Page 177 - CW E-Magazine (11-2-2025)

Special Report

Biochar – a sustainable fuel

ince the time our ancestor Homo agency representatives, etc., acknow- A.K. DAS
erectus invented and learned to ledged a common interest to promote Retd. Industrial Adviser
Scontrol fi re during the early Stone research, development, demonstration, Dept. of Chemicals & Petrochemicals
Age, biomass was being used as the only deployment (RDD&D) and commercia- Govt. of India
source of energy. Even now, biomass – lisation of the technology of biochar Email: amiyakantidas2010@gmail.com
cow dung, agricultural wastes, wood production.
etc. – is used as a reliable energy source the reduction zone and 800-1000°C in
and provides about one-third of primary Biochar is lightweight black rem- the combustion zone. The specifi c yield
energy consumed by the developing nants, consisting of carbon and ashes, from pyrolysis is dependent on pro-
world, including rural India. Globally, remaining after pyrolysis of biomass, cess parameters such as temperature,
it isestimated that one-seventh of the and is a form of charcoal. The word heating rate and residence time. Tem-
primary energy consumed in the world “biochar” is a late 20th century Eng- perature range of 400-500°C produces
is derived directly from biomass. lish neologism derived from the Greek more char, whereas temperature above
word bios, “life” and “char” ( charcoal 700°C favours the yield of liquid and
In India, industrial units in rice produced by carbonisation of bio- gas fuel components. Typical yields
producing areas use rice husk as a mass). It is recognised as charcoal that are 60% bio-oil, 20% biochar and 20%
source of energy. Sugar mills also participates in biological processes syngas. For typical inputs, the energy
meet their thermal energy needs by found in soil, aquatic habitats and in required to run a “fast” pyrolyser is
burning bagasse. Where cogeneration animal digestive systems. approximately 15% of the output.
facility has been installed, this meets
the in-house electricity demand and Production methods Production temperature infl uences
surplus electricity is added to the The process of making biochar is biochar properties in several ways. The
national grid or sold to customers. an ancient practice said to imitate the molecular carbon structure of the solid
Over the years, variants from biomass earth’s natural cycle. It locks away biochar matrix is particularly affected.
have been developed for domestic and carbon instead of releasing it and has Initial pyrolysis at 450-550°Cleaves an
industrial use. been recognised as a form of carbon amorphous carbon structure, whereas
sequestering by the UN International temperature above this range will re-
What is biochar? Panel on Climate Change. Carbon sult in the progressive thermochemical
Biochar is a carbon-rich mate- dioxide (CO ) is the most commonly conversion of amorphous carbon into
2
rial produced by pyrolysis – a process producedgreenhouse gas. Carbon turbostatic graphene sheets.
that thermally decomposes biomass sequestration is the process of capturing
(such as agricultural wastes, wood and and storing atmospheric CO . It is one of Small scale methods
2
other organic materials) in absence of the methods of reducing the amount of Smallholding farmers in developing
oxygen, preventing combustion. This CO in the atmosphere with the goal of countries easily produce biochar with-
2
produces a mixture of solids (biochar), reducing global climate change. out special equipment. They make piles
liquid (bio-oil) and gas (syngas). Bio- of crop waste (e.g., maize stalks, rice
char has been defi ned by International It has been reported that pre- or wheat straw), light the piles on the
Biochar Initiative (IBI) as the “solid Columbian Amazonians produced bio- top and quence the embers with dirt or
material obtained from the thermo- char by smoldering agricultural waste water to get biochar. This method greatly
chemical conversion of biomass in an (i.e., covering burning biomass with reduces smoke, compared to traditional
oxygen-limited environment.” soil) in pits or trenches. It is not known methods of burning crop waste. This
if they intentionally or unknowingly method is known as the ‘top-down
IBI was formed in July 2006 at the used biochar to enhance soil producti- burn’ or ‘conservation burn’.
World Soil Science Congress in Phila- vity.
delphia. During the meeting individuals, Alternatively, more industrial meth-
representatives from academic In the US gasifi ers are the most used ods can be used on small scales, while
institutions, commercial ventures, in- method of producing biochar. Tempera- in a centralised system, biomass is
vestment bankers, NGOs, US federal tures during pyrolysis is 250-550°C in brought to a central plant for processing

Chemical Weekly February 11, 2025 177

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