The gemorah states that the kohen has to go to the "goren" to get the Terumah.
This is difficult because Terumah and Maaser require "reeas penei habayis" (to enter the persons house through the door).
If so, in the goren there is no "din" of Tevel/Terumah. The yisroel can eat it all himself.
BINYOMIN, ny, usa
Your question is based on a number of incorrect assumptions. First, Re'iyas Penei ha'Bayis is a Halachah in Ma'aser alone, and not in Terumah.
Second, even before Re'iyas Penei ha'Bayis, the Tevel is Asur b'Achilas Keva, and is Mutar only for Achilas Arai.
Third, only produce that is designated for personal use becomes Chayav with Re'iyas Penei ha'Bayis. Produce that is earmarked for sale, and not for personal consumption, does not need Re'iyas Penei ha'Bayis to become Chayav; it is Chayav even without Re'iyas Penei ha'Bayis.
In addition, the Shitah of the Ra'avad is that *grain* does not need Re'iyas Penei ha'Bayis in order to be Chayav.
Finally, there are five other ways to be Kove'a produce for Ma'aser (without Re'iyas Penei ha'Bayis), such as separating Terumah or selling the Tevel.
D. Zupnik