Turning wastewater into fertilizer is feasible and could make agriculture more sustainable


Graphical summary. Credit score: Science of The Whole Atmosphere (2022). DOI: 10.1016/j.scitotenv.2022.159499

The wastewater draining from huge swimming pools of sewage sludge has the potential to play a job in more sustainable agriculture, in keeping with environmental engineering researchers at Drexel College.

A brand new examine, taking a look at a technique of eradicating ammonia from wastewater and changing it into fertilizer, means that it isn’t solely technically viable, but additionally could assist to scale back the environmental and vitality footprint of fertilizer manufacturing—and may even present a income stream for utilities and water remedy amenities.

A sustainable nitrogen supply

The manufacturing of nitrogen for fertilizer is an energy-intensive course of and accounts for practically 2% of worldwide carbon dioxide emissions. Within the final a number of years researchers have explored alternate options to the Haber-Bosch nitrogen manufacturing course of, which has been the usual for more than a century. One promising risk, lately raised by some water utility suppliers, is gleaning nitrogen from the waste ammonia pulled from water throughout remedy.

“Recovering nitrogen from wastewater would be a desirable alternative to the Haber-Bosch process because it creates a ‘circular nitrogen economy,'” stated Patrick Gurian, Ph.D., a professor within the School of Engineering who helped lead the analysis, which was lately printed within the journal Science of the Whole Atmosphere.

“This means we are reusing existing nitrogen rather than expending energy and generating greenhouse gas to harvest nitrogen from the atmosphere, which is a more sustainable practice for agriculture and could become a source of revenue for utilities.”

A cleaner method to clear

Underneath the Clear Water Act of 1972 municipal water remedy amenities have been challenged to satisfy water high quality requirements for water that they discharge into waterways. More and more ammonia is seen as each a priority for aquatic environments as elevated ranges of ammonia can lead to overgrowth of vegetation in streams and rivers which might endanger fish species. The choices for eradicating ammonia are typically time and area consuming and might be energy-intensive undertakings.

One possibility being explored by a number of amenities in North America and Europe is a course of known as air-stripping. It removes ammonia by elevating the temperature and pH of the water sufficient to transform the chemical into a gasoline, which might then be collected in concentrated type as ammonium sulfate.

However deciding on making the funding to transform to air-stripping requires a fancy examine—known as a lifecycle evaluation—of its technological and monetary viability.

Exploring the choice

The group, led by Gurian and Sabrina Spatari, Ph.D., from Technion Israel Institute of Know-how, frequently carry out these analyses to take inventory of the complete environmental and financial affect of assorted choices for recycling and reuse of waste or side-stream merchandise as sustainable options. Their evaluation of this wastewater situation suggests there is a complementary relationship that could lead to a more sustainable path for each farmers and water administration authorities.

“Our analysis identifies a significant potential for environmental mitigation and financial profit from implementing air-stripping know-how at wastewater remedy vegetation for producing ammonia sulfate fertilizer,” they wrote.

“In addition to ammonia sulfate production as a marketable product, the benefit of reducing the ammonia load in the side-stream before it is recycled into the wastewater stream at the wastewater treatment plant provides an additional justification for adopting air stripping.”

Utilizing knowledge from Philadelphia’s water remedy facility and a number of others throughout North America and Europe, the group carried out its lifecycle evaluation and financial feasibility research. They checked out elements starting from the price of putting in and sustaining an air-stripping system, to the focus of ammonia and circulate price of the wastewater; to the sources of vitality used to drive the gathering and conversion course of; to the manufacturing and transportation value and market value of the fertilizer chemical substances.

Promising outcomes

Findings of the life-cycle evaluation present that air-stripping emits about 5 to 10 occasions much less greenhouse gasoline than the Haber-Bosch nitrogen-producing course of and makes use of about 5 to fifteen occasions much less vitality.

From an financial perspective, the general value of manufacturing fertilizer chemical substances from wastewater is low sufficient that the producer could promote them at a value more than 12 occasions decrease than Haber-Bosch-produced chemical substances and nonetheless break even.

“Our study suggests that recovering ammonia can be cost-effective even at low concentration,” they write. “Although high ammonia concentration is environmentally favorable, and can simultaneously support marginal production of ammonium sulfate with lower environmental impact, particularly for life cycle energy, greenhouse gas emissions, and several human and ecosystem health indicators, compared to the Haber-Bosch production.”

As well as, the examine means that water remedy amenities might take pleasure in vitality financial savings by air-stripping the ammonia to scale back ranges earlier than the water it reenters the waste remedy course of. This is as a result of it could lower the time and processing wanted to deal with the water and suits in nicely with softening processes that assist to gradual chemical deposition on the remedy plant infrastructure.

Whereas the group acknowledges that air-stripping would churn out fertilizer in smaller quantities than the commercial Haber-Bosch course of, having the ability to accumulate and reuse any amount of assets helps to enhance the sustainability of economic agriculture and prevents them from turning into water pollution.

“This indicates that air-stripping for recovery of ammonium sulfate could be a small part—but an important step—toward recovering and reusing the massive amount of nitrogen we use to sustain global agriculture,” Spatari stated.

“And, significantly it presents an alternative for chemical production that does not have the same level of deleterious environmental and human health effects as the current process. This research suggests that water utility providers could also consider investing in technologies that would capture phosphorous and recycle it for agricultural use.”

More data:
Saurajyoti Kar et al, Life cycle evaluation and techno-economic evaluation of nitrogen restoration by ammonia air-stripping from wastewater remedy, Science of The Whole Atmosphere (2022). DOI: 10.1016/j.scitotenv.2022.159499

Supplied by
Drexel College

Turning wastewater into fertilizer is feasible and could make agriculture more sustainable (2022, November 18)
retrieved 18 November 2022
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