× Expand Helping Put the Earth Back in the Black Soil samples indicate the effectiveness of bio char on crop yields.

By Dan Bolton

TALAWAKELLE, Sri Lanka

The leaves that pluckers harvest take with them tons of essential minerals and trace metals that must be replaced to sustain the health and yields of tea bushes.

Constantly generating new leaves stresses tea bushes that over 150 years have consumed great quantities of soil nutrients. Replenishing these chemicals is expensive in countries like Sri Lanka that lack a domestic fertilizer industry. Soil inputs are expensive and they expend petroleum, contributing to greenhouse emissions. Island countries like Sri Lanka bear the additional shipping expense of hauling millions of tons of minerals across the sea.

Helping Put the Earth Back in the Black Working biochar into the soil

Biochar is a promising answer.

Senior soil scientist Dr. R. S. Dharmakeerthi calls Biochar “a black gold that could improve the living standards of the poor in Sri Lanka in many ways while protecting our environment.”

Dr. Keerthi Mohotti, deputy director of research at the Tea Research Institute of Sri Lanka, the nation’s premier institution for tea research, explains that unlike other perennial plantation crops tea requires high soil fertility.

“In Sri Lanka it is provided through integrated soil management strategies that are laborious and costly. Climate change has led to frequent heavy rains that speed up soil degradation. Hence, alternative and grower friendly options are a necessity to meet such challenges today,” he said.

What is biochar?

The International Biochar Initiative (IBI) (www.biochar-international.org) describes biochar as a modern adaptation of the 2000-year-old practice of burning agricultural waste to improve the soil. Biochar holds carbon, boosts food security, increases soil biodiversity, and discourages deforestation, according to IBI. “The process creates a fine-grained, highly porous charcoal that helps soils retain nutrients and water. It acts as a charcoal filter to concentrate and prevent minerals from leaching into groundwater and causing pollution.”

Even more amazing, once introduced it can hold carbon in soils for hundreds to thousands of years.

Helping Put the Earth Back in the Black Dr. Keerthi Mohotti, dep. dir. of research at the Sri Lanka Tea Research Institute

It does not matter what feedstock the growers use: pruned twigs, green manure, leaves, coconut shells, spent tea, neem, ash from wood-fired dryers, or common weeds. Biochar is produced through pyrolysis or gasification ― techniques that do not give off CO2. Biochar is neither ash or soot. It contains a high concentration of cellulose. Carbonization is the thermochemical conversion of biomass in an oxygen-limited environment at temperatures below 700 centigrade. The process is called pyrolysis when no oxygen is present and gasification when small amounts of oxygen are used. The process mirrors the production of charcoal which generally requires heating wood chips to between 600 and 900 degrees Celsius.

Biochar is simple to produce, sustainable, and climate friendly. Agricultural workers using biochar stoves experience lower exposure to carbon monoxide, smoke and particulates generated by open cooking fires. A common 55-gal. metal drum can be easily fashioned into a biochar kiln.

What it can do

During the 1980s Sri Lanka’s department of agriculture introduced a low-temperature, low-cost method of using paddy husk to produce Kara anguru that rejuvenated soil quality and raised crop yields in rice paddies. Kara anguru is a type of low-grade biochar. The Rubber Research Institute of Sri Lanka in 2009 advanced the concept by producing biochar from firewood used in rubber manufacturing. Adding biochar to the soil reduced fertilizer use, cut down on leaching and improved the growth of rubber trees. A slow-release urea fertilizer combination was developed using biochar.

Mohotti explains that the porous, crystalline biochar structure absorbs bio-oils, nitrogen, phosphorus, and other nutrients. Biochar has a very high surface area ideal for holding water and food consumed by soil microorganisms. These nutrients are bioavailable to plants.

“Another advantage is due to its compressed nature. A tiny amount is required whereas ordinary organic soil amendments such as agro wastes, oil cakes and composts etc. must be applied in kilograms and metric tons.

In his office, Mohotti displayed biochar made from several different feedstocks. “Paddy husk and coconut shell sources are the most promising,” he said.

To facilitate grower participation, his vision was to utilize locally available feed stocks to produce biochar using a simple unit as well as to provide sustainable avenues to the tea growers.

So far, his research team has been successful in demonstrating how biochar works to enhance tea soils, reduce nitrogen leaching, capture soil elements including soil pesticides, and promote the enumeration of inherent beneficial soil organisms that strengthen root systems. The tea research institute is also working to charge biochar with soil nutrients and soil pesticides as a means of reducing dosage. “This will immensely benefit the environment while reducing the cost of inputs,” he said.

Garden trials

When biochar was applied at Rilhena Estate in Rakwana yields increased to 800 kilos of green leaves per hectare, as detailed in a June 2016 Tea Research Institute presentation by Mohotti. A conventional field in the experiment produced 600 kilos per hectare. At Harington Estate in Kotagala the application of biochar was demonstrated to increase the average number of kilos of made tea per hectare indicating healthy full leaves.

Dilhan C. Fernando, a director at Dilmah tea writes that “Biochar is something that I have enormous confidence in as an element in the future of our tea industry.”

“In 2012 we successfully adapted the principle of biochar in tea, at our Dilmah conservation sustainable agriculture research center in Moratuwa. We have since then applied biochar across a significant extent of our Kahawatte Plantations with very positive results. The most exciting aspect is that whilst allowing us to progressively eliminate the use of artificial inputs, biochar is also a formidable component of climate resilience whilst also enhancing the quality of the tea.”

Helping Put the Earth Back in the Black Restoring soil without chemical fertilizer requires bulky organic soil amendments.

Clearing the kitchen of smoke

Dr. R. S. Dharmakeerthi with IBI estimates 80% of Sri Lanka’s households still use firewood as their cooking fuel. He explains that the price of LP gas has increased steadily in the last decade, much faster than the rise in prices of other petroleum fuels. To some extent, this sharp increase in the price of LP gas has kept households from switching from cooking over firewood to cooking with LP gas. A more appropriate solution is specially designed biochar stoves, he explains.

According to the World Health Organization, indoor air pollution is the fourth worst cause of poor health and avoidable deaths of women and small children in the least developed societies. Carbon monoxide causes premature and under-weight babies, plus general weakness in adults. Fine particulate matter in the smoke causes lower respiratory diseases that shorten lives, and also contributes to climate change. “When biochar stoves are used instead of the traditional 3-stone stoves and their deviations available in the market, biofuel is gasified more efficiently reducing the generation of smoke down to a very low level. This will help to minimize the health problems associated with the smoke in the kitchen,” according to Dharmakeerthi.

Dr. J.C. Krishnaratne, director of r&d at the Biochar Initiative Co., explains that biochar not only enriches the soil, it has the potential to generate wealth for small growers.

Writing in the Business Times he calculates a grower using biochar on three hectares, “based on a guaranteed price of SLRs 5 per kilo, each family could earn an annual income of SLRs 300,000 ($1,975) after the second year from planting.”

“Many other cascading benefits, including economic and social, have been factored into a program of this nature,” he wrote in an article titled: Biochar: Can it put the tea industry back in the black?

Black soil

The impact from applying biochar varies, according to Mohotti. It will likely take many years to return Sri Lanka’s depleted acreage. He says that testing should continue to determine the best application time, assess long-term impacts, and opportunities to couple the production of biochar with microbial inoculations, biofertilizer applications to insure a favorable return on investments. He cites the following proven benefits:

• Soil microbial activity is enhanced

• Root rhizosphere is strengthened

• Moisture holding capacity of the soil is improved and nitrogen retention increased.

Ultimately you can see the difference. Spreading fertilizer encourages root growth near the surface instead of penetrating deeper down to reach moisture. As top layers dry up during droughts the roots are starved of moisture.

Black dirt is a sign of soil health. Using biochar darkens the soil over time. Mohotti says “dark is gold.”