The application of biochar can significantly improve the health and quality of soil, meaning it can play a crucial part in mitigating the environmental challenges of climate change, global warming, sustainable farming, pollution and resulting habitat destruction, disruption of the natural balance of ecosystems, and ecological imbalance.
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How is biochar produced?
Biochar is produced through the thermochemical process of pyrolysis, whereby biomass materials decompose as a result of exposure to very high temperatures, typically between 300⁰C - 1000⁰C.
Biomass used in the creation of biochar may utilize the following feedstocks: wood and paper-based (woodchips, pinewood, and wood bark), manure (human, dairy, and poultry), and crop waste (rice husk, sugar beet tailing, plant residue, empty fruit bunches) (Oni et al, 2019). Using waste as a feedstock is beneficial for the environment as it negates the need to use up other resources in the manufacturing process.
The resulting biochar comprises carbon and ash predominantly but also contains minerals such as potassium, nitrogen, and calcium, and some metals such as nickel, chromium, copper, manganese, and lead. It has differing properties depending on the feedstock used in its production and the temperature at which it was heated.
It is primarily the physical structure of biochar that determines its soil amendment and remediation capabilities. Its macropores enable air and water distribution, soil bearing capacity, healthy root movement, and soil aggregate stability. Its mesopores facilitate solid and liquid absorption into the soil, and its micropores provide surface area and further absorption rates.
How can biochar remediate soil?
Soil contains bioremediating microorganisms which endeavor to break down pollutants, and this process is accelerated when biochar is applied because the sorption ability of biochar is much greater than naturally occurring organic matter in the soil.
This is beneficial for the environment because it can negate the harm caused by toxic pesticides, herbicides, and other synthetic means of pest and disease control. It can prevent toxifying chemicals from running off the land into aquatic ecosystems. Pollution entering the hydrological cycle leads to pollution on land-based ecosystems and in the air, so the positive implications of biochar soil application are far-reaching.
Biochar is characterized by resistance to degradation, negative charges, and large internal surface areas. These properties allow biochar to remove contaminants by absorbing them into its own surface, and consuming them, thereby reducing the amount of pollution that can be absorbed by the soil itself.
It can remediate acid soils by adsorbing harmful elements such as aluminum and manganese, and also remediate soils that have been contaminated with arsenic, copper, lead, nickel, and cadmium through adsorption.
How can biochar promote sustainable farming?
As well as removing pollutants from soil, which makes crop growing conditions more favorable, biochar has the ability to alter soil properties to more optimal conditions for agriculture, which is extremely desirable for sustainable farming initiatives.
Biochar accelerates the manifestation of microorganisms such as mycorrhizae, which help vital nutrients such as nitrogen and phosphorous reach the roots of plants more easily due to increased surface area around the root. This is advantageous for the plant, as it means it can access water and nutrients that it may not usually be able to reach.
Biochar can increase the pH of the soil, which can enable some soils to achieve the pH level for optimal growing conditions, which is around pH 6/7. It needs to be applied sensitively according to both its own pH value and that of the soil, as not all soils need their pH level raised.
Because the properties of biochar allow the soil to absorb nutrients, water, and air more easily, this is advantageous for agriculture as it can lead to reduced nutrient leaching and improved nutrient retention, which in turn leads to higher crop yields.
How can biochar affect climate change?
When biochar is present in soil it can improve the porosity of the soil, enabling it to retain moisture more effectively, and thus become more robust when faced with drought and unpredictable precipitation.
Greater liquid retention is a characteristic that can also reduce the potential for soil erosion, and when combined with higher nutrient retention and enhanced mycorrhizae, these properties of biochar can give soil greater aggregate stability. In turn, this can improve the bearing capacity of the soil, and help soil withstand the effects of extreme temperatures and weather events, such as heavy storms.
Biochar can slow the effects of climate change by reducing the number of emissions from greenhouse gases. It improves carbon sequestration in soil, thus reducing the amount of carbon dioxide released into the atmosphere, and it reduces nitrous oxide emissions in acidic soil, especially when the biochar is created using poultry manure and green waste.
Methane emissions can be reduced when biochar is applied to the soil by increasing the methanotroph pmoA gene and decreasing methanogenic archaea, which are both necessary in methane reduction. When certain types of biochar have been added to cattle feed, it has also been found to reduce the amount of methane produced by ruminants, who are one of the largest emitters of methane.
Summary
Biochar has enormous potential to substantially benefit the environment through its soil amendment and remediation capabilities, its ability to improve soil quality. It can increase crop yield by creating optimum soil conditions for water and nutrient uptake, aiding the plight of global sustainable farming globally.
Its ability to reduce greenhouse gas emissions, while not being enough on its own, is still significant enough to make a real difference.
Sources:
- Oni B.A., Oziegbe O., Olawole O.O. (2019) Significance of biochar application to the environment and economy. Annals of Agricultural Sciences, Volume 64, Issue 2, December 2019, Pages 222-236. https://doi.org/10.1016/j.aoas.2019.12.006
- Huang, Y., Wang, C., Lin, C., Zhang, Y., Chen X., Tang L., Liu C., Chen Q., Onwuka M.I., Song T. (2019) Methane and Nitrous Oxide Flux after Biochar Application in Subtropical Acidic Paddy Soils under Tobacco-Rice Rotation. Scientific Reports volume 9, Article number 17277 (2019). https://doi.org/10.1038/s41598-019-53044-1
- Man K., Chow, K.L., Man Y.B., Mo W.Y., Wong M.H. (2020) Use of biochar as feed supplements for animal farming. Critical Reviews in Environmental Science and Technology, Volume 51, 2021, Issue 2, Pages 187-217. https://doi.org/10.1080/10643389.2020.1721980
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