*3.1.6 Improving crop productivity*

The impactof biochar application is more prominent in highly degraded acidic or nutrient depleted soils. Several studies have reported positive responses of biochar on net primary crop production, grain yield and dry matter (**Table 2**). Little addition of charcoal (0.5 t ha−1) have shown significant impact on various plant species, whereas higher rates caused plant growth inhibition [30]. Biochar if applied in combination with inorganic or organic fertilizers, can result into increased crop yields, particularly on tropical soils [19].

## **3.2 Environmental implications of biochar**

#### *3.2.1 Biochar and carbon sequestration*

According to Turral et al. [31], agriculture generates around a fifth of the world's greenhouse gas emissions. The application of biochar is proposed as a novel approach to establish a significant, long term, sink for atmospheric carbon dioxide (CO2) in terrestrial ecosystems. Biochar addresses two important sources of environmental problems, by sequestering CO2 into the soil and by reducing water pollution through enhancing soil nutrient retention [32]. It was observed that biochar plays important role for emission of carbon and also essential to meeting global climate targets [33]. Biochar-bioenergy systems can play an important role in a global strategy favorably helps in carbon capture and storage at lower carbon prices whereas biochar addition to soils delivers significant increases in crop yields. Hence, effective use of biochar plays significant role in carbon sequestration.

#### *3.2.2 Biochar and climate change*

Now-a-days excessive amount of carbon dioxide is being released to the atmosphere due to the burning of fossil fuels and decomposition of biomass, which increases the carbon levels in the atmosphere day by day. Application of biochar helps in decreasing the emission of carbon dioxide as it has the ability to store 50% of the carbon from feedstock [34]. Biochar is highly stable and having the capacity to emit less carbon dioxide from organic decomposition significantly. So that it plays an important role in monitoring the release of methane and nitrogen dioxide from the soil, which are the major cause of climate change in recent days. This reduction in the release of nitrogen dioxide ensues because of the capacity of biochar to adsorb and retain the ammonium in soils and then lessen the availability of nitrogen for denitrification process. It is observed that in the fields, methane emissions were 34% higher from the fields which are treated with biochar. Though the emissions of nitrogen dioxide were found 40–51% less in soils than that of those soils which are not treated with biochar, thus global warming gases from soils decreases by amending soils with biochar [35].
