Vinegar can be produced naturally by decomposition of plant products under anaerobic conditions. Acetic acid, commonly called ethanoic acid, with a chemical formula CH3COOH, is formed by the fermentation of alcohol. Vinegar of about 5% acetic acid concentration is prepared from wine (grapes), cider (apples), or malt (grain). The biological process of vinegar manufacture involves conversion of sugars into alcohol and carbon-dioxide through fermentation. By an oxidative process, the alcohol in presence of certain bacteria reacts with air to form vinegar. Concentrated acetic acid as used in industry is prepared by several synthetic processes, such as the reaction of methyl alcohol and carbon monoxide (CO) in the presence of a catalyst, or the oxidation of acetaldehyde or petroleum. This synthetic process is not acceptable for agricultural use by the organic community. Acetic acid concentration of vinegar derived from plant sources can be increased from 5 % to 15% via distillation and to 30% via freeze evaporation or other processes. The organic community approves of these processes for agricultural use.

Environmental fate of acetic acid: Acetic acid readily degrades in water and shows little potential for bioaccumulation. It is biodegradable (MITI Report 1984, Ministry of International Trade and Industry, Tokyo). In an experiment conducted at Swedish Agricultural University it was found that addition of 24 % vinegar to a peat soil decreased the pH of the soil from 7.3 to 5.6. However, after 48 hours the pH values of the soil returned to 7.0-7.5. (David Hansson, personal communication) Research Results from BARC
Greenhouse and field research have been conducted at Beltsville, Maryland, to determine the efficacy of vinegar for controlling weeds. The results indicate that vinegar can kill several important weed species at several growth stages. Vinegar at 10, 15 or 20 % acetic acid concentration provided 80-100 percent kill of selected annual weeds, including giant foxtail up to 3 inches in height, common lambsquarters up to 5 inches, smooth pigweed up to 6 inches, and velvetleaf up to 9 inches. Control of annual weeds with vinegar at the 5 % acetic acid concentration was variable. Canada thistle shoots were highly susceptible with 100 percent kill by 5 % vinegar. However, there was re-growth from Canada thistle roots.

Potential applications for using vinegar for controlling weeds:
" An inexpensive, environmentally safe herbicide for spot treatment on organic farms.
" Control of unwanted vegetation along roadsides and range lands
" Control of weeds by homeowners around yards, brick walls and patios
" Weed control in cracks in pavements (It is registered for this use in Sweden, David Hansson, Personal communication)

Vinegar products used in this project include:

1. A commercially supplied white vinegar distilled from grain with acetic acid concentrations ranging from 5- 30 %.
2. A vinegar made from apples at concentrations up to 14 % acetic acid. There may be other sources of vinegar. However in order for vinegar to be allowed in organic agriculture, production must be from a natural source by natural fermentation methods. Vinegar purchased at the supermarket is 5 % acetic acid.

WARNING: Note that vinegar with acetic acid concentrations greater than 5% may be hazardous and should be handled with appropriate precautions.