National Organic Standards Board

Crops Subcommittee

Petitioned Material Proposal

Calcium Acetate

January 29, 2019

Summary of Petition [Calcium Acetate]: 

Calcium acetate can occur naturally but is more often formulated by chelating finely ground limestone 

(calcium carbonate) with acetic acid. During this process calcium acetate is formed and comprises about 

5% of the calcium in the final product. The remainder of the final product is primarily calcium 

carbonate. Other materials such as xantham gum and/or humic acids may be added to make a 

proprietary product.

Calcium acetate has a variety of potential uses. This petition asks for approval for organic use as a soil 

amendment, plant micronutrient, soil pH adjuster and as a sunscald protectant. Calcium acetate is also 

currently registered for yellowjacket control in conventional crops. In each of these uses, the calcium 

acetate product is mixed with water and applied by spray to the crop, soil, or structure/covering.

In the crops/soils use, the calcium acetate has an advantage in that it is much more water soluble than 

calcium carbonate and is more readily available to the plant. Other traditional sources of calcium, such 

as calcium carbonate, do not become water soluble until they have been acted on by soil microbes or 

acidic conditions. Products that include calcium acetate as well as other slower acting calcium sources 

can have both an immediate impact on the plant as well as an extended release effect as those less 

soluble materials are made plant available. 

For sunscald protection, the material acts to block direct transmission of sunlight due to its opacity. 

Sunscald occurs when exposure to sunlight overheats crops and causes scarring. This scarring can affect 

keeping quality, cosmetic appearance, taste, and texture. An aqueous mixture containing calcium 

acetate may be sprayed on black plastic to lower soil temperatures or as a coating on greenhouses to 

lower inside temperatures. The opacity of the material is primarily due to the calcium carbonate 

remaining in the product after the calcium acetate is formed (2018 TR).

Summary of Review: 

Several public comments were received during the Fall 2018 NOSB meeting in which a discussion 

document on this petition was part of the agenda. One commenter indicated that they would support 

the addition of calcium acetate to the National List if the petitioner was able to document better calcium 

uptake than other available products. The commenter recommended an annotation be added, “For use 

as a foliar spray to treat a physiological disorder associated with calcium uptake.” However, another 

commenter noted that this product should not be approved since good organic practices should resolve 

calcium deficiencies and that this product is not essential. 

With regard to sunscald, one commenter noted that they might support listing with the annotation, “For 

use on plants, greenhouses, and plastic films for protection against excess sun

exposure.” Another commenter stated that the need to approve one synthetic product to remediate 

issues with another synthetic product, such as black plastic, is non-sensical for organic production.

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The 2018 TR reviewed international certification agencies and found no listing for calcium acetate by 

other certifiers. Calcium acetate is not listed for organic production by the Canadian General Standards 

Board Permitted Substances, CODEX Alimentarius Commission, European Economic Community, 

Japanese Agricultural Standard or the International Federation of Organic Agriculture Movements.

The petition and the 2018 TR concur that the environmental and human health impacts of calcium 

acetate are minimal. Since calcium is already common in the environment and calcium acetate can and 

does occur naturally, the use of this material for plant nutrition or pH adjustment is unlikely to cause 

unwanted environmental impacts. It is rapidly utilized and integrated into plant and soil systems. 

While there are numerous calcium disorders documented in crops and supplemental calcium may need 

to be applied to ameliorate these disorders, the 2018 TR notes that other, already approved, chelating 

agents can improve bioavailability of existing calcium sources in the soil and cites references for various 

alternatives. These alternatives include calcium chloride and several other chelated calcium products. 

While this product might be slightly different than other products already approved for organic 

production, it is difficult to make the argument that this product is essential for organic production. 

Without compelling evidence that the currently available alternatives are not effective, this material is 

not essential to organic production.

For sunscald protection, this material is easy to apply and environmentally benign as well as being readily 

adapted to changing conditions. However, alternatives already exist, and this material is not essential for 

organic production.

Category 1: Classification 

1. For CROP use: Is the substance Non-synthetic 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. 

Calcium acetate is made from finely ground limestone which is chelated with acetic acid. It is a 

naturally occurring substance, which is produced and broken down in the metabolic cycles of 

humans and animals (2018 TR), however, it is most commonly synthesized by the neutralization 

of acetic acid and calcium carbonate. The petitioner and the 2018 TR both state that the 

material is synthetic.

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?

The petitioner is asking for calcium acetate to be classified as a synthetic compound under 

vitamins and minerals. In its use as a plant micronutrient or, possibly, as a pH adjuster, the use 

would fall under minerals. For its use as a sunscald protectant or shading material it could be 

interpreted as a 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)]

Calcium is widely used and available in agricultural ecosystems and calcium acetate is simply a 

more soluble form of calcium that is rapidly bioavailable. In general, calcium products are 

positive additions since calcium forms the building blocks of cell structures and functions. 

However, the 2018 TR notes two potential negative impacts. First, calcium acetate could bind 

phosphates, thus making them unavailable to plants as a nutrient source. This would primarily 

happen with the improper use of phosphoric acid. Phosphoric acid is only approved as an 

equipment cleaner and should have no direct contact with organically managed land or 

livestock. Secondly, if overapplied it could cause an over adjustment of pH and could result in 

increased soil alkalinity. 

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 2018 TR states that there are no published studies on the environmental persistence of 

calcium acetate. Various EPA documents are cited noting that calcium acetate may be present in 

the metabolic cycles of animals; therefore, no risk is posed to the environment. The EPA has 

placed calcium acetate on the Safer Chemical Ingredients List (SCIL) for processing aids and 

additives as a safer replacement for traditional ingredients. Moreover, the EPA has designated 

calcium acetate as “verified to be of low concern based on experimental and modeled data,” 

and has “not identified any toxic endpoints for birds, plants, aquatic, or soil organisms” (2018 

TR).

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

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

In general, the environmental impacts of this material should be minimal, but the 2018 TR notes 

that the greatest potential for environmental degradation is the mining necessary to source the 

calcium carbonate. This mining could degrade or disrupt ground water, surface water, and 

ecosystems in the vicinity of the mine and could cause contamination from spills. There could 

also be additional carbon dioxide released to the atmosphere due to fossil fuel burned by 

mining equipment.

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

§6518(m)(4)]. 

Calcium acetate is widely used for human health as treatment for calcium deficiency and to 

treat patients with hyperphosphatemia in end stage renal disease. It can be used as a stabilizer 

and preservative in many food substances. The 2018 TR quotes various sources in that it has 

been authorized for human consumption without limitation by the Joint FAO/WHO Expert 

Committee on Food Additives, FDA has granted it GRAS status as a sequestrant and direct food 

substance, and EPA has placed it on the Safer Chemical Ingredients List for processing aids and 

additives.

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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)] 

When used as petitioned, calcium acetate is applied as an aqueous mixture with calcium 

carbonate. While the calcium carbonate could provide calcium, it is not readily absorbed by 

plants. Calcium acetate has been reported to increase plant absorption of calcium ions (Ca2+) 

compared to salts with other organic and inorganic anions (e.g., lactate, citrate, oxalate, 

chloride, nitrate) (2018 TR). Calcium is necessary for cell wall formation and stabilizes lipids 

within cell membranes. It helps to regulate cell processes such as transport across cellular 

membranes and enzymatic functions (2018 TR). It may also aid in the uptake of other 

micronutrients and may increase the storage life of fruits and vegetables. Common symptoms 

of insufficient calcium in fruits and vegetables include blossom end rot in tomatoes and bitter 

pit in apples.

Calcium is common in the environment and the application of calcium acetate simply makes 

calcium more readily available for absorption. EPA has “not identified any toxic endpoints for 

birds, plants, aquatic, or soil organisms” (2018 TR) so the application of calcium acetate should 

not have negative ecosystem effects except in the case of where it might be overapplied and 

create excess soil alkalinity. 

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

There are no published studies on the environmental impacts of calcium acetate; however, the 

EPA has “not identified any toxic endpoints for birds, plants, aquatic, or soil organisms” (2018 

TR) The 2018 TR goes on to note that calcium acetate acts as a water-soluble and bioavailable 

source of calcium, especially important in soils with high pH. The petitioned substance also 

increases the pH of the soil. Additionally, when used as petitioned, the substance can provide

protection from sunscald as well as act as a mechanism for regulating plant temperature due to 

the opaque nature of the applied liquid. Once introduced into agricultural soils, the salt may 

result in several different outcomes, including absorption by plants, reacting with acidic 

chemicals in the soil, or dissolving and entering water systems, depending on the environmental 

conditions of the soil. 

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)]

Calcium carbonate can also act as a soil amendment, pH adjuster, and micronutrient source, but 

is less rapidly available. The 2018 TR notes that other, already approved, chelating agents can 

improve bioavailability of existing calcium sources in the soil and cites references for various 

alternatives. Lignin sulfonate, or lignosulfonate, is a synthetic chelating agent that is approved 

by the NOP for use in organic agricultural production, at 7 CFR 205.601. Lignosulfonates can 

form chelates with cationic micronutrients, increasing their water solubility and bioavailability. 

Humic acids have also been shown to increase plant absorption of micronutrients, while also 

promoting the growth of soil microorganisms. Additionally, sodium carbonate (Na2CO3) and 

potassium bicarbonate (KHCO3) are capable of pH adjustments and, due to their water solubility, 

provide a more suitable alternative to calcium acetate than calcium carbonate mineral sources, 

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calcium hydroxide, and lime sulfur. Calcium chloride is readily available to plants but may not 

be compatible with other organic materials such as oils and can cause phytotoxicity under some 

environmental conditions. 

A compost program can also be an alternative to calcium acetate. The 2018 TR cites literature 

that organic compost includes micronutrients, natural chelates, and microbes that produce 

natural chelating agents and when used as part of a program could alleviate the need for 

additional calcium applications.

For sunscald, alternative practices include pruning, and the installation of shade cloth or 

overhead sprinklers. Applications of clay-based sprays to plastic, structures, or the crop itself 

may reduce temperatures of soils and crops. Conversely, pruning and the installation of shade 

cloth can be labor intensive and expensive, and the use of clays may cause problems with 

packing equipment and cleaning the produce for market. 

2. In balancing the responses to the criteria above, is the substance compatible with a system of 

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

Since calcium is already common in the environment and calcium acetate can and does occur 

naturally, the use of this material for plant nutrition or pH adjustment is unlikely to cause 

unwanted environmental impacts. It is rapidly utilized and integrated into plant and soil 

systems. Based on the evidence reviewed in the TR and public comments, it was determined 

that this material is not essential for organic production. It does potentially provide a faster 

means to deliver calcium to plants, but there are other materials already available to growers 

that make the same claim, for example, calcium chloride or several chelated calcium products. 

Without compelling evidence that the currently available alternatives are not effective, this 

material is not essential to organic production. 

For sunscald protection, this material is easy to apply and environmentally benign as well as 

being readily adapted to changing conditions. However, alternatives already exist. Without 

compelling evidence that other natural alternatives are ineffective, adding a new synthetic 

material to the National List is not essential for organic production. 

Classification Motion: 

Motion to classify calcium acetate as synthetic

Motion by: Steve Ela

Seconded by: Harriet Behar

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

National List Motion:

Motion to add calcium acetate at §205.601

Motion by: Steve Ela

Seconded by: Emily Oakley

Yes: 0 No: 6 Abstain: 1 Absent: 1 Recuse: 0

Approved by Steve Ela, Subcommittee Chair to transmit to NOSB, January 29, 2019

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