Recovery of Ammonia from Anaerobic Digestate

Published on by for PRD Tech, Inc.

Recovery of Ammonia from Anaerobic Digestate

Bio-Ammonia – A new Twist to an Old Molecule

Ammonia is used as a household chemical for cleaning, is used in fertilizer production (ammonium sulfate, nitrate and phosphates), and has even been studied as a replacement for hydrogen.  About 180 million tons of ammonia are produced every year.  Did you know that ammonia is known with different colors?  Yes, there is Grey Ammonia, which is also known as Brown Ammonia and is produced by chemically combining hydrogen with nitrogen at a high temperature and pressure (Haber-Bosch process). Hydrogen is produced from methane which produces Carbon dioxide, an earth warming gas. Blue Ammonia is Grey (Brown) ammonia in which the carbon dioxide produced during hydrogen production is captured. Green ammonia is produced from hydrogen obtained by electrolysis of water using green electrical energy (hydroelectric, air turbines, solar panels, etc.). Finally, there is Turquoise ammonia in which the hydrogen used is produced by pyrolysis of methane to form pure carbon and hydrogen.  While ammonia gas has no color, its method of production has been used to assign a color to its name.

And now PRD Tech (www.prdtechinc.com) introduces Bio-Ammonia , which is truly green since it is degassed from anaerobic digestate (anaerobic digestion of biomass, food waste, wastewater solids, etc.).  It represents an example of nitrogen, in the form of ammonia, separation, recycle and reuse as fertilizer, fuel, etc. Anaerobic Digestate is the liquid left in the anaerobic reactor after the organic feed (waste biomass, wastewater solids, agricultural waste, waste food, etc.) has been used to generate biogas.  Since there is no nitrogen in biogas, the liquid left behind (digestate) is rich in nitrogen and phosphorus.

While the exact composition of digestate depends on the organic feed, typically for agricultural waste, waste biomass, each ton of organic waste contains 2.1 – 3.8 tons of Nitrogen, which equates to 2.55 – 4.6 tons of ammonia.  With the large volumes of organic waste produced in the USA each year, 78.7 million tons of organic municipal solid waste, 335 million tons of animal manure, and 130 million tons of biosolids and 103 million tons of wasted food, there is potential to develop a viable Bio-Ammonia industry via anaerobic digestion (AD) that can boost the economy and provide a reliable, distributed source of renewable energy and fertilizers while reducing greenhouse gas emissions.  The production of ammonia in the US is about 15 million tons in 2020.

In addition to making fertilizers, Bio-Ammonia has many other applications. One application is its use in the transportation sector as a shipping and marine fuel, since it has zero-carbon emissions and has no sulfur content. This causes ammonia fuel to be compliant with IMO 2020 and IMO 2050.  Ammonia has also been considered as an alternate to hydrogen, especially since hydrogen is difficult to store.

According to Argus estimates, at current electricity prices the levelized cost of hydrogen would be around $4-5/kg, which would result in an ammonia cash cost of over $650/ton. This cash cost only refers to operating cost, excluding capital costs for both hydrogen and ammonia itself.  In comparison, Bio-Ammonia can be produced from anaerobic digestate at 1/10 the cost ($65/ton).  This is a significant reduction in ammonia cost compared to grey, green, blue or turquoise ammonia.

Information

Media

Taxonomy