City explores ways to transform commercial food waste into renewable energy

Everytime you throw scraps of vegetables or leftover food into your garbage disposal, the organic matter gets liquefied and transported through Philadelphia’s sewage system to water pollution control plants, where they’re then transformed into energy.

Water waste plants in southwest and northeast Philadelphia break down that liquified organic matter through an anaerobic digestion process to create biogas and biosolids. The resulting gas is then combusted to generate electricity and heat, and the solids are turned into little pellets of fertilizer or fuel.

According to Philadelphia’s Office of Sustainability, the biogas cogeneration plant in the Northeast Water Pollution Control Plant currently creates 34 million kilowatt hours of energy annually — the equivalent to installing solar energy in more than 5,800 houses — which can provide up to 85 percent of all the electricity used by the water treatment facility.  

But there’s capacity — and the necessity —  for more.

In December 2016, Mayor Jim Kenney announced a city-wide goal to reduce the amount of waste that ends up in landfills and incinerators 90 percent by 2035. Members of the Zero Waste and Litter Cabinet told PlanPhilly that the only way to achieve the goal was by increasing the organic diversion, i.e. keeping more food and other biodegradable matter out of the trash can by alternative disposal means. 

The Philadelphia Streets Department estimates that food waste constitutes 18.3 percent of the municipal solid waste that ends up in landfills, about 240,609 tons of food waste per year. About 78 percent of food waste is commercial — coming from restaurants, groceries, and other businesses.

Looking for ways in which the city could accept more organic material, the Philadelphia Water Department assessed the capacity on its anaerobic digesters and realized there was room for more waste if they were directly fed with pre-treated, liquefied food waste.

In June, the Water Department issued a food waste co-digestion Request For Information (RFI) to solicit ideas and possible business plans from potential vendors and evaluate possible scenarios for accepting pre-processed food waste.

“We were considering doing the direct decomposition of food in our anaerobic digesters, so the RFI is: Does anyone wants to do that with us?” Philadelphia Water Department’s Paul Kohl said. “We received interest, people showed up for the informational meeting, people are asking questions. So yes, there’s interest in the market place.”

To submit a response the interested vendors are asked to detail the process they would use to obtain, process, and deliver the liquefied food waste to one of the waste water plants. But the Water Department is not saying exactly how much extra capacity the plants have. Kohl said the idea is to start small, and part of the information they want to find out is what’s the minimum amount of food waste vendors would need to make a viable proposal.

Kohl said they expect most of the interest coming from companies dealing with commercial waste. Since 2015, what’s known as the “dumpster bill” prohibits businesses from mixing food waste with non-recyclable waste. Business owners are required to dispose food waste in garbage disposals or arrange for private collection for composting, anaerobic digestion or for use as farm livestock feed.

The Water Department has heard from large national waste hauling companies, pretreatment manufacturers, engineering firms, energy service companies and other companies who handle liquefied food waste. The information session sign in sheet showed  potential interest from firms like Waste Management, Denali Water Solutions, BioHighTech, Trenton Biogas, and Veolia.

Waste Management representative John Hambrose said his company is preparing a response presenting a solution for Philadelphia based on their experience delivering the slurry organic product to municipal anaerobic digesters in New York City, Los Angeles and Boston. Sam Holloschutz from Circle Compost, a local food waste company, told PlanPhilly they were looking into the RFI to see if they can come up with a proposal.

The Zero Waste and Litter Cabinet is expected to present its plan next week, with organic diversion playing a big role on it. There’s been a lot of interest in finding ways to make composting commercially viable, but Kohl implied anaerobic decomposition could be a better alternative because requires less land.

“We’re not saying yes to one and no to the other, is just that everyone should be aware that composting takes up a lot of land,” said Kohl.

If the RFI leads to a Request For Proposals, the implementation of this alternative will also produce more renewable natural gas.  

“If we get more organic mass diverted from landfills, we put more of it into anaerobic digesters, we produce more biogas, then we have more energy. Next thing you start saying is hey, what is the highest invest use of this biogas?” Kohl said. “But that is outside the scope of this RFI.”

Philadelphia’s Office of Sustainability Adam Agalloco said that if the Water Department creates more biogas that they could use, then there are opportunities of cross collaboration with the rest of the city’s agencies. Biogas production is carbon-neutral and doesn’t add to greenhouse gas emissions. According to the Water Department, the biogas cogeneration plant avoids 32,300 metric tons of CO2 emissions each year, equivalent of taking 5,000 cars off the road.

Agalloco said the city is investigating projects for renewable energy production and that the Energy Master Plan to be released later this year will outline opportunities to invest in renewable energy on City-owned property.

Kenney administration’s goal is to reduce Philadelphia’s carbon emissions 80 percent by 2035. In June, the mayor announced his support for a goal of transitioning Philadelphia to 100 percent clean, renewable energy.

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