tempo is there to combat the effects that happen to your body the day after a hard speed or speed endurance session.
so if you do a tempo session before those effects have happened…
Well training 2 times a week. I’d work on speed one day and tempo the other. Sure you can’t find 20min for a quick 10x100m tempo session on grass another time a week?
when i am pushed for time, i can still manage to run from home, do some tempo repeats on the grass beside the road, and be home 15-20min later, shower and that 30min total and i feel awsome after feeling like crap before the run. At least it is something.
Or, find a hard spot on your house, and do med ball throws against that, during sets, do some drills. Though i find that goes for 30min, but hey, your at home, no travellin time involved.