Many challenges remain in bioenergy
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Developing bioenergy to address energy pressures has become a global consensus. However, bioenergy faces several major obstacles: the very low photosynthetic efficiency of crops, raw material issues, and technical challenges. “The photosynthetic efficiency of crops is very low, at around 1%, while microalgae have a slightly higher efficiency, but it’s still only about 6%. ”An industrial biotechnology expert said, “This means that the production of bioenergy cannot increase.” Furthermore, the issues related to raw materials and technology remain quite complex. ” He said that bioenergy can only dance in shackles. The \"shackles\" on photosynthetic efficiency, said Zhao Zongbao, a researcher at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Photosynthetic efficiency primarily refers to the efficiency of utilizing solar energy; it is the ratio of the energy contained in the organic substances produced by plants through photosynthesis to the light energy absorbed during photosynthesis. “Plants absorb solar energy, and through photosynthesis, this solar energy is converted into glucose and stored within the plant. The ratio of the stored energy to the absorbed light energy is what constitutes the efficiency of photosynthesis. ”Zhao Zongbao explained further. Dr. Chen Hui, a researcher at the Institute of Botany, Chinese Academy of Sciences and an expert in photosynthesis, told reporters that as long as solar energy is used, there will be issues with conversion efficiency regarding both the yield of crops such as rice and wheat, as well as the power generation from photovoltaic cells and solar energy. “If solar energy could be converted 100%, then there would be no need to worry about energy issues, right? Hasn’t the world become richer? ”Chen Hui said with a smile on the phone. Chen Hui told reporters that, based on current literature, a photosynthetic efficiency of 1% to 6% “is considered a relatively reasonable range”. The development of bioenergy is inherently hindered by limitations in photosynthetic efficiency. Wang Xieqing, an expert in bioenergy and an academician of the Chinese Academy of Engineering, said in an interview with reporters: “The estimates of these experts are fairly scientific.” ” Wang Xieqing explained, “Biomass energy is a low-density energy source; in other words, the amount of energy produced per unit area is not very high. Therefore, if you build a facility with a capacity of hundreds of thousands or even millions of tons, the radius required for transportation and storage would be too large, which would likely result in extremely high costs.” ” Academician Min Enze, an expert in petrochemicals, also told reporters that biomass energy represents the solar energy accumulated over one year, whereas coal and oil underground represent solar energy accumulated over many years. “We can drill a well that produces thousands of tons of oil per year, but for biomass energy, a large area is required to produce just one amount of oil. ” Even with a production capacity of hundreds of thousands of tons, it is already quite challenging; faced with China’s demand of tens of millions of tons, bioenergy seems somewhat inadequate. “In my estimation, over the next 10 years or even longer, it would be quite good if bioenergy could account for 10% as a substitute fuel for cars. ” Wang Xieqing told the reporters. Since the development of bioenergy is not as promising as initially estimated, why do countries continue to invest substantial funds in it? “Besides that, do you have any other options? ”Zhang Xu, an associate professor at the School of Life Sciences at Beijing University of Chemical Technology, countered by saying that photovoltaic cells, wind energy, nuclear energy, etc. are also among the alternatives to fossil fuels, but they are primarily used for power generation. “Power generation from solar and wind energy is unstable, as the weather is unpredictable and the wind blows intermittently. Bioenergy, on the other hand, utilizes the energy stored in plants, which is stable. ”Academician Wang Xieqing said. Challenges related to raw materials and technology: In addition to the inherent limitations in photosynthetic efficiency, the development of biomass energy faces many practical difficulties. The most important issue is the raw material problem. The policy framework for developing bioenergy in our country is one that avoids competing with food production for land and resources; thus, non-food sources have become the preferred approach. Oil-rich plants, corn straw, cassava, sugarcane bagasse, used cooking oil, livestock manure, and organic waste are considered to be suitable raw material sources. Statistics show that China generates over 600 million tons of agricultural and forestry waste each year, in addition to a large amount of used cooking oil that can be further utilized to produce bioenergy. Although the data looks attractive, these wastes are scattered throughout the country, and collecting and transporting them will pose a huge challenge. Liu Dehua, a professor at Tsinghua University, said that due to China’s high dependence on imported edible oils, herbaceous oil crops such as soybeans cannot be used as raw materials. It remains to be further studied whether the costs of woody oil plants such as jatropha and chinaberry are acceptable for use in bioenergy production. In addition, technical maturity is crucial. “Technically speaking, the microalgae-based biodiesel production technology, which is highly favored worldwide, is a solution suitable for at least the medium term or even the long term; cellulose, on the other hand, is still a long way away in terms of technological development. ”An expert said. Zhao Zongbao told reporters that, from a technical perspective, there are still many further technologies related to microalgae. “It is technically feasible, but the cost is still extremely high; it’s by no means something that can be used on a large scale within 5 years. ” Professor Andy Lau said that aside from technical factors, the policy environment is even more important. For example, in 2008, when oil prices rose, **huge subsidies for fossil fuels made it more difficult to develop bioenergy. “In a sense, in the early stages of industrial development, policy takes precedence, even over technology itself. ” Among biomass energy products, the more mature ones are fuel ethanol, biodiesel, and methane. China has now become the third-largest producer of fuel ethanol, with its production capacity set to reach 20,000 tons by 2010. Biodiesel and biomethane are considered to have broad development prospects. Currently, countries generally view the use of microalgae to produce biodiesel positively. In June, the U.S. Department of Energy released the \"U.S. Algal Biofuel Technology Roadmap,\" allocating $24 million in funding. Two researchers from Wageningen University in the Netherlands recently stated in the journal Science that it is possible for humans to develop technologies for large-scale extraction of biofuels from algae within 10 to 15 years. They say that currently, 6,000 liters of biofuel can be produced from rapeseed grown per hectare, but the same area used for growing algae can yield 80,000 liters of biofuel. Recent domestic news reports that our country has successfully converted large seaweeds into biooil. Zhang Shicheng, an associate professor in the Department of Environmental Science and Engineering at Fudan University and a key researcher on this project, told reporters that current experimental data show that 1 ton of seaweed can be converted into 230 kilograms of biooil, with the amount possibly increasing slightly when scaling up the process. Regarding the development of bioenergy, the mainstream view in the country is that it will primarily be used as fuel for vehicles and aircraft. Academician Min Enze told reporters that for the important transportation fuels today—gasoline, diesel, and aviation fuel—it is still necessary to produce biodiesel using microalgae. ” Min Enze said that the key to developing biodiesel lies in the selection and source of raw materials. It is necessary to expand the raw materials for biodiesel, including ways to utilize oil-rich plants and waste cooking oil as well as to develop new sources; moreover, process routes suitable for producing biodiesel from such raw materials need to be developed. Meanwhile, another process route suitable for waste cooking oil is the use of biological enzymes as catalysts. Academician Wang Xieqing told reporters that when developing bioenergy, energy consumption throughout the entire life cycle must be taken into account. Starting from the raw materials, all processes such as sowing, weeding, fertilization, and irrigation must take into account the consumption of non-biological energy, with an overall assessment being required. “You can’t determine how much ethanol fuel or biodiesel can be produced at a particular stage of biomass energy utilization. ” Wang Xieqing said, “We can’t just look at how strong he is at the age of 18 while working; we need to consider the cost of his growth from conception to death in order to achieve sustainable development on a scientific basis.” ”
In modern China, the most ideal way to utilize solar energy is to use photosynthesis to grow plants or algae, which are then subjected to anaerobic fermentation to produce biogas. On a moderate scale, this gas is collected through pipelines and separated to obtain methane, which is what constitutes natural gas.
Coal, oil, and natural gas buried underground should be extracted as little as possible, or not at all, because the level of carbon dioxide in the atmosphere is already high. The products of photosynthesis are not converted and utilized in a timely manner, resulting in a feedback loop: large amounts of carbohydrates are once again converted into carbon dioxide (and methane) and released into the atmosphere under natural conditions.
I am quite optimistic about the production of high-value chemicals from biomass
Future energy sources should be diversified, with various options competing among themselves, each having its own advantages and uses
The biggest constraint is policy discrimination – wind power, photovoltaic power generation, ethanol, and so on all receive policy support, not to mention coal, oil, and natural gas. The National Development and Reform Commission is on their side; it would be great if everyone could be treated equally. If a carbon tax were implemented, then biomass energy would have a chance to thrive! Raw material supply, technical bottlenecks, and photosynthetic efficiency are not really any kind of constraints.
If biomass is not utilized, it may exacerbate the greenhouse effect. Let’s do a rough estimate: Assume that 60 CO2 molecules are used in photosynthesis to produce 10 molecules of biomass, represented by glucose (C6(H2O)6). If 5 molecules of this biomass are stored… ； 4 molecules of biomass are directly oxidized, producing 24 molecules of carbon dioxide ； 1 molecule of biomass is anaerobically fermented to produce 3 molecules of carbon dioxide and 3 molecules of methane ； According to available data, the greenhouse effect potential of methane is 21 times that of carbon dioxide; 3 molecules of methane are equivalent to 63 molecules of carbon dioxide ； A total of 90 molecules of carbon dioxide are produced—in other words, even if the biomass storage rate reaches 50% and anaerobic fermentation accounts for only 10%, 60 molecules of carbon dioxide will still be turned into 90 molecules of \"carbon dioxide\". of
If the goal is to create a greenhouse effect, photosynthesis could be a way to do that: 6CO2+6H2O=C6(H2O)6+6O2; C6(H2O)6=3CO2+3CH4; CH4=21CO2; 6CO2=66CO2
Developed countries primarily adopt comprehensive economic and fiscal policies to reduce greenhouse gas emissions, including: voluntary agreements, energy/carbon dioxide taxes, emission trading, quotas for renewable energy or combined heat and power production, energy efficiency standards, and direct financial incentives for renewable energy sources such as preferential rates, grants, tax exemptions, and so on. However, these policies are also constantly changing due to differences in their implementation. Taking energy/CO2 taxes as an example, they have shifted from being mere taxes to a format of “taxes + subsidies”. Since the early 1990s, some developed countries have begun to implement energy taxes or CO2 taxes based on the carbon content of fuels, in order to increase fiscal revenue and/or reduce their dependence on foreign oil supplies. Since energy/CO2 taxes help reduce energy consumption and greenhouse gas emissions, many developed countries use them as an important measure to cut greenhouse gas emissions. However, later on, in order to prevent energy/CO2 taxes from affecting the competitiveness of their domestic industries in the global market, some countries applied lower tax rates to energy-intensive sectors. Norway reduced the CO2 tax rate for offshore oil and gas production, while Sweden’s CO2 tax rate for its manufacturing industry was lowered to 35% of the standard rate; the tax rates for certain energy-intensive industries there were even reduced to almost zero. In the UK, the tax rate for energy-intensive industries is only 20% of the standard rate. To encourage the development of energy-saving technologies while avoiding a negative impact on the competitiveness of domestic industries in international markets, many countries have **changed taxes into subsidies**. Tax incentives or reductions have been introduced for renewable energy and high-efficiency technologies such as cogeneration, in order to encourage their supply and consumption. From the supply side, this mainly involves incentives or exemptions for various taxes related to renewable energy production or cogeneration, such as production taxes, fixed asset taxes, value-added tax, and import duties. The UK has introduced tax incentives to promote the development of cogeneration. In 2002, the installed capacity for cogeneration in the UK was 4700 MW. In line with its goals, it aimed to have 10,000 MW of efficient cogeneration capacity in place by 2010; to this end, the UK government did not impose a climate change tax on cogeneration and provided financial incentives in the form of tax breaks to companies that invested in cogeneration projects. France reduces the corporate tax for CHP companies by 50%, while local authorities **can increase this reduction rate to up to 100%. Tax incentives have also been introduced for the use of renewable energy; through these incentives and reduced value-added tax rates, companies’ costs associated with purchasing renewable energy equipment are reduced by 15%. Additionally, companies that invest in renewable energy can benefit from accelerated depreciation rules after one year.