This article is part of an educational series to spread free & quality sustainability knowledge for all.

Key takeaways

• Biochar is a charcoal-like grain that’s made by burning biomass through a controlled process
• Biochar is often used as a substitute for fertilizer in the agricultural industry to enrich the soil and promote fertility
• Aside from its agricultural industries, biochar may also help mitigate the effects of climate change by way of carbon sequestration, utilized in wastewater treatments, as a renewable energy source, and used in the medical field

Introduction

The rate of climate change has dramatically increased in the last few years due to rising concentrations of greenhouse gasses. Biochar refers to fine-grained charcoal that’s made by burning organic matter through a controlled process and is deemed as one of the technologies that can help mitigate climate change and its effects.

Currently, biochar is mainly used in agriculture to improve soil fertility, but the carbon-based organic material can mean so much more for our planet. In this article, we’ll get to know biochar, its environmental impacts, how it’s produced, and what the future holds for biochar. Let’s find out if biochar can be a feasible option for a more sustainable future! 

Biochar’s history and characteristics

Although biochar is considered a new terminology, its use is based on a 2,000-year-old practice in the Amazonian basin. To boost soil fertility, the locals created patches of land called terra preta or Amazonian dark earth (ADEs). These areas are strikingly different from the surrounding nutrient-poor red or yellow soils near them. At first, it was thought that terra preta soils were created by nature, but experts have concluded that the area was man-made. It was found that they created terra preta by making charcoal and ash from biomass and sweeping it onto the land to nourish the plants.  

After years of fieldwork, scientists have found that not only are terra preta soils more fertile, but it also locks away more carbon dioxide than normal soils. This started the global research effort into the potential of climate mitigation properties of the use of charcoal to enrich agricultural soils, thus biochar is created. Biochar’s physical properties contribute directly to how it affects soil fertility. It’s highly porous with a large surface area, making it perfect as a soil mix. This characteristic means biochar reduces soil density and hardening, increases the ability of the soil to retain moisture, attracts beneficial fungi and microbes, and better preserves the nutrients in the soil.

In terms of its chemical properties, biochar can reduce the soil’s acidity due to its high pH. It also adds more nutrients to the soil and increases the availability of C, N, Ca, Mg, K, and P to plants. Biochar also helps by reducing the use of harmful pesticides and lessening their impact on the environment.   

Understanding carbon dioxide and carbon sequestration

Before we go into how biochar might help mitigate climate change, let’s find out what carbon sequestration is and its role in the race against global warming. Carbon sequestration is the process of capturing and storing atmospheric CO2. Sequestering carbon is one of the ways to keep control of global temperature as CO2 is a heat-trapping gas that contributes to climate change. 

There are many types of carbon sequestration, namely biological, geological, and technological. Biologically, carbon dioxide is absorbed by oceans, forests, grasslands, and soils. It’s captured into the soil by plants and through photosynthesis to be stored as soil organic carbon or SOC. Soil carbon pools are second only to the ocean, storing enormous amounts compared to atmospheric pools, living plants, and animals. Due to the industrial revolution and careless agricultural practices, the amount of SOC has been depleted, releasing carbon into the atmosphere, increasing levels of carbon dioxide and global temperature.

The role of biochar in carbon sequestration

As mentioned, one of the reasons biochar was created is for carbon storage and agricultural uses, making it different from normal charcoal which was only for fuel or energy sources. Due to its large surface area and porous structure, biochar is an effective carbon dioxide adsorbent. Carbon dioxide and oxygen fill the spaces inside biochar’s highly porous surface area, sequestering it from the atmosphere. Biochar’s surface chemistry also influences its CO2 adsorption. Its adsorption is increased when there’s higher alkalinity or higher pH. 

There are other ways of removing and storing carbon from the atmosphere, such as:

• Tree restoration, or restoring the vegetation by reforestation, agroforestry, and others. The issue with reforestation is it may take a longer time to see the results
• Direct air capture, which chemically captures carbon dioxide from ambient air and stores it in durable products like concrete. It’s a highly effective and straightforward measure. The downside is it’s costly and requires substantial energy-generated
• Carbon mineralization is turning carbon dioxide into a solid and keeping it off the atmosphere. This process happens naturally slowly, but scientists are currently finding ways to speed it up
• Ocean-based carbon removal by leveraging coastal plants, seaweed, or phytoplanktons. This approach is still in the development stages and needs time to find the best strategy

Although biochar is relatively new, it’s more actionable than the several options mentioned above. It is important to note that there’s also a need for further research in biochar. Particularly, defining the relationship between raw materials and production conditions with biochar’s characteristics to create the optimum version. 

Biochar production process

There are several ways of producing biochar. These are thermochemical techniques and their parameters include temperature, types of biomass, residence time, heating rate, pressure, and others. The most common techniques used to produce biochar are pyrolysis, hydrothermal carbonization, gasification, and torrefaction.

1. Pyrolysis

The pyrolysis process includes the thermal decomposition of biomass in the absence of oxygen and it’s the primary method of creating biochar. The pyrolysis temperature needed ranges between 250 to 900 degrees C. This technique uses various types of reactors, such as paddle kilns, fluidized beds, wagon reactors, and agitated sand rotating kilns. 

There are two types of pyrolysis: fast and slow. Fast pyrolysis is more time efficient, but slow pyrolysis results in better yield. 

2. Hydrothermal carbonization

Unlike hydrolysis, hydrothermal carbonization is done at lower temperatures between 180 to 250 degrees C. In this technique, the biomass is blended with water and placed in a closed reactor. The temperature is slowly increased and a series of reactions will follow. The biomass will go through condensation, polymerization, and intramolecular dehydration to produce biochar. The resulting product is sometimes referred to as hydrochar to differentiate it from other techniques. 

3. Gasification

gasification is decomposing carbonaceous materials into gaseous products, such as syngas. The raw material will be processed at high temperatures, between 650 to 900 degrees C. The major product of gasification is syngas, and the char is a by-product of the process. That’s why the yield from gasification is considerably less than other techniques.

4. Torrefaction

This technique is sometimes referred to as a mild version of pyrolysis, as it employs a similar process but at lower temperatures. In Torrefaction, biomass is heated in the absence of oxygen at a temperature of 300 degrees C using a decomposition process. There are several ways to perform torrefaction, which are: steam, wet, and oxidative torrefactions. Although torrefaction might require a longer time than pyrolysis, it yields more biochar in the end. 

Applications and uses of biochar

Biochar was created mainly to improve soil fertility, but it also has potential benefits in other fields. Here are some of the ways we can utilize biochar, from agriculture to wastewater treatment, to medical applications. 

1. Agriculture, horticulture, and forestry

As mentioned, biochar can improve soil quality and plant growth due to its porosity, surface area, and chemical structure. The substance can potentially increase water retention in soil, prevent nutrient losses from fertilizers, and provide an environment for beneficial microorganisms to thrive. 

Some examples of biochar use in agriculture, horticulture, and forestry are as follows:

• Biochar application in Oregon dryland wheat cropping system can increase crop yields and plant growth by almost 30%
• The biochar application on young trees by cacao growers in South America shortens production time by half
• Biochar may potentially replace perlite and peat moss as greenhouse growing media, due to its ability to retain nutrients better 

2. Wastewater treatments

Biochar is also a more sustainable and renewable alternative to wastewater treatment. Because of its physical and chemical properties, biochar application effectively remediates contaminated wastewater. The substance can remove unwanted toxic heavy metals and organic pollutants from wastewater, making it safe for disposal. 

On the other hand, there are several technical and economic challenges. Namely, further understanding is still needed to optimize its catalytic activity in wastewater treatments. There’s also the need for more research to assess its life cycle in wastewater treatment and ultimately how sustainable it is to use. 

3. Medical applications

The application of biochar in the medical field is newly developed, but it has shown great promise. Some of its potential applications in the medical field are:

• Immobilization of contaminants, such as removing heavy metals, pollutants, antibiotics, and harmful substances
• Particular research found that modified biochar may have the potential to recycle bio-liquid wastewater
• Because of its physical and chemical properties, biochar exhibited greater qualities than other drug carriers when it was compared to other nanocarriers. It has the potential for use in the treatment of illnesses that require regular, long-term dosing such as diabetes 

4. Renewable energy and greenhouse gas emissions

Rather than biochar itself, the byproducts of its production process can create clean energy. During its heat-intensive production, the byproducts are volatile gasses such as methane, carbon monoxide, hydrocarbons, and oxygen. All these greenhouse gases can be captured and condensed into renewable fuels, such as industrial chemicals, synthetic gas, and bio-oil. All these substances can be sold or reused for future heat treatment, creating a green cycle that reduces greenhouse gas emissions. 

5. Carbon credits 

Biochar can also be a form of carbon credit, as it’s a stable form of carbon storage. A carbon credit is an intangible product that represents the reduction, avoidance, and sequestration of atmospheric carbon dioxide or its equivalents. With carbon credits, companies can offset their emissions. The demand for biochar credits has increased, and it’s expected to grow 20-fold over the next ten years. 

6. Environmental risks

One of the challenges of biochar is environmental risks. An example of this is the sourcing of raw materials. Some believe that producing biochar may lead to environmental degradation, as its raw material is usually biomass such as wood and plants. This could potentially harm vegetation as people cut down viable trees and forests to gather more raw materials. A way to offset this issue is by collecting biomass materials from agricultural waste and forest biomass waste instead. The biomass may include corn husks, rice hulls, or timber harvesting due to land management. 

Another way that biochar could potentially harm the environment is the discharge of contaminants into the environment. There’s a possibility that when the biomass used is contaminated with harmful material, this could then seep into the soil and groundwater when biochar is used. Researchers have also found biochar could lower the variety of helpful bacteria and increase the likelihood of excessive salinity due to an increase in pH causing nutrient precipitation. 

7. Scalability

Another challenge for biochar is scalability. Producing biochar requires more biomass feedstock as its raw material. There needs to be collective efforts to source environmentally friendly materials. There’s also the issue of creating a proper facility for industrial-scale processes. It would require massive heat-treatment plants and an adequate amount of financial investments. 

8. Product consistency

Both its raw material and process could potentially alter the resulting biochar, such as its porosity. This in turn could affect its efficiency in carbon sequestration and improving soil fertility. The research found that different temperatures lead to different surface areas and pore sizes, with higher temperatures leading to better-quality biochar. The feedstock or raw materials used can also affect the quality of the product. For example, biochar from feedstocks that include animal litter could have more potassium contents than ones made purely out of wood. There needs to be a guideline on how to create biochar, with both feedstock and process in mind. With the guide, manufacturers can decide which technique they should adopt and what materials to source. 

9. Widespread adoption of biochar

Biochar is a relatively new concept that is not universally known, especially in smaller regions. This limited awareness means a smaller target market for biochar producers. To create demand, biochar should be integrated into existing industries through policies and incentives by the government. Authorities should also educate the public on the benefits of using biochar to drive more awareness of the properties of biochar.  

10. Current policies and governing bodies on biochar

These are the organizations that are currently involved in developing guidelines for the biochar industry:

• International Biochar Initiatives, which is a global platform that fosters stakeholder collaboration, good industry practices, and standards supporting biochar systems
• The European Biochar Certificate is a voluntary industry certification in Europe. Switzerland has made it obligatory for all biochar sold for agricultural use to have the EBC
• The US created the Biochar Policy Project in 2019 to support the development of a sustainable biochar and biofuel industry that works with communities, scientists, farmers, ranchers, and foresters

FAQs

Are there any regulations or standards for biochar production and use? 

Two of the most eligible regulations for biochar are the International Biochar Initiative Standards and the European Biochar Certificate Standards. The IBI Standards are used internationally, while EBC is currently used in Europe. 

Does biochar have any potential negative environmental impacts? 

Biochar’s potential negative impacts include adding greenhouse gases during production, impacts on soil amendments due to components inside biochar, and deforestation to source more biomass as raw material. That’s why governmental bodies need to create proper standards of practice as a way to offset its negative impacts.

How does biochar improve soil health and fertility? 

The use of biochar may improve soil health and fertility due to its characteristics, such as a large surface area, porous structure, and abundant surface. The lightweightness and porous structure mean biochar can be a habitat for many beneficial microorganisms in the soil that can promote soil health. 

Is biochar the same as charcoal?

No, biochar and charcoal are not the same. Biochar has a larger surface area and more porosity than charcoal. This characteristic made biochar a better choice for promoting soil health. Another difference is that biochar is made through a more controlled process than charcoal. 

How do you make biochar?

The most common way of making biochar is called pyrolysis, which is the breaking down of biomaterial using heat while excluding oxygen. Other ways include hydrothermal carbonization, gasification, torrefaction, and flash carbonization. You can also create biochar at home using a kiln or charcoal maker. 

What is an example of biochar?

An example of naturally occurring biochar is the terra preta, which is a very dark and fertile soil in the Amazon Basin. Other examples are urban waste or biomass from crop residue that is further processed through the pyrolysis technique. 

Why is biochar not widely used?

The use of biochar is still more costly compared to traditional fertilizer as it’s still not widely available. Most farmers are also still unaware or skeptical of the benefits of using biochar as a way of improving soil health.  

Conclusion

Biochar is a useful substance that was created to improve soil fertility and support carbon sequestration. There are several ways that we can produce biochar but all techniques involve heat treatment in a controlled environment. It has also shown other potential uses, such as clean energy, wastewater treatments, and medical use. More efforts are needed in terms of spreading awareness, creating sound infrastructures, and implementing guidelines in production, but biochar remains a promising solution to our planet’s exacerbated global warming. 

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