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Recently, the Climate Ambition Summit to commemorate the fifth anniversary of the Paris Agreement was held, with the participation of heads of state of more than 70 countries around the world. The results of countries' implementation of the paris agreement commitments were reviewed at the conference, and some countries set new targets to combat climate change at the conference.
In fact, since the last century, human beings have been constantly pursuing a balance between environmental protection and economic development, and trying to find a sustainable development path. Among the many environmental protection issues, reducing carbon dioxide emissions has always been one of the main goals of countries around the world. For example, the Paris Agreement has made reducing greenhouse gas emissions and controlling global warming and climate change one of its main tasks.
In this context, ethanol gasoline as a clean fuel has become one of the key points of renewable energy development. Ethanol is a flammable, volatile, colorless and transparent organic compound at room temperature and pressure, commonly known as alcohol, which can be mixed with gasoline or used as internal combustion engine fuel alone. According to the source of raw materials and production processes, ethanol can be roughly divided into biological ethanol and chemical ethanol. At present, the main application of biological to ethanol method is used in global ethanol production.
Biofuel ethanol is an important branch of renewable energy, mainly based on agricultural products and agricultural and forestry wastes, such as corn, sugar cane, straw and so on. Currently, more than one-third of the world's countries are promoting the use of fuel ethanol. Since 2000, global biofuel ethanol production has grown rapidly, with an average annual growth rate of more than 18% in the past decade, and global biofuel ethanol production is expected to exceed 100 million tons in 2020. It can be said that biofuel ethanol has become a new force in the development of the world's new energy industry and is pinned on high hopes. The development of biofuel ethanol in various countries in the world is mainly based on national strategic considerations such as stimulating agriculture, protecting the environment, and achieving energy substitution, and this article will mainly introduce the contribution of biofuel ethanol to carbon emission reduction.
The U.S. government has set standards for renewable fuels and promoted fuel ethanol
The United States is the world's largest producer and consumer of fuel ethanol. In order to protect the environment and ensure energy security, the United States began to vigorously develop fuel ethanol in the 1980s. To ensure growth in ethanol consumption, congress developed renewable fuel standards (RFS) under the Energy Policy Act of 2005 and the Energy Independence and Security Act of 2007. The standard specifies the amount of fuel ethanol that the United States needs to use each year, and allocates this ethanol use as an indicator based on the amount of oil refined by each refinery in the previous year.
According to the current renewable fuel standard (RFS II, revised rfs), the full life cycle greenhouse gas emissions of biofuels must be at least 20% lower than those of alternative fossil fuels to be called renewable fuels. The standards, in legal form, determine that the full-life cycle emissions of biofuel ethanol must be much lower than those of fossil fuels they replace, and ensure that the corresponding biofuel ethanol is actually added to gasoline and used every year.
Carbon emission reduction analysis of corn ethanol greenhouse gas emissions throughout the life cycle
Compared with the use of non-renewable energy sources represented by gasoline and diesel, the use of renewable biofuel ethanol, represented by corn ethanol, can greatly reduce the greenhouse gas emissions of the whole life cycle of fuels. The most basic reason is that in the process of growing corn and other agricultural products, crops absorb a large amount of carbon dioxide, and after crops are made into ethanol, the carbon dioxide emitted by its combustion is roughly equivalent to the absorbed carbon dioxide, achieving carbon emission balance and achieving carbon neutrality.
On August 8, 2018, the U.S. Department of Agriculture released a report titled "The Greenhouse Gas Benefits of Corn ethanol-Assessing Recent Evidence." Based on the data on the use of biofuel ethanol in the United States for many years, the report analyzes the impact of the use of fuel ethanol on greenhouse gas emissions in the United States from multiple dimensions, such as land use change, farm operations, fuel production, etc., and concludes that the greenhouse gas emissions of the whole life cycle of corn-based biofuel ethanol in the United States are currently 39% lower than those of isoorific gasoline, while the greenhouse gas emissions of fuel ethanol from fuel ethanol plants powered by natural gas are 43% lower than that of equivalent calorific gasoline. According to the current emission reduction measures and development trends of fuel ethanol plants in the United States, the greenhouse gas emission reduction of corn-based ethanol in the United States is expected to reach 47%-70% in the next few years.
The report takes into account a number of factors, such as land-use changes such as emissions directly related to the conversion of land from other uses to maize production, indirect emissions from the development of new farmland to supplement these crops as farmers use more existing farmland to grow maize, and fossil energy emissions from the production of ethanol By-product contributions include dry corn lees (DDGS), a by-product of ethanol production, which replaces some corn and other crops with high-protein feed for animals, thereby reducing farmland use.
Based on the current overview of corn ethanol emissions, the USDA has set two projected emission scenarios for 2022. The first, called business as usual (BAU), predicts that the current trend will continue until 2022: first, corn yield per hectare (125.7 kg/ha per year); second, refineries replacing coal with natural gas as a process fuel; and third, improving the fuel efficiency of heavy-duty diesel trucks. The BAU programme reflects the expected improvement in greenhouse gas emissions from corn ethanol in 2022 in the absence of measures taken by refineries to reduce emissions. The second prediction is a High efficiency-high conservation scenario (HEHC), which adds to the BAU scenario some of the actions that refineries may take to reduce the greenhouse gas intensity of corn ethanol. These include agreements with farms to grow maize in a low-emission manner (reduced tillage, cover crops and nutrient management), switching to sustainably produced biomass as process fuels, and closed livestock rearing operations near refineries.
According to the above data, whether in the BAU scenario or in the HEHC scenario, the emissions from the use of corn ethanol are much less than those from gasoline replaced by ethanol.
Not long ago, a third-party assessment agency was commissioned by the National Energy Administration to evaluate the pilot situation of fuel ethanol in China. The evaluation results show that the goals of improving the agricultural economy, rationally using inedible food for people and livestock, alternative energy, and environmental protection set by China when demonstrating whether to use ethanol gasoline have been achieved, and the results are remarkable. China's fuel ethanol production technology has basically reached the world's advanced level in the development process of nearly ten years, and the next step of promotion plan is safe and feasible. The further use of fuel ethanol nationwide is of great significance to optimizing China's energy structure, improving the quality of the atmospheric environment, reducing vehicle exhaust emissions and promoting sustainable economic and social development.
It can be seen that biofuel ethanol can effectively reduce carbon emissions throughout the life cycle, which will help China to achieve the emission reduction commitments made in the Paris Agreement at an early date and contribute to the cause of low-carbon green.