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Biochar composition

Biochar composition is affected by raw materials which are used for biochar preparations. Feedstocks, which are rich in carbon and nitrogen, have more carbon and nitrogen concentration in biochar. Researches have been done for comparing different biochars (derived from different sources) regarding their elemental and functional properties. Researches were carried out on effects of different feedstocks (wheat straw and rice straw) on nutritional composition of biochar and it was found that rice straw biochar is rich in nutrient content with respect to wheat straw biocliar.

Sources

Rural areas are the main sources of raw material for biochar production, which includes crop residue from the harvesting of crops, charcoal from chulhas (villages), rice husk by products, different forest wastes, weed biomass, etc.

Amendment of soil and environment through biochar

Burning of rice straw is a major problem all over the world, causing nuisance in the environment, soil and human health. In India, Punjab is the major rice-wheat growing state, where the area under paddy (rice) is approximately 3.0 million ha, which produces 20 million tons of paddy straw, out of which 75 per cent of the straw is burned in the fields only. Burning of rice straw generally gives rise to 1515 kg per tons of CO-,, 92 kg/tons of CO, 3.83 kg/tons of NO,, 0.4 kg/tons of SO,, 2.7 kg/tons of CH4,199 kg/tons of ash (PM) and 5.7 kg/tons of non methane volatized substances. These are the major greenhouse gases (GHG) contributing to global warming. So, its management becomes very imperative. To solve this problem, biochar production is one of the best option. Biochar is the key to many problems like waste management, energy production, soil fertility and productivity, carbon sequestration and mitigation of greenhouse gases (CO„ CH4 and N,0). Biochar is being promoted as a way to initiate a “doubly green revolution” as it potentially address soil organic matter, GHG emission and food securities.

Waste management

The waste produced from various sectors like agriculture, industries, forest, animal and municipal solid waste can be managed by intelligent utilization, i.e., exploiting the pyrolysis technique for biochar production (Figure 2). The management of the waste in this way is not only sustainable to the environment, and cost effective, blit also one of the best method to curb the environment pollution. In India, about 130-150 million tons of agricultural waste like acacia wood, coconut shell, etc. are dumped without any use. This clearly indicates that the biocliar production potential is very high. Biochar produced from coconut shell increases the survival of microbial inoculants by up to six months, as it is free from toxic elements and is eco-friendly (Saranya et al. 2011). Biochar also has the potential to be used as an alternate carrier to lignite for the preparation of biofertilizers.

Soil management. Improvement in soil fertility’

Biochar (Figure 1) plays an important role in the management of soil either by increasing the fertility potential or by remediating the soil pollution (heavy metal pollution).

Biochar can be extensively used as an amendment in the fields, which not only improves the overall quality of the soil, nutrient cycling, carbon sequestration but also helps in the curbing of soil pollution. It contains about 48 per cent carbon, 1 per cent nitrogen, 0.7 per cent phosphorous and 3.3 per cent potassium. There is no release of any harmful gases from the biocliar. Soil biochar application offers the potential to stabilize carbon and recycling of nutrients present in the straw. Early trends suggest beneficial effects of biocliar on crop yields (rice-wheat and potato-anion) and C content in soil. Biocliar improves the soil water holding capacity and thus the water retention for a longer duration, which is attributed to the highly porous structure (Keech et al. 2005, Liang et al. 2006). So, the problem of water scarcity can be combated as it will reduce the amount and intensity of water requirement of any crop. The biocliar addition will increase the soil pH and EC (Glaser et al. 2002). This is due to the presence of ash residue that is dominated by carbonates of alkali and alkaline earth metals and some amount of silica, heavy metal and organic and inorganic nitrogen. Thus, it will have a liming effect on the acidic soil. It will also suppress the enzymatic activities of microbes involved in the conversion of nitrite to nitrous oxide, thereby increasing nitrogen availability in the soil and suppressing nitrogen losses. Shenbagavalli and Mahimairaja (2012) produced the biocliar from Prosopis sp. woods by pyrolysis material under high temperature. The characterization of this biochar revealed that it contains high carbon and was neutral in nature. When this biocliar was added to soil with pH 8.42, it was found that the pH was decreased to 7.92 during the incubation with rise in CEC and organic carbon. However, the pH raised to 5.93 on application of biocliar to acidic soil (pH 4.20) (Zwieten et al. 2010). Ibrahim et al. (2017) reported that soil pH. total nitrogen and total carbon, dissolved organic carbon and ammonium nitrogen were increased while available concentration of Cd. Pb and As decreased along with nitrate-nitrogen in biocliar amended soils. Biochar also reduces the leaching losses of the nutrient to groundwater, so in addition to improving the economy it improves the ecology too. This is attributed to high CEC of the biocliar because of more surface area and porous structure. Therefore, it holds the nutrients more strongly and improves the nutrient use efficiency of soils.

 
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