Story by Robin Brunet
Dual Mechanical Ltd. of Surrey is no stranger to complicated projects. In fact, this company is quickly gaining a reputation for its expertise in wastewater and alternative energy development. Dual Mechanical Ltd. received a Gold award from the Vancouver Regional Construction Association (VRCA) in 2012 for the mechanical systems at the Annacis Wastewater Centre in Vancouver, B.C.
Fulfilling Ladner-based Seabreeze Farm Ltd.’s plan to use anaerobic digestion to provide energy domestically was a new and exciting challenge. It also earned the company another 2015 Gold Award.
Engineered and supported by CH Four Biogas, a company specializing in anaerobic digestion, the Seabreeze project would convert manure from 250 milking cows into natural gas for about 1,000 Metro Vancouver homes. The manure would also be turned into cost-efficient cow bedding and a solid, compacted nutrient for use as fertilizer.
In order to achieve this, an anaerobic digester bio-gas plant had to be built that would produce the methane gas; the excess nutrients from the digester would, thanks to a Trident Bedding and Nutrient Recovery System, be converted into fibre for the auxiliary products. Additionally, a Trident Nutrient Recovery System would convert the remaining liquid material into water and concentrated NPK nutrients.
For Dual Mechanical Ltd. estimator/project manager Stuart Burnside, the project correlated nicely with the skills of his colleagues.
“We’ve worked on manure conversion projects in the past in the Fraser Valley, albeit on a small scale, and on a personal level I’ve been in plumbing for 30 years and love work that is new and challenging.”
Following a feasibility study carried out in 2010, Dual Mechanical Ltd was contacted about a year ago by Kloot Construction, Seabreeze’s general contractor, and construction began in the spring of 2014. Dual was responsible for the heating, domestic water, drainage and process piping for the project, and it consulted extensively with CH Four Biogas to determine the correct components for the manure conversion process.
Burnside said that “In some ways, even projects of this scope are basically pipe jobs, running from A to B with the challenge being to ensure there are no leaks. But on a regulatory level alone, things have changed. For wastewater projects, it’s essential you use the right materials for the project.”
The three tanks comprising the plant are a 2500m3 manure digester, a 20-foot liquids tank for organic oils, and a same-size hydrolyzer tank for food waste from Metro Vancouver. The heating component for the digester required “thirteen kilometers of pipe, with 24 runs around its circumference,” says Burnside.
Unlike in past projects, the construction of the tanks required crews to do more than merely wrap the pipes around the structures. These tanks were built using the Octaform PVC stay-in-place concrete forming system, meaning the pipe had to be threaded through webbing between the layers of skin comprising the tank walls. “It took four people an entire week to complete,” says Burnside.
Adjustments to equipment procurement and contracting ultimately benefitted the project. Originally, hydraulics would have opened and closed gates within the processing plant, but electric motors were chosen instead. “It would be one less thing to go wrong,” explains Burnside. “However, we had to source explosion-proof motors, given the hazards of methane gas build-up.”
Originally Dual Mechanical Ltd earmarked a local company to build two 15-foot flare towers for the plant, but the owners instead went with an American firm and Burnside says the outcome was favourable. “Although there was a lot of back and forth to make sure everything was CSA approved, we actually achieved a significant cost savings,” he says.
A variety of pumps were required for both the processing and heating portions of the waste conversion, and special attention was given to the 20-horsepower pump that would sit at the bottom of the hydrolyzer tank. “It had to operate reliably and handle six loads of waste daily from Metro Vancouver,” says Burnside.
Components for the pump came from Switzerland and Peru and were assembled in Ontario, but when the pump arrived on site and was tested, it was discovered that it had been assembled incorrectly. In collaboration with the manufacturer, “we had to take it apart and re-assemble,” laughs Burnside.
Although construction was completed in March of this year, in some ways the most important part of the project remained: tweaking the system to ensure it performed at optimum efficiency.
“During that time, for example, I replaced a lot of copper pipe and switched fittings with stainless steel, because the methane turned out to be incredibly hard on copper,” says Burnside.
As of September, Seabreeze was producing 225 cubic metres of methane gas daily for FortisBC. Annual production is pegged at approximately 12,000 tons/yr of off-farm organics, with the biogas cleaned (carbon dioxide and hydrogen sulfide is removed) and then sold to FortisBC for injection into the existing natural gas pipeline.
Dual Mechanical Ltd is heavily involved in another project for the client: the installation of a generator to power the entire farm and back feed into the BC Hydro line. Burnside says, “Feasibility testing is underway, and we’re also busy working on the system to extract sulfur from the gas produced at Seabreeze…that should be installed by the end of 2015.”
Doug Stout, FortisBC’s vice-president of energy solutions and external relations, told media that while projects like Seabreeze represent energy solutions that are still in their early days, his company is evaluating large participants and is optimistic about future growth:
“We would see potentially 2 to 3 per cent of our total natural gas distributed coming from renewable natural gas in the next few years.”