文章 Articles

Storing carbon in the fields

Reducing carbon emissions doesn’t have to be a high-cost, high-technology operation, writes Jiang Gaoming. Simple solutions can be found in China’s farmland.


Article image

[UPDATE: The figures relating to carbon storage in the second paragraph were updated on March 30, 2009]

Reducing emissions of greenhouse gases, mainly carbon dioxide, is a crucial task. Current measures include using technology to improve energy efficiency, planting forests to store carbon and promoting nutrient recycling so that carbon can be used to enrich the soil. The first two techniques are far more costly than nutrient recycling.

Storing 39.28 trillion tonnes of carbon, the oceans (including sea surface, deep sea and marine sediment) are the world’s biggest carbon sink. On land there are about 1.96 trillion tonnes of carbon, contained within vegetation and soil. There are approximately 775 billion tonnes in the atmosphere. Of the land-based carbon, soil is the most important sink: it holds between 1.4 and 2.2 trillion tonnes: two to three times the amount held in the atmosphere. In theory, all of the planet’s atmospheric carbon could be stored in the land, but the soil’s storage capacity depends on how it is used. If forests and grasslands, where the soil is rich in organic carbon, are turned into fields -- and those fields are treated with chemical rather than organic fertiliser -- the soil will become a source of carbon rather than a store. Appropriate farming techniques can maintain high levels of carbon in the soil, and agricultural land can fix huge quantities of carbon. Carbon can also be found in surface soil in forests, grasslands, marshes, high-altitude wetlands and even farmland.

Carbon storage in the soil mainly means fixing organic carbon from animals, microorganisms and dung. All of these break down to form humus, which is relatively stable. Unfortunately, many countries have a long history of using land, rather than managing it, which has caused the organic content of the soil to deplete. China’s northeast is one of the world’s most fertile regions, but soil degradation, which covers an area of 350,000 square kilometres, has released a lot of fixed carbon into the environment. The region feeds over one-tenth of China’s population, but at a high price. Data from the Chinese Academy of Sciences and research institutions in Heilongjiang province, northeastern China, show that in the last six or seven decades, the depth of fertile soil in the northeast has dropped from between 80 to 100 centimetres to 20 to 30 centimetres. Organic soil content has been reduced from 12% to 1% or 2%, and 85% of the soil lacks nutrients. In Heilongjiang province, 0.6 to 1 centimetre of soil is lost every year and in northeast China’s Jilin province, 42% of the land has only 30 centimetres or less of soil coverage.

There are 1.2 million square kilometres of farmland in China, with an average carbon storage capacity of 1.2 tonnes per square metre. Raising organic soil content by 1% would be the equivalent of absorbing 30.6 billion tonnes of carbon dioxide from the atmosphere. Even if this were to take three decades, one billion tonnes of carbon could be fixed in the soil each year. China’s net annual carbon emissions arising from economic activity are currently around seven billion tonnes, and this is likely to rise to over 10 billion tonnes by 2015. Thus, there is a huge potential for carbon sequestration in the soil, with easy-to-implement technology.

China’s farmland has been worked for millennia and organic content tends to be low; less than half that of similar soil types in Europe. This means there is a greater potential for improvement. Soil in Chinese paddy fields has organic content of 1% to 3%, while 31% of dry fields have less than 1%. Optimistic estimates state that organic content is increasing in 53% to 59% of China’s fields, decreasing in 30% to 31% of the fields and remaining stable in 10%. This suggests an increase of 311 to 401 million tonnes of stored carbon. However, there is huge, and as yet unrealised, potential for carbon storage in China’s soil. Making use of unwanted straw, rather than burning it off every year, would prevent the carbon fixed in crops from being emitted into the atmosphere.

It is clear that increasing the organic content of farmland can significantly reduce atmospheric carbon, but how can we achieve this? I propose that straw is collected at the same time that grain crops are harvested, before being processed and stored in order to provide fodder for livestock. The energy stored in the dung produced by livestock can be used in rural households for methane electricity generation. This would also serve to reduce competition for fossil fuels between rural and urban areas. The waste products of this process are high-quality fertilisers that can be returned to the fields, thus reducing the emissions incurred in manufacturing chemical fertilisers and increasing the organic content of the soil.    

Increasing the soil’s organic content will not only fix carbon and reduce emissions, it will also improve the soil’s ability to retain water and nutrients and resist pests and droughts. The result will be larger and higher-quality harvests. Tests show that every 0.1% rise in organic soil content increases potential grain production by between 600 kilograms and 800 kilograms per hectare. Carbon sequestration in the soil will bring about multiple benefits: saving energy, reducing pollution and increasing soil fertility.

In order to achieve these aims, China should develop a straw-fed livestock industry, increasing the use of organic fertiliser and encouraging new rural energy sources while reducing the use of chemical fertiliser and fixed carbon in the soil. China should differentiate the prices of agricultural products for different buyers in order to help 5% to 10% of China’s farmland become organic and free of chemical fertilisers, pesticides, additives or herbicides. Urban residents should pay a premium for organic grain, meat, eggs, milk and vegetables, increasing rural incomes and funding further carbon sequestration. China should promote the use of organic waste as fertiliser, farming without tilling and the decay of organic material in the soil. Full use should be made of traditional agricultural techniques that combine raising ducks and fish with rice farming, or poultry with grain cultivation. Finally, policy support should also be given to carbon sequestration in soil, so that it can ultimately become part of the global carbon-trading system.

Jiang Gaoming is a professor and Ph.D. tutor at the Chinese Academy of Sciences' Institute of Botany. He is also vice secretary-general of China Society of Biological Conservation and board member of China Environmental Culture Promotion Association. He is known for his concepts of "urban vegetation" and allowing damaged ecosystems to recover naturally.

Homepage photo by go_elsewhere


Now more than ever…

chinadialogue is at the heart of the battle for truth on climate change and its challenges at this critical time.

Our readers are valued by us and now, for the first time, we are asking for your support to help maintain the rigorous, honest reporting and analysis on climate change that you value in a 'post-truth' era.

Support chinadialogue

发表评论 Post a comment

评论通过管理员审核后翻译成中文或英文。 最大字符 1200。

Comments are translated into either Chinese or English after being moderated. Maximum characters 1200.

评论 comments

Default avatar
匿名 | Anonymous



Difficulty of non-pesticide

In fact, pesticides have been considered as a necessary part of the planting of foods & vegetables. Taking herbicides as an example, they can make the weeding much easier. Now farmers are less focused on planting, but rely more on doing business or working in the industry for income. The income from agriculture is too low – it’s a fact for China’s most rural districts.

(by Fangfang CHEN)

Default avatar
匿名 | Anonymous



Collecting straw, rasing livestock, and replacing gas

As for the famers, they can collect the straw after grain crops are harvested, and use the straw to provide fodder for livestock. The dung produced by livestock can be used for methane electricity generation, while the waste products of this process can be returned to the fields as fertilisers. This process of "collecting straw, raising livestock, and replacing gas" can provide fodder for the livestock, while at the same time, it reduces the cost of grain production, and saves the cost for chemical fertilisers. In the long run, it helps to ease the problem of energy shortages.

Default avatar
匿名 | Anonymous



Need to Be Patient

Increasing the land's organic carbon content is a great idea, but we don't know how many years it will take to make it successful in most places.
(Translated by Jacob Fromer)

Default avatar
匿名 | Anonymous



make a difference?

Will such simple methods really make a difference in China's carbon output?

Default avatar
匿名 | Anonymous



Educating the farmers

Persuading ordinary people in the countryside to do this kind of work, which is not repayed in the short term, is very difficult and if the relevant parties push ahead there is a strong possibility that a situation will emerge in which people agree with it in public but oppose it privately. Ultimately, we should start with education and change the habit of everyone only looking after their own interests. (Translated by Jodie Gardiner)

Default avatar
匿名 | Anonymous



A bit far-fetched

Organic fertiliser and ecology agriculture are both excellent ideas. But it’s not necessary to link them with climate change risks. [In general] you should do your own things, but there is no need to expand your actions to everyone because of climate change

(by Fangfang CHEN)

Default avatar
匿名 | Anonymous


另一个问题,就是教育宣传问题,特别是消费者。实际上现在大多消费者并没有认识到“有机农产品”比一般的好在哪里,甚至都没听说过。市场不能启动,农民那边也就不会有积极性。 这个就要让企业来起作用,政府如果对固碳型有机农业出台谢优惠支持政策,相关有机农产品企业和有一定规模的农户积极推进宣传,加上令人信服的认证体系,各方合力把这个市场做起来才是解决之道。 商品社会任何事情都需要市场来推动,没有市场都是空谈。
--liu guo

How to implement it

Professor Jiang, I was thinking could this issue be integrated with organic farming certification? Carbon-absorption in organic farming could, within a short time, affect the efficiency and production of the agricultural industry whilst improving the appearance and quality of the products. These factors could greatly influence the farmers’ enthusiasm to advance organic farming. If those products which had been certified as “organically farmed”, especially ones which didn’t look amazing could be sold at the market for a good price, then this could really work.

However, it seems that there is currently no authoritative certification system in place, and random certification institutions will just serve to discredit organic products in the eyes of the consumers.

Another question is concerning education and communication issues, particularly towards consumers. In actual fact, the majority of consumers don’t recognise where the advantage of buying organic produce lies, or may not even have heard of it before. Before the market has taken off, farmers are obviously not going to be enthusiastic about getting involved. Enterprises have a role to play here. If the government implements preferential policies to support carbon-absorbing organic-farming, both the linked organic farming enterprises and a large number of farmers will promote the industry. If this was to be coupled with a dependable certification system, then the market could be built up properly. In an era of commodity economy, the market needs to be the main driving force – with out the market, it is all just empty talk. --Liu Guo
(Translated by Tian Liang)

Default avatar
匿名 | Anonymous



Is this scientific?

I don't know if there is documented data or not, but our research has shown that organic farming can raise the soil's ability to breathe, and releases more carbon dioxide. Is this scientifically accurate?
(Translated by Tian Liang)

Default avatar
匿名 | Anonymous


提高土壤有机质含量的一个方法是广泛使用矿石烃(FHC)焦炭 ― 农业炭。这个方法的原理和生物炭是类似的,作为黑土层增加土壤肥沃度,并储存炭- FHC如果不是作为农业炭而是作为燃料,这些炭就会被释放到空气中。中国的煤炭储量丰富,它的热解会在挥发的过程中产生能量并产生丰富的焦炭。把将焦炭作为农业炭使用,可以提高土壤肥沃度,进而提高生物能产量,如果我们把这个也考虑在内,那么也许我们有必要去考虑这个方法。 [email protected]
(by Fangfang CHEN)

One alternative

One way to increase soil organic content is to sow fossil hydrocarbon (FHC)coke as it were an agrichar. This may work as a biochar works, i.e., generating fertility as a terra-preta and capturing carbon that otherwise would be emitted to the atmosphere if the FHC was used as a fuel instead of as an agrichar.
Pyrolysis of coal (China has plenty) will produce some energy from the volatiles, and abundant coke. If we take into account that the increase of soil fertility resulting from the use that coke as agrichar will result in an increase bioenergy production, thus, it may be worthwhile to consider this alternative.
[email protected]

Default avatar
匿名 | Anonymous



Develop carbon dioxide agriculture

Cultivating crops with sensitive response to carbon dioxide would solve the food and energy problems.