Just what makes a sewer nice?
Does it offer to buy you coffee? Say please and thank you?
At the recent New York Water Environment Association’s 86th Annual Conference named, “Utilities of the 21st Century: Going from Net Zero to Net Positive” ‒ the hot topic was maximizing energy production utilizing additional feedstocks for anaerobic digestion, especially from commercial and industrial sources. A panel discussion by five wastewater people spent a lot of time on the addition of food waste to digesters from source-separated organics processed at the treatment plants. That’s a lot of work. Nobody on the panel mentioned food waste disposers. One of disposers’ chief benefits is that the waste generator does all of that work for you.
When prompted by a question from the audience about using “in-sink grinders” a panelist stated “…They only make sense for other cities with nice sewers.”
I guess that would make his city’s sewers mean. Of course not– the panelist was referring to his home city’s combined sewers. With that type of system, there is the potential of a wet weather combined sewer overflow, when food waste may end up in local waterways. The greater environmental health hazard from combined sewer overflows are the pathogens in raw sewage, not microscopic ground food waste. (I have noted numerous times in this blog that despite some misconceptions, “chunks” of food are not disbursed to sewers by disposers.)
Furthermore, according to Metcalf & Eddy’s 5th Edition of Wastewater Engineering, ground food waste makes up only about 20% of the suspended solids and biochemical oxygen demand in sewage.
Communities with combined sewers should be eliminating them, and are required by the EPA to do so as part of their Long Term Control Plans. Hopefully some day we will see the demise of the mean sewer. In the meantime, food waste is, and will continue to be, a small fraction of the total composition of wastewater.
It’s “Super Bowl” time of year, and the national news is full of all your critical need-to-know’s such as psychic zoo animals predicting the game’s outcome. I’m about as clairvoyant as those creatures are – but there’s one thing about the game I could put money on: at the end of it, there will be lots of food waste to discard. That will be as true for households across America as it will be for MetLife Stadium at the Meadowlands, which is expected to produce several tons of food waste. Take a guess how many.
It should be roughly 7-8 tons. All due to one short game…think about it. Does that not make you wonder how much food waste the game of football is indirectly responsible for generating, from August to February? And what do stadiums do with all that food waste?
Used to be, it was all sent to the landfill though lately, more stadiums tried composting. But now there is another option, as undertaken by the Cleveland Browns at the end of the season just concluded. FirstEnergy field now has an organics recycling system that grinds food scraps into slurry and discharges it to a holding tank, which is pumped and hauled to an anaerobic digester for conversion into renewable energy and soil amendment. The Browns estimate they will produce enough methane to heat 32 homes for an entire month. Think of the energy that could be produced if all college and pro football stadiums used an organics recycling system. (I could come up with the calculation myself, but I need to get ready for the game now, which means a trip to the store for nachos ingredients, among other things.)
Full disclosure: the system installed at the Browns’ stadium is called Grind2Energy™ and it’s from InSinkErator, my employer. So I am not going out on a limb with this football-related prediction: by Super Bowl Sunday next year, there will be more football stadiums and sports arenas of all kinds converting food scraps into renewable energy. And to those who follow this blog and care about food scrap diversion — that will be something to cheer.
Travel to and around the UK is my excuse for the long time between postings here. (I had never been there before so I had to at least check out St. Paul’s Cathedral and the Tower of London.) One of the reasons for my visit was participation in the European Wastewater Management Conference in Manchester where I shared a paper by Harold Leverenz and George Tchobanoglous on the energy balance and nutrient removal impacts of food waste disposers . To my surprise, audience questions focused on the same concerns I often address in other technical settings back home. One person claimed food waste ends up getting screened out at the headworks of treatment plants, which is untrue because the particles are much too small ‒ less than 3 mm ‒ the typical size of the smallest screens. Some questioned the use of disposers due to the potential impacts on collection systems, i.e. settling in sewers, the contribution to fats, oils and greases, and increased maintenance costs. But sewers designed to transport human waste are perfectly capable of transporting ground food waste. I took the opportunity to educate attendees about FOG and calcium soaps. It seems wastewater professionals still view blockages as grease when in fact they are something entirely different. I was struck how the issues and questions were the same that I’ve heard many times before, thousands of miles away at North American events, until I realized what’s more surprising is – I didn’t expect them.
The highlight of the trip came on the following day when I spoke at the Royal Society at an event hosted by AMDEA to discuss food waste disposers. The Royal Society was founded in 1660 and in centuries past, members included history’s most distinguished scientists including Christopher Wren, Isaac Newton and Charles Darwin. To speak in such a historical setting was quite an experience, to put it mildly! Speakers for the AMDEA event (pictured in order) included Paolo Battistoni from Marche University of Italy, Per Henrik Nielson from Odense, Denmark, yours truly, Douglas Herbison of AMDEA, Jonathon Mattsson from Lulea University in Sweden, and Per Andersson from Surahammar, Sweden.
Speakers of the AMDEA Food Waste Disposer Roundtable at the Royal Society.
During the event we discussed the use and impact of disposers; namely how disposers are helping communities like Surahammar and Odense meet waste diversion goals. But we also discussed more complex issues like the potential concerns of settling in sewers and particulate transformation of organics in sewers, as well as the social implications of whether disposers will help reduce overall “arisings” of waste – otherwise known as generation in the US. This was an interesting point of view that I will discuss in my next post. How about you? Has your work taken you to historic or significant places in history? I’d enjoy hearing from you.