Twenty-nine new anaerobic digesters have come online at wastewater treatment plants since 2020, according to a new report from the American Biogas Council.

The figure is the trade group's latest tally of built capacity in the wastewater segment of the biogas industry. It counts digesters that have actually started operating at municipal and utility-run treatment works over the past four-plus years — not projects that are merely announced, permitted or under construction.

That distinction matters for readers tracking the material stream. Wastewater solids represent one of the most reliable feedstocks for anaerobic digestion in North America: the sludge arrives at a fixed location, in predictable volumes, every day of the year. Unlike food waste or agricultural digester projects, which depend on aggregating dispersed feedstock, wastewater AD is anchored to infrastructure that already exists — the treatment plant itself.

Each new digester installed at a plant converts that solids stream into two outputs: biogas, which can be burned for process heat and power or upgraded to renewable natural gas, and digestate, which can be dewatered and land-applied or further processed.

What does the count tell us?

The American Biogas Council's report does not simply list projects. It charts adoption — how many treatment utilities have moved from flaring or discarding their biogas to capturing it as a product.

Twenty-nine operating units since 2020 works out to roughly six to seven new wastewater digesters entering service per year on the council's accounting. That is a buildout rate the industry can measure against future editions of the report, and against the pipeline of projects that utilities and developers have announced but not yet commissioned.

The count also gives public agencies and investors a denominator. Any claim about "growing adoption" of wastewater AD now has a published baseline: 29 units, in a defined window starting in 2020, from a named industry body.

Built versus announced

Circular Wire's desk treats the 29-digester figure strictly as built capacity, per the council's framing of projects that have "come online." Announced wastewater digester and RNG-of-triage projects across the sector routinely outnumber commissioned ones in any given year, and the gap between the two categories is where most project risk sits — permitting delays, interconnection queues, gas-uptake agreements and offtake pricing.

Readers should therefore benchmark future announcements against this operating count. A utility or developer touting a wastewater AD project should be asked two questions: has it reached commissioning, and in which year?

Who is the American Biogas Council?

The organization is the Washington-area trade association for the U.S. biogas industry, covering landfills, wastewater, agriculture and food waste segments. Its reports aggregate operating data from member companies and public agencies, and its digester counts are widely cited as the reference figures for U.S. biogas capacity.

The council's headline number for wastewater reflects projects at treatment plants — the segment where the feedstock is municipal sewage solids and the biogas is generated on site.

What comes next

The milestone to watch is the next edition of the count. If the number of operating wastewater digesters added since 2020 climbs meaningfully above 29 in subsequent reports, the sector's adoption curve is steepening; if it flattens, the constraint is likely economics or permitting rather than feedstock availability.

For now, the American Biogas Council's report establishes the baseline: 29 new wastewater digesters online since 2020, and a published series the industry will be measured against going forward.