via Drexel University
The wastewater draining from massive pools of sewage sludge has the potential to play a role in more sustainable agriculture, according to environmental engineering researchers at Drexel University.
A new study, looking at a process of removing ammonia from wastewater and converting it into fertilizer, suggests that it’s not only technically viable, but also could help to reduce the environmental and energy footprint of fertilizer production — and might even provide a revenue stream for utilities and water treatment facilities.
A Sustainable Nitrogen Source
The production of nitrogen for fertilizer is an energy-intensive process and accounts for nearly 2% of global carbon dioxide emissions. In the last several years researchers have explored alternatives to the Haber-Bosch nitrogen production process, which has been the standard for more than a century. One promising possibility, recently raised by some water utility providers, is gleaning nitrogen from the waste ammonia pulled from water during treatment.
“Recovering nitrogen from wastewater would be a desirable alternative to the Haber-Bosch process because it creates a ‘circular nitrogen economy,’” said Patrick Gurian, PhD, a professor in Drexel’s College of Engineering who helped lead the research, which was recently published in the journal Science of the Total Environment. “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 Way to Clean
Under the Clean Water Act of 1972 municipal water treatment facilities have been challenged to meet water quality standards for water that they discharge into waterways. Increasingly ammonia is seen as both a concern for aquatic environments as elevated levels of ammonia can result in overgrowth of vegetation in streams and rivers which can endanger fish species. The options for removing ammonia are generally time and space consuming and can be energy-intensive undertakings.
One option being explored by several facilities in North America and Europe is a process called air-stripping. It removes ammonia by raising the temperature and pH of the water enough to convert the chemical into a gas, which can then be collected in concentrated form as ammonium sulfate.
But deciding on making the investment to convert to air-stripping requires a complex study – called a lifecycle analysis — of its technological and financial viability.
Exploring the Option
The team, led by Gurian and Sabrina Spatari, PhD, from Technion Israel Institute of Technology, regularly perform these analyses to take stock of the full environmental and economic impact of various options for recycling and reuse of waste or side-stream products as sustainable solutions. Their analysis of this wastewater scenario suggests there is a complementary relationship that could result in a more sustainable path for both farmers and water management authorities.
“Our analysis identifies a significant potential for environmental mitigation and economic benefit from implementing air-stripping technology at wastewater treatment plants 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.”
Using data from Philadelphia’s water treatment facility and several others across North America and Europe, the team conducted its lifecycle assessment and economic feasibility studies. They looked at factors ranging from the cost of installing and maintaining an air-stripping system, to the concentration of ammonia and flow rate of the wastewater; to the sources of energy used to drive the collection and conversion process; to the production and transportation cost and market price of the fertilizer chemicals.
Promising Results
Findings of the life-cycle analysis show that air-stripping emits about five to 10 times less greenhouse gas than the Haber-Bosch nitrogen-producing process and uses about five to 15 times less energy.
From an economic perspective, the overall cost of producing fertilizer chemicals from wastewater is low enough that the producer could sell them at a price more than 12 times lower than Haber-Bosch-produced chemicals and still 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.”
In addition, the study suggests that water treatment facilities may enjoy energy savings by air-stripping the ammonia to reduce levels before the water it reenters the waste treatment process. This is because it would cut the time and processing needed to treat the water and fits in well with softening processes that help to slow chemical deposition on the treatment plant infrastructure.
While the team acknowledges that air-stripping would churn out fertilizer in smaller amounts than the industrial Haber-Bosch process, being able to collect and reuse any quantity of resources helps to improve the sustainability of commercial agriculture and prevents them from becoming water pollutants.
“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 said. “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.”
Original Article: Study: Turning Wastewater into Fertilizer Is Feasible and Could Help to Make Agriculture More Sustainable
More from: Drexel University | Technion-Israel Institute of Technology
The Latest Updates from Bing News
Go deeper with Bing News on:
Wastewater into fertilizer
- Carbon markets could finance green wastewater infrastructure for a huge win-win-win
Researchers found that green wastewater infrastructure could achieve stringent water quality standards, sequester 4.2 million metric tons of carbon emissions—and save $679 million per year.
- Waste Deep
This investigation included Tyson facilities that piped wastewater directly into waterways ... phosphorus, and manure fertilizer—which can run off into waterways, resulting in serious environmental ...
- The future of fertilizer? Pee, says this Brattleboro institute.
The institute, its partners and others in the sustainability industry see the practice — dubbed “peecycling” — as a cheap, easy and less-destructive method than synthetic fertilizer.
- Turning human waste into fertilizer? Lakeland is considering it with a $120K study
T he city of Lakeland is thinking about getting into the fertilizer business — and using tons of human waste it already collects to do it. Commissioners recently voted to spend $120,000 on a six-month ...
- Recovering phosphorus from sewage sludge ash to address problem of diminishing supplies of phosphorus ores
Valuable supplies of phosphorus could be recovered from sewage sludge ash, which remains after the sludge has been burned for electric power generation. The method has been developed by chemical ...
Go deeper with Bing News on:
Circular nitrogen economy
- Using Industrial Waste to Fight Pollution in Brazil
Biogas production involves extracting energy from filth, from the most disgusting environmental pollution, and at the same time avoiding the worsening of the global climate crisis ...
- A circular economy for a healthy people and planet
General, calls for a shift towards a circular economy to achieve global goals and address inequalities, speaking on behalf of UNEP Executive Director Inger Andersen.
- Should Bioplastics Be Allowed in Organic Compost?
The USDA will decide if synthetic, biodegradable food packaging and service ware should be allowed as a feedstock in certified organic compost.
- From cradle to cradle: Why industry must embrace the circular economy
Analysts estimate that to bring human activity in line with safe limits for the planet, we need to reduce material extraction and consumption by one-third. Efficient and more circular use of materials ...
- The Challenges — and Opportunities — of Establishing a More Circular Mushroom Economy
As demand flourishes, managing the waste from the growing process (known as substrate) poses some problems but brings solutions that could ensure a sustainable future for the market ...