National Organic Standards Board

Crops Subcommittee Petitioned Material Proposal

Carbon Dioxide

July 5, 2022

Summary of Petition: 

The NOSB received a petition requesting the addition of synthetic carbon dioxide (CO2) at § 205.601 

Synthetic substances allowed for use in organic crop production as (a) algicide, disinfectants, and 

sanitizer, including irrigation system cleaning systems and (j) As plant or soil amendments.

Carbon dioxide is currently allowed for use as an ingredient in organic labeled processed food products: 

§ 205.605 Nonagricultural (nonorganic) substances allowed as ingredients in or on processed products 

labeled as “organic” or “made with organic (specified ingredients or food group(s)).” (b) Synthetic 

allowed: - Carbon dioxide. This petition requests the allowance of carbon dioxide in organic crop 

production under the two sections listed above. 

Subcommittee Review:

Carbon dioxide is understood to be a material with inherently low risk and is approved as a processing

aid. Nonsynthetic sources are not available due to lack of infrastructure at ethanol plants. Because the 

petitioned material is synthetic, the Crops Subcommittee discussions focused on the need and benefits

of using carbon dioxide over other allowed alternatives. 

Some farming areas have alkaline water sources that can hinder nutrient availability and optimal crop 

growing conditions. Currently, organic farmers can use citric acid and sulfur burners to acidify irrigation 

water. It is a naturally occurring substance in the atmosphere and has no apparent negative effect on 

other materials used in organic farming systems. In a greenhouse environment, atmospheric CO2 levels 

are depleted quickly as it is required for plants to photosynthesize. Greenhouse operations may have 

limiting levels of carbon dioxide and may benefit from this material as a plant and soil amendment. The 

Crops Subcommittee questions the potential uses of this material in other growing systems. Previous 

commenters have also shown interest in further information for this listing. The Crops Subcommittee

understands that this product is inherently low risk and is a suitable alternative to current water 

acidifiers at § 205.601(a).

However, the Crops Subcommittee is seeking more information about the requested use at § 205.601(j) 

and has requested a limited-scope Technical Report (TR) to understand the use frequency, the 

application rates, and all methods of applications.

Category 1: Classification

1. For CROP use: Is the substance Non-synthetic or ___X Synthetic?

Is the substance formulated or manufactured by a process that chemically changes a substance

extracted from naturally occurring plant, animal, or mineral sources? [OFPA §6502(21)] If so,

describe, using NOP 5033-1 as a guide.

Carbon dioxide (empirical formula CO2, CAS Reg. No. 124-38-9) occurs as a colorless, odorless,

noncombustible gas at normal temperatures and pressures. The solid form, “dry ice”, sublimates under 

atmospheric pressure at a temperature of −78.5 °C.

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Carbon dioxide is prepared as a byproduct of the manufacture of lime during the “burning” of

limestone, from the combustion of carbonaceous material, from fermentation processes, and from 

gases found in certain natural springs and wells.

2. Reference to appropriate OFPA category:

Is the substance used in production, and does it contain an active synthetic ingredient in the

following categories: [§6517(c)(1)(B)(i)]; copper and sulfur compounds; toxins derived from

bacteria; pheromones, soaps, horticultural oils, fish emulsions, treated seed, vitamins and

minerals; livestock parasiticides and medicines and production aids including netting, tree wraps

and seals, insect traps, sticky barriers, row covers, and equipment cleansers; or (ii) is used in

production and contains synthetic inert ingredients that are not classified by the Administrator of 

the Environmental Protection Agency as inerts of toxicological concern?

Carbon dioxide falls under the category of production aid.

Category 2: Adverse Impacts

3. What is the potential for the substance to have detrimental chemical interactions with other

materials used in organic farming systems? [§6518(m)(1)]

Carbon dioxide is already allowed as an organic processing substance. It occurs naturally in the

atmosphere, has little chemical interactions with other substances, and has no apparent negative effect

on other materials used in organic farming systems.

4. What is the toxicity and mode of action of the substance and of its breakdown products or any

contaminants, and their persistence and areas of concentration in the environment?

[§6518(m)(2)]

The action to dissolve carbon dioxide (CO2) in water (H2O) makes carbonic acid (H2CO3): H20 + CO2 -> 

H2CO3. Carbonic acid is dissociated in water to: HCO3

-

 + H+. This hydrogen lowers water pH. This is a

common, naturally occurring reaction in the soil ecosystem from carbon dioxide in the atmosphere.

In soils with high pH, applying water with a reduced pH can increase nutrient availability and increase

plant health. Additionally, the activity of carbon dioxide in water can help prevent clogging of irrigation

systems by algae and other plant contaminants.

Carbon dioxide can also be used for pest control in storage areas, however, that is not the subject of this

petition.

5. Describe the probability of environmental contamination during manufacture, use, misuse, or

disposal of such substance? [§6518(m)(3)]

As a basic component of the atmosphere, carbon dioxide has a high environmental persistence. This is 

not a negative, except to the overarching concern of global warming. At the rates occurring in the

atmosphere, it is completely non-toxic and is exempt from having a lethal dose. The water pH 

adjustment process can be manually controlled, as well as automatically controlled, by adding a pH

probe and controller that adjusts the carbon dioxide injection to maintain target pH values in the water.

Water cannot drop below pH 5.0 when carbonic acid (dissolved CO2) is used in the acidification process.

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This characteristic makes the use of carbonic acid the safer and most secure process for water pH 

adjustment when compared to alternatives.

6. Discuss the effect of the substance on human health. [§6517(c)(1)(A)(i); §6517(c)(2)(A)(i);

§6518(m)(4)].

Suffocation can occur in pure carbon dioxide but is due to the lack of oxygen, not toxicity of carbon 

dioxide. There are no other direct effects on human health from the substance.

7. Discuss any effects the substance may have on biological and chemical interactions in the

agroecosystem, including the physiological effects of the substance on soil organisms (including

the salt index and solubility of the soil), crops and livestock. [§6518(m)(5)]

The use of dissolved carbon dioxide to reduce water pH is an acidifying method that occurs naturally, 

i.e., atmospheric carbon dioxide from biological processes enters water through equilibrium. Carbon 

dioxide dissolves in water, including water in soil solution, to form carbonic acid. Carbonic acid breaks 

down into carbon dioxide.

8. Are there any adverse impacts on biodiversity? (§205.200) 

Carbon dioxide is a greenhouse gas and can contribute to climate change. Its increase in the

atmosphere has altered the biodiversity in many ecosystems. However, the use of this product in 

accordance with the petition will not add to the increase of carbon dioxide. The petitioned use is for 

carbon dioxide produced as a byproduct of other processes. The carbon dioxide would be released to 

the atmosphere regardless of the petitioned use.

Category 3: Alternatives/Compatibility

9. Are there alternatives to using the substance? Evaluate alternative practices as well as 

nonsynthetic and synthetic available materials. [§6518(m)(6)]

Alternatives used in organic production to lower pH levels in irrigation water are sulfur burners and 

citric acid. Because water pH cannot drop below 5.0 when carbon dioxide is used as an acidifier, this

method may be considered more secure as a pH adjustment compared to alternatives.

Sulfur burners create sulfurous acid by dissolving the fumes of burning sulfur in irrigation water. Pure 

sulfur is an odorless, tasteless, light-yellow solid usually sold in blocks or pellets. Sulfurous acid is slightly 

irritating to the skin, and strongly irritating to the eyes of rabbits. Under acidic conditions, sulfurous acid 

may liberate sulfur dioxide, which is known to induce respiratory irritation in humans.

Citric acid is a non-synthetic substance widely used in food processing. It is used as an ingredient,

acidulant, pH control agent, flavoring, and sequestrant. It is also used as a dispersant in flavor or color 

additives. Citric acid is listed as GRAS (Generally Recognized As Safe) by the FDA. 

As a plant and soil amendment, there are no substitutions to carbon dioxide since carbon dioxide is 

needed for photosynthesis. In greenhouse conditions, carbon dioxide can be a limiting resource and its

replacement would be needed.

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10. In balancing the responsesto the criteria above, is the substance compatible with a system of

sustainable agriculture? [§6518(m)(7)]. 

Because carbon dioxide is approved as an organic processing substance, is already being produced, and 

its listing at § 205.601(a) would be considered a recycling process, the Crops Subcommittee finds it

compatible with a system of sustainable agriculture. 

The Crops Subcommittee is seeking additional information about the requested use at § 205.601(j) and 

will develop a proposal for a future NOSB meeting. 

National List Motion:

Motion to add carbon dioxide at § 205.601(a) algicide, disinfectants, and sanitizer, including irrigation 

system cleaning systems

Motion by: Logan Petrey

Seconded by: Rick Greenwood

Yes: 6 No: 0 Abstain: 0 Recuse: 0 Absent: 2 

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