**Abstract**

In the last decades increased global environmental concerns to water and soils pollution. The main concerns are related to the contamination of the ecosystem, food security, and human health since many of the contaminants present in soil and water (residues of pesticides and antibiotics, genes of resistance to antibiotics, and heavy metals) are absorbed by plants and enter the food chain. Remediation of the contaminated water and soil to ensure sustainable water supply and food production is urgently needed. The use of biochar can have a positive effect on this remediation process. There are several studies that demonstrate the biochar's ability to block/reduce the contaminating effect of pesticides, antibiotic residues, antibiotic resistance genes, and heavy metals. The objective of this chapter is to carry out a comprehensive review of the effect of using biochar on the availability/transmission of these contaminants to the soil and food supply chain.

**Keywords:** antibiotics, biochar, environment, food, human health, heavy metals

#### **1. Introduction**

Currently, water and soil pollution is a global concern due to its negative effect on ecological safety and health risks [1, 2]. Soil contamination through inorganic and organic contaminants is a well-known problem [1, 3]. Contamination of agricultural soils is due to the long-term application of pesticides, fertilizers, plastic film, wastewater irrigation, sewage application, and other activities [4]. Organic contaminants, such as organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), phthalate esters (PAEs), and polycyclic aromatic hydrocarbons (PAHs), are characterized by high toxicity, persistence, and bioaccumulation in the environment [5]. Soil is a major reservoir for a variety of pollutants and is a secondary emission source of contaminants to groundwater and surface water [4].

In the last years has been increasing interest amongst the scientific community in the development of technologies to remediate contaminated sites [6]. Soil remediation techniques are categorized as physical, chemical, or biological, based on the specific nature of the remediation mechanism employed [1]. Physical and chemical methods are costly, inefficient, and result in further pollution, especially in the case of chemical methods [1]. Adsorption is one of the most efficient biological methods for removing contaminants from water and wastewater [7]. The mechanism and capacity of adsorption are influenced by many factors: physicochemical properties of the adsorbent; type and nature of the adsorbate; the related affinity of the adsorbate for the adsorbent; and process conditions.

Therefore, the use of biological materials derived from organic material is considered an eco-friendly and sustainable approach [8]. The application of proper amendments such as biochar is a known efficacious and environmentally friendly method for reducing the availability and mobility of potentially toxic elements in contaminated soil via *in situ* immobilization [3, 9]. Biochar is a sensible and robust material for the enhancement of soil fertility and management of contaminated soils for sustainable agriculture and mitigation of climate change [1, 10]. Is a carbon-rich material that can be prepared from various organic waste feedstocks [1], like from various biomass, both woody (primarily residues from forestry and trees) and non-woody (agricultural crops and residues, animal waste, urban and industrial solid waste). The term biochar is used to designate carbonaceous materials, produced from biological sources, due to the incomplete combustion of fossil fuels and vegetation and constitute an important carbon sink due to their stability to microbial and chemical degradation [11]. Thus, biochar is a porous carbonaceous material largely containing carbon jointly with the inorganic components of the biomass utilized, such as alkali and alkaline earth metals.

For these organic wastes to be transformed into biochar, they are subjected to pyrolysis, gasification, or hydrothermal carbonization. These are the most common methods for biochar preparation [12, 13]. Biochar properties are highly dependent on the temperature (300–1000°C), time of pyrolysis, final acidity, and feedstock from which the biochar is made [14]. According to the residues types, biochar can present diverse physiochemical properties biochar's content of volatile matter, dissolved organic matter, ash, and carbon [1, 15]. Additionally, the pyrolysis condition may influence the physicochemical and chemical properties of biochar [16, 17]. However, there are characteristics that are always present, such as rich carbon content, high cation exchange capacity, large surface area, and stability structure [1, 13]. These characteristics, namely specific surface area, porosity, and cation exchange capacity, are responsible for the high adsorption capacity that gives it the ability to remove organic pollutants and heavy metals [13]. Also, the solution pH has a great influence on the adsorption capacity of biochars [16]. Moreover, biochar will improve the soil's biological activities, nutrient retention, water-retention capacity, an increase of pH value, and amount of soil organic matter.

In last year's, the utilization of biochar has been widely used in environmental applications such as soil remediation and water remediation. According to Krasucka et al. [7] the use of "green", low cost, or sustainable biochar for contaminant sorption yields economic and environmental benefits, furthermore, agrees with global trends in generating a circular economy and sustainable development. Biochar has been a common material for environmental contamination due to the widespread availability of its raw materials, its simple preparation process, low cost, and strong adsorption performance [18].

The application of biochar can improve soils that pose abiotic stresses because of the presence of heavy metals, salt, or organic contaminants [1]. Biochars produced from pyrolysis of biomass materials have received worldwide attention due to their broad usage in contaminant adsorption, soil remediation, and wastewater treatment [19]. Biochar application can reduce the bioavailability and mobility of soil pollutants including pesticides, antibiotics, heavy metal, and antibiotic resistance genes in soil microorganisms [20].
