Chapter 171 Erwinia (additional update)
June 29.
It was also the day after Jiang Miao arrived at the Monan branch.
Jiang Miao borrowed the laboratory set up by United Mining near the county seat of Jiayuan County. This laboratory was previously a small breeding laboratory invested by a cattle and sheep breeding company, but in 23 years that company operated a After solving the problem, it was acquired by United Mining in April and used as an experimental base for research on bio-mining technology.
The laboratory is located in the southeast of the county and covers an area of 240 acres. Although the equipment inside is not very good, it can at least satisfy some microbial research work.
Regarding Jiang Miao's loan, Lin Yonghua originally planned to let him use it for free, but Jiang Miao refused and asked them to prepare a rental contract. After all, he did not lack the money, and United Mining was not wholly owned by Hailufeng Company. Subsidiaries should pay more attention to this kind of thing.
In a simple laboratory.
Jiang Miao got the various bacteria and fungi stored here. After all, this laboratory is going to study bio-mining technology, so there must be relevant microbial strains.
Last night, Jiang Miao got an inspiration during the conversation with Wu Song.
Wu Song mentioned that at the breeding base, with the expansion of the scale of cattle and sheep breeding, the cow and sheep manure excreted by cattle and sheep must be processed as soon as possible.
Generally speaking, there are usually four ways to deal with cattle and sheep manure in farms.
One is to stack it directly in the open air, then dry it and use it as fuel.
One is to sell it to other enterprises or self-employed individuals in need.
One is to ferment compost, and then return the fermented soil to the fields as organic fertilizer, or sell the organic fertilizer.
One is to first use it for fermentation to produce biogas, and then process the biogas residue and liquid into organic fertilizer for a second time, which can be used for personal use and sold.
Currently, the Monan Breeding Base adopts the third option, fermenting it into organic fertilizer.
As for why the fourth option with better economic benefits is not adopted, the answer is climate reasons.
The climate in eastern Monan is similar to that in Northeast China. The weather is too cold.
You must know that in biogas fermentation, the temperature with better fermentation efficiency is 30 to 35 degrees Celsius. The number of days with daytime temperatures above 30 degrees Celsius in eastern Monan is only 30 to 40 days per year.
Even if a cellar-type fermentation field is used to keep warm underground, the surface temperature still needs to be higher than 20 degrees Celsius, and the number of days when the daytime temperature is higher than 20 degrees Celsius in eastern Monan is only 90 to 120 days.
If artificial warming is used to maintain the fermentation temperature, is it still meaningful to ferment biogas?
After all, fermented biogas is used as energy. Using artificial heating to maintain the temperature of the fermentation tank in low-temperature weather will significantly increase production costs. The production-to-cost ratio is too low and has no economic benefits.
In China, in the early 2000s, small household biogas fermentation systems were vigorously promoted in the Yangtze River Basin. As a result, now, those biogas fermentation cellars have been basically abandoned. The reason is that when the temperature drops, the fermentation efficiency drops significantly. Gas production dropped sharply.
Now only some areas in Guizhou Province still have villagers using biogas. This is because the climate in Guizhou Province is relatively hot. The number of days with daily temperatures above 20 degrees Celsius is about 200 to 250 days per year, especially in Guangxi Province. In the southern coastal area of the province, the temperature is higher than 20 degrees Celsius for almost 250 days. This environment allows the biogas fermentation system to operate efficiently for a long time.
So Wu Song never thought about building a biogas fermentation system near the farm in Jiayuan County. After all, such a project would be thankless.
But Wu Song's words reminded Jiang Miao.
Cow and sheep dung is actually a very complex resource.
It can be used as organic fertilizer raw material, edible fungus cultivation substrate, directly as fuel, or to produce biogas through fermentation.
This is because cattle and sheep cannot completely digest the roughage they eat, that is, they cannot completely digest the pasture, and a large part of the cellulose and lignin in the pasture will remain.
In dry cow and sheep manure, cellulose, hemicellulose, and lignin account for 70 to 80%, and the remaining components are humus, water, and inorganic salts.
This is also the fundamental reason why cattle and sheep dung can be used as fuel after drying, because it is rich in carbon sources.
In the case of complete combustion, the caloric value of 1 ton of dry cow and sheep manure from grass-fed cattle and sheep is almost equivalent to 0.75 tons of thermal coal; if the proportion of grain-fed cattle and sheep manure is relatively high, the caloric value per ton is equivalent to at 0.7 tons of thermal coal.
This is inappropriate bio-coal.
As for why no thermal power plant uses cow dung and sheep dung as fuel, there are many reasons.
For example, the channels for obtaining raw materials are complicated, difficult to collect, and the production areas are scattered, which is not conducive to the stable production of thermal power plants; there are certain differences in the calorific value of cattle and sheep dung in various places, which increases the difficulty of heat management during the power generation process; If cattle and sheep manure is not dried in advance, it will increase the difficulty and cost of transportation, and the smell will be very unpleasant.
At the same time, the price of thermal coal used as fuel is only 500 to 800 yuan per ton.
Therefore, no thermal power plant will use cattle and sheep dung as fuel.
However, some herdsmen in the Monan, Western and Snowy Regions in China will dry cattle and sheep dung and use it as fuel in their daily lives.
Jiang Miao did not build a thermal power plant just for the hundreds of tons of fresh cow and sheep dung every day.
He thought of another technology that can utilize these cow and sheep dung: microbial fuel cells.
The so-called microbial fuel cell technology is a technology that uses the electron migration generated by extracellular electrogenic bacteria among microorganisms during the metabolic process to achieve biopower generation.
The advantage of this technology is environmental protection.
The disadvantage is that the efficiency is too low. Each cubic meter of high-carbon source culture medium can only generate 10 to 20 kilowatt-hours of electricity; while direct combustion for power generation can produce about 500 kilowatt-hours of electricity.
The two are not comparable.
And the so-called power generation per cubic meter of high carbon source culture medium is also a result achieved in a very good laboratory environment.
For example, in a paper published on June 23, 2024, a research team led by Chinese scientists Duan Xiangfeng and Huang Yu developed a new type of microbial flow fuel cells (MFFCs) by using artificial electron mediators in the flow medium. It can transfer bacterial metabolism electrons with medium and high efficiency, and its maximum power density can reach 17.6mW/cm (equivalent to 176 watts per cubic meter).
According to the data investigated by Jiang Miao, their experimental system can only run for about 90 hours in a laboratory environment, and then the efficiency plummets.
According to this data, after converting into cubic meters, during the peak period of stable power generation, it can generate almost 15.84 kilowatt-hours. With subsequent low-power power generation, it can reach 20 kilowatt-hours at most.
The maximum power of microbial fuel cells per cubic meter is only a few tens of watts under laboratory conditions.
Of course, under non-laboratory conditions, because bacteria do not decompose organic matter very quickly, the power generation time will be extended to several months, so the total power generation is still about 10 to 20 degrees.
If the power generation per cubic meter is 176 watts and can last for one month, then the power generation in one month is 126.72 kilowatt-hours, in two months it is 252 kilowatt-hours, and in three months it is 378 kilowatt-hours.
Is it possible to achieve stable power generation for a long time under high power conditions?
The answer is yes.
At present, the energy conversion efficiency of extracellular electrogenic bacteria is 10-30% under non-laboratory conditions, and can reach 60-70% under laboratory conditions.
And there is a situation that requires special attention.
That is, the organic matter in the culture medium ≠ the organic matter consumed by extracellular electrogenic bacteria.
Extracellular electrogenic bacteria can only break down and digest a small portion of organic matter.
For example, Pseudomonas aeruginosa, one of the extracellular electrogenic bacteria, has a diet that only includes: glucose, xylose, and starch from carbohydrates
; amino acids from nitrogenous compounds, Urea; triglycerides and phospholipids in fatty substances; aromatic compounds.
From here we can know that many extracellular electrogenic bacteria cannot directly digest cellulose, hemicellulose and lignin in cattle and sheep manure.
If cellulose, hemicellulose, and lignin can be decomposed into glucose, monosaccharides, and aromatic compounds, they can be directly utilized by some extracellular electricity-producing bacteria.
In fact, a small number of extracellular electricity-producing bacteria can also decompose cellulose, hemicellulose, and lignin, but the decomposition efficiency is relatively low.
What Jiang Miao needs to do now is to develop extracellular electricity-producing bacteria that can efficiently decompose cellulose, hemicellulose, and lignin. In fact, a relevant scientific research team in the European Union has used genetically modified technology to transform Escherichia coli, giving it the ability to metabolize and generate electricity, while also allowing it to decompose part of hemicellulose.
It is not difficult for Jiang Miao to conduct such directional research.
Screening and cultivating efficient specialized extracellular electricity-producing bacteria is Jiang Miao's specialty.
He doesn’t even need to use genetically modified technology, he can just force the extracellular electricity-producing bacteria to mutate directly through various artificial environmental pressures. The bacteria reproduce very quickly and mutate very quickly, which is very beneficial. Specialized cultivation of bacterial strains.
Using current, pH, chemical substances, freezing, high temperature, ultraviolet and other methods, plus various simulated cultivation environments, in just three days, Jiang Miao will obtain a specialized extracellular electricity production bacteria.
The parent strain of this extracellular electrogenic bacterium is the ErwiniabillingiaeQL-Z3 strain. Among its original characteristics, if lignin is used as the only carbon source, its lignin degradation rate can reach 25.24 %.
After multiple mutations, screening and cultivation, the bacterium can not only degrade lignin, but also cellulose and hemicellulose, with a maximum degradation rate of about 97%.
Of course, this optimal degradation rate is certainly not easy to achieve.
To be precise, this brand-new bacterium, named "Irving Power Bacteria" by Jiang Miao, needs to meet very stringent conditions to achieve the best degradation rate. There are four conditions, namely:< br>
First, the temperature of the living environment should reach 20 to 28 degrees Celsius.
Second, it requires symbiosis with a specialized Gram-negative bacterium. This Gram-negative bacterium secretes a substance called a quorum sensing signal molecule during its growth. When the bacterial density reaches At a certain threshold, these signal molecules will initiate a series of gene expressions to promote the reproduction of itself and Erwinia electrogenic bacteria, and the metabolites of the two can promote each other.
Third, a specific dose of soybean genistein (estrogen-like hormone) needs to be added to stimulate the Erwinia electrogenic bacteria to further reproduce and degrade lignin, cellulose, and hemicellulose.
6◇9◇Book◇Bar
Fourth, the oxygen concentration in the environment needs to reach 32%.
In fact, during the experiment, Jiang Miao did not find other mutant bacteria with even fewer degradation conditions, but it was precisely because of the lack of conditions that Jiang Miao did not dare to use them.
Because the less restrictive the breeding conditions are, it means the stronger the ability to spread widely in nature.
Erwinia is a plant saprophytic bacterium. If its ability to degrade lignin, cellulose, and hemicellulose is so strong, and there are no restrictions on reproduction, then it will not take a few years to destroy all the flowers and plants in the world. The trees were destroyed.
If one of the above conditions is not met, the degradation efficiency of Erwin's power-generating bacteria will plummet.
Furthermore, this bacterium has no resistance to the Bacillus species that are widely present in the soil, especially the metabolites of Bacillus subtilis, which can directly cause the Erwinia genus to be unable to reproduce, resulting in large-scale death.
It was this harsh living condition that allowed Jiang Miao to select it from among the billions of mutant bacteria.
Under optimal conditions, it is estimated that Owen's power-generating bacteria can remove 97% of cellulose, hemicellulose, and wood from cattle and sheep manure with a moisture content of about 80% in only 143 hours. The maximum power generation power is 473 watts per cubic meter, so it can generate 67 kilowatt-hours of electricity.
But this optimal degradation condition is not the optimal power generation condition.
When Owen's power-generating bacteria is exposed to a specific dose of soy genistein and 26.4% oxygenated air at 23 degrees Celsius, its power generation power will drop to 320 watts per cubic meter, but its stable power generation time reaches 360 hours. It can reach about 115 degrees.
However, in this case, the degradation of lignin, cellulose, and hemicellulose will be incomplete, and about 20 to 30% will remain.
In front of Jiang Miao was a simple cow dung solution battery.
In order to ensure that the electrons in the battery solution were transferred efficiently, in the next few days, he tried various anode and cathode materials, trying to find cheap and easy-to-use materials.
After some attempts, he found that the materials with the best transfer efficiency were gold plate negative electrodes and stainless steel anodes, and the electron transfer efficiency could reach about 98%.
However, stainless steel, as the anode of the microbial fuel cell, has a fatal problem, that is, during use, the stainless steel will be corroded little by little. As the operating time goes by, the electron transfer efficiency of the stainless steel anode will become lower and lower. It is expected that It can only be used for 500 to 600 hours before the stainless steel plate needs to be replaced.
So Jiang Miao chose a graphite plate that will not be consumed as the anode material. The electron migration efficiency of this material is 92%.
As for the gold plate, this thing will not be consumed. Although using gold as the battery cathode is a bit luxurious, it is not a consumable material. At most, over time, the layer of the gold plate that contacts the battery fluid will There is a trace amount of gold element migrating, but the amount of migration is very small. According to the data observed by Jiang Miao from the identification panel, it is estimated that it will take hundreds of years for one-tenth of the gold element to migrate out.
Since the optimal power generation reaction conditions of Owen's power generation bacteria are relatively harsh, and an expensive gold plate cathode is required, it certainly cannot be used as a mobile power source.
But as a fixed power generation equipment, there is not much problem.
The five constraints are relatively easy to solve in a fixed environment.
The temperature can be controlled by equipment such as central air conditioning.
The oxygen content of the air can be measured through an oxygen sensor and an air separator to produce pure oxygen, which can then be injected quantitatively into the battery room.
If you cannot come into contact with Bacillus, then perform high-temperature sterilization of the raw materials.
Specific Gram-negative bacteria can be cultivated on a large scale.
Soybean genistein can be refined through soybean meal, and its usage is not large, so it does not increase the cost much, but it is a consumable.
Gram-negative bacteria and soybean genistein are also critical raw materials for the entire system, because these two things can affect the degradation efficiency of Owen's power generation bacteria, thereby affecting the power generation, which makes this microorganism The power generation output of fuel cells has become highly controllable.
Jiang Miao estimated that the Monan Branch’s breeding farm currently produces about 300 tons of fresh cow and sheep manure (moisture content 60-85%) every day, which can be directly disinfected and then planted with Owen’s power-generating bacteria. , special Gram-negative bacteria, and then add a certain amount of soy genistein to create a microbial fuel cell of 300 cubic meters.
A 300 cubic meter microbial fuel cell can produce almost 31,700 kWh of electricity.
As long as the cycle is established, 31,700 kilowatt hours of electricity can be produced every day, and 11.41 million kilowatt hours of electricity can be produced in a year.
Of course, to achieve circulation, you must prepare a battery with a capacity of at least 4,500 cubic meters. Taking into account the casing and other supporting facilities, the volume in the power generation room must reach at least 30,000 cubic meters, which is an area of 5,000 square meters and a height of about 6 meters. of factory buildings.
Industrial land less than 8 acres is not a problem.
But what really troubles Jiang Miao is the gold plate that serves as the cathode of the battery.
He adjusted it several times. Even if the usage is improved to the minimum, each cubic meter of battery still requires 0.4 kilograms of gold.
4500 cubic meters requires 1800 kilograms of gold.
Of course, instead of using gold, you can also use platinum. Platinum is relatively cheaper at about 227 million yuan per ton. If you bite the bullet, Hailufeng Company can still afford it with its financial resources.
Jiang Miao thought over and over again and decided to abandon the use of gold and platinum as cathodes and replace them with high-purity manganese oxide sheets that would have lower efficiency. This reduced the electron migration efficiency to 86%.
After completing these experiments, Jiang Miao has stayed in Monan for nearly a month.
He destroyed all experimental records and temporary power generation devices, leaving only 10 strains of Owen's power generation bacteria.
Four of them were stored by him in the chairman's special safe at the Taminchagan base.
He ordered the company's logistics driver to transport the remaining 6 copies back to Shanmei in three ways. Just in case, he set up a simple device in the strain storage container. Without the assistance of his identification panel, If someone else opens it by force, the hydrochloric acid and nitric acid stored inside will be mixed into aqua regia, thereby destroying the Erwin power-generating bacteria stored inside.
The four culture storage containers stored in the Taminchagan base also have the same settings.
Of course, even if the storage container can be opened safely by chance, the bacteria inside still need special conditions to wake up, otherwise you will only get a small bottle of useless bacteria powder.
All the technologies of this microbial fuel cell system have been recorded in Jiang Miao’s mind.
However, he knew that this kind of microbial technology would most likely have to be left to Shuya, including the previous bio-mining technology.
There is actually room for further development of this technology.
For example, improving the materials of anodes and anodes can improve electron migration efficiency.
Or continue to improve the power generation power of bacteria. According to Jiang Miao's current progress, the energy generated by Owen's power generation bacteria in the process of decomposing organic matter is about 300 degrees per cubic meter. However, the energy change of only 115 degrees of electricity is When it becomes electrical energy, the efficiency is about 38%.
(End of this chapter)