Grate the fresh ginger using a fine grater or food processor.

In a saucepan, combine the grated ginger, sugar, and 2 cups of water. Heat over medium until the sugar dissolves completely.

Remove the saucepan from heat and stir in the lemon juice.

Pour the mixture into a mixing bowl and add the remaining 6 cups of cold water.

In a small bowl, mix the active dry yeast with a few tablespoons of lukewarm water and let it sit for about 5 minutes.

Add the activated yeast to the ginger mixture and stir well.

Transfer the ginger beer mixture to a clean 1-gallon glass jar. Seal it tightly with a lid or cover it with a cloth.

After 5-7 days, when bubbles form and the mixture smells aromatic, it's ready to bottle. Use a funnel to pour into plastic bottles, leaving some air at the top.