The city of Grand Rapids, Mich., was named “America’s Greenest City” and has received worldwide recognition for its efforts. One of its newest initiatives is the construction of a biodigester, which will convert food to waste to energy.
The $57 million biodigester is expected to be fully operational by the beginning of next year. The biodigester will play an important role in Grand Rapids’ effort to develop 100% renewable energy to power city buildings by 2025. The city expects gas produced by the project will generate 60% of the electricity needs for the city’s wastewater plant.
The system requires pumps and mechanical equipment to power the biodigester, and workers need access to that equipment for repair and inspection. The project’s general contractor, The Christman Co., selected 19 products from The Bilco Co., including floor doors and roof hatches, that will allow workers access to equipment when the biodigester becomes operational. Architectural Building products of Byron Center, Mich., provided the doors.
The project includes eight 4x4 roof hatches with safety railings on the roof exterior. There are also 11 floor doors of various sizes, including some with drainage. The doors are made with stainless steel hardware and corrosion-resistant materials. They also include engineered lift assistance for one-hand operation.
The safety grate provides a permanent means of fall protection. It includes a safety-yellow powder coat paint finish, and stainless steel hardware for corrosion resistance. Bilco, which has been manufacturing specialty access products for more than 90 years, can install grates on doors prior to shipment. Retrofit kits are also available for field installation.
“Bilco provides a wide range of sizes that we need and could deliver to the project on time, including very large custom-built units,’’ said Eric Sawatzki, the assistant project manager for Christman. “A really appealing feature is the fall protection grating option for our standard-sized floor openings. This provides immediate protection from falls through the floor opening for construction personnel as well as users at the plant. It saves the expense of installing a rail system around every opening.”
The Grand Rapids system revolves around three tanks with a capacity of 1.4 million gal. Two tanks will be used for municipal biosolids. The other tank is an anaerobic membrane bioreactor that will quickly reduce organic waste. Electricity production from the biodigester is expected to offset the costs of the investment, and will help keep consumer rates steady.
Biodigesters are uncommon in the U.S. According to the American Biogas Council, there are only 1,241 wastewater treatment plants in the U.S. using an aerobic digester, and fewer than 900 use the biogas they produce.
“As energy recovery becomes more valuable, a lot of other communities will be looking at biodigesters,’’ said Mike Lunn, Grand Rapids’ utilities director. “We’ve always been engaged in resource recovery. This is a project that could be a template for a lot of other communities.”