Turning Air into Industrial-Grade Water: AWH Pathways for Ultrapure Water in Arid Regions

Original Authors: Han Fu, Amin Mojiri, Anjali Mulchandani, Casey De Finnda, Menachem Elimelech, Shahnawaz Sinha, Paul Westerhoff

Original paper is accessible at: https://doi.org/10.1002/wat2.70086

Why AWH matters beyond drinking water

Atmospheric water harvesting (AWH) is often discussed as a solution for drinking water, emergency water supply, or off-grid communities. This review shifts the conversation toward a different and increasingly important application: ultrapure water (UPW) production for industrial systems.

Industries such as semiconductor manufacturing, pharmaceuticals, beverage production, specialty chemicals, energy production, and advanced manufacturing require large volumes of high-quality water. In many facilities, municipal tap water must first undergo extensive treatment—pretreatment, reverse osmosis, polishing, ion exchange, ultraviolet treatment, and ultrafiltration—before reaching ultrapure specifications.

This creates a central question:

Can atmospheric water become a decentralized, high-quality feed source for industrial ultrapure water systems?

The authors argue that AWH-derived water is especially attractive because it is naturally low in dissolved inorganic ions and particles, making it a potentially easier starting point for UPW production than conventional tap water.

AWH as an alternative water source for CII sectors

The review frames AWH as a potential on-site water source for commercial, industrial, and institutional (CII) users. These sectors can account for 20% to more than 50% of total potable tap water demand in larger municipal areas, and their water needs are becoming harder to meet through conservation and reuse alone.

In semiconductor manufacturing, for example, ultrapure water is essential for tool cooling, humidity control, and chip washing. The paper notes that fabricating a single wafer requires about 8 m³ of water, with approximately 75% of total water use dedicated to single-use processes. With nearly 30 million wafers produced globally each month, the water footprint is substantial.

Against this background, AWH offers a way to produce water directly from air, bypassing conventional surface water, groundwater, or seawater sources. This is especially relevant for arid and inland regions where long-distance water transport, desalination, or new water infrastructure can be expensive and logistically difficult.

Three major AWH pathways

The review compares three primary AWH technology families:

1. Fog harvesting

2. Dew-point condensation

3. Desiccant-based AWH

Each pathway has a different energy profile, climate suitability, and scalability potential.

The authors summarize the key trade-off clearly: fog harvesting is the lowest-energy option but geographically limited; dew-point condensation is commercially available but performs best in humid climates; desiccant-based systems are more adaptable across climates and especially promising for arid or low-humidity regions.

This comparison is important because industrial UPW systems require not only water production, but also reliability, predictable operation, water quality control, and integration with existing infrastructure.

Fog harvesting: low energy, limited scale

Fog harvesting is the most passive AWH option. It typically uses vertical mesh collectors that intercept wind-driven fog droplets, allowing coalesced water to drain into gutters and storage tanks. The review describes this as essentially a net-zero energy approach, because it relies on ambient wind and fog rather than active cooling or thermal regeneration.

However, fog harvesting is highly site-specific. It works best in coastal or high-altitude regions where fog is frequent and wind exposure is reliable. It can be useful for domestic or limited agricultural water supply, but the review emphasizes that it is unlikely to meet large CII water demands in most settings.

The standardized metrics reported in the review show fog harvesting at approximately:

• ~0 kWh/m³ for passive collection, excluding conveyance or pumping

• ~1.4–16.6 $/m³ depending on site yield, labor model, storage, and distribution assumptions

Mesh design matters. In a comparative study from the Moroccan highlands, spacer fabric reached 7–8 L/m²/day, while Raschel mesh collected about ~3.0 L/m²/day, showing that material and architecture can strongly influence yield. But even with improved meshes, large-scale industrial supply would require very large collection areas.

Dew-point condensation: commercially available but energy intensive

Dew-point condensation systems cool air below its dew point, causing water vapor to condense. These systems are already commercially available and commonly use vapor-compression refrigeration, similar to air conditioners or dehumidifiers.

Their performance is strongly climate-dependent. Warm, humid air contains more water vapor and therefore produces more condensate per unit of air processed. The review notes that manufacturers often rate systems under favorable conditions around 26–30°C and 70–80% RH, and under such conditions industrial units can exceed 5000 L/day. However, the energy requirement rises sharply in arid and semi-arid climates.

Reported specific energy consumption values are:

• 100–600 kWh/m³ under favorable conditions

• >2000 kWh/m³ in arid and semi-arid climates

This makes dew-point condensation scalable but energetically challenging, especially for inland desert regions where industrial water needs are growing.

The review also discusses membrane-assisted condensation as a strategy to reduce energy use. By selectively enriching water vapor before condensation, membranes can reduce the need to cool large volumes of dry air. Reported examples show energy reductions from ~1202 MJ/m³ to ~583 MJ/m³, or from ~1125 kJ/kg water to ~687 kJ/kg water, depending on system design.

Desiccant-based AWH: strongest potential for arid regions

Desiccant-based AWH systems capture moisture using hygroscopic materials and later release it through thermal regeneration. These systems include:

• solid desiccants such as silica gel, zeolites, and MOFs

• liquid desiccants such as LiCl, LiBr, and CaCl₂

• hybrid composites such as salt-loaded hydrogels and LiCl-infused porous supports

The main advantage is climate adaptability. Unlike direct condensation, desiccant systems can capture water even under lower humidity conditions, making them especially promising for arid and semi-arid industrial regions.

The review notes that current desiccant systems remain relatively small, typically <1000 L/day, but may scale to >10,000 L/day within a few years.

From an energy perspective, the major advantage is that desiccants can decouple moisture capture from cooling. Their regeneration step can potentially be driven by low-grade heat, including industrial waste heat or solar thermal energy, reducing dependence on electrical cooling.

However, challenges remain: material cost, regeneration energy, corrosion in liquid-desiccant systems, crystallization risk, carryover, and the need for reliable control of heat and mass transfer.

The thermodynamic challenge: extracting water from air is energy intensive

One of the strongest parts of this review is its standardized energy framing.

The paper emphasizes that extracting water from air is inherently more energy-intensive than desalinating seawater because ambient air contains far less water than saline water contains salt. At 25°C and 50% RH, the minimum theoretical work for AWH is approximately:

• 26.5 kWh/m³

By comparison, the thermodynamic limit of seawater reverse osmosis is about:

• ~1.06 kWh/m³

This highlights the fundamental energy gap that AWH systems must overcome.

The review uses specific energy consumption (SEC) as a standardized metric, reported in kWh/m³ of produced water, to compare technologies across different studies and system boundaries.

The challenge is not simply to make AWH work; it is to make it efficient enough for industrial deployment.

Why AWH water is attractive for UPW

Although AWH has an energy disadvantage compared with conventional water treatment, it has a major advantage in source water quality.

Municipal tap water typically contains significant inorganic salts, alkalinity, silica, metals, organic matter, particulates, and disinfection byproducts. By contrast, AWH water generally contains very low levels of inorganic ions and particles. The review states that AWH water is significantly cleaner than conventional tap water used as make-up water for UPW systems.

This matters because UPW production is not only about removing water volume from a source; it is about removing contaminants to extremely low levels.

For example, Table 3 compares water quality benchmarks:

• municipal tap water conductivity: 50 to >1500 µS/cm

• AWH water conductivity: <100 µS/cm

• semiconductor-grade UPW conductivity: 0.05 µS/cm, corresponding to resistivity >18 MΩ·cm

• municipal tap water ions: 10 to >250 mg/L

• AWH water ions: <1 mg/L

• semiconductor-grade UPW major anions/ammonium: 50 ng/L 

So AWH water is not automatically UPW, but it begins closer to UPW than municipal tap water in terms of inorganic salts, metals, and conductivity.

Water quality is still not automatic

The review is careful not to overstate AWH water quality. Although AWH water is generally cleaner than tap water, it may still require treatment depending on the application.

AWH water can contain:

• low molecular weight organic acids

• aldehydes

• VOC-derived compounds

• airborne contaminants

• dust-derived trace metals if air filtration is inadequate

• site-specific pollutants

The review notes that while AWH values often remain within drinking water standards, they can still exceed UPW thresholds by several orders of magnitude. This means polishing is still essential before AWH water can be used in semiconductor or pharmaceutical systems.

This is a critical distinction:

AWH water may reduce pretreatment burden, but it does not eliminate the need for UPW polishing.

Integration with existing UPW systems

Rather than proposing that AWH replace municipal water entirely, the review frames AWH as a supplemental auxiliary stream that can feed into existing industrial polishing and distribution systems.

This is a practical and realistic framing. AWH can reduce stress on municipal water infrastructure, improve resilience, and lower treatment burden when properly monitored and validated.

The review states that AWH integration can enhance resilience, support sustainability goals, and reduce the load on conventional treatment infrastructure. It can serve as an auxiliary stream feeding into the same UPW polishing and distribution systems already used in CII facilities.

This makes the technology particularly relevant for semiconductor hubs and other high-value industries located in arid regions.

The DARPA benchmark and the cost challenge

One of the most important benchmarks discussed in the paper is the DARPA target:

• 42 kWh/m³

• approximately ~$2/m³

The review emphasizes that current AWH technologies are still far from this target, especially under dry conditions. However, it also argues that advances in sorbents, hybrid systems, automation, thermal integration, and waste heat recovery create a realistic roadmap toward better performance.

For sorption-based AWH, reported energy input ranges from approximately:

• 116–1021 kWh/m³

with reported levelized costs around:

• ~6.5–11 $/m³ 

This shows why AWH is not yet broadly cost-competitive for bulk water supply, but may still be attractive for high-value industrial water where source quality and decentralization are important.

Waste heat as a key energy pathway

The review identifies waste heat-driven sorbent regeneration as one of the most promising strategies for reducing energy consumption.

Many industrial and commercial facilities already release large amounts of waste heat from cooling towers, HVAC systems, condenser lines, flue ducts, and process equipment. The paper highlights that waste heat is often available at 40–80°C, while emerging sorbents capable of regeneration below 60°C could directly use this energy stream.

This is especially important for desiccant-based AWH. If regeneration can be powered by otherwise wasted thermal energy, the effective energy cost of water production could decrease substantially.

The authors conclude that a 5–10× reduction in energy consumption through better sorbents, thermodynamically efficient device design, thermal recovery, automation, and waste heat utilization could allow AWH platforms to approach DARPA’s performance targets.

Hybrid systems, automation, and modular design

The review also emphasizes that future AWH progress will not come from materials alone.

Several system-level strategies are important:

Hybridization

Combining desiccant capture with condensation can improve thermal integration and allow systems to adapt to changing humidity and temperature conditions.

Phase-change materials and heat recovery

Thermal buffering and latent heat recovery loops have been shown to improve energy efficiency by about 20% in laboratory-scale prototypes.

Modular design

Cartridge-based sorbent modules and plug-and-play atmospheric water generators can reduce installation complexity and standardize maintenance.

Automation and control

Sensors for humidity, temperature, pressure drop, and water quality can feed automated controllers that optimize cycle timing, regeneration temperature, airflow, and fault detection.

This matters because AWH performance depends strongly on weather, operating schedule, and system configuration. Fixed operating conditions are unlikely to be optimal across real industrial environments.

Key insights

1. AWH is not only a drinking-water technology. It may become a supplemental feed source for industrial UPW production.

2. AWH-derived water is naturally low in inorganic salts, which can reduce pretreatment requirements compared with municipal tap water.

3. Water quality remains application-dependent. AWH water still requires polishing for UPW because organic compounds, VOC-derived contaminants, and trace pollutants may be present.

4. Fog harvesting is lowest-energy but geographically limited.

5. Dew-point condensation is commercially mature but energy-intensive in arid climates.

6. Desiccant-based AWH is the most promising pathway for low-humidity and arid regions, especially when paired with low-grade or waste heat.

7. Energy remains the central bottleneck. The DARPA target of 42 kWh/m³ (~$2/m³) is ambitious but provides a useful benchmark.

8. Waste heat at 40–80°C could be transformative for sorbent regeneration.

9. Hybridization, automation, modularity, and thermal recovery are as important as sorbent chemistry.

10. Industrial deployment requires a system-level roadmap, not just better materials.

Takeaway

This review reframes atmospheric water harvesting as more than an off-grid drinking water technology.

Its most important contribution is showing that AWH may have a high-value role in industrial ultrapure water production, especially in arid and water-stressed regions where conventional water sources are limited, expensive, or infrastructure-constrained.

The opportunity lies in the combination of:

• high-quality atmospheric condensate

• reduced inorganic pretreatment burden

• desiccant-based capture in dry climates

• waste heat-driven regeneration

• hybrid system design

• automated modular operation

The challenge is equally clear: AWH must reduce energy consumption, improve reliability, and demonstrate cost-effective integration into existing UPW systems.

In short, the future of AWH for industry will depend on moving from “water from air” as a stand-alone concept toward integrated, energy-optimized, high-purity water systems.