In most countries, there is a legal distinction between two methods of farming: organic and conventional. While there are other differences between the two, the main distinction, which will be discussed here, is fertilizer type. Organically grown crops are prohibited from using synthetic fertilizers, whereas conventionally grown crops typically use some synthetic and some organic fertilizers.
Organic fertilizers can either be derived from plants or animals. The following animal sourced materials are commonly used as organic fertilizers:
As organically grown crops are not allowed to use synthetic fertilizers, they tend to use more animal sourced fertilizers than conventionally grown crops. Therefore, the purchase of organically grown crops subsidizes animal agriculture more than the purchase of conventionally grown crops, allowing the farms and slaughterhouses to increase their margins or reduce prices. The questions that must be asked are:
This section contains data and calculations to determine the extent to which the purchase of organically grown products supports animal agriculture compared to conventionally grown products.
The data and calculations (as well as references) analyzed here has been compiled in the below spreadsheet. Gathered data is intended to be an up-to-date reasonable average for the industry. Some data may not be research-grade, but the calculations are a valuable proof-of-concept.
Spreadsheet: https://docs.google.com/spreadsheets/d/1o0YD03WLdU9SDbfKrD1-6JzoUcBkx9DKh67sL02S5p4/edit?usp=sharing
This study collected data from US farms on which types of fertilizer is used for which type of crop (supp. data pg. 39).
The following table shows percentage usage of fertilizers than are animal-sourced for conventional and organic farming, for different types of crops: