Biochar
Biochar briquettes | Wikimedia commons
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Bengaluru: It is no secret that farmers in India are adversely affected every year by many troubles related to the monsoon, crop quality, disappearing yields, and soil fertility. Since they have no viable way to dispose of residual crop waste each season, they often resort to crop burning in North India and this causes a spike in air pollution every year.

An ancient method of fertilising could come to the rescue.

Biochar, a form of burned organic matter, could be the potential solution to several of these problems and has gained significant scientific importance in recent times.

It is essentially organic matter that is burned without oxygen to produce a black residue that can enhance soil fertility when mixed into it.

Research worldwide into biochar has increased drastically over the past decade, and in India specifically, the number of studies on biochar have gone up in the past five years.

Ancient cultures like settlers along the Amazon River and Native American tribes have successfully used it to improve soil fertility by burning organic matter inside covered pits.

Further evidence suggests that the process also helps store or sequester carbon, thus helping reduce pollution.


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A lab in University of Zurich, is working on understanding how biochar can be effectively used in India, and what its pros and cons are. The university’s soil science and biogeochemistry department researchers are attempting to understand its impact and improving the biochar production process to enable both soil fertility and carbon sequestration. They are aided by field trials spanning a period of over a decade in India.

The carbon cycle 

“As a biogeochemist, I study the carbon cycle, starting with how carbon enters plants through photosynthesis and how it moves into the soil, to the life cycles of related compounds responsible for soil health such as nitrogen and phosphorus,” says Samuel Abiven, group leader of the university research group.

Abiven’s research students also study carbon that’s released by fire and the link between carbon and other cycles like those of nitrogen and phosphorus.

According to Abiven, biochar is a “custom made” organic matter produced from fire or heat that can be applied in agriculture or industrial applications. It is similar to charcoal but is produced artificially for specific use.

Organic waste (called ‘feedstock’ when it’s in the form of raw material) is transformed through heating without oxygen (to prevent combustion), into charcoal-like material producing heat and energy, as well as byproducts like bio oil and fuel gases, which are sources of clean energy. This process of heating is known as pyrolysis.

Biochar also lasts in the soil for a very long time and thus is an effective form of carbon storage.


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Carbon sequestration

The amount of carbon available globally is finite and is stored naturally on earth. Fossil fuel, for example, is stored carbon that is collected over millions of years and buried deep under the ground. Carbon is found in large quantities in soil and sediments as well, as this layer of earth is the first to collect organic matter.

Carbon in the soil works with nitrogen and acts as a fertiliser to the plants, and soil is generally healthier and more fertile if there’s more organic matter in it.

There are exceptions to this, of course. Permafrost — permanently frozen ground that is thawing today because of our climate crisis and global heating — contains a lot of frozen carbon but isn’t really fertile land for farming.

“What is interesting about soil is that you can act on it,” explained Abiven. “You can change it and allow for it to absorb more carbon to be stored.”

Studies have shown that biochar has multiple merits – it can increase fertility, mitigate pollution, and store carbon. It is especially efficient on the last front since it lasts for a very long time in the soil and microbes don’t break it down as fast as regular organic matter.


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The production process

Biochar can be made of any organic matter, including wood, animal excreta, plant waste, household organic waste, and crop remains that would otherwise be burned. The biochar produced is usually 50% of the raw material’s volume.

The process of pyrolysis can also be done in many ways. Digging a pit into the ground, dumping the feedstock in it, covering it, and lighting it is the easiest way and has been practiced for thousands for years. Today, kilns are used instead.

Biochar’s quality depends not just on the method, but also the quality of raw materials, the amount of oxygen that seeps into the process, and the temperature. In fact, the higher the temperature, in the 400°C to 1000°C range,the longer the biochar lasts in the soil.

A delicate balance is needed when applying and creating biochar. Since it’s porous, it helps hold on to more water and increase moisture content in the soil, but this means that it could also end up absorbing nutrients from the soil.

Thus, the type of biochar to be produced and its retention potential needs to be adjusted for the site of use.

“Woody biochar, for example, absorbs a lot more nutrients,” says Abiven. “But if the nutrients aren’t tightly packed into the biochar structure, plants can still tap into it for their benefit.”


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Abiven’s research into biochar systems has also led to surprising discoveries. A field trial, conducted in Zambia, indicates that biochar results in extensive root systems that increase in both quantity and reach, which then increase crop yield.

UZH and Abiven’s team has conducted field trials in Germany, Spain, Italy, Norway, Nepal, North America, Indonesia, Madagascar, Zambia, and of course India.

Biochar in India

In India, UZH collaborates with GKVK College of Agriculture and the Indian Institute of Science (IISc) in Bengaluru, and has been doing so for over 12 years.

Abiven’s team’s most recent field trial is still ongoing in the town of Mandya, Karnataka. The team also collects samples from biochar use in the outskirts of Mysore and Godavari watersheds ranging from Pune to Mumbai.

Before applying biochar to a farmer’s soil, Abiven obtains consent by explaining how biochar works. The team then proceeds to understand how composting is already being implemented, what the farmers’ investment capacities are and whether they can obtain subsidies. They then evaluate the farm area for its needs.

The kind of biochar produced for use here will depend on all of these factors.

“What is surprising is that most of the times, Indian farmers don’t need technical information,” explains Abiven. “Does it work? That’s all they want to know before they adopt it.”

It has worked in most cases, several farmers have seen an increase in yield that has been noticeable enough for them to continue biochar.

However, sometimes, there is negative yield in the crop that can prove to be a huge disadvantage.

“One suspect is ‘sodic soil’, where there’s a high salt content in the soil,” elaborates Abiven. “In general, soil with pH tends to be unfavourable for biochar.” He also states that soil with a extremely high levels of organic matter does not work well in conjunction with biochar, either.

More research would be needed to understand the efficiency of biochar in India, adds Abiven, and “When done right, it can provide a big solution for both crop yields as well as carbon sequestration.”


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