Hou Li'an, academician of the Chinese Academy of Engineering: low energy consumption and even negative energy consumption pollutant treatment methods are an important starting point for realizing the "dual control" of carbon emissions

At present, climate change is a global issue of general concern to the international community, and controlling carbon emissions and mitigating global warming is one of the important issues for the sustainable development of human society. In the face of the threat of rapid growth in carbon emissions, countries around the world have taken measures such as legislation and policy pledges to carry out emission reduction actions, and 127 countries have pledged to carbon neutrality, of which 5 of the world's top 10 coal-fired power countries have made corresponding commitments. China's goal of achieving carbon neutrality by 2060 is a manifestation of China's responsibility as a responsible major country, which is not only an important starting point for China to accelerate the construction of ecological civilization and achieve high-quality development, but also meets the requirements of the Paris Agreement. According to the "dual carbon" goal, carbon neutrality needs to go through four decades, a total of eight five-year plans. From the perspective of emission reduction deployment, the four decades can be divided into four stages: transformation and transition momentum, energy structure switching, near-zero carbon emission development, and comprehensive neutralization and decisive victory. In 2021, China's carbon emission intensity was reduced by 3.8% compared with 2020 and 50.8% compared with 2005, exceeding the target of 40%-45% reduction by 2020 promised to the international community, basically reversing the rapid growth of carbon dioxide emissions. However, China's carbon emissions still reached 10.52 billion tons in 2021, still the world's largest carbon emitter.

In order to achieve the "dual carbon" goal, low-carbon and green treatment of pollutants is an important part. In the new stage of coordinated governance of pollution reduction and carbon reduction, the relationship between pollution reduction and carbon reduction is not simply additive, not "carbon reduction +", or "+ carbon reduction", but completely integrated. In September 2021, the CPC Central Committee and the State Council issued the Opinions of the CPC Central Committee and the State Council on Completely, Accurately and Comprehensively Implementing the New Development Concept and Doing a Good Job in Carbon Peak and Carbon Neutrality, in October 2021, the State Council issued the Action Plan for Carbon Peaking Before 2030, and in June 2022, the Ministry of Ecology and Environment and other seven departments jointly issued the Implementation Plan for Synergy in Pollution Reduction and Carbon Reduction. In April 2023, the National Standards Committee and other departments issued the Guidelines for the Construction of Carbon Peak and Carbon Neutrality Standard System, and in October 2022 and September 2023, the Beijing Municipal People's Government and the Beijing Municipal Bureau of Ecology and Environment also issued the Beijing Carbon Peak Implementation Plan and the Beijing Municipal Pollution and Carbon Reduction Synergy Implementation Plan.

With a series of national and local actions, China has also made remarkable progress in carbon reduction and pollution reduction. First, the construction of green ecological barriers continues to advance. In 2021, China's forest coverage rate reached 24.02%, forest stock reached 19.493 billion cubic meters, becoming the country with the largest increase in forest resources in the world, the comprehensive vegetation coverage of grasslands reached 50.32%, and the wetland protection rate reached 52.65%. Second, the green and low-carbon energy transformation is advancing in a steady and orderly manner. By the end of 2022, the installed capacity of wind power and photovoltaic power generation in China exceeded 700 million kilowatts, ranking first in the world in terms of installed wind power and photovoltaic power generation capacity, and the proportion of coal consumption dropped to 56%, down 12.5 percentage points from 2012. Third, the battle against pollution has achieved remarkable results. Specifically, it includes: (1) The quality of the water environment has been significantly improved. In 2022, the proportion of surface water with excellent water quality in China will increase by 20% compared with 2016, reaching 87.9%, which is close to the level of developed countries. (2) The discharge of industrial water and wastewater is decreasing year by year. In 2022, the discharge of industrial wastewater decreased to 14.67 billion tons, a decrease of 22.8% from 2017. (3) The sewage treatment rate has been significantly improved. By the end of 2021, the number of sewage treatment plants exceeded 2,700, the sewage treatment capacity exceeded 200 million cubic meters per day, and the sewage treatment rate was 97.5%, an increase of 5.1% compared with 2016. (4) Steady improvement in air quality. According to the "Atmospheric China 2023: China's Air Pollution Prevention and Control Process" released by the Asian Clean Air Center, in 2022, the average annual evaluation concentrations of six conventional pollutants in 339 cities at and above the prefecture level in China can meet the requirements of China's "Ambient Air Quality Standards". (5) Solid waste treatment has achieved remarkable results. It is embodied in three aspects: completely banning the entry of "foreign garbage", continuously improving the domestic solid waste recycling system, and actively promoting the construction of "zero-waste cities".

Behind these developments, there are concerns that cannot be ignored. To achieve the "dual carbon" goal, there are still three challenges: coal is still the main energy source, renewable energy consumption and storage are limited, and the cost and maturity of low-carbon, zero-carbon, and carbon-negative technologies need to be further optimized. The report of the 20th National Congress of the Communist Party of China proposed to improve the regulation and control of total energy consumption and intensity, focus on controlling fossil energy consumption, and gradually shift to a "dual control" system of total carbon emission and intensity. However, the pollutant remediation process is often accompanied by a large amount of energy consumption. With the improvement of environmental quality and pollutant emission standards, China's pollutant treatment still tends to adopt the treatment method of high energy consumption and high consumption, and the "dual control" of carbon reduction and pollution reduction and carbon emission needs to be considered in tandem. Taking sewage treatment as an example, there are urgent problems of energy consumption, incapacity and carbon emissions in China's urban sewage treatment process. In terms of energy consumption. At present, the electricity energy consumed by urban sewage treatment accounts for about 1% of the total electricity consumption of the whole society, and according to the traditional sewage treatment operation mode, its proportion of energy consumption will be larger and larger; in terms of disability, the organic chemical energy contained in the typical domestic sewage with a COD concentration of 500mg/L can reach nearly 5 times the energy consumption required for the treatment of traditional biological oxidation, and the residual temperature and waste heat of urban sewage accounts for about 40% of the total urban waste heat emission In terms of carbon emissions, if the treatment technology with activated sludge as the main process is continued, the total carbon emissions of the entire sewage treatment industry will reach 365 million tons of carbon dioxide equivalent, accounting for 2.95% of the total carbon emissions in the country.

Facing "dual carbon" and "dual control",Pollutant treatment methods with low energy consumption or even negative energy consumption are important starting points to achieve "dual control" of carbon emissions. The specific coping strategy can include the following three aspects:

The first is the research and development of healthy drinking water guarantee technology. For example, in the face of the challenge of new pollutants in drinking water, we will strengthen the research and development of cutting-edge new technologies and strive to achieve "no carbon increase in standards", and give full play to the green and low-carbon advantages of membrane water treatment technology to meet the challenges of new pollutants in drinking water.

The second is the research and development of low-carbon treatment technology for domestic sewage. For example, propulsion membrane technology, advanced oxidation, The combination of adsorption and other technologies to promote the green and low-carbon treatment of sewage according to local conditions; the use of three-dimensional ecological technology to build a garden-style sewage treatment plant, the microorganisms in the sewage from low-level training to high-level, high-level microorganisms regurgitate low-level pollutants, accelerate the metabolism and self-replacement of microorganisms of different levels, to achieve efficient oxidation and decomposition of various pollutants in sewage; the construction of landscape plant scaffolds, so that the root system of plants rooted in the ecological medium of the sewage treatment plant, participate in sewage purification, and at the same time, plant vines climb on the bracket to form a garden-like landscape belt。

The third is the research and development of industrial wastewater and radioactive wastewater treatment and utilization technology. For example, membrane integration technology is used to treat mixed heavy metal wastewater, starting from the source of industrial wastewater, recovering heavy metals and purifying the wastewater generated in the production process, using palladium-silver alloy membrane coupled catalytic bed reactor to recover tritated molecular hydrogen from tritated water through water-gas change reaction, using zeolite inorganic membrane to treat different forms of tritium and its compounds at the same time for pre-concentration stage, followed by palladium-based catalytic membrane reactor for tritium recovery. In addition, in terms of water treatment, it is also necessary to develop forward-looking "smart water plants" based on the comprehensive utilization of big data and the breakthrough of the whole membrane combined process technology to improve the efficiency and safety of water resources.

Fourth, the research and development of green buildings and indoor air purification technology. For example, in terms of building design, more "passive technology" is adopted to save energy through the building itself, and at the same time, certain building technology is used to improve the energy-saving level of the building, so as to achieve green building and reduce carbon emissions; in order to better cope with the risks and challenges brought by pathogenic microorganisms to the health of residents, strengthen the research and development of air purification technology and equipment, especially strengthen the indoor air purification guarantee for imported cold chain, buildings and industrial plants, and develop relevant safe, green and low-carbon sanitize technologies.

Fifth, the research and development of solid waste co-treatment and resource and energy utilization technology. For example, through the technical ideas of machine classification, intelligent compatibility, optimal coupling, intensive utilization, etc., urban and rural waste, which has both pollution and resource attributes, can be efficiently converted into resource and energy products to realize its carbon-negative treatment and utilization; On the issue of relying on fossil fuels for the synthesis of aviation fuel and other fuels, we will develop technologies for the synthesis of green fuels from organic waste raw materials such as catering waste oil and biomass, such as catalytic transesterification, pyrolysis gasification/anaerobic fermentation coupled catalytic reforming/Fischer-Tropsch synthesis, pyrolysis/hydrothermal and product composite blending, and develop recycling and reuse technologies for retired photovoltaic modules brought about by increasingly widely used photovoltaic technologies, so as to better exploit the carbon reduction potential of photovoltaic technologies.

In general, from the perspective of the "dual carbon" goal, carbon reduction and pollution reduction are organically integrated. In recent years, China has made considerable achievements in carbon reduction and pollution reduction, but it still faces challenges in the research and development of low-carbon treatment technologies for pollutants, the coupling of pollutant treatment with new energy utilization, resource energy and other processes, and the recycling of waste energy and environmental materials. In order to better achieve the goal of carbon reduction and pollution reduction and "dual carbon", scientific and technological innovation should be strengthened, and new technologies such as low-carbon/zero-carbon water treatment, low-carbon air sanitization, organic solid waste co-treatment and resource energy, low-carbon utilization of unconventional water resources, industrial wastewater resource recovery, recycling and reuse of retired membrane products and photovoltaic modules should be fully utilized, so as to achieve low-carbon, zero-carbon and even negative carbon treatment of pollutants.

(The above content is based on the speech of Hou Li'an, academician of the Chinese Academy of Engineering, at the Green Productivity Forum)