Electricraft Inc. Wraps up Waste Digester Plant in California

Liquid byproduct and biogas tank (left rear), 1-MW biogas cogen (green containers with exhaust stack), desulfurization tank and flare stack. Photos courtesy of David Horton.

For most electrical contractors, the majority of their projects are similar in nature—work they have done before and will continue to do into the future. For some, though, new opportunities occasionally come along and redefine what it means to be an electrical contractor. One such project is now front and center for Electricraft Inc. of San Luis Obispo, Calif.

The company is involved in the construction of a state-of-the-art digester plant designed to gather food waste, process it, break it down through composting, burn the gas in a cogeneration plant (which features a 1-megawatt generator), and sell the power back to the local electric utility.

In addition, the plant will turn the residual liquid and solid byproducts into fertilizer to sell to local agricultural operations. In specific, housed in a large tank, the liquid byproduct will be turned into liquid fertilizer, and the remaining solids will be screw-pressed, removed from the digester, taken to large indoor concrete drying fields with ventilation, and then sold as solid fertilizer.

"The plant will be receiving organic waste from restaurants, breweries, wineries and other places that generate organic waste, which they would otherwise have to pay to have the waste transported to landfills," said Dave Horton, Electricraft's project manager for this digester plant project.

The plant owners, Hitachi Zosen Inova USA, hired an individual to handle the general contracting in-house.

"He had previously worked for a large general contractor in California," Horton said.

After doing some research and talking with local electrical distributors, contractors and other project owners in the region, the contractor reached out to Electricraft to see if it would be interested in taking on the electrical portion of the project.

"It was still in the design phase at that time, and we did have some competition from some other electrical contractors in the state," he said.

Overhead power and control cable tray runs through an existing building (now reception building) that did not allow new underground installation. Partial crane assembly in background.
Overhead power and control cable tray runs through an existing building (now reception building) that did not allow new underground installation. There is a partial crane assembly in background. Photos courtesy of David Horton.

Through experience, Electricraft has learned that, in some industrial projects, the electrical design is the final segment to be completed, because some of the mechanical equipment, piping, etc. from vendors has to either be done or at least on its way before the owners can start determining motor sizings and other electrical details.

"At first, the owners solicited bids for just the underground portion, which we were successful with and got our foot in the door," Horton said.

The owners were happy with Electricraft's efforts, including its production, teamwork and paperwork, so they backed away from competitive bidding on the rest of the project's electrical portion and used Electricraft for the rest of the project.

After completing the underground portion, Electricraft began work on the electrical equipment portion, which included switchboards, motor control centers (MCCs), motor starters, etc., at the same time the design team was finishing up the final design.

"We actually had to build concrete trenches within the electrical room that ran the entire length of the room, since the MCC lineups and switchboard lineups weren't yet known," Horton said. "We got the conduits into those trenches as best as we could, and fortunately, the locations all ended up working out by the time the final design was completed."

Facility electrical room consisting of distribution switchboard, three intelligent motor control centers, Crane PLC/MCC, facility PLC, safety PLC, 24V battery system for 12-kV switchgear, and ethernet/network head-end. Photos courtesy of David Horton.

Electricraft then shifted to the utility interconnect portion, which is a 12-kilovolt, multidirectional tie-in that involves both underground and overhead construction.

The next phase was getting started on the top-out portion, which, according to Horton, is the bulk of the project—the termination, cabling, cable trays, lighting, controls, control infrastructure, etc.

"We have since picked up the network and ethernet portion of the project, including installation of the instrumentation devices," he said. "We will also be installing some battery systems, which will be part of the utility interconnect. There is also some talk about installing solar."

Right now, the company is about 75 to 80 percent complete with the electrical work.

"We are about two weeks out from making the interconnect with PG&E to energize the facility," he said. Horton said the commissioning process would likely continue through August and prior to the company's contract completion.

New service consisting of (left to right) 12-kV metal-clad switch and controls, 1,500 kVA transformer, and main switchboard. Photos courtesy of David Horton.

The owners had to make an agreement with PG&E to initially energize only one-way—from the utility to the project—because PG&E has to make some upgrades and additions to its outlying infrastructure and local substations before it can handle a backfeed of the size this digester project will generate via the methane gas and cogeneration. However, according to Horton, one-way at this point is not a problem because the plant needs initial power to commission itself.

"For example, all of the motors have to be started, the conveyor belts have to be fine-tuned, and the digester has to start digesting," he said.

It can take 45 to 60 days before the digester is able to create the gas and liquids it will use for fuel and fertilizer.

Biogas cooler and process piping between co-gen and desulfurization. Photos courtesy of David Horton.

To date, the project has gone smoothly. Horton attributes that to a number of things, including the fact that Electricraft has always operated with a teamwork mentality.

"We work with owners as part of a team, rather than contractor versus owner," he said.

In addition, Horton said the company has a strong focus on value engineering—helping owners keep the costs where they need to be.

"We identify deficiencies and potential problems, such as cost and lead-time issues, and then engage in value engineering so we can keep the project on time and within budget," he said.

Conveyor belt feeding digester, digester head-end with platform assembly. The digester was just insulated prior to final cladding install. Photos courtesy of David Horton.

Horton said the contractor's future looks bright.

"There are several more of these digester projects being planned throughout the state, and we would love to be a part of these, too," he said.

Now with this plant under its belt, Electricraft has a better chance of winning those bids.

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