Though most don’t think about what happens after a toilet is flushed, Dario Presezzi and his team of five have been hunkered down in trailers at a Redwood City wastewater treatment plant for the last five years laser focused on just that.

Presezzi is the CEO of Bioforcetech, a company working on a system that creates the energy required to turn the human waste collected from wastewater treatment plants into a rich fertilizer.

Starting in April, the small team of Italian natives that make up the Bioforcetech team have the opportunity to make a large dent in a problem most prefer not to think about — what happens to the truckloads of human waste processed at wastewater treatment plants — when they will begin processing half, or 7,000 tons, of the Silicon Valley Clean Water treatment plant’s biosolids, a friendly term the Bioforcetech team uses for human waste.

For Daniel Child, manager of the Silicon Valley Clean Water treatment plant, the Bioforcetech team’s work offers another option for solving a problem with few tried and true solutions. Currently, the biosolids that come through the plant are spread out on land to be dried by the sun for days before they are trucked out of the plant to fertilize farms in Solano County or nearby cities like Sacramento or Modesto. “Disposal of biosolids is an ongoing challenge in the state of California,” he said. “It’s always good to have more than one option.”

When Presezzi and a few colleagues came to the Silicon Valley Clean Water treatment plant from Italy to explore how their system could work in the United States in 2011, it wasn’t clear the marshy land at the tip of Redwood Shores would become home to their offices.

But ever since 2011, when the plant treating wastewater from Redwood City, San Carlos, Belmont and other jurisdictions voiced support for their team, the six members of the Bioforcetech team have been hard at work refining a college project. “It wasn’t really that we dreamed about doing this our whole lives,” said Presezzi.

The CEO, who is now 29, came up with the idea to find a new way of dealing with the biosolids collected at wastewater treatment plants with two other friends studying biotechnology at the University of Milan some six years ago.

“Usually, this process was approached by engineers, so nobody thought [about] using bacteria and life to try to dry biosolids,” he said. “So we came up with this idea and we tested it a little bit and it worked on a small scale.”

Spreading the solids out on land or using a gas dryer to shrink them before they are shipped to farms as fertilizer are two methods currently used, causing Presezzi and his friends to wonder if biology might be used to accelerate the process and generate the energy needed to fuel it.

Their curiosity has led them to design a set of large cylinders aimed at accelerating a process similar to compost, in which oxygen-fueled bacteria break down the solid matter into smaller pieces. “In 48 hours, we are able to dry biosolids without using any gas from about 80 percent water to 20 percent water,” he said.

Presezzi said the process to dry the biosolids using a composting method could take up to 20 days if not accelerated. Once dried, the shrunken biosolids are then ushered into another machine that heats them up in the absence of oxygen to about 1,100 degrees Fahrenheit, causing more of the mass to evaporate and creating the energy used to fuel the two machines. The process, called pyrolysis, also produces thousands of small, black particles with large pores and a volume that is 8 percent of the volume of the waste fed into it.

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