Tag: wastewater

OM in the News: Making Renewable Natural Gas Directly from Waste

A new method for treating sewage sludge from a wastewater treatment plant efficiently created renewable natural gas while reducing the cost of the treatment. The work could help communities sustainably clean up waste while getting renewable natural gas for their energy needs.

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When workers at Washington State U. pretreated sludge collected from a nearby wastewater facility, they produced 200% more renewable natural gas compared to current practices and reduced the final disposal cost by nearly 50%. Renewable natural gas could be used in the same way as fossil-fuel based natural gas for a wide variety of uses, including for electricity generation, home heating, or for transportation without the same climate effect as fossil fuels.

“This technology basically converts up to 80% of the sewage sludge into something valuable,” said Prof. Ahring in WSU Insider (April 21, 2016). The WSU team added a pretreatment step, treating the sludge at high temperature and pressure with oxygen added before the anaerobic digestion process. The small amount of oxygen under high-pressure conditions acts as a catalyst to break down the long polymer chains in the material. The team showed that their pretreatment resulted in reduced cost to treat the sewage from $494 to $253 per ton of dry solids.

“This approach not only enhances carbon conversion efficiency and methane yield but also enables direct production of pipeline-quality renewable natural gas with minimal CO2 content — addressing two major limitations of existing sludge-to-energy systems into a single, scalable methodology,” said Ahring.

Wastewater treatment facilities use large amounts of electricity to clean up municipal wastewater, making up between 3% and 4% of the total electricity demand in the U.S. They are often the largest user of electricity in a small community. Their treatment processes also contribute to global warming, adding about 21 million metric tons of greenhouse gases to the atmosphere annually.

About half of the 15,000 wastewater treatment plants in the U.S. use anaerobic digestion to reduce sewage waste and make biogas, but the process, in which microbes break down the waste, is inefficient and struggles to break down all the complex molecules in the sludge.

Classroom discussion questions:

  1. Why is wastewater such an important issue?
  2. Referring to Supplement 5 in your Heizer/Render/Munson text, how does this support the triple bottom line?

Guest Post: Drinking Graywater Beer?

Prof. Misty Blessley, at Temple U., raises an interesting sustainability issue.

Every drop of water on Earth is part of a continuous cycle. The same water brewed into beer eventually  travels through wastewater systems before being treated and returned to the environment, ready to be consumed again. Gray water is defined as: wastewater from showers, baths, bathroom sinks, and washing machines, excluding toilet water (blackwater) and water from kitchen sinks/dishwashers.

A San Francisco firm, Epic Cleantec, makes this cycle explicit by brewing beer with recycled graywater from showers and laundry. Buildings globally use 15% of all potable water, yet almost none reuse it. Partnering with nearby Devil’s Canyon Brewing Company, it created two beers—Shower Hour IPA and Laundry Club Kölsch, using water purified through a multi-stage system until it meets or exceeds potable water standards. Their approach demonstrates how scarce resources can be sourced in new and innovative ways.

Reusing waste water can help counteract climate change

The supply chain implications are significant. Brewing is water-intensive, requiring several gallons of water for every gallon of beer produced. As climate volatility and drought increasingly pressure municipal water supplies, integrating recycled water helps mitigate supply risk. Pairing this with drought-tolerant barley and hops further enhances supply chain resilience by mitigating upstream agricultural vulnerabilities.

Epic Cleantec’s model represents circular economy principles in action: closing loops, recapturing resources, and turning waste streams into valuable inputs. Many other food and beverage companies are embracing similar strategies. Rubies in the Rubble (UK) creates condiments from surplus produce that would otherwise be discarded. Upcycled Foods, Inc. (U.S.) produces SuperGrain flour to make bread from spent brewing grain. Planetarians (U.S.) transforms spent yeast and soybeans into a vegan meat product that is competitively priced compared to chicken and below beef.

Epic Cleantec emphasizes the circularity of its inputs to build consumer acceptance, hoping customers celebrate the closed loop. For details on the “circular economy” see Supp. 5 of your Heizer/Render/Munson text.

Classroom Discussion Questions:
1.  Forecasting is covered in Ch 4 of the Heizer/Render/Munson textbook. How would you forecast demand for beers made with recycled graywater, given potential consumer hesitation?
2.  TQM Tools are covered in Ch 6. Which tools should the two firms use to ensure water quality and process reliability throughout treatment and brewing?