The question of whether a person can “make their own water” has two distinct answers depending on the definition of “make.” One refers to the literal chemical process of creating a water molecule (H2O) from its constituent elements, which is a complex and high-energy endeavor. The other, more practical interpretation involves the harvesting or extraction of existing water vapor or non-potable liquids from the environment. While synthesizing water is a scientific reality, obtaining usable water for drinking or other needs relies almost entirely on collection and purification techniques. This distinction shifts the focus from laboratory-scale chemistry to applied environmental science and survival skills.
The Chemical Reality of Water Synthesis
Water is created chemically through a synthesis reaction involving hydrogen gas (H2) and oxygen gas (O2), following the balanced equation \(2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}\). This reaction is highly exothermic, meaning it releases a significant amount of heat once initiated. To start the process, an activation energy is required, typically supplied by a spark or sufficient heat to break the bonds holding the hydrogen and oxygen molecules together.
The reaction, essentially the combustion of hydrogen, is extremely rapid and can result in a dangerous explosion if large quantities of gas are involved. Furthermore, the raw material—free hydrogen gas—is not readily available on Earth, as most of it is already chemically bonded. To obtain the hydrogen, it must first be extracted through energy-intensive processes like the electrolysis of water, which splits water back into hydrogen and oxygen. This requirement for high initial energy input and the inherent danger make the chemical synthesis of water entirely impractical and inefficient for meeting daily water needs.
Harvesting Atmospheric Moisture
The most common way to “make” usable water is by capturing the moisture already suspended in the air, a process known as Atmospheric Water Harvesting (AWH). The fundamental principle behind all AWH technologies is condensation, which occurs when warm, moist air cools below its dew point. This cooling causes the water vapor to change phase and turn into liquid droplets that can be collected.
One simple, low-tech method is the use of a solar still, which can be designed to pull moisture from the air or wet ground. The still uses solar energy to heat and evaporate water, which then rises and condenses on a cooler surface, like plastic sheeting, before dripping into a collection vessel. Dew condensers are another passive technique, using surfaces that cool down below the surrounding air temperature at night, causing dew to form and collect.
For a more automated and efficient process, mechanical systems like Atmospheric Water Generators (AWGs) or dehumidifiers use refrigeration cycles. These devices actively cool a surface to a very low temperature, forcing condensation to occur even when the relative humidity is not extremely high. While refrigeration-based systems are effective, they require a significant energy input, making their efficiency dependent on local energy costs and humidity levels. Newer technologies are exploring the use of specialized materials, such as desiccants or metal-organic frameworks, which absorb water vapor even in arid conditions and then release it upon heating for collection.
Extracting Water from Biological Sources
In survival situations, water can be extracted from living matter, distinct from atmospheric vapor. The process of plant transpiration can be harnessed to collect clean water vapor released by leaves. This technique involves placing a clear plastic bag over a leafy, non-toxic branch and sealing it tightly around the stem.
Sunlight heats the bag, causing the plant to release moisture through its stomata, which then condenses on the inside of the cooler plastic. The collected water runs down to the lowest point of the bag, where it can be consumed. Since the water is essentially distilled by the plant’s natural filtration system, it is often clean, though one may need to set up several bags for four to five hours to yield a usable amount, potentially up to half a liter from a single setup.
In extremely dry environments, some plants, such as specific cacti or vines, naturally store water in their roots or fleshy parts, which can be a source of hydration. However, caution is necessary, as many plants and their saps are toxic, and identifying safe species requires specialized knowledge. Obtaining water from animal sources, such as the eyes or blood of fish or game, is an absolute last resort due to the high risk of contamination and the presence of salts, which can worsen dehydration.
Reclaiming Highly Contaminated Water
Another form of “making” water involves converting existing, non-potable liquids into safe drinking water through purification and reclamation. This process is used extensively in municipal “potable reuse” projects, where advanced treatment turns wastewater into water that meets drinking standards.
Distillation
Distillation is an effective method for removing non-volatile contaminants, including salts, heavy metals, and many pathogens. The process involves boiling the contaminated water, capturing the resulting steam, and then condensing it back into a purified liquid. This technique is applicable to highly polluted sources, including saltwater or, in extreme scenarios, reclaimed greywater or urine, as the process leaves behind the dissolved solids and most contaminants.
Advanced Filtration
Advanced filtration methods, like multi-stage filters or systems based on reverse osmosis (RO) principles, are employed to remove suspended solids, pathogens, and chemical contaminants. RO uses pressure to force water through a semipermeable membrane, effectively filtering out most dissolved nonvolatile organic materials. While boiling or using chemical disinfectants like chlorine or iodine can kill biological contaminants, only distillation and advanced filtration effectively remove non-volatile chemicals and salts from severely polluted sources. Regardless of the initial source, reclaimed water must undergo rigorous testing to ensure it meets safety regulations before it is deemed potable.