I packed some spent coffee grounds and brought it home. The amount I brought was enough to make a cup. I was wondering why some fellow were bringing it home and making hot coffee out of it! It was obvious that an acceptable cup could be made out of it but it should not be done according to ground rules.
I was guessing, they were making coffee by boiling it in unmeasured amount of water for unrecorded amount of time. I tried replicating this method. I placed the spent coffee grounds in small casserole. I poured some water. Fired the stove and waited until the mixture reached running boil. Put off the flame and let the boiled coffee stand for few minutes to allow settling of grounds.
Based on my pure subjective judgement. The coffee made from spent ground was still good tasting. It was good as free, bad otherwise. The overall acceptability was reduced to more than half, reduced aroma, acidity, body and bitterness. The color intensity was also reduced.
I don’t think doubling the amount of spent ground could cope up with the original the original taste. The prime flavors are already taken off during the first preparation.