Biochar is a carbon-rich charcoal made by heating organic matter — such as clean wood, crop residuals, and other biomass — in a low-oxygen process called pyrolysis. Production of biochar from biomass reduces potential waste and when used as a soil amendment improves soil health, helps soil retain water, and effectively traps carbon.
Creating biochar is an industrial process that must follow environmental regulations, including air emissions, waste management, and stormwater exposure. This guide explains these requirements to help businesses producing biochar.
Feedstock and products
To understand the air and waste regulations surrounding the production and management of biochar, you must first identify what material you are using (feedstock) and what is being produced (biochar or waste).
Clean cellulosic biomass (CCB) refers to residual (left-over) organic matter from plants (e.g., forest thinning, tree trimmings, stumps, agricultural crop residues) that do not contain contaminant levels above what is typical for virgin plant matter.
To determine if a feedstock qualifies as CCB rather than a solid waste, there are some key questions to consider:
- Is the biomass only plant material (e.g., wood, forest residues, agricultural residues) and not plant materials mixed with wastes?
- Is the material free of contaminants beyond what is typical for virgin biomass (i.e., free from chemical treatment or any coatings, etc.)?
- Has the material been collected and managed separately from “discarded” waste (municipal solid waste (MSW) or construction & demolition debris)?
Certain operating conditions can trigger federal and state rules that have more extensive requirements and permitting. Some examples include:
- producing a waste, such as ash, instead of biochar
- mixing CCB with solid waste
- using materials that have been treated (e.g., chemically treated wood, painted lumber, or contaminated wood)
Air emissions
All businesses must determine if they need an air permit by calculating potential emissions and determining applicability to federal New Source Performance Standards (NSPS). Relevant activities at a biochar facility may include pyrolysis units, material handling, grinding, and engine/generator use.
TIP: To calculate your facility's potential air emissions, you must assume the worst-case scenario: operating at maximum capacity, 24 hours per day, 7 days a week, even if you plan to run equipment less often or at a lower rate. You must account for all air pollutants, not just those listed in the manufacturer’s data.
Permit type
When a facility’s potential emissions exceed one or more permitting threshold, an air permit is required. The type of permit needed can depend on the facility’s actual air emissions and NSPSs that apply.
For example, a biochar facility that uses only CCB may have potential emissions that exceed permitting thresholds, requiring an air permit. The permit needed could be the less complex registration option D permit depending on the actual amount of CCB burned and biochar produced. A facility using non-CCB feedstock or not operated to produce biochar could require the more comprehensive Part 70 permit.
Federal regulations - incinerators
Facilities that use only CCB to produce biochar are not regulated as solid waste incinerators under Clean Air Act Section 129. This exempts them from various complex state and federal rules.
While federal exemptions now exist for air curtain incinerators burning only clean wood, lumber, and/or yard waste, MPCA regulations still require a Part 70 permit if a facility generates waste instead of a functional biochar product.
Federal regulations – engines
Federal regulations apply to stationary engines and generators used for backup, power generation, or grid support. The specific regulation depends on the date the unit was constructed, fuel type, size, and use.
Portable engines—those with wheels, skids, or mounted on a trailer—are exempt from stationary engine rules. However, if a portable engine remains in one location for more than 12 consecutive months, it becomes a stationary engine and must comply with federal regulations.
Determining permit requirements
If you are uncertain whether a rule applies or if an air permit is required, you can submit an applicability determination request using MPCA form CH-16, along with other supporting forms and data. Additionally, businesses may ask for a pre-application meeting with air permitting staff.
Waste management
Like air quality, waste management requirements depend on the type of feedstock used and what is produced (biochar or waste).
When CCB-feedstock is used to produce a functional product, such as biochar, neither the feedstock nor the product is considered waste. If the feedstock is not used to produce a functional product, both the feedstock and the resulting ash are classified as waste.
Any material that fails to meet CCB or non-hazardous secondary material standards must be managed as solid waste. Managing or treating solid waste requires a permit from the MPCA before building, modifying, or operating the facility.
Hazardous waste
Burning concentrates pre-existing heavy metals, such as lead, cadmium, and arsenic, within the resulting ash. While biochar is typically non-hazardous, using feedstocks other than CCB — such as treated wood or municipal waste — greatly increase the risk of creating hazardous waste residuals.
Businesses must verify that process residues do not exhibit hazardous characteristics. For non-CCB feedstocks, performing a toxicity characteristic leaching procedure (TCLP) is essential to determine if any residuals are hazardous wastes.
Any facility that generates hazardous waste is a hazardous waste generator and must comply with a series of requirements.
Industrial stormwater
Biochar facilities must manage runoff to prevent pollutants like dust and debris from reaching local water bodies. The need for an industrial stormwater permit or no exposure certification is determined by your business’s SIC or NAICS codes. A permit is required if equipment, materials, or work areas are exposed to rain or snow. If your entire operation is indoors or protected from the elements, you may qualify for a no exposure certification.
Even if a permit isn't required by your industry code, implementing best management practices is recommended to manage runoff effectively.
Construction stormwater
Construction or expansion projects disturbing one acre or more of soil require a stormwater permit. This includes smaller projects that are part of a larger development plan. This ensures your business manages runoff and erosion to protect local water bodies from sediment pollution.
Zoning and land use
While the MPCA manages air, water, and waste permits, biochar production facilities must acquire proper land use approval from their local city or county government. Because biochar production is typically classified as an industrial activity, these facilities must follow local zoning and planning regulations.
Beyond compliance
The Small Business Environmental Improvement Loan Program offers zero-percent interest loans of up to $75,000 to small businesses. These loans are available to help businesses meet or exceed environmental regulations and to cover costs associated with projects, equipment, investigation, and cleanup. Examples of projects include:
- upgrading monitoring and capture equipment for feedstock or biochar processing and transfer (e.g., baghouse filters, wet scrubber, or cyclone pre‐separator)
- installing thermal oxidizers to reduce VOCs and other emissions from pyrolysis
- installing biochar or ash handling equipment such as sealed conveyors, dust suppression, and filtered storage to contain fine particulates and prevent leachate or runoff of feedstock or biochar residues