Compost Tea Products

Does OMRI restrict compost tea products?

By Annie Amos

Compost tea is made by steeping compost in water. Typically, manufacturers aerate the tea during the steeping process, and then filter it to get a liquid product that will not clog irrigation or spray lines. Manufacturers may add other ingredients such as molasses or yeast to increase microbial growth. Crop producers use compost tea for a variety of purposes, including plant disease control and soil fertility. Because it is a liquid, the microbial biomass, fine particulate organic matter and soluble chemical components of compost tea are easily applied to plant and soil surfaces. 

Compost teas are made from different types of compost. Manufacturers (including farmers) produce some compost with manure-feedstocks, and others entirely without manure. Some teas are made using uncomposted manure, which OMRI reviews and categorizes separately. The process of making compost tea intentionally creates a hospitable environment for microorganisms, which are beneficial to plants and soil. At the same time, there is the potential for pathogens harmful to humans to bloom in tea made from compost. 

So, what do the USDA organic regulations require for compost tea? There are currently no regulations specifically regarding compost tea in the USDA organic regulations. The regulations describe how producers must manage plant and animal materials (including compost and manure), but do not mention teas anywhere. Compost that teas are made from are described in the regulations, and we have written about these standards elsewhere.

The National Organic Standards Board (NOSB) published a Compost Tea Task Force Report in 2004 and a Crops Committee Recommendation for Guidance for use of Compost, Vermicompost, Processed Manure, and Compost Teas in 2006. Both of these documents discuss the potential for human pathogen growth in compost tea, especially when made with additives to increase microbial biomass. The NOSB Crops Committee recommendation included guidelines for compost tea to be made with potable water and compliant compost, equipment sanitizing, and pathogen testing requirements for compost made with additives. 

When the National Organic Program (NOP) published Guidance NOP 5021: Compost and Vermicompost in Organic Crop Production in 2011, they adopted some of the earlier NOSB recommendations, but they did not include guidance for how to consider compost tea. In their response to comments, the NOP wrote, “A number of commenters requested adoption of the NOSB recommendation for compost tea in this guidance. The NOP believes that some aspects of the NOSB recommendation, including requirements for testing certain types of products, require further research and review before issuing guidance on this topic.”

In the past, OMRI restricted compost tea products similarly to raw manure, with a “days-to-harvest” restriction. However, in 2016 the NOP published Guidance NOP 5034-1: Materials for Organic Crop Production, which indicated that tea, made from compliantly composted plant or animal materials, did not carry the same restriction as raw manure or manure tea. Around the same time (2016), OMRI was also in the process of updating the OMRI Standards Manual^©. In the process of developing the update, the OMRI Board voted to change the way that OMRI restricted compost tea, eliminating the “days-to-harvest” restriction for compost tea made from compliant compost. 

Currently, OMRI lists compost tea in several categories with different statuses, depending on how it is made and used. 

• Prohibited when made with sewage sludge.
• Allowed as both a crop and soil amendment and as a crop pesticide when made from compliant compost, without manure feedstocks.
• Restricted (“must be used in a manner that does not contribute to contamination of crops, soil, or water by pathogenic organisms in accordance with §205.203(c)”) as both a crop and soil amendment and as a crop pesticide, when made with composted manure. 

This article first appeared in the summer 2013 edition of OMRI Materials Review newsletter, and was revised in October 2023 by Research and Education Manager Peter Bungum.