Transforming Wastewater into Useful Chemicals

“Transformations” of all kinds are happening during this season.  Landscapes change from green to gray; streets take on lighted decorations; store speakers are suddenly playing “I’ll be Home for Christmas.”  I am into transformations, as I sit at my terminal transfixed by the complexity of transformations of nitrogen. Nitrogen is: reduced to ammonia, oxidized to nitrate, immobilized from ion to organic form, mineralized from organic to ion. All of this involves species and domains of life unknown to scientists just a few decades ago, transformed as the science is by tools of genomic technologies.

For the November’s Biosolids TOPICS, I had intended just to delve into biosolids-borne nitrogen transformations.  The importance of understanding “plant available nitrogen” (PAN) from biosolids applications had been reawakened for me in a sidebar remark at the November 14th, MABA Annual Symposium Biosolids Facilities Master Planning.  Apparently, DC Water’s Bloom product derived from thermal hydrolysis and digestion has been proving unexpectedly different from normal “MAD” [mesophilic anaerobically digested] cake in its PAN delivery to field crops, and I was hoping to understand why.

I hadn’t given PAN much thought in recent years.  After all, regulatory agencies have their tried-and-true worksheets for its calculation. For instance, in Pennsylvania, DEP’s Volatilization and Mineralization Rate Tables simply take half of the ammonia in surface applied MAD cake and 20% of the organic nitrogen to calculate the nitrogen available for crops during the first year after biosolids application.  This is just the way it is when filling out: “SUPPLEMENTAL WORKSHEET PART 2.a.2.  RESIDUAL ORGANIC NITROGEN FROM BIOSOLIDS APPLICATION IN CURRENT YEAR.”

PAN calculations in state regulations are based on sound science.  A key reference for nearly two decades has been Managing Nitrogen in Biosolids. Regulators responsibly have relied upon gold-standard research, for instance Decomposition and Plant-Available Nitrogen in Biosolids.

Yet, PAN is such a key aspect of delivering the nutrient needs of crops with biosolids that all of us -- regulators, public agencies, and farmers alike -- want to get the application rates right, and we need to re-visit the science, if circumstances warrant.  Perhaps that’s where we are today, as treatment technologies change and improve. One recent article, A critical review of nitrogen mineralization in biosolids-amended soil, the associated fertilizer value for crop production and potential for emissions to the environment, said “better characterization of biosolids used in N release and mineralization investigations is therefore necessary to improve comparison of system conditions.” This is because increased biological stabilization and product storage significantly reduced available nitrogen for crops.

But then this week’s Chemical & Engineering News arrived, emblazoned with the feature article “Wastewater Alchemy.” Alchemy is “a seemingly magical process of transformation, creation, or combination.“  Wow! How serendipitous could this be!?  I jumped to the last line at the bottom of page 34: “The merger of the wastewater and chemical industries is under way.”  The article’s tagline asserted “With sometimes offbeat technology, innovators seek to extract useful chemicals from waste.” I scanned it quickly, with my eye hitting on references to Ostara and AirPrex, but I could see it went to places that I had never before heard.  Oh, man, this article on “useful chemicals” deserves a close read!  So much for a deeper dive into nitrogen transformations.

The article, less dramatically titled online “Tapping sewage as a source of useful materials”, starts out: “Sewage stinks. It causes pollution. Few people care where it goes. Fewer chemists want to work with it. And yet, with the help of the right technology, sewage could become a reliable, low-cost feedstock for chemicals and other materials.”  The transformations described here involve much more than nitrogen.

Phosphorus extraction is a key message point in the article, and one already familiar to our biosolids industry. Because the article’s author is in United Kingdom, reference facility descriptions for P extraction are from Europe, not the United States. The article explains that Energy & Raw Materials Factory (ERMF), a consortium of Dutch municipal water treatment companies, helped develop the phosphorus recovery system at the WRRF in Amersfoort, the Netherlands, which was later “commercialized by Vancouver-based Ostara Nutrient Recovery Technologies.” The article goes on to say, “A few other phosphorus technologies are also in use around the world, including Berlin Waterworks’ AirPrex process” at the Amsterdam WRRF. The Dutch are BIG into P extraction, likely as they have had several more centuries than the U.S. to experience P accumulation in soil.

The C&E News article branched out in an unexpected direction – cellulose extraction. It described another ERMF project: “Cellulose can be readily recovered from wastewater in a simple pretreatment phase using fine sieves (“Sieving wastewater – Cellulose recovery, economic and energy evaluation“ Water Res. 2013, DOI: 10.1016/j.watres.2012.08.023).” “After the recovered cellulosic material is pressed to remove water, it can be used as feedstock for biofuels or higher-value industrial chemicals. Removing cellulose can also cut the energy consumed in conventional sludge treatment by up to 40%.”

C&E News then described polyhydroxyalkanoate (PHA) as another wastewater-derived chemical.  The article explains that “PHA is a biodegradable polymer with properties similar to polylactic acid, a bioplastic commonly used to make disposable cutlery…. research for making PHA from wastewater appears to be gathering pace.” The article goes on to report that “Veolia halted an effort to make PHA from municipal wastewater and shut down a pilot plant in Belgium.” But I have been tracking Mango Materials, a California firm, which has been operating a WRRF-based bioreactor to produce from sludge digester biogas a biodegradable fiber from PHA.  They seem to be doing alright.

Alginates is another category of chemicals that C&E News brought to my attention. The extracellular polymeric substances that are so troublesome for dewatering may be valuable. These are high-molecular-weight polymers “similar to alginate, a fairly expensive polymer extracted from seaweed and used in applications such as food and paint thickening.” C&E News reports that the European Commission is supporting a four year test by Waste2NeoAlginate of a “two-step process of extracting and refining alginate-like exopolymers from sewage sludge,” at a plant due ”to open in early 2019 with the capacity to make 400 metric tons per year of alginate-like exopolymers.”

C&E News introduced me then to furanics, another class of chemicals that can be derived from organic wastes. C&E News also introduced me to the complex interplay of governmental and industrial organizations in Europe that are evolving the Green Chemistry discipline.  One such is Biorizon, “a cross-border initiative …that aims to include the global leaders in the fields of feedstock, conversion, equipment and end products as participants…in production of functionalized biobased aromatics.” One of Biorizon’s subsidiaries is  Waste2Aromatic experimenting with a “first biphasic reactor …that converts biogenic waste [sludges] into furanic building blocks“ (Waste2Aromatics takes production of furanics to the next level”).

The next valuable chemical in this article is oleic acid.  Could wastewater alchemy be complete without algae? C&E News reports on the pre-pilot oleic acid production concept, still looking for investors in a demonstration plant and for a host wastewater plant, championed by California-based T2Energy, for “harnessing algae to convert municipal wastewater, glycerin, and CO2… into oleic acid—a building block chemical—or fuels.”

If you can embrace the entrepreneur with the dream of “providing local sources of water, energy, and organic food from recycled wastewater,” you can welcome C&E News's introduction to NuLeaf Tech .  Also in the concept stage, looking for investors, the firm’s Nutree device is a “3-m3, treelike structure that uses microbial fuel cells to pump wastewater to its crown. Plants and microbes commonly found in wetlands digest the waste and convert it into a liquid fertilizer while releasing electrons to power the fuel cells.” NuLeaf Tech is looking for a host, ideally a microbrewery, of course, to host its pilot facility. Got it??

In my favorite holiday season tradition, I will re-read Charles Dickens’ A Christmas Carol, if for no other reason than to catch the most amazing of all transformations. This happens at this slim book’s fifth and final “stave” 5, in which Ebenezer Scrooge dances for joy when he awakes to discover he has been given the chance to transform his life. The C&E News article is replete with entrepreneurial joy at the chance to transform wastewater into useful chemicals. We biosolids professionals are accustomed to urging resource recovery, but let us go even further in a joyful embrace of Biosolids Alchemy.