. Arrange all the prepared ingredients around the pot, and let everyone cook their chosen ingredients in the broth. As the water evaporates, add boiling water to the pot as needed. Enjoy the hot pot with your chosen dipping sauce!

How a startup in 2016 began exporting leftover grease

In 2016, a startup in Chengdu, China, began exporting leftover grease from the city's restaurants to Europe and Singapore. The process of creating the perfect Sichuan hot pot involves a lot of fat, and this ritual results in about 12,000 tons of waste oil each month in Chengdu alone. The startup collects this used oil and removes impurities such as sodium and metal particles. The end product is a biofuel precursor called industrial mixed oil, which is then exported to companies like Neste Oyj, BP, and Eni, where it is further refined into biodiesel or jet fuel.

The aviation industry is responsible for around 2% of the world's total emissions of planet-warming gases, and there is pressure to find greener alternatives to power jet engines. While sustainable aviation fuel is currently much more expensive than its conventional counterpart, several major airlines, including British Airways, Cathay Pacific Airways, and Delta Air Lines, have pledged to replace about 10% of their jet fuel with a sustainable alternative by 2030. More than 50 airlines have begun experimenting with sustainable fuels, and governments and industry regulators are tightening rules to meet emissions targets.

Waste oil from kitchens has emerged as a significant source of sustainable jet fuel because it does not displace food production or encourage deforestation. China, with its large population and love for greasy hot pots, is already the largest exporter of waste oil for jet fuel. The startup in Chengdu, called Sichuan Jinshang Environmental Technology, was originally set up during China's food safety crisis to stop contaminated "gutter oil" from being sold back to food vendors. In 2016, the company began exporting the leftover fat for industrial use when they noticed the growing demand for biofuels from international refiners.

The recycling process into jet fuel

The aviation industry is under pressure to find greener ways to power its jet engines, as it is responsible for around 2% of the world's total emissions of planet-warming gases. In 2016, a startup in Chengdu, China, began collecting waste oil from the city's hot pot restaurants and exporting it to Europe and Singapore, where it is recycled into jet fuel. This fuel is then purchased by major airlines such as British Airways, Cathay Pacific Airways, and Delta Air Lines, who have pledged to replace about 10% of their jet fuel with a sustainable alternative by 2030.

The process of converting waste oil into jet fuel begins with the collection of the used oil, which is then transported to a facility where it undergoes several treatments to remove impurities such as sodium and metal particles. The oil is then heated to between 300°C and 900°C in an oxygen-free environment, breaking it down into fuel and other chemicals through a process called pyrolysis. The fuel produced from this process is then blended with conventional jet fuel to create a sustainable aviation fuel (SAF).

The use of SAF has the potential to significantly reduce the carbon emissions associated with air travel. Researchers have identified locations in the United States where large airports are in close proximity to major waste-producing centers, making them ideal sites for the construction of waste-to-fuel refineries. It is estimated that up to 100 refineries could be built across the country, producing 3-5 billion gallons of SAF annually and lowering the carbon intensity of the aviation industry by 10-18%.

While the concept of recycling waste oil into jet fuel is not new, advancements in technology have made it more efficient and environmentally friendly. The use of catalysts and solvents, such as n-hexane and ruthenium-on-carbon, maximizes reaction rates and improves the quality of the fuel produced. However, some critics argue that the process is impractical, particularly when scaled up for commercial use, due to the high energy requirements and the potential environmental impact of the chemicals involved.

Despite the challenges, the recycling of waste oil into jet fuel holds promise for reducing the aviation industry's carbon footprint and contributing to global efforts to avert catastrophic global warming.

The environmental impact of the aviation industry

The aviation industry has a significant environmental impact. Aircraft engines produce gases, noise, and particulates from fossil fuel combustion, which affects both the environment and local air quality. In 2018, global commercial flights generated 2.4% of all carbon dioxide (CO2) emissions, or 895 million tonnes. This figure is expected to triple by 2050. CO2 emissions are the most significant and best-understood contribution to climate change from aircraft. However, other emissions, such as nitrogen oxides, contrails, and particulates, also have an impact. The radiative forcing of these emissions is estimated to be 1.3 to 1.4 times that of CO2 alone.

The aviation industry is under pressure to find greener ways to power its flights. Several major airlines, including British Airways, Cathay Pacific Airways, and Delta Air Lines, have pledged to replace about 10% of their jet fuel with a sustainable alternative by 2030. More than 50 airlines have begun experimenting with sustainable fuels, and biofuels are being explored as a quick way to reduce emissions with minimal aircraft modification. However, biofuels are restricted by scale and feedstock availability, and few are low-carbon.

One innovative way to create sustainable jet fuel is by recycling waste oil from restaurants. For example, a startup in Chengdu, China, collects used oil from hot pot restaurants and exports it to be recycled into jet fuel. This waste oil is a significant source of sustainable jet fuel as it does not encourage deforestation or displace food production.

To reduce aviation's environmental footprint, several measures can be taken, including:

• Improving fuel economy in aircraft.
• Optimising air traffic control and flight routes.
• Using aviation biofuel, emissions trading, and carbon offsetting.
• Banning short-haul flights.
• Encouraging train connections.
• Increasing aviation taxation.
• Decreasing subsidies.
• Replacing fuel-powered aircraft with hybrid, electric, or hydrogen-powered aircraft.

The future of sustainable aviation fuel

The aviation industry is under increasing pressure to reduce its environmental impact, with aircraft accounting for 9-12% of US transportation-related greenhouse gas (GHG) emissions. With jet fuel demand expected to double pre-pandemic levels by 2050, the development of sustainable aviation fuel (SAF) is critical to achieving net-zero emissions targets.

Wet Waste to Flight

Scientists at the National Renewable Energy Laboratory (NREL) and other institutions have published research outlining a biorefining process using food waste and other wet waste to produce SAF. This fuel is compatible with existing jet engines and enables net-zero-carbon flight by eliminating the GHG emissions associated with jet fuel combustion. The process involves using a catalyst to add carbon to volatile fatty acid (VFA) molecules, creating energy-rich paraffin hydrocarbons chemically identical to those in conventional jet fuel but with a much lower carbon footprint.

Commercialisation of SAF

The commercialisation of SAF is gaining momentum, with several companies already producing and supplying SAF to airports worldwide. World Energy, Neste, and Montana Renewables LLC are three known commercial producers, and additional new domestic plants are expected. Many airlines have signed agreements with SAF producers, and the US Environmental Protection Agency (EPA) estimates that approximately 24.5 million gallons of SAF were consumed in 2023.

Policy Support

The Sustainable Aviation Fuel Grand Challenge, announced in 2021, aims to expand domestic consumption of SAF to 3 billion gallons in 2030 and 35 billion gallons in 2050 while reducing lifecycle greenhouse gas emissions by at least 50%. The International Civil Aviation Organization (ICAO) has also implemented the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), capping net CO2 aviation emissions at 2020 levels through 2035 and setting a net-zero carbon goal by 2050.

Benefits of SAF

In addition to reducing GHG emissions, SAF offers several other benefits. It is compatible with existing aircraft and infrastructure, does not displace food production or encourage deforestation, and can improve aircraft performance by reducing local emissions of harmful compounds during take-off and landing. SAF production also creates new economic opportunities, improves the environment, and supports American jobs in various sectors, including farming, construction, manufacturing, and aviation.

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