Text snapshots from relevant blogs & white papers:

http://www.biofuelsdigest.com/bdigest/2016/04/10/could-renewable-diesels-boom-be-cut-short-by-feedstock-access-and-availability/

New supplies of feedstocks must be developed, such as trap oil, DAF oil, camelina, jatropha, etc. in order for the biofuel industry to grow appreciably. Not many noticed that Mexican and Brazilian jatropha oil were conditionally approved as RIN-producing pathways by EPA for biofuel in 2015.

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The US produces about 2 billion pounds (263 million gallons) of yellow grease annually. This production level has not grown appreciably in the last 5 years.

In 2015 the biodiesel producers used 1.254 billion pounds (165 million gallons) of yellow grease. Thus 63% of available yellow grease was used for domestic biodiesel production.

In 2015 the US exported .58 billion pounds (73 million gallons) of yellow grease, primarily to Europe for biofuel production. Thus 28% of available yellow grease was exported.

Therefore, only 9% of yellow grease was used domestically for purposes other than biodiesel, a surprisingly small number.

https://greet.es.anl.gov/files/tallow-13

Currently, tallow is used mainly as livestock feed, and also for the production of soap, lubricants, paint and varnish in a limited quantity. If the majority of tallow is diverted from the current application to fuel production, it may cause indirect effects such as the use of other crops and materials to replace the diverted tallow. In this study, the indirect effects are not considered.

http://www.ucsusa.org/sites/default/files/attach/2015/07/Brorsen-RFS-Biodiesel-Feedstock-Analysis.pdf   

Yellow grease is a mature market. It may not have that much more room to grow. Biodiesel currently uses half of yellow grease produced (EIA; Swisher 2015). This amount of yellow grease is enough to produce about 140M gallons of biodiesel. While yellow grease use in biodiesel production has grown quickly, it is unlikely to continue this rate of growth. An 8%/year increase would provide feedstock for an increase of 11M gallons of biodiesel a year. This increase would come from reducing the amount of yellow grease going to animal feeds. The amount going to biodiesel may continue to increase, but the size of these increases is going to tail off as it becomes difficult to bid yellow grease away from other uses.

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Animal fats have been a major contributor to biodiesel with a total of 986M pounds of feedstock in 2014. Animal fats are a small part of animal value, so there is not going to be much price response. Per capita consumption of meat in the United States continues to trend downward (ERS 2015). Consistent with this, Table 7 shows a slight downward trend in the rendering of animal fats. There is little potential for increasing the total quantity of animal fats, so biodiesel would have to bid animal fats away from other uses. These other uses include livestock feed (especially poultry), pet foods, and the oleochemical industry as well as edible products (Swisher 2015). Swisher describes pet foods and aquaculture, where fats and oils are replacing fish meal, as growth areas for the rendering industry.

http://www.theicct.org/sites/default/files/publications/Biodiesel%20Availability_ICCT_20160707.pdf

We predicted that soybean oil, corn oil, and tallow will be used in industrial products based on their low price and availability. Increased use in industrial products is a direct result of increased demand for biodegradable lubricants and oils.

... we took an average of the relatively flat soap production over the last five years and projected a continued trend of constant production. The remaining industrial uses (fatty acids, paint and varnish, resins and plastics, and other inedible products) were averaged over the 30-year period of available data (1980-2010) and assumed to remain constant as we were not able to identify any trends for these categories (USDA-ERS, 2016f).

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Inedible corn oil consumption was previously dominated by use in livestock feed but has been used increasingly as a biofuel feedstock over the past five years. However, inedible corn oil production has been relatively flat since the end of 2013 and is expected to remain flat as extraction yield improvements and the number of producers fractioning out corn oil have leveled off (Jessen, 2013).

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Increased meat production will also have the effect of increased tallow consumption in livestock feed. In addition, increased consumption of lubricants, one of several industrial uses of FOG, will increase the consumption of tallow. Overall, increased production is expected to outweigh increased consumption resulting in about 53.5 million pounds or 7 million gallons of biodiesel equivalent growth in availability per year.

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[White/poultry fat]"other grease" availability for biodiesel production to increase by about 23 million pounds or 3 million gallons of biodiesel equivalent per year.

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The amount of yellow grease used in biodiesel has steadily increased over the past five years and was the second largest input for biodiesel production in 2015 (Figure 2). However, this trend is likely a result of bidding yellow grease stocks away from formerly prominent uses in livestock feed and export. We predict that yellow grease consumption in livestock feed will remain constant as a result of constant production, and that other FOG will be used increasingly in livestock feed. We also expect that yellow grease exports will have dropped to zero by 2016 and will remain at this level. Thus, total consumption and total availability for BBD are expected to remain constant throughout the projection period.

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**BBD imports**

Imports necessary to meet the RFS mandate are expected to increase year over year as the deficit between available feedstock and required volumes increases. In 2015, the United States imported roughly 334 million gallons of biodiesel and 204 million gallons of renewable diesel (EIA, 2016b, c)

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A continued RFS BBD requirement increase of 100 million gallons per year compared with an average of 31.5 million gallons of increased FOG availability per year will result in exceedingly larger deficits over the projection period... Based on a continued 700 million gallon gap between the BBD mandated volume and BBD needed to fulfill the total advanced and renewable mandate (EPA, 2016a), we expect a deficit of 1.274 billion gallons in 2018 that must be imported; an amount more than double the 2015 BBD import levels. Increased BBD requirements greater than increases in domestic feedstock production will put pressure on feedstock commodity markets and negatively affect other domestic sectors that depend on these resources.