Policies and strategies for sustainable use of biochar in Indian agriculture

Abstract

Agriculture plays a fundamental role in India’s economy, supporting 70% of rural households. While often perceived as non-productive, agricultural waste harbors materials potentially beneficial to humans through the creation and utilization of biochar in the production and processing of agricultural goods. This study conducts a comprehensive exploration into the advantages and risks associated with biochar application, considering its role as a soil amendment, bioremediation agent, and its broader implications for human health and the environment. Biochar, primarily composed of stable carbon, was initially proposed as a soil amendment to sequester carbon. Efficient resource utilization has emerged as a viable means to address global environmental challenges associated with waste disposal. This review delineates diverse agricultural waste types and sources, identifies related environmental risks, and advocates for government-led measures aligned with circular economy principles to manage such waste. Furthermore, it offers insights into potential management strategies, policy considerations, and practical approaches, fostering sustainable agriculture practices and environmental conservation in India.

Full Article

Policies and Strategies for Sustainable Use of Biochar in Indian Agriculture

Peeyush Sharma, Vikas Abrol,* Neetu Sharma, Reetika Sharma, Divya Chadha, Shrdha Anand, Stanzin Khenrab, Maanik, Haziq Shabir, Priti Singh, Shruti Kumari and Divyansh Verma

Agriculture plays a fundamental role in India’s economy, supporting 70% of rural households. While often perceived as non-productive, agricultural waste harbors materials potentially beneficial to humans through the creation and utilization of biochar in the production and processing of agricultural goods. This study conducts a comprehensive exploration into the advantages and risks associated with biochar application, considering its role as a soil amendment, bioremediation agent, and its broader implications for human health and the environment. Biochar, primarily composed of stable carbon, was initially proposed as a soil amendment to sequester carbon. Efficient resource utilization has emerged as a viable means to address global environmental challenges associated with waste disposal. This review delineates diverse agricultural waste types and sources, identifies related environmental risks, and advocates for government-led measures aligned with circular economy principles to manage such waste. Furthermore, it offers insights into potential management strategies, policy considerations, and practical approaches, fostering sustainable agriculture practices and environmental conservation in India.

DOI: 10.15376/biores.19.3.Sharma

Keywords: Biochar; Environment pollution; Policy challenge; Soil properties; Waste management

Contact information: Sher-e-Kashmir University of Agricultural Sciences & Technology of Jammu, Chatha, J&K-180009, India; *Corresponding authors: abrolvics@gmail.com

GRAPHICAL ABSTRACT

INTRODUCTION

India generates a substantial volume of agricultural wastes, which has been estimated to be between 350 and 990 million tons per year; this waste encompasses crop residues such as leaf litter, seed pods, stalks, aquaculture waste, agro-industrial waste, and livestock waste (Sadh et al. 2018; Premalatha et al. 2023). In the prevalent rice-wheat cropping system in India, farmers commonly burn residues to clear fields for the next crop due to their low nutritive value and as a cost-saving measure.

The management of agricultural waste has become a crucial issue, demanding a shift towards sustainable practices. Utilizing these wastes as raw materials presents an opportunity to cut production costs and reduce environmental pollution. These residues, often rich in bioactive chemicals, hold potential for beneficial use.

Biochar is a recalcitrant compound that is produced after various thermochemical conversions under low oxygen supply (pyrolysis) conditions. It has been getting attention due to its porous nature and large surface area. Its multipurpose qualities cover a wide range of applications, including improving soil health, acting as a carrier of microbes and nutrients, immobilizing organic contaminants and toxic metals in soil and water, acting as a catalyst in industrial settings, and acting as a porous material to reduce odorous compounds and greenhouse gas emissions and nutrient absorption. However, the kind of feedstock and the pyrolytic circumstances affect the unique characteristics of biochar (Oni et al. 2019).

A new opportunity has developed with the potential to address several of the shortcomings of traditional agriculture, such as excessive fertilizer use, poor yield, and organic agriculture (Jones et al. 1997). Biochar, sometimes known as “black gold” in the agricultural industry, is a carbon-rich substance. Biochar has high concentrations of C, H, and O and low concentrations of N, S, P, K, Na, Mg, Al, Fe, Ca, and Si. Biochar doesn’t represent a single product with fixed chemical or physical properties. It encompasses diverse forms of black carbon, varying in properties based on the feedstock, pyrolysis unit, and processing conditions (Spokas 2010).

Moreover, biochar production using all types of agricultural waste, animal manure, and municipal waste is a smart way of recycling agro-waste. According to Abrol and Sharma (2019), among its many advantageous qualities are the improvement of soil fertility, crop output, and food security. However, the exact mechanism of biochar induced increase in crop productivity is still not well known. This review emphasizes the importance of environmental awareness in handling agricultural biomass wastes. Additionally, it offers strategic suggestions for policymakers to establish and execute agriculture waste management programs in line with circular economy principles. Thus the study concludes with a comprehensive review covering the biochar advantages, limitations, technological readiness, operational obstacles, and prospects.

RESIDUE BURNING AND AIR POLLUTION

The cultivation of rice, paddy, and wheat is a major industry in the states of Haryana, Punjab, Rajasthan, and western Uttar Pradesh. According to data from NPMCR, the states of Uttar Pradesh and Punjab generate the most agricultural leftovers, respectively, at 60 and 46 MT yearly, with 92 MT being burnt. Almost 70% of these wastes come from rice and wheat activities. Unfortunately, these regions are notorious for the common practice of burning straw and stubble after harvest, resulting in significant nutrient and resource loss.

Rice contributes the most significant portion at 43%, followed by wheat at approximately 21%, sugarcane at 19%, and oilseed crops at around 5% (Jain et al. 2014). This burning process results in significant soil nutrient loss, including the loss of organic carbon (3850 million kg), nitrogen (59 million kg), phosphorus (20 million kg), and potassium (34 million kg), in addition to deteriorating the quality of the air. Moreover, it emits significant amounts of COX, CH₄, NOX, and SOX into the atmosphere (Kumar et al. 2015).

Consequently, soil fertility is adversely affected by this open-field burning, leading to a decline in overall soil nutrients. Severe health concerns are associated with the poisonous gases released during this procedure, which can lead to respiratory conditions such asthma, emphysema, bronchitis, eye irritation, corneal opacity, and skin problems. Breathing in the released particulate matter might worsen pre-existing lung and heart conditions, which may cause early mortality in those who are impacted. Figure 1 shows the crop residue generation in India (Sahu et al. 2021).

Fig. 1. Crop-wise distributions of crop production, residue generated, and residue burnt in India for the year 2018 (Porichha et al. 2021; Re-used under CC BY 4.0)

Fig. 2. Advantages of biochar

BIOCHAR AS SOIL AMENDMENT

Soil Physical Properties

The porous nature and extensive surface area of biochar significantly enhance various soil physical properties such as total porosity, moisture content, water retention capacity, soil aggregation, and hydraulic conductivity (Zhang et al. 2021). The increased soil porosity facilitates microbial growth and elongation of roots, while its elevated cation exchange capacity (CEC) enhances nutrient retention and availability (Glaser et al. 2002). Notably, biochar helps prevent nutrient leaching, thereby fostering soil fertility (Jeffery et al. 2011). Soil bulk density is an important characteristic to control aeration and nutrient transformation in soil (Sharma et al. 2021). By preventing nutrient losses through leaching or gaseous emissions, biochar helps maintain soil fertility. Its aromatic nature results in biochemical resistance, generating negatively charged surface groups like carboxyl and phenolic groups (Liang et al. 2006; Cheng et al. 2008). Biochar incorporation can enhance soil structure, promoting better water retention and drainage, which is conducive to root growth and overall soil health (Graber et al. 2010). Figure 2 shows the various advantages of biochar on soil health.

Furthermore, biochar improves water sorption, decreases soil density, changes aggregate properties, and increases pore volume—all of which support the growth of soil microorganisms and plants (Abrol et al. 2016; Sharma et al. 2019). According to Razzaghi et al. (2020) and Edeh et al. (2020), biochar having large specific surface area and hydrophilic domains enhances its ability to retain water, which boosts agricultural yield (Bonanomi et al. 2017; Rawat et al. 2019).

The application of biochar, especially at higher levels, significantly increases soil field capacity (Singh et al. 2017). These effects are particularly advantageous in non-irrigated regions, augmenting available water for crop growth and reducing water stress between rainfall events (Sharma et al. 2021). According to Adekiya et al. (2020), biochar was applied at four levels 0, 10, 20, and 30 t ha⁻¹ for the experiment in 2017 and 2018 and the study showed reduction in the soil’s bulk density by 74.7% and an increase in porosity by 65.0% in the second year. Application of biochar at 10, 20, and 30 t ha⁻¹ reduced bulk density and increased porosity by 4.3, 8.3, and 18.7%, respectively, in the second year compared with the first year.

With regard to the soil physical properties, Table 2 shows that the application of biochar increased the cation exchange capacity up to 45% (Singh et al. 2022). Rice husk biochar reduced soil bulk density up to 1.5% (Sharma et al. 2021) and increased water use efficiency (Abrol et al. 2024). Mixed wood biochar reduced soil bulk density, increased infiltration, and decreased runoff (Abrol et al. 2016). Corn stover biochar increased macro aggregates (Hearth et al. 2013). Miscanthus biochar helped to decrease bulk density by 31% and increased porosity by 12% to 41% (Liu et al. 2016).

Soil Chemical and Biological Properties

The alkaline properties of biochar aid in neutralizing acidic soils, thereby enhancing pH levels and fertility (Lehmann 2019). Studies have consistently showcased biochar’s efficacy in elevating soil pH (Chu et al. 2011), leading to enhanced nutrient assimilation (Zwieten et al. 2010). Over the long term, tropical soil treated with biochar exhibits increased nutrient availability (Lehmann et al. 2003; Rondon et al. 2007). Incorporating biochar reduces the need for nitrogen fertilizers and enriches soil carbon content (Widowati et al. (2012), functioning as a stable soil conditioner and fertilizer that mitigates nitrogen leaching (Steiner et al. 2008). The augmentation of aromatic carbon content from biochar positively influences soil properties (Knicker et al. 2013). According to Sukartono et al. (2011), biochar, due to its porous structure, has significant impact on nutrient retention through high CEC levels.

In reference to Table 2, oil palm empty fruit bunch biochar helps improve soil chemical properties via increasing the soil available potassium up to 37% over RDF (Bindu et al. 2020); tobacco stalk biochar helps increase the soil pH (Bindu et al. 2016); biochar from eucalyptus wood, bamboo, and rice husk helped decrease exchangeable AI by 34.4 to 95.7% (Geng et al. 2022); rice straw biochar helped increase soil pH by 8.5% to 79.2%. Cacao shell biochar increased soil pH by 0.5 units (Martinsen et al. 2015).

Soil hosts a variety of organisms influenced by soil conditions, climate, and land management. Biochar has the potential to impact soil microbial communities by supporting beneficial populations and mitigating certain pathogens, positively affecting nutrient cycling, and soil health (Lehmann et al. 2011). The exact influence of biochar on soil biota is an ongoing area of study. Some research emphasizes bacteria, mycorrhiza, and earthworms. Additionally, Graber et al. (2010) found increased colonies of specific bacteria and yeasts with higher biochar rates but reduced culturable filamentous fungi. The porous structure of biochar likely facilitates microbial colonization and growth.

CROP PRODUCTIVITY

Applying biochar has proven to have the ability to increase soil productivity in terms of its physical, chemical, and biological properties (Lehmann et al. 2003; Chan et al. 2007). In particular, Chan et al. (2007) found that biochar application enhanced soil structure, increased soil water retention capacity, and decreased soil compaction. Moreover, studies by Liang et al. (2006) and Yamato et al. (2006) indicated that biochar application elevates soil pH and enhances cation exchange capacity (CEC). For instance, Zwieten et al. (2010) demonstrated that combining paper mill waste biochar with inorganic fertilizer led to greater biomass production in soybean and radish compared to the exclusive use of inorganic fertilizer. Similarly, Widowati et al. (2012) found that the use of biochar made from municipal trash and chicken dung boosted the biomass of maize. Biochar’s capacity to raise soil pH and CEC is linked to increased crop production (Liang et al. 2006; Yamato et al. 2006). Figure 2 depicts the use of biochar in wastewater treatment.

REMEDIATION OF SOIL AND WATER

Heavy metal and persistent organic pollutant (POP) contamination in soil, such as polycyclic aromatic hydrocarbons and polychlorinated biphenyls, poses severe threats to environmental sustainability, food safety, and human health. Biochar exhibits a remarkable capability to immobilize metals, including Cd, Cu, Ni, Pb, and Zn, thus reducing their availability in soil and water. This immobilization occurs through several mechanisms such as electrostatic attraction, ion exchange, and changes in soil pH induced by the addition of carbonates and phosphates. Various processes such as partitioning, pore filling, electrostatic attraction, π–π electron interactions, and the hydrophobic effect contribute to this effectiveness. Biochar’s high porosity, surface area, buffering capacity, ash content, alkalinity, and aromatic qualities are associated with its effectiveness. However, the materials used and the pyrolysis process’s circumstances have an impact on biochar’s effectiveness (Wiedner et al. 2013). Table 1 shows the effect of biochar on different soil pollutants.

SYNGAS AND BIODIESEL FORMATION

Biochar serves as a versatile component in both syngas production and soil enhancement. Its role as a feedstock for syngas provides a renewable energy source, while its application in soils boosts agricultural productivity and environmental health (Huber et al. 2006; Kang et al. 2020). The two main processes for producing syngas are biomass gasification and pyrolysis, which allow for the large-scale, quick conversion of solid organic resources. As an alternative fuel to petro-diesel that is carbon neutral, biodiesel is made by esterifying and transesterifying vegetable or animal oils using homogeneous (e.g., KOH, NaOH, HCl, H₂SO₄) and heterogeneous catalysts (e.g., CaO, zeolite, amberlyst resins, SiO₂, TiO₂, Al₂O₃).

MITIGATING GREENHOUSE GASES

Adding biochar to soil helps reduce N₂O emissions and aids in the storage of carbon (Sapkota et al. 2024). According to a meta-analysis by Verhoeven et al. (2017), there were average decreases in N₂O emissions of between 9% and 12%.

But according to a different study, soil amended with biochar emitted around 50% less N₂O than unamended soil (Cayuela et al. 2014).

Additionally, soil amended with biochar alongside inorganic fertilizers enhanced soil organic carbon (SOC) storage and reduced C mineralization. Biochar can aid in reducing emissions of greenhouse gases including carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) from the soil, acting as a carbon sink (Sohi et al. 2010). Figure 2 shows the advantages of biochar application on CH₄ and N₂O mitigation.

Fig. 3. Applications of biochar in soil (Redrawn with inspiration from Malyan et al. 2021)

Policies and Strategies for Biochar-related Activities

India has promoted biochar to increase soil fertility through programmes such as the National Mission on Sustainable Agriculture. To lessen reliance on fossil fuels, the National Policy on Biofuels promotes the production and application of biochar for sustainable agriculture.

The “National Biochar Initiative” was started by the Indian Ministry of Environment, Forests, and Climate Change as part of the government’s efforts to support soil health enhancement, carbon sequestration, and sustainable agriculture.

Soil Health Cards scheme was implemented by the Govt. of India in the year 2015 with an aim to provide soil health cards to famers to apply appropriate recommended integrated nutrient management practices. Under this component, biochar can be used as soil amendment in acidic and saline soils where there is a scope to improve the water holding capacity.

India BioChar and Bioresources network is a platform that is committed to significantly reduce the greenhouse gases, increase carbon sequestration and improve various farm related problems in India. This organization helps aims to innovate across the value chain of biochar and bioresources in India.

Biochar integration can enhance soil water retention as part of the Pradhan Mantri Krishi Sinchayee Yojana, which focuses on water usage efficiency. The ICAR-established Krishi Vigyan Kendras are essential to the spread of biochar-related practices. The goal of this extensive programme, which is laid out in a five-year plan, is to include biochar into agricultural practices all throughout the nation. The main goals include improving soil fertility, lowering carbon emissions through sustainable practices, and lessening the negative environmental effects of agriculture. The programme is a critical step in resolving issues with burning agricultural waste and soil deterioration. Additional information on the execution, advancement, and consequences of this programme is available in the official records furnished by the Indian government.

CONCLUSIONS

1. Policy recommendations have been outlined in this work for a pragmatic framework for policymakers, fostering a circular economy in waste management. Investing in biochar research, technology, and policy in India is a key move towards promoting a sustainable future.
2. Utilizing biochar in biomass energy systems and as a renewable carbon source for fuel generation is a way to promote clean, green energy. Its carbon-neutral qualities make it a greener fuel compared to fossil fuels, crucially mitigating climate change by capturing carbon in soil.
3. Biochar’s role in alleviating water and soil contamination emerges as a cost-effective, environmentally friendly strategy. Enhancing soil quality, fertility, and microbial activity, biochar serves as a natural soil amendment and compost. Its potential in water treatment resonates with sustainable development goals, particularly those focusing on health, sanitation, and access to clean water.
4. Furthermore, the biochar industry and related sectors generate jobs, bolsters environmental sustainability and accelerates GDP growth.

Table 1. Effect of Biochar on Different Soil Pollutants

Table 2. Quantitative Effect of Biochar on Different Soil Parameters and Crop Productivity

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Article submitted: December 7, 2023; Peer review completed: March 2, 2024; Revised version received and accepted: June 6, 2024; Published: July 31, 2024.

DOI: 10.15376/biores.19.3.Sharma