Application of Biochar in Soil Improvement and Heavy Metals

Remediation

Yuan Zhou

1,2 a

, Yujin Long

, Li Feng

, Long Yang

1,* d

, Siyu Wang

, Min Zhang

and Yangyang Chu

China Urban Construction Design & Research Institute Co. Ltd, 100120, Beijing, China

State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua

University, 100084, Beijing, China

Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water

Pollution Source Control and Eco-remediation, Beijing Forestry University, 100083, Beijing, China

Keywords: Biomass Pyrolysis, Biochar, Soil Improvement, Heavy Metals, Soil Remediation.

Abstract: With porous structure, large surface area and rich oxygen-containing functional groups, biochar has been

concerned widely as a soil conditioner for its potential use in soil improvement and remediation. In this

paper, the characterizations of different biochar were firstly studied, then the application of biochar in

improving soil fertility and repairing heavy metal pollution were summarized. Finally, future perspectives of

biochar were also proposed. It was found that effects of biochar on soil improvement mainly included soil

properties increasement, such as pH, cation exchange capacity (CEC) and nitrogen content, plant growth

and crop yield enhancement, and microbial community improvement. In soil remediation of heavy metals

pollution, biochar prepared from different raw materials could immobilize heavy metal ions by direct

functions of electrostatic adsorption, ion exchange, complexation, precipitation, and indirect reactions with

plant uptake and soil microorganism. Through this study, it can provide a reference for the application of

biochar in soil improvement and pollution remediation, and give alternative method for resource utilization

of solid wastes.

1 INTRODUCTION

With the rapid development of industry and

agriculture, soil environment faces increasingly

serious challenges. According to the investigation

report of soil pollution by the Ministry of Ecology

and Environment, the over-standard rate of heavy

metals in cultivated land in China reached 19.4%,

and the pollution of heavy metals in soil was 82.4%

(Guo 2020, Xing 2021). Therefore, it is urgent to

carry out remediation of farmland soil to ensure the

safety of agricultural products. Biochar is regarded

as an excellent material for soil improvement and

https://orcid.org/0000-0003-2907-3804

https://orcid.org/0000-0002-3379-8798

https://orcid.org/0000-0003-3871-5856

https://orcid.org/0000-0002-2549-5658

https://orcid.org/0000-0003-1185-2893

https://orcid.org/0000-0003-1783-8961

https://orcid.org/0000-0003-1079-8960

remediation because of its strong adsorption of

heavy metals and porous structure (Xing 2021, Peng

2020). Besides, the preparation of biochar from

biomass by pyrolysis can realize resource utilization

of solid wastes and avoid environmental pollution

caused by burning of solid wastes.

At present, many studies have made explorations

on the preparation, effect and mechanism of

different biochar, as well as its application in soil

improvement and heavy metal passivation (Guo

2020, Peng 2020, Lyu 2020). However, due to

different characteristics of biochar and various soil

conditions, there is still lack of comprehensive study

of biochar from different sources and its complex

application in soil. Therefore, on the basis of

summarizing the characterization of biochar in

recent years, this paper reviewed the effect and

mechanism of biochar in improving soil fertility and

repairing heavy metals pollution, aiming to provide

a reference for biochar application and soil

remediation.

Zhou, Y., Long, Y., Feng, L., Yang, L., Wang, S., Zhang, M. and Chu, Y.

Application of Biochar in Soil Improvement and Heavy Metals Remediation.

DOI: 10.5220/0011508100003443

In Proceedings of the 4th International Conference on Biomedical Engineering and Bioinformatics (ICBEB 2022), pages 1273-1278

ISBN: 978-989-758-595-1

1273

2 DEFINITION AND

CHARACTERIZATION OF

BIOCHAR

Biochar is a kind of carbon-rich product obtained by

pyrolysis of various biomass materials, such as

agricultural and forestry wastes, livestock and

poultry manure, municipal sludge, under the

oxygen-limited atmosphere (Xing 2021). On the one

hand, biochar has the characteristics of porosity,

large specific surface area, abundant chemical

functional groups, strong ion exchange capacity, and

thus has a strong adsorption of many pollutions,

which can reduce the availability of heavy metals in

soil (Xing 2021, Peng 2020, Lyu 2020).

On the other hand, biochar contains various

components such as fixed carbon, soluble organic

matter, ash and minerals, which is beneficial for the

improvement of carbon content, soil water holding

capacity and soil structure, providing nutrients for

plant growth and microorganism activity (An

2020).This effect was similar to that of chemical

fertilizers, but biochar had the advantage not only of

providing nutrients, but also of enhancing their

efficiency and controlling their release (Kookana

2011, Ren 2017). In addition, most biochar was

alkaline, so its application into acidic soils can alter

the acid-alkaline environment, thus affecting the

ionic status of various nutrients, and ultimately

improving plant uptake of these substances (Zhang

2017). Studies also have confirmed that biochar can

change the exchangeability of soil salt by increasing

soil pH value, strengthen the plant availability of soil

nutrients, and thus ensure plant growth in good

condition (Kookana 2011, Nie 2018, Ren 2017,

Zhang 2017).

3 APPLICATION OF BIOCHAR

IN SOIL IMPROVEMENT

Biochar has been widely used in environmental

protection, especially in soil improvement and

remediation, as a cheap and simple carbon material

(Xu 2014, Baquy 2019, Vidya Vijay 2019). Studies

founde that biochar contained large amounts of

organic matters that could be released into the soil

for plant growth, so it can be added directly to the

soil as a nutrient (Beesley 2011, Gaskin 2010). At

the same time, biochar added to soils can enhance

soil fertility by altering the physical, chemical

property, and structure of the soil (Aller 2016).

The greatest advantage of biochar lied in its wide

range of materials, such as agricultural and forestry

wastes (Kloss 2012), from which biomass with

certain organic components can be used as biochar

raw materials, including straw, twigs and leaves, as

well as sewage sludge from wastewater treatment

(Zhang 2016). Because there were many kinds of

raw materials of biochar and most of the wastes can

be used to produce the product, resource recovery

became another great advantage of biochar. At

present, crop straw was one of the major problems in

the disposal of agricultural wastes in China, so it

was an effective way to make the crop straw into

biochar and use it for soil conditioner or pollution

remediation. However, the physical and chemical

properties and function of biochar made from

specific raw material were not always in line with

the actual needs, therefore, in the process of

developing biochar, it was necessary to improve the

quality of biochar by means of modification, so that

it can played its role efficiently.

Due to its porous structure, large surface area,

high carbon and mineral contents, and rich

functional groups, the effects of biochar on soil

improvement mainly include enhancement of soil

physical and chemical properties, such as pH, cation

exchange capacity (CEC) and nitrogen content,

increasement of plant growth and crop yields, and

improvement of microbial community, as shown in

Figure 1.

Figure 1: Effects of biochar on soil improvement.

3.1 Effect of Biochar on Enhance

Physical and Chemical Properties

Biochar can directly provide nutrients such as

nitrogen and carbon, which mainly depends on the

raw materials for preparation. Meanwhile, properties

of biochar, such as pH, CEC, porosity and specific

surface area, can affect its function in soil. Studies

found that biochar prepared by pyrolysis at high

temperature was more efficient and feasible for

reducing soil acidity and promoting nutrients

retention (Guo 2020, Peng 2020, An 2020). The

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functional groups on the surface of biochar,

especially oxygen-containing functional groups (e.g.

-COOH, -OH), made outstanding contributions to

soil CEC improvement and contaminants adsorption.

It was found that the negative charge functional

groups of biochar could increase soil CEC from 88.4

mmol/kg to 211.3 mmol/kg, which was important

for soil fertility (An 2020).

3.2 Effect of Biochar on Improve

Microbial Community

The porous structure on the surface of biochar can

provide favorable conditions for the growth of soil

microorganisms. At the same time, biochar can

stimulate the metabolic activities of microorganisms

and optimize the microbial community structure by

increasing soil aeration, water holding capacity and

providing nutrients for microorganisms (Peng 2020).

Nie found that the number of soil microorganisms

(i.e. rhizosphere bacteria, ammoniated bacteria,

actinomycetes, fungi, nitrogen-fixing and

denitrifying bacteria) increased with the increase of

biochar proportion in spinach soil (Nie 2018). It’s

worth noting that the influence of biochar on soil

microorganisms was very complex and different

microorganisms may need different specific growth

environments.

3.3 Effect of Biochar on Increase Plant

and Crop Yields

Many researchers demonstrated that biochar can

strengthen the long-term effect of soil fertility,

release nutrients slowly into the soil, promote plant

growth and crop yield by participating in nitrogen

transformation (Peng 2020, An 2020). It was found

that applying eucalyptus biochar in sandy soil could

increase corn yield by more than one time. The

results of pot experiment showed that pine sawdust

biochar could increase sorghum yield by 18%-22%

(Peng 2020). The promotion of biochar on plant

growth and crop yield was mainly achieved

indirectly by improving soil fertility and related

physical and chemical properties, such as soil pH,

CEC, nutrient content and availability (Guo 2020,

An 2020). The improvement effect was also related

to the physical structure and chemical composition

of soil itself, characteristics of biochar, the adding

form, action period and type of crops, and so on (Nie

2018).

4 APPLICATION OF BIOCHAR

IN SOIL REMEDIATION OF

HEAVY METALS POLLUTION

There are a variety of remediation techniques for

heavy metal pollution in soils, it can be mainly

devided into two methods: in situ remediation and

ectopic remediation from the perspective of

remediation methods (Derakhshan 2017). According

to the types of adopted technologies, it can be

divided into physical remediation, chemical

remediation and bioecological methods. Physiccal

and chemical methods generally used leaching,

adsorption, transformation, transfer and other

methods to achieve the removal of heavy metal

pollution components, or to make it more stable in

the soil, which enabling the heavy metals couldn’t

be transferred with water, while it was also difficult

for organisms to absorb and use (Ko 2006). The bio-

ecological method was more concerned with

avoiding the risk of secondary pollution and

reducing the cost of treatment, and was based on

animals, plants and microorganisms, building an

ecosystem of contaminated soils and enhancing their

removal or fixation of heavy metals components

(Babu 2013).

How to select appropriate treatment technology

to remediate heavy metal pollution of soil in

practical engineering application, factors such as

technology maturity, economic cost input, treatment

efficiency, risk of secondary pollution and duration

period of effect need to be considered. Therefore, it

was urgent to explore a technically reliable and

economically feasible solution. Biochar can not only

recycle many kinds of biomass wastes, but also be

used as a kind of adsorption material for heavy

metals.

Jiang conducted field experiments on lead (Pb)

and cadmium (Cd) contaminated farmland near the

mine, and the remediation of Pb and Cd pollution by

litchi biochar was investigated. It was found that

litchi biochar could significantly improve soil

properties, such as pH, organic matter and CEC, it

was also found to reduce heavy metals accumulation

in crop plants (Jiang 2020). Luo conducted a

sequential batch experiment to study the effects of

soil samples contaminated with cadmium and

arsenic (As) in corncob biochar (COB) (Luo 2020).

It was found that the COB had good fixation effect

on the two heavy metal pollutants, they were

transformed into forms that were difficult to migrate

or utilize due to biochar’s physical and chemical

characteristics such as specific surface area, total

Application of Biochar in Soil Improvement and Heavy Metals Remediation

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pore volume, average pore size and C/O ratio.

Biochar also provided nutrients such as carbon and

nitrogen for soil and soil microbial communities.

4.1 Effect of Biochar on Soil

Remediation of Heavy Metals

Pollution

Biochar also had good properties for remediation of

heavy metal contamination in soils, stabilizing heavy

metal ions in soils and reducing their bioavailability

(Awasthi 2016, Huang 2017, Meng 2018, Wang

2019). A large number of studies demonstrated that

biochar made from different feedstocks (e.g.

municipal sludge, hardwood, straw) had excellent

adsorption effects on heavy metals and reduced the

toxicity of heavy metals in soil and plant (Gascó

2019), as shown in Table 1. Wang conducted field

experiments in farmland polluted by lead and

cadmium, and found that litchi biochar significantly

improved the soil properties, such as pH, organic

matter and CEC, and alleviated the accumulation of

lead and cadmium in crops (Gascó 2019). The

adsorption efficiency of biochar was determined by

its pore structure, specific surface area and

functional groups, thus affecting its adsorption and

fixation of heavy metals (Chen 2020, Gascó 2019,

Wang 2021).

Table 1: Effects of different biochar on soil remediation of heavy metals pollution.

Feedstock Pyrolysis Temp. Remediation effect Ref.

Sewage sludge 500

C increased pH and decreased

available heavy metal in soil

(Xing 2021, Chen

2020)

Livestock manure 450

C decreased heavy metal

content in Brassica napus

(Guo 2020,

Gascó 2019)

Rice husks 450

C reduced the toxicity of heavy

metals in soil and increased

plant productivity

(Guo 2020, Xing

2021)

Hardwood 600

C Ni, Zn contents in soil

declined by 83%-98% in

three years

(An 2020)

Straw 500

C decreased Cd content in soil (Guo 2020, Peng

2020)

Bagasse 450

C Cd decreased by 76%, Pb

decreased by 49.1% in plant

(Nie 2018)

Maize straw 400

C available Cd in soil

decreased b

21%-56%

(Xing 2021)

Litchi 500-550

C improve soil properties,

reduce Pb and Cd

accumulation

(Jiang 2020)

4.2 Mechanism of Biochar in Soil

Remediation

At present, various studies have made efforts for the

explanation of biochar adsorption of heavy metals

and the mechanism could be mainly divided into the

following aspects (Nie 2018, Chen 2020, Gascó

2019, Wang 2021): (i) electrostatic adsorption:

biochar was generally electronegative, so it can

adsorb cations when adding to soil; (ii)

complexation: the metal ions can be fixed by

forming complexation with functional groups on the

surface of biochar; (iii) precipitation: mineral

components (such as carbonate and phosphate) can

transform heavy metals into more stable forms by

coprecipitation and reduced their pollution risks; (iv)

ion exchange: by increasing soil CEC, biochar can

improve the ion exchange and adsorption of heavy

metals. Oxygen-containing functional groups also

played an active role in ion exchange of heavy

metals; (v) indirect effect: biochar can also

immobilize heavy metals in soil through the

complex, simultaneous and interact functions among

soil, animals, plants and microorganisms (Nie 2018,

Antonangelo 2021). Thus, we can not only use

biochar to remove and fix the metal pollutants in the

soil, but also can select different kinds of raw

materials according to the different kinds of metal

pollution, to ensure optimal repair effect.

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5 CONCLUSION AND

PROSPECTS

Biochar has promising application in soil

improvement and remediation for its comprehensive

effects on soil fertility, microbial activity, plant and

crop growth, and heavy metals immobilization.

Although biochar can improve soil fertility and

repair polluted soil, the mechanisms of biochar on

soil remediation of heavy metal pollution and other

emerging pollutants (Antonangelo 2021), especially

the interact role of microorganisms, are still unclear.

The different performances of biochar in different

types and properties of soil, long-term stability and

toxicity of biochar, as well as field application, all

need in-depth researches in the future.

ACKNOWLEDGEMENTS

This work was supported by the the Science

Foundation of China Urban Construction Design &

Research Institute Co., Ltd. (Y09S21009) and the

Science and Technology Planning Project of

Ministry of Housing and Urban-Rural Development

of the People’s Republic of China (No. 2019-K-142)

for financial support.

REFERENCES

Aller, M.F., (2016). Biochar properties: Transport, fate,

and impact. J. Critical Reviews in Environmental

Control 46, 1183-1296.

An X, Wu Z, Yu J, et al. (2020). Co-pyrolysis of biomass,

bentonite, and nutrients as a new strategy for the

synthesis of improved biochar-based slow-release

fertilizers. J. ACS Sustainable Chemistry &

Engineering, 3181-3190.

Antonangelo J, Sun X, Zhang H. (2021). The roles of co-

composted biochar (COMBI) in improving soil

quality, crop productivity, and toxic metal

amelioration. J. Journal of Environmental

Management, 277, 111443.

Awasthi, M.K., Wang, Q., Huang, H., Li, R., Shen, F.,

Lahori, A.H., Wang, P., Guo, D., Guo, Z., Jiang, S.,

(2016). Effect of biochar amendment on greenhouse

gas emission and bio-availability of heavy metals

during sewage sludge co-composting. J. Journal of

Cleaner Production 135, 829-835.

Babu, A.G., Kim, J.D., Oh, B.T., (2013). Enhancement of

heavy metal phytoremediation by Alnusfirma with

endophytic Bacillus thuringiensis GDB-1. J. Journal of

Hazardous Materials 250-251, 477-483.

Baquy, M.A.-A., Jiang, J., Xu, R., (2019). Biochars

derived from crop straws increased the availability of

applied phosphorus fertilizer for maize in Ultisol and

Oxisol. J. Environmental Science and Pollution

Research 27, 5511-5522.

Beesley, L., Moreno-Jimenez, E., Gomez-Eyles, J.L.,

Harris, E., Robinson, B., Sizmur, T., (2011). A review

of biochars' potential role in the remediation,

revegetation and restoration of contaminated soils. J.

Environmental pollution 159, 3269-3282.

Chen Y, Wang R, Duan X, et al. (2020). Production,

properties and catalytic applications of sludge derived

biochar for environmental remediation. J. Water

Research, 187, 116390.

Derakhshan Nejad, Z., Jung, M.C., Kim, K.H., (2017).

Remediation of soils contaminated with heavy metals

with an emphasis on immobilization technology. J.

Environmental Geochemistry and Health 40, 927-953.

Gascó G, Alvarez M, Paz-Ferreiro J, et al. (2019).

Combining phytoextraction by Brassica napus and

biochar amendment for remediation of a mining soil in

Riotinto (Spain). J. Chemosphere, 231, 562-570.

Gaskin, J.W., Speir, R.A., Harris, K., Das, K.C., Fisher,

D.S., (2010). Effect of Peanut Hull and Pine Chip

Biochar on Soil Nutrients, Corn Nutrient Status, and

Yield. J. Agronomy Journal 102, 623-633.

Guo X, Liu H, Zhang J. (2020). The role of biochar in

organic waste composting and soil improvement: a

review. J. Waste Management, 102, 884-899.

Huang, H., Yang, T., Lai, F., Wu, G., (2017). Co-pyrolysis

of sewage sludge and sawdust/rice straw for the

production of biochar. J. Journal of Analytical &

Applied Pyrolysis 125, 61-68.

Jiang, S., Liu, J., Wu, J., et al., (2020). Assessing biochar

application to immobilize Cd and Pb in a

contaminated soil: a field experiment under a

cucumber-sweet potato-rape rotation. J.

Environmental geochemistry and health,

https://doi.org/10.1007/s10653-10020-00564-10659.

Kloss, S., Zehetner, F., Dellantonio, A., Hamid, R., Ottner,

F., Liedtke, V., Schwanninger, M., Gerzabek, M.H.,

Soja, G., (2012). Characterization of Slow Pyrolysis

Biochars: Effects of Feedstocks and Pyrolysis

Temperature on Biochar Properties. J. Journal of

Environmental Quality 41, 990-1000.

Ko, I., Lee, C., Lee, K., Lee, S., Kim, K., (2006).

Remediation of soil contaminated with arsenic, zinc,

and nickel by pilot-scale soil washing. J.

Environmental Progress 25, 39-48.

Kookana, R.S., Sarmah, A.K., Zwieten, L.V., Krull, E.V.,

Singh, B., (2011). Biochar Application to Soil:

Agronomic and Environmental Benefits and

Unintended Consequences. J. Advances in Agronomy

112, 103-143.

Luo, M., Lin, H., He, Y., et al. (2020). The influence of

corncob-based biochar on remediation of arsenic and

cadmium in yellow soil and cinnamon soil. J. Science

of the Total Environment,

https://doi.org/10.1016/j.scitotenv.2020.137014.

Application of Biochar in Soil Improvement and Heavy Metals Remediation

1277

Lyu H, Tang J, Cui M, et al. (2020). Biochar/iron (BC/Fe)

composites for soil and groundwater remediation:

synthesis, applications, and mechanisms. J.

Chemosphere, 246, 125609.

Meng, J., Tao, M., Wang, L., Liu, X., Xu, J., (2018).

Changes in heavy metal bioavailability and speciation

from a Pb-Zn mining soil amended with biochars from

co-pyrolysis of rice straw and swine manure. J. Sci.

Total. Environ. 633, 300-307.

Nie C, Yang X, Niazi N, et al. (2018). Impact of sugarcane

bagasse-derived biochar on heavy metal availability

and microbial activity: a field study. J. Chemosphere,

200, 274-282.

Ren, J., Wang, F., Zhai, Y., Zhu, Y., Peng, C., Wang, T.,

Li, C., Zeng, G., (2017). Effect of sewage sludge

hydrochar on soil properties and Cd immobilization in

a contaminated soil. J. Chemosphere 189, 627-633.

Peng X, Deng Y, Liu L, et al. (2020). The addition of

biochar as a fertilizer supplement for the attenuation of

potentially toxic elements in phosphogypsum-

amended soil. J. Journal of Cleaner Production, 277,

124052.

Vidya Vijay, M., Sudarsan, J.S., Nithiyanantham, S.,

(2019). Sustainability of constructed wetlands using

biochar as effective absorbent for treating

wastewaters. J. International Journal of Energy and

Water Resources 3, 153-164.

Wang J, Shi L, Zhai L, et al. (2021). Analysis of the long-

term effectiveness of biochar immobilization

remediation on heavy metal contaminated soil and the

potential environmental factors weakening the

remediation effect: a review. J. Ecotoxicology and

Environmental Safety, 207, 111261.

Wang, Z., Xie, L., Liu, K., Wang, J., Zhu, H., Song, Q.,

Shu, X., (2019). Co-pyrolysis of sewage sludge and

cotton stalks. J. Waste Management 89, 430-438.

Xu, H., Wang, X., Li, H., Yao, H., Su, J., Zhu, Y., (2014).

Biochar Impacts Soil Microbial Community

Composition and Nitrogen Cycling in an Acidic Soil

Planted with Rape. J. Environmental Science &

Technology 48, 9391-9399.

Xing J, Xu G, Li G. (2021). Comparison of pyrolysis

process, various fractions and potential soil

applications between sewage sludge-based biochars

and lignocellulose-based biochars. J. Ecotoxicology

and Environmental Safety, 208, 111756.

Zhang, Y., Chen, T., Liao, Y., Reid, B.J., Chi, H., Hou, Y.,

Cai, C., (2016). Modest amendment of sewage sludge

biochar to reduce the accumulation of cadmium into

rice (Oryza sativa L.): A field study. Environmental

pollution 216, 819-825.

Zhang, G., Guo, X., Zhu, Y., Han, Z., He, Q., Zhang, F.,

(2017). Effect of biochar on the presence of nutrients

and ryegrass growth in the soil from an abandoned

indigenous coking site: The potential role of biochar in

the revegetation of contaminated site. J. Sci. Total

Environ. 601-602, 469-477.

ICBEB 2022 - The International Conference on Biomedical Engineering and Bioinformatics

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