UPSC Civil Services 2020 Prelims General Studies Paper I

The term “bio” is in reference to organic residues and “char” for charcoal. Biochar is made by pyrolysis, which involves carbonizing residues in the absence of flame and in very low oxygen concentration. Biochar is a high-carbon form of charcoal.

Biochar, when applied to soils is reported to enhance soil carbon sequestration and provide other soil productivity benefits such as reduction of bulk density, enhancement of water-holding capacity and nutrient retention (Hence statement 3 is correct), stabilization of soil organic matter, improvement of microbial activities, and heavy-metal sequestration.

The usage of biochar can be also interesting for the urban farming industry. In fact, green roofs (vertical farming) are seen as “privileged areas” for retaining rainwater and reducing the effects of urban heat islands. Hence Statement 1 is correct.

Biochar's immense surface area and complex pore structure (a single gram can have a surface area of over 1000 square yards) provides a secure habitat for micro-organisms and fungi including nitrogen fixing microorganisms. Certain fungi form a symbiotic relationship with plant root fibers, and this allows for greater nutrient uptake by plants. Hence, Statement 2 is correct.