National Organic Standards Board

Crops Subcommittee Petitioned Material Proposal

Carbon Dioxide

January 18, 2022

Summary of Petition:

The NOSB received a petition requesting the addition of synthetic carbon dioxide 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.

Subcommittee Review:

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

aid. Because carbon dioxide is a synthetic material, the Subcommittee discussions focused on the need

and benefits of using carbon dioxide over other allowed alternatives?

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.

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.

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Category 2: Adverse Impacts

1. 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.

2. 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 CO2 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.

CO2 can also be used for pest control in storage areas, however, that is not the subject of this petition.

3. 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 (CO2) 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. This characteristic makes the use of carbonic acid the safer and most secure process for water

pH adjustment when compared to alternatives.

4. 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 of human health from the substance.

5. 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. It dissolves in

water, including water in soil solution, to form carbonic acid. Carbonic acid breaks down into carbon 

dioxide.

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6. 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

1. Are there alternatives to using the substance? Evaluate alternative practices as well as non- synthetic

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. 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 widely used in food processing. It is used as an ingredient, acidulant, pH 

control agent, flavoring, and as a sequestrant. It is used as a dispersant in flavor or color additives. Citric 

acid has GRAS status (generally recognized as safe) by the FDA. 

2. In balancing the responses to 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 would be considered a recycling process, the Crops Subcommittee finds it

compatible with a system of sustainable agriculture.

Subcommittee Vote:

Classification Motion:

Motion to classify carbon dioxide as synthetic

Motion by: Logan Petrey

Seconded by: Rick Greenwood

Yes: 8 No: 0 Abstain: 0 Absent: 0 Recuse: 0 

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: 7 No: 0 Abstain: 1 Absent: 0 Recuse: 0

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National List Motion:

Motion to add carbon dioxide at §205.601(j) As plant or soil amendments. 

Motion by: Logan Petrey

Seconded by: Steve Ela

Yes: 7 No: 1 Abstain: 0 Absent: 0 Recuse: 0

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