Processes are provided for producing a diesel fuel product having a sulfur content of 15 wppm or less (e.g., 10 wppm or less) from feed sources that include a biocomponent feedstock. The biocomponent feedstock can be initially co-processed with a mineral feed in a fluidized bed stage, such as an ebullating bed processing stage. Ebullating bed processing can mitigate the impact of the biocomponent feed on other hydrotreatment aspects of a diesel boiling range feed. Challenged biocomponent feeds can be handled by introducing the biocomponent feed into the ebullating bed reactor in a manner that reduces the fouling impact of the feed.