Even carbon dioxide can dissolve in the groundwater, causing the water to be naturally carbonated. This water is sometimes sold as mineral water. Groundwater can be heated by magma below the Earth's surface. The heated water can create hot springs, springs with water that is naturally hot (Figure 13.23). Some hot springs are used as natural hot tubs and are considered therapeutic and spiritual by some people. However, hot springs can be dangerous, too.
We used a level tablespoon of salt in a cup of water. The batteries we have shown here are more correctly called cells. An actual battery is made up of two or more cells. The zinc-air cell produces about three quarters of a volt.
Our mechanical process is able to recover 100% of the steel in each battery for reuse. 60% of the battery is made up of a combination of materials like zinc, manganese and potassium. These materials are all earth elements. This combination of material is 100% recovered and reused as a micro-nutrient in the production of fertilizer to grow corn. The remaining 15% by weight is made up of paper and plastic.