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a recent piece of news caught my attention and was also promoted on our video account.

reuters reported on the 28th that according to data released by the us government, in the first half of this year, the united states imported about 1 million tons of waste cooking oil (commonly known as "gutter oil"), of which about 60% was imported from china. in 2023, china accounted for 50% of the united states' "gutter oil" imports, and in 2022, this proportion was only 0.1%. industry insiders predict that the united states' imports of waste cooking oil from china are expected to reach a new high in the coming months.

so why does the united states import this waste oil? and how should we view this phenomenon?

in fact, the purpose of the united states purchasing waste cooking oil is not that complicated. it is to produce sustainable aviation fuel (saf). "waste cooking oil" is an important raw material for making biofuel, which is then mixed with conventional aviation fuel to produce sustainable aviation fuel. this process can be said to be turning waste into treasure.

the advantage of using sustainable aviation fuel (saf) is that it can reduce carbon emissions, and some of its raw materials are renewable, making it more environmentally friendly, but the disadvantage is that it is more expensive than conventional aviation fuel.

reuters also found through combing data that the united states was still a net exporter of "gutter oil" in 2021, but became a net importer in 2022. the reason behind this is mainly policy-driven. in the past two years, the united states has vigorously developed the biofuel industry and introduced a number of subsidy incentive policies, which greatly promoted biofuel production capacity and demand for raw materials. the reason for importing large quantities from china is obviously because imports from china are of good quality and low price.

then some friends will definitely ask,if the united states can do it, why can’t we in china do it?

according to a report by huanqiu.com, in recent years, china has continuously promoted the development and application of sustainable aviation fuels in the process of energy transformation. on july 31 this year, the cpc central committee and the state council issued the "opinions on accelerating the comprehensive green transformation of economic and social development", which clearly mentioned the need to "strengthen the research and development and application of sustainable aviation fuels". at present, china has mastered the technology of independently developing bio-aviation fuels.

however, from the technical principles to the final large-scale promotion and use, all countries still have a long way to go.

let’s talk about the technical principles first, which is also the reason why the cost of saf is relatively high.

the process of converting “gutter oil” into sustainable aviation fuel usually includes the following steps:

1. collection and pre-treatment: first, waste cooking oil from restaurants, households and other sources is collected. these oils need to be pre-treated to remove food residues, water and other impurities.
2. conversion: pre-treated oils and fats can be converted into fuels in several different ways:
a. esterification reaction: through a chemical reaction, oils and fats are reacted with methanol or ethanol to produce fatty acid methyl esters or ethyl esters. these esters are the main components of biodiesel.
b. hydroprocessing: using catalysts at high temperatures and pressures to hydrocrack oils and fats, converting them into hydrocarbon compounds that are similar to petroleum-based jet fuel.
3. purification: the converted fuel needs to go through a purification process to remove any remaining impurities and catalysts.

this process requires advanced technology and equipment, as well as strict quality control to ensure the performance and safety of the final product.
it is worth noting that although it is technically feasible, we have all seen the above steps. at present, the cost of this conversion process is relatively high, which limits its widespread application. of course, with the advancement of technology and the increase in demand for renewable energy, this situation may change. as long as the demand is large enough and the production capacity increases, the scale effect will reduce the average production cost. in addition, the raw material cost of "gutter oil" in china is relatively low, and then the total cost of saf will have a chance to drop.

some people may ask why they should spend more money to use saf. this is mainly because of the difference in carbon emissions between saf and traditional aviation fuel:

carbon emissions from the life cycle: saf's greenhouse gas emissions throughout its life cycle are generally lower than those of traditional aviation fuels. this is because saf's raw materials can absorb carbon dioxide from the atmosphere during growth, thereby partially or completely offsetting the carbon emissions from its production and combustion processes. however, the carbon emissions of petroleum-based fuels almost all come from underground, which is a new addition to the atmosphere.

moreover, part of the raw materials of saf are renewable, while traditional aviation fuels are almost entirely dependent on limited fossil resources. with the advancement of technology and the expansion of production scale, the carbon footprint of saf is expected to be further reduced.

therefore, the conversion of “gutter oil” into aviation fuel is a sustainable practice because it makes rational use of waste, reduces environmental pollution, reduces dependence on fossil fuels, and reduces carbon emissions in the environment.

generally speaking, it is definitely something that benefits the country and the people. the only two conditions are technology and cost.