Basics of Biochar: Understanding Its Definition and Diversity

This article comprehensively explores biochar, highlighting its diverse forms, from its production via pyrolysis of various organic materials to its multifaceted applications in enhancing soil health, water retention, and environmental remediation, underscoring its role as a versatile and sustainable solution in agriculture and ecological stewardship.

Carol Wong
Sam Dunlap
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In the realm of sustainable environmental solutions, biochar emerges as a multifaceted player. This article delves into the intriguing world of biochar, unraveling its definition and the diverse array of its forms. By understanding its core concept and the variety it offers, we can appreciate biochar's role in modern environmental and agricultural practices.

What is Biochar?

Biochar is often mistaken as a singular product, but in reality, it's a spectrum of materials with varying characteristics. At its essence, biochar is a carbon-rich product obtained from the pyrolysis of organic biomass in an oxygen-limited environment. This process, a controlled and sustainable method, transforms various organic materials into a stable form of carbon. The unique aspect of biochar is its longevity in the environment, often remaining intact for centuries, thereby acting as a significant carbon sink.

Exploring the Spectrum of Biochar Varieties

The world of biochar is intricate, influenced by a range of factors from feedstock to pyrolysis conditions. Here we delve into these elements in greater detail:

Feedstock Variability

The source material for biochar production, known as feedstock, is incredibly diverse. Commonly used materials include:

  • Woody Biomass: Such as branches, wood chips, and sawdust, often resulting in biochar with high carbon content and stability.
  • Agricultural Residues: Including corn stover, rice husks, and straw. These feedstocks can produce biochars with varying nutrient profiles, useful in soil amendment.
  • Specialized Organic Wastes: Like nutshells, husks, or manure, these feedstocks can create biochars with unique properties, such as high nutrient levels or specific absorption capabilities.

Pyrolysis Process

The method of creating biochar significantly affects its properties. Key factors include:

  • Temperature: Ranging typically between 300°C to 700°C, higher temperatures often lead to biochar with increased porosity and surface area.
  • Heating Rate and Duration: Fast heating rates can produce biochar with different pore structures compared to slow pyrolysis. Duration also plays a role in determining the final chemical and physical structure of the biochar.
  • Atmospheric Conditions: The presence or absence of oxygen, along with other gases in the pyrolysis chamber, can alter the chemical composition of the biochar.

Intended Use and Application

The final use of biochar guides its desired characteristics. Notable applications include:

  • Soil Amendment: Biochar used in soil often aims to improve water retention, nutrient availability, and microbial activity.
  • Water Filtration: Certain biochars are effective in adsorbing pollutants and heavy metals from water, making them suitable for filtration systems.
  • Carbon Sequestration: Biochars with high stability and carbon content are ideal for long-term carbon storage, aiding in climate change mitigation efforts.

The Versatility of Biochar

The adaptability and multifunctionality of biochar are underscored by its diverse applications across various fields. Let's delve deeper into its role in agriculture and environmental remediation, highlighting how its unique properties benefit these sectors.

In Agriculture: Enriching Soils and Supporting Plant Growth

  1. Soil Health Improvement: Biochar's porous structure improves soil aeration, vital for root respiration and microbial activity. This enhanced aeration also prevents soil compaction, promoting better root growth and development.
  2. Water Retention and Drought Resistance: One of the most significant benefits of biochar in agriculture is its ability to retain water. This characteristic is particularly valuable in arid regions or during dry seasons, helping plants withstand drought conditions.
  3. Nutrient Retention and Efficiency: Biochar can adsorb and retain nutrients, making them more available to plants over time. This slow release of nutrients not only improves plant growth but also reduces the leaching of fertilizers into waterways, thus minimizing environmental pollution.
  4. pH Balance and Toxicity Reduction: Certain biochars can neutralize soil pH, particularly beneficial for acidic soils. Moreover, biochar can bind with harmful substances like heavy metals, reducing their bioavailability and mitigating soil toxicity.
  5. Enhancing Soil Fertility with Biochar-Compost Mixtures: Mixing biochar with compost creates a synergistic effect, enhancing soil fertility beyond what either amendment could achieve alone. This mix provides a habitat for beneficial microbes, which play a crucial role in nutrient cycling and organic matter decomposition.

In Environmental Remediation: Purifying Water and Soil

  1. Contaminant Adsorption: The high surface area and porosity of biochar make it an excellent medium for adsorbing pollutants from water and soil. This includes heavy metals, pesticides, and other organic pollutants.
  2. Water Filtration Systems: Biochar can be incorporated into water filtration systems to remove contaminants and improve water quality. Its effectiveness in adsorbing toxins and heavy metals has been recognized in both small-scale and larger municipal water treatment applications.
  3. Soil Remediation: In contaminated lands, such as those affected by industrial waste, biochar can play a pivotal role in immobilizing contaminants, thereby reducing their mobility and bioavailability. This application is particularly relevant in rehabilitating sites with historical industrial pollution.
  4. Green Infrastructure Integration: Biochar is increasingly being integrated into green infrastructure, such as bioretention cells and rain gardens. These applications leverage biochar's water retention and pollutant adsorption capacities, enhancing the effectiveness of these systems in managing urban stormwater.


The exploration into the world of biochar reveals a material of remarkable diversity and adaptability. Understanding the spectrum of biochar varieties is pivotal for harnessing its full potential. As we continue to innovate and apply biochar in various environmental and agricultural contexts, this knowledge becomes a cornerstone in our pursuit of sustainable solutions. Biochar is not a mere product; it is a testament to the ingenuity in environmental stewardship, symbolizing a harmonious intersection between human ingenuity and nature's resilience.

Exploring the Basics of Biochar: A Presentation Overview


Thank you all for joining today. In our "Back to the Basics" series, we've had numerous discussions and questions about biochar at the center, so we thought it would be a great opportunity to talk about what exactly biochar is. I want to start by saying that there is a wealth of information and new research on biochar out there, and here at CDW, we are by no means the complete experts on everything that's happening. This presentation will cover just the basics of what we know about biochar, and for more detailed information, we plan to send out a resource sheet next week.

The Growing Field of Biochar Research

To give you an idea of the momentum in biochar research, as of 2022, there were almost 28,000 publications on biochar, with 80% of those published in the last five years. This is a testament to the growing interest in and possibilities of biochar. It's an exciting time to learn about biochar, especially considering its potential roles in the stormwater and watershed world.

Historical Context of Biochar

Interestingly, biochar was discovered in the Amazon about 30 years ago, and those pieces were dated back to 2000 years ago. Initially, it was used for soil fertility, making it an old technology that we're now reviving for soil health and expanding its purposes.

What is Biochar?

So, what exactly is biochar? I think a better question would be, what are biochars? This is an important takeaway from this presentation—there are many different types of biochar. It's not just one product. Depending on what you're putting into its creation and how you're processing it, the product that comes out on the other end can vary significantly. There are many uses and purposes for biochar, and based on these factors, there are also a variety of chemical and physical properties that can be called biochar.

Biochar Production: The Pyrolysis Process

Biochar is a solid material obtained from the conversion of biomass in an oxygen-limited environment. The temperature and the oxygen limit are really important in the production of biochar. If you've ever had a campfire and blown air into it to catch a flame, that's combustion. But when biochar is created, it's in an oxygen-limited setting. This lack of oxygen and the slightly lower temperatures create biochar, rather than ash, as seen in combustion.

Pyrolysis, the process used to create biochar, happens at around 660 to 1,000 degrees Fahrenheit, as opposed to combustion, which occurs at much higher temperatures of about 1,400 to 2,200 degrees Fahrenheit.

Biochar Production Variations

There are many different ways to produce biochar. For instance, you can use various organic masses like trees, corn, coconut, or poultry litter. It's important to be intentional about the kind of biomass you're using, as some materials can cause more harm than good.

Biochar's Potential and Uses

Biochar has many amazing benefits, including storing carbon, improving soil health, promoting plant growth, retaining pollutants in runoff, and utilizing waste material. However, because there are many different types of biochar, you cannot say that one particular biochar will solve all problems. There are nuances to consider when discussing biochar.

Biochar Production: A Closer Look

  • Homogeneous Feedstock and Processing: The nature of the feedstock, whether it's homogeneous or varied in size, impacts the quality and consistency of the resulting biochar. Homogeneity in feedstock leads to a more uniform pyrolysis process, making it easier to evenly process each batch.
  • The Pyrolysis Machine: The type of pyrolysis machine, whether it resembles an incinerator or varies in size and design, significantly affects the production process. The structural design of the machine, whether it's upflow or downflow, alters how pyrolysis occurs.
  • Pre-treatment and Reaction Time: Pre-treating the biomass and the duration it spends in the pyrolysis machine also determine the biochar's final characteristics.

Varieties of Biochar

  • Examples of Different Types: From turkey litter to pine chips, each type of feedstock produces biochar with distinct properties. The diversity in biochar types is further enhanced by the processing methods.
  • Post-Production Processing: Once produced, biochar can undergo additional processing, like pelletizing, granulating, or blending with compost or manure, to suit specific purposes.

Importance of Correct Biochar Selection

The right type of biochar must be matched to its intended use. Factors such as pore volume, which influences the biochar's ability to absorb and retain contaminants, and surface characteristics, which determine its interaction with water, are critical considerations.

Research and Standards in Biochar

  • Innovative Research: Ongoing research in the field of biochar is shedding light on how different production temperatures and feedstocks affect biochar at a microscopic level, influencing its effectiveness in various applications.
  • Biochar Standards: Organizations like the International Biochar Initiative and the European Biochar Certificate have set standards for biochar, focusing on aspects like chemical properties and intended uses.

Current and Potential Uses of Biochar

  • Soil Health and Agriculture: Biochar is widely used for enhancing soil health, with NRCS codes supporting its use in agricultural settings. It's beneficial for crop growth, water retention, and more.
  • Building Material and Environmental Applications: Beyond agriculture, biochar finds applications in building materials and other environmental projects. It's used in ponds and lakes for capturing pollutants and in urban settings for soil profile rebuilding and improving tree growth.
  • Renewable Energy: The byproducts of biochar production, such as syngas, offer potential for renewable energy generation.

Exploring Biochar's Potential in Carbon Markets and Beyond

The conversation around biochar takes a fascinating turn as we delve into its potential in the carbon market. While biochar is technically eligible for sale on platforms like Pure Earth, its classification as a waste product remains a subject of debate. This aspect is crucial for understanding its role in carbon credit schemes. The intriguing possibility of growing biomass specifically for biochar production, a relatively new concept, also comes into focus. Traditionally, biochar production has emphasized waste reuse, but this new approach of cultivating biomass, already practiced for energy production, opens new avenues for biochar use.

Introducing Sam Dunlap and the Cincinnati Biochar Project

Sam Dunlap, the founder and owner of Carbon Harvest LLC, steps into the spotlight. He established the company with a mission to create soil amendment products that address climate change by diverting waste and restoring soils. Under his guidance, the Cincinnati Biochar Project (CBP) was launched, backed by a significant grant from Bloomberg Philanthropies. The CBP, set to begin production in 2024, aims to tackle a range of environmental and social issues, from urban canopy restoration to waste reduction and youth education.

Unpacking Biochar's Ancient Roots and Modern Relevance

Sam emphasizes biochar as an ancient soil improvement technology, now rediscovered for its modern applications. He sheds light on its production through pyrolysis, a process that consumes volatile components in biomass, leaving behind a carbon-rich residue. This characteristic of biochar makes it a carbon-negative product, as it locks in carbon that would otherwise return to the atmosphere during decomposition.

Biochar and the Stockholm Model

The city of Stockholm, Sweden, serves as a pioneering model for municipal biochar projects. Stockholm's approach to transforming yard waste into biochar, utilizing waste heat for district heating, and applying biochar for soil enrichment sets a benchmark for others to follow. The Stockholm tree pits, integrating water filtration with tree planting, exemplify how biochar can simultaneously address urban forestry and stormwater management.

Carbon Harvest LLC's Approach to Biochar Production

In Cincinnati, the biochar project aligns with the city's Green Cincinnati Plan, contributing to urban canopy growth, stormwater management, and climate resilience. The project, hinged on turning waste into resource, revenue, and resilience, will utilize advanced pyrolysis equipment to convert wood chips into biochar. A noteworthy aspect of the project is its strategy to harness waste heat from the pyrolysis process for practical purposes, such as heating a greenhouse, thereby improving the overall environmental footprint.

Applications and Impact of Biochar

The biochar produced in Cincinnati is slated for diverse uses. In urban forestry, it aims to enhance tree survival and growth, addressing the urban heat island effect and supporting the city's environmental justice initiatives. In stormwater management, biochar's role in increasing infiltration and integration into green infrastructure projects is highlighted. The project also envisages selling biochar and carbon credits, contributing to the city's economic and environmental goals.

Addressing Environmental Concerns with Biochar in the Chesapeake Bay

The conversation around biochar takes a comprehensive turn as we explore its role in the Chesapeake Bay. Carol shares insights into a project aimed at integrating biochar amendments in urban landscapes to support runoff reduction and improve water quality. In partnership with USBI, University of Delaware, and Infinite Solutions, the initiative focuses on identifying and addressing bottlenecks in biochar use for water quality purposes. The project is a testament to the commitment to overcoming limitations within finite resources.

Understanding Biochar's Role in Water Quality and Soil Health

Carol emphasizes the complexity of biochar's impacts, especially in water holding capacity. She points out the challenge in aggregating information from numerous studies, each with different types of biochar. The project's goal is to specify the needs for stormwater management in the Chesapeake Bay, particularly concerning nitrogen and phosphorus, and to develop specific specifications for biochar use in these contexts.

Biochar Accreditation and Its Implications

The project faces the challenge of biochar not being an accredited Best Management Practice (BMP) in the Chesapeake Bay, a region with specific Total Maximum Daily Load (TMDL) requirements. Through discussions and literature reviews, the team is working towards accrediting biochar as a soil amendment and as an additive to bioretention systems, recognizing the distinct needs of urban and agricultural settings.

The Search for Ideal Biochar Applications

The team is actively seeking projects that require biochar within the Chesapeake Bay urban environment. Their goal is to fill information gaps for municipalities and to develop specifications for biochar use, considering factors like size and feedstock. The flexibility in applications, whether for soil amendment, tree planting, or conservation landscaping, highlights biochar's versatility.

This presentation was partially funded by the National Fish and Wildlife Foundation Innovative Nutrient and Sediment Reduction Grant Program.

Disclaimer: The views and conclusions contained in this video are those of the authors and should not be interpreted as representing the opinions or policies of the I.S. Government or the National Fish and Wildlife Foundation and its funding sources. Mention of trade names or commercial products does not constitute their endorsement by the U.S. Government, or the National Fish and Wildlife Foundations or its funding sources.

Statement: This material is based on work supported by the U.S. Environmental Protection Agency (Assistance Agreement No. CB96358201) and the National Fish and Wildlife Foundation’s Chesapeake Bay Stewardship Fund, which promotes community-based efforts to develop conservation strategies to protect and restore the diverse natural resources of the Chesapeake Bay.