Biochar as a sustainable product for remediation of petroleum contaminated soil

Globally, petroleum has been the largest source of energy consumption compared to other energy sources such as natural gas and coal. As a result of high demand for petroleum as an energy source, contamination takes place due to maintenance, production, exploration, storage, transportation and accidental release, yielding in substantial ecological impacts. The contaminations of petroleum in the presence of soil have a negative impact on human health and the development of plant growth. According to this, there is an imperative need to investigate on environmental-friendly remediation strategies to eliminate petroleum contaminants in soil. Among different remediation technologies, bioremediation is recognized as a clean soil treatment technology due to its advantages of safety, no secondary pollution, and economy. For bioremediation of contaminated soil, biochar (BC) applications may provide new solution for polluted soil problems. BC has displayed a good potential to remedy soil contaminants owed to its wide availability of the necessary feedstock, sustainable nature, cost-effective feasibility, high efficiency, large internal surface area and desirable physicochemical surface properties. The usage of BC may include sequestration of carbon, improvement fertility of soil, remediation, as well as recycling of agricultural waste. This paper provides a review on current properties and preparation of BC and its usage as an ameliorant, amendment or sorbent for remediation of contaminated soil. Different research and published papers in this field reveal that the potential of biochar for contaminated soil remediation relies on its physical and chemical properties, which are considerably influenced by the feedstocks, pyrolysis conditions and pyrolysis technologies. The results show that the pyrolysis conditions can affect the BC structure and composition and thus its adsorption capacity. Pyrolysis temperature influences the adsorption characteristics of BC by changing the surface functionality, surface area, pore distribution and mineral concentration of BC. It is important to produce BC at optimum pyrolysis temperatures to maximize inorganic and organic contaminant adsorption. The results also indicate that BC obtained through microwave pyrolysis has better yield and quality than those produced from conventional pyrolysis.