NOVELTY - The method involves treating an off-gas stream from a fluid catalytic cracking reactor (105) to remove hydrogen sulphide and carbon dioxide, the treated off-gas stream having a hydrogen content of not more than 25 percent, and hydroprocessing a feedstock (119) comprising a biocomponent portion in a reactor in the presence of the treated off-gas stream, a catalyst with hydrogenation activity, and steam under effective hydroprocessing conditions to produce a vapor effluent, an aqueous effluent (132), and a diesel boiling range product (142).    USE - Hydroprocessing method for biocomponent feedstock using value low refinery stream as energy source. Uses include but are not limited to rapeseed or canola oil, peanut oil, sunflower oil, tall oil, corn oil, soy oils, castor oil, jatropha oil, jojoba oil, olive oil, flaxseed oil, palm oil, and combinations of oils.    ADVANTAGE - Reduces needed hydrogen consumption by adding sulphur-containing compound to the biocomponent feed. Minimizes or avoids the need to reduce production of another product in order to treat the biocomponent feed. Processing costs are reduced by using a relatively low cost water gas shift catalyst, such as iron oxide (Fe3O4), as the hydrotreatment catalyst. Co-processing of the biocomponent product with a mineral feed has reduced or minimized amount of catalyst suppression/deactivation problems because majority of the oxygen is removed in a dedicated process. Biocomponent feeds suppresses hydrodesulphurization (HDS) activity, making co-processing of a biocomponent feed challenging. Allows for production of a biocomponent based diesel product at reduced expense and with little or no significant impact on other refinery resources.    DETAILED DESCRIPTION - The catalyst is a water gas shift catalyst which comprises an oxide of iron, copper, zinc, chromium, or a combination of the elements. The feedstock is free of sulfur. The vapor effluent is used as a refinery fuel gas. An INDEPENDENT CLAIM is also included for a system for hydroprocessing a biocomponent feed.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic block diagram of a reaction system for performing the process.    Fluid catalytic cracking reactor (105)    Reactor (105)    Feedstock (119)    Aqueous effluent (132)    Separator (135)    Diesel boiling range product (142)