National Organic Standards Board 

Crops Subcommittee Petitioned Material Proposal 

Carbon Dioxide 

August 3, 2021 

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. Carbon 

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 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. 

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. 

Classification Motion: 

Motion to classify carbon dioxide as synthetic 

Motion by: Logan Petrey 

Seconded by: Rick Greenwood 

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

National List Motion: 

Motion to add carbon dioxide at §205.601 

Motion by: Logan Petrey 

Seconded by: Brian Caldwell 

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

Approved by Rick Greenwood, Crop Subcommittee Chair, to transmit to NOP August 3, 2021 

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