In a large mixing bowl, combine the grated ginger, sugar, and boiling water. Stir until the sugar dissolves, creating a ginger syrup.

Let the ginger syrup cool to room temperature.

Once cool, sprinkle the active dry yeast over the ginger mixture. Stir gently to combine.

Cover the bowl with a clean cloth and let it sit at room temperature for about 24 hours.

After 24 hours, strain the ginger mixture through a fine mesh strainer into another large bowl.

Stir in the lemon juice and cold water to the strained ginger liquid.

Using a funnel, pour the ginger beer into clean glass bottles, leaving some space at the top for carbonation. Seal the bottles tightly.

Refrigerate the bottles for at least 4 hours before serving.