Environmental pollution is the result of human activities, which causes carbon accumulation on the earth. The accumulated carbon resides not only in CO2, but also in urban garbage, aquatic weeds, agricultural refuses and other wastes. The forced carbon circulation (FCC) strategy aims to bringing the accumulated carbon back to the ecological cycle through carbonization and carbon reduction. The former changes all refuses to gaseous fuel (ca. 10 wt%) and inorganic carbon; the latter changes all acid/acidic gases (SO2, NOx, CO2) to inoffensive/useful substances with the inorganic carbon. Application of FCC strategy will effectively alleviate environmental pollution in a simple way. However, the essence of environment pollution is the heavy population that cannot be sustained by the earth. Therefore, no technical measure, but politics can solve the problem thoroughly.
The environment would not be polluted should human being be not alive on the earth; therefore, human activity is the origin of pollution. Two things are inevitable in human activities: food and fuels in order to satisfy energy needs. Both food and fuels are composed mainly of elements carbon and hydrogen, and the products of con- suming energy are CO2 and H2O. H2O is not offensive, but the accumulated CO2 causes abnormal climate change. The author indicated [
Correlation between global CO2 emi- ssion and world population since 1850
The landfill garbage at suburb of a city in Zhejiang Province (Taken on November 7, 2009)
garbage is only part of solid wastes of human activities, and large quantity of agricultural refuses is generated in farming and relevant activities. Aquatic weeds flourish in lakes, rivers and oceans due to pollution with nutri- tious wastes (
Because carbon and hydrogen are the most abundant elements in food and fuels and in the products of consum- ing food and fuels as well, forced carbon circulation (FCC) is proposed to bring the carbon element back to eco- logical cycle from refuses through carbonization and carbon reduction. Most organic and/or biomass refuses can be carbonized at relatively low temperature (300˚C - 500˚C), and poisonous gases such as dioxins do not occur at such temperature. In addition, quite many heat sources of low heat value are available in industry. Inorganic carbon and flammable gas are major products of carbonization as shown in
Urban garbage is finely classified and reutilized in developed countries; however, garbage classification seems difficult in practice for developing countries as is the situation of China, and only minor part of refuses is reuti- lized. Garbage incineration relies on large quantity of additional fuel, and poisonous gases such as dioxins occur
Aquatic weeds covered Lake Dianchi, Kunming (left) and sea water at Tsingdao (right), Shandong Province
. Result of catalytic carbonization of coking and lean coals
Coking coal | |||
---|---|---|---|
Catalyst | Gas, wt% | Combustible Fraction, % | Tar, wt% |
Ni/Ce-ZrO2/γ-Al2O3 | 13.62 | 89.37 | 4.29 |
9%Ni/10%MoO3/γ-Al2O3 | 13.92 | 91.93 | 4.57 |
Ni/La2O3-MgO/γ-Al2O3 | 15.12 | 90.38 | 3.59 |
Lean coal | |||
Ni/γ-Al2O3 | 11.31 | 94.44 | 1.14 |
Ni/CeO2/γ-Al2O3 | 8.32 | 96.32 | 2.58 |
Ni/La2O3-MgO/γ-Al2O3 | 8.86 | 96.58 | 2.68 |
at the incineration temperature. Therefore, garbage incineration often encounters protest of nearby residents and most cities depend on landfills of garbage. It occupied quite large field and deteriorates the near-by environment. According to FCC strategy, garbage is classified just into two groups: that can be carbonized (CBC) and that cannot be carbonized (CNBC). The management of garbage becomes simple: carbonize CBC at about 300˚C - 500˚C and use CNBC to build up dams on sea coast or spread it over deserts. Additional fuel may not be re- quired for carbonization since flammable gas is generated in the process of carbonization. The resulted inorganic carbon is directly applied in the reaction of carbon reduction as described in subsequent section.
How to deal with aquatic weeds is a headache for Dianchi Lake, Kunming, Yunnan Province and quite many other lakes, rivers, and coastal water of China. According to FCC, the aquatic weeds provide large quantity of energy in a simple way: get the aquatic weeds out of water, and dry them up, then carbonize them at relatively low temperature and normal pressure. About 10 wt% flammable gas is expected to obtain in addition to inor- ganic carbon. The same applies to agricultural refuses. Instead of in-situ burning, farmers may sell stalks to a professional contingent. As much as 8.4 × 107 tons of flammable gas will be obtained in China if 1/10 of the to- tal stalks transforms to. The obtained inorganic carbon can be used as chemical reductant or just back to culti- vated land as potassium fertilizer. The carbonized agricultural stalks usually have developed porous structure with specific surface area raged in an order of magnitude 10 to 102 m2/g. They deserve well of cheap adsorbent for waste water treatment and once again carbonization is resorted to when saturated.
Fossil fuels will soon be exhausted and natural renewable energy cannot, as pointed out by David MacKay [
The yielded CO2 disappears in the reaction of carbon reduction at 900˚C:
All reactions proceed at ambient pressure without the aid of catalysts. The carbon generated in FCC can be here used as reductant. The net product of the cycle is H2 and CO. They are normally obtained through SMR (steam methane reforming) process at 700˚C - 1100˚C from natural gas with the aid of catalysts and used for the synthesis of chemical products such as methanol, fertilizer, artificial fiber, plastics, etc.
Coal is a major energy source and a major pollution source either. It provides the largest share of total energy used for electricity generation, for example, 78% in China, 69% in India and 50% in the United States. Removal of acid gases (SO2 and NOx) from the flue gas of coal combustion doubled the cost of power generation, and the capture of CO2 costs at least equivalent to double the market price of power coal [
Reactions (4) and (5) are endothermic, and their conversion can be calculated based on fundamental thermo- dynamic data as that listed in
Technical strategy and/or methods known to us are essentially useless for the elimination of carbon emission and the abnormal climate change it caused. The CCS strategy is not practical because the capture cost is too high to be applied in practice and it can only capture the centralized emission. However, the centralized emission ac- counts for only 1/4 to 1/3 of the total. Electricity driven vehicles are something like that said by a proverb: plug one’s ears while stealing a bell because the electricity is most likely produced in burning coal so that the global carbon emission unchanged while some places are locally cleaned. Natural energy cannot satisfy the energy needs presently and even for the future. Compared to them, the FCC strategy is practical and efficient to alle- viate environmental pressure.
However, as the linear relationship between global CO2 emission and world population revealed that the es- sence of environment problem is the problem of population. People must realize the crisis, the living crisis, is stepping closer and closer if considering environmental problem in connection with the depletion schedule of natural resources. Think about the situation 65 years later. The world population will be doubled (more or less
. Thermodynamic data required for conversion calculation of Reactions (1) and (2)
25oC | C (s) | CO2 (g) | CO (g) | H2O (g) | H2v(g) |
---|---|---|---|---|---|
0 | -393.51 | -110.53 | -241.826 | 0 | |
0 | -394.36 | -137.17 | -228.6 | 0 | |
T, K | |||||
298.15 | 8.536 | 29.141 | 37.135 | 33.598 | 28.836 |
300 | 8.61 | 29.142 | 37.22 | 33.606 | 28.849 |
400 | 11.974 | 29.34 | 41.328 | 34.283 | 29.181 |
500 | 14.537 | 29.792 | 44.627 | 35.259 | 29.26 |
600 | 16.607 | 30.44 | 47.327 | 36.371 | 29.327 |
700 | 18.306 | 31.17 | 49.569 | 37.557 | 29.44 |
800 | 19.699 | 31.898 | 51.442 | 38.8 | 29.623 |
900 | 20.832 | 32.573 | 53.008 | 40.084 | 29.88 |
1000 | 21.739 | 33.178 | 54.32 | 41.385 | 30.204 |
1100 | 22.452 | 33.709 | 55.423 | 42.675 | 30.58 |
1200 | 23 | 34.169 | 56.354 | 43.932 | 30.991 |
1300 | 23.409 | 34.568 | 57.144 | 45.138 | 31.422 |
1400 | 23.707 | 34.914 | 57.818 | 46.281 | 31.86 |
1500 | 23.919 | 35.213 | 58.397 | 47.356 | 32.296 |
Theoretical conversion of major reduction reactions at different temperature.
around 14 billion) if the present growth rate (1.14%) is keeping on, and the global emission of CO2 is almost doubled either. Oil and natural gas have been run out, and the other natural resources are also either empty or closing depletion. Fresh water may be in very short since glaciers may have been disappeared and rivers lost headstreams and draught. Food may also be in very short because most farm land might have been severely pol- luted. Competition and fighting for the last living resources to survive would be severer year by year. The earth likes just a ferryboat. It would sink when the ferryboat passengers are overloaded. People can imagine what would happen on the boat when it is sinking. The most important for us to do is not the development of econo- my following conventional model, but to survive human civilization gently, i.e., switching the growth rate of world population to negative immediately. The curve of world population growth rate (
World population growth rate since 1950 (red)
markable yet gentle decrease is shown for 1970’s due largely to the “One Child Policy” of China issued in 1975. Of course nobody wants Mao’s policy returned, but the world’s attention must switch from “carbon emission” to “breeding control”. The personal right and freedom to breed must subordinate the world No. 1 target of surviv- ing human civilization. Lao Tzu told people “following nature (Dao Fa Zi Ran)”. It means human activities must be compatible with natural limitation. Any theory or policies are not valid or harmful if it does not consider the compatibility of its consequence with nature.