Cavendish Farms Bio-Gas Facility

The Cavendish Farms plant in New Annan, Prince Edward Island, processes potatoes into french fries. The “Irving Renewable Energy Project” completed in 2008 enabled its potato waste to be used as a fuel source for the facility.

By converting the waste to energy, the plant is now less dependent on oil and has reduced its waste disposal issues. The use of biogas as fuel is a carbon neutral process with respect to greenhouse gas emissions.

The project involved the construction of four primary digesters, two secondary digesters, and a material handling building to receive the raw waste. The project also added process equipment associated with biogas transfer, a hydrolysis tank, effluent dewatering, and waste water treatment. A major boiler was also upgraded to use the biogas to provide steam for the potato processing plant.

Converting waste to energy and the use of biogas has numerous benefits. The process takes normally discarded organic waste streams, which can be hard to dispose of, and changes them into a renewable fuel that can be used for mechanical/thermal or electrical energy. Biogas is an attractive renewable fuel source, since there will always be organic waste available for use as feed stock. Biogas does not add to the greenhouse effect and emissions of nitrogen oxides, carbon oxide, carbon monoxides and hydrocarbons are extremely low in comparison to the combustion of fossil fuels.

As prime consultant, Stantec worked directly with Cavendish Farms throughout the project. Stantec’s work included the preliminary design of flow diagrams, general arrangements, budgeting and scheduling. Teamed with a consultant in the field of digestion and biogas technology, Stantec provided the detailed process design, as well as civil, mechanical, electrical, instrumentation and control design. Stantec also provided construction support and was a major contributor to the commissioning of the plant.

Turning waste into value

Continuous, transparent communi- cation was necessary between Stantec and Cavendish Farms throughout the project. They dealt with variables stemming from the characteristics of the potato waste substrate, equipment availability, the automation requirements, geotechnical issues, and planning for a shutdown. The construction was completed with minimal interference for the existing operations.

Also, since some of the recommended European equipment vendors did not meet North American standards, Stantec had to find alternative equipment suppliers.

The plant processes 100,000 tons of waste per year. Previously, Cavendish dealt with the large volumes of waste primarily by depending upon numerous small third-party end users, such as farmers. The demand from these users varied based on market conditions and the quality of the waste available. The distance between the processing plant and the end users also made delivery very costly.

Today, the residual dewatered sludge, discharged from the centrifuge, is being used as a fertilizer, and can be used to create value added, environmentally sustainable products for the retail, horticultural, and large-scale agricultural markets.

The project was completed on a fast track schedule and was commissioned and ready for operation on time by the end of 2008.

During the budgeting phase major concerns were the potential gas output and the comparative cost of fossil fuels. While the gas output remains proprietary information, it can be said that the results outperform expectations.

Project name: Irving Renewable Energy Project, New Annan, P.E.I.

Award-winning firm –prime consultant: Stantec Consulting, Fredericton, N.B. (Darrin Mayo, P. Eng., Glenn Hawkins, Tech., Randy Wedge, P. Eng., Rick Grey, P. Eng., Collin Sleep, P. Eng.)

Owner: Cavendish Farms

Other key players: Krieg and Fischer (digestion & biogas consultant)