# Duality of Biochar and Organic Manure Co-Compositing on Soil Heavy Metals and Enzymes Activity
## 1 Introduction  
There is an increasing concern about human and environmental health effects resulting from the manufacturing, use, and dumping of several organic and inorganic compounds that enhance agriculture, industry, and domestic detergents. The use of fertilizers and pesticides is necessary in agriculture to meet the increasing need for food production worldwide, which ultimately contributes to the increased entry of pollutants into the environment. Therefore, an important environmental concern of the 21 st century is preserving the integrity of crops, soil, and water resources. A high rate of food production necessitates better plant and soil management techniques that reduce reliance on the expensive agrochemicals used in the production processes. It will be beneficial for farmers with limited resources to increase crop output and fruit quality at a reasonable cost when using animal manure and other soil amendments in agricultural production systems as alternatives to the overpriced synthetic elemental fertilizers [1, 2]. Heavy metals, synthetic pesticides, inorganic fertilizers, and other pollutants are the cause of environmental contamination, which has become a national concern. The discharge of environmental pollutants from inadequate soil management practice, the disposal of industrial waste into rivers and streams, mining operations, toxic metal contaminants, the use of N and P fertilizers (that cause the eutrophication of natural waterresources), and the disposal of pharmaceuticals and their metabolites, antibiotics, and hormones that contaminate soil and natural water resources, all require imminent and emerging solutions. The biomass conversions of wood, manure, and plant leaves are operated under high temperatures to produce biochar, an inexpensive organic adsorbent product. The conversion of biomass to biochar lowers the atmospheric concentration of CO\({}_{2}\) and produces sustainable energy in the form of synthetic gas and bio-oil. Biochar's high surface area, functional groups, and hygroscopic and porous structure (Figure 1) hold water molecules and water-soluble nutrients, making this material a home for many beneficial microorganisms. Biochar production for agricultural applications is a viable technique for carbon sequestration and improving soil productivity, as it improves nutrient availability to growing plants, soil physical, chemical and biological qualities, and environmental quality [3]. When added to soil, biochar acts as a long-term carbon storage solution by improving soil characteristics [4]. Biochar decreases soil acidity via ion exchange, which reduces nutrient leaching from agricultural soils. Biochar's large surface area absorbs contaminants from soil while also benefiting soil biota [5; 6] by hosting and sheltering algae, protozoa, fungi, and bacteria. According to the literature review, when compared to other soil amendments, the enhanced structure, nutrient usage efficacy, aeration, permeability, and water-holding capacity of soil containing biochar is all likely to increase crop yield [7]. Biochar can restore degraded soil, and play a significant role in preventing water molecules and nutrient minerals in the upper soil surface from evaporating following rainfall or rainfall and irrigation events, as it contains numerous tiny tunnels that retain water and minerals in the soil layers, increasing water availability for plants. This boosts crop cost-savings and decreases the need for inorganic elemental fertilizers. The minerals (C, H, N, S, O, etc.) that make up biomolecules like cellulose, hemicelluloses, and lignin give biochar its characteristics. Biochar's application to soil increases soil fertility by improving nutrient retention and uptake by developing plants. Additionally, biochar adsorbs nutrients on its surfaces, reducing the amounts of nutrients (NO\({}_{3}-\)N, NH\({}_{4}+\)-N, and PO\({}_{4}\)\({}^{3-}-\)P) that leach after fertilizer application [8].