City officials say limited regional composting capacity constrains curbside program expansion

At the Sept. 18 hearing, administration staff described how collected food waste is handled and why that matters for diversion goals. Chris Osgood and Brian Swett explained that roughly 15–20% of curbside food waste goes to high‑quality composting; the majority—about 80–85%—is co‑mingled with wastewater and processed by anaerobic digestion, producing biogas and a limited solid digestate.

Brian Swett said both composting and anaerobic digestion reduce greenhouse‑gas emissions compared with landfill disposal, but the end uses differ: composting yields a product that can be returned to soil, while anaerobic digestion captures energy but produces a blended solid that is less suitable for direct agricultural use. Swett added that "we just don't have the capacity in Massachusetts or locally" to compost at the scale needed, and that the city is exploring regional partnerships and different collection/processing contracts to expand options.

Councilors pressed staff on siting and permitting constraints. Staff noted contamination concerns—PFAS and food packaging stickers—that make some composters cautious about accepting residential material, and emphasized the need to coordinate with the commonwealth and neighboring municipalities to scale compost facilities before attempting a full citywide expansion.