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There is a scientific consensus for the potential role of biochar in carbon sequestration, climate change mitigation, renewable bioenergy, waste management and soil improvement. This seems to be a panacea, but what is biochar? And, how can the developing world benefit from its utilization?

Biochar is one of the byproducts produced when biomass goes through the process of pyrolysis: heating in an oxygen-depleted environment. The pyrolysis process produces gas and oil that can be used for energy or heat, but also fixates about one quarter of the original carbon content as a solid called biochar, a type of charcoal used for soil amendment (Figure 1). It is estimated that when incorporated into the soil, it can remain under this stable form for hundreds to thousands of years.

Figure 1. Biochar produced from different raw materials. University of California at Davis.

The most suitable raw materials for the production of biochar consist of biomass waste materials such as field residues and processing residues (e.g. nut shells, fruit pits, sugar cane bagasse, etc), as well as agricultural and forestry wastes, and even animal manure and human wastes. The properties of the produced biochar will depend on the nature of the feedstock and the processing conditions.

When applied to low-fertility soils, biochar enhances nutrient availability, soil water retention capacity, and in some cases absorbs residues from chemical fertilizers and lowers soil nitrates and methane emissions. Indeed, adding charcoal to soil to enhance its fertility is an age-old practice in many cultures, best exemplified by Terra Preta of Indio anthropogenic soils in South America.

Accordingly to the Food and Agriculture Organization, this technology could have great climate-change mitigation potential in agriculture by:

(1) Sequestrating carbon dioxide from atmosphere;

(2) Reducing nitrate emissions from fertilizer use;

(3) Reducing soil nitrates and methane emissions; and

(4) Potentially reducing emissions from deforestation and household emissions (See Figure 2 for a schematic carbon balance of biochar).

Biochar carbon balance. Cornell University.

Figure 2. Biochar carbon balance. Cornell University.

Biochar utilization could represent a sustainable opportunity, especially for the developing world, both for adaptation to and mitigation of climate change. For example, in Costa Rica, biochar’s impact starts before it enters the soil through the use of biochar-producing cooking stoves (Figure 3):

(1) These stoves use about half the amount of fuel than a conventional open fire, emitting less smoke and carbon monoxide and thus improving respiratory health;

(2) As deforestation is exacerbated by ever increasing cooking fuel demands, these stoves provide an alternative, especially because owners can use any type of biomass as fuel including agricultural wastes; and

(3) Stove owners use their own biochar, created in the cooking process, to amend their soils or to sell it to larger consumers like farmers.

Stoves for biochar production. Estufa Finca. SeaChar Inc.

Figure 3. Stoves for biochar production. Estufa Finca. SeaChar Inc.

Another case example is the pyrolysis of human waste (Figure 4). There have been efforts to design processes and to implement an economic value chain in rural populations that have no access to sanitation, for example in Kenya and India.

These projects comprise an innovative breakthrough in managing human solid waste that can eliminate the need for externally delivered power, water or sewers, while being financially sustainable. Pyrolysis can be used to process the waste from thousands of people per day, by converting it to biochar that can be used for the purposes mentioned before.

Human waste pyrolysis. The Climate Change Foundation.

Figure 4. Human waste pyrolysis. The Climate Change Foundation.

Biochar has undeniable advantages over many alternative approaches. Will it play a major role in mitigating global warming? Does it have the potential to be utilized in the developing world? With the challenges of finding alternatives to fossil fuels, the rising costs of energy, and the ever increasing environmental challenges, the production and implementation of biochar is a technology too promising to be overlooked.

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