Anaerobic Digester

In order to comply with new Massachusetts regulations preventing the disposal of food waste in landfills, Ahold Delhaize sought a way to beneficially reuse unsalable organic material from their grocery stores throughout the New England region.

The solution engineered by Dennis Group and Ahold was to build a Product Recovery Operation (PRO) at Ahold’s distribution center. Food that would normally be destined for a landfill – either inedible scraps or food unsuited for donation – is now collected from 212 regional supermarkets and shipped back to the distribution center. Within 24 hours of being fed into the digester, microorganisms break down the biodegradable food waste into a biogas comprised of methane and carbon dioxide which is used as a power source. This process takes place in a closed, oxygen-free, odorless environment. The facility is processing an average of 130 tons of food daily and generating 1.25 megawatts of clean electricity, which provides approximately 40% of the distribution center’s energy needs. Leftover organic material is turned into fertilizer and compost.

This unique project was particularly challenging because unlike other digesters, which process a material that is already liquified, the Ahold digester had to be able to handle packaging materials such as cardboard, egg cartons and onion bags. Collaboration among all parties was required to solve this unique engineering challenge.