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Research Project Information

Research Project Summary Information

Designing a Pilot Testing Program for Biogas Cleaning & Emission Control at a NYC DEP WPCP(ST9402-1)

Malcolm Pirnie, Inc.


At four of the NYC DEP’s fourteen water pollution control plants (WPCPs), anaerobic digester gas (ADG) is burned in internal combustion (IC) engines. NYC is classified as severe non-attainment for ozone, and the NYC DEP’s IC engines are a major source of nitrogen oxide (NOx) emissions, a pre-cursor of ozone. The NYS DEC promulgated new NOx RACT (Reasonably Available Control Technology) regulations for IC engines in January 2004. The DEP’s IC engines do not meet the new (lower) NOx RACT limit, and therefore DEP is required to evaluate various NOx control technologies for the engines as part of a RACT analysis. A NOx RACT analysis includes an economic as well as technical evaluation.

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Project Description

Selective catalytic reduction (SCR) was previously identified as a viable option for controlling NOx emissions from ADG-fueled IC engines. Nevertheless, SCR has not been proven to have long-term effectiveness for ADG-fueled IC engines due to impurities in the ADG (eg., sulfur, siloxanes, moisture). Consequently, activated carbon was identified as a viable pretreatment technology for the ADG. The project had three primary objectives: 1) to perform a technical and economic feasibility study of using SCR with activated carbon for control of NOx emissions from ADG-fueled IC engines; 2) to develop preliminary equipment operating parameters and schematics for a potential future pilot test of SCR with activated carbon, and 3) to assess the potential for using the system for other combustion equipment.


The project provided important information about SCR, with activated carbon for removing NOx from ADG, which could assist the NYC DEP in meeting air permitting requirements. Use of SCR with activated carbon could potentially 1) result in reduced operating and maintenance costs, if shown to reduce engine build-up, and 2) allow the DEP to increase its use of ADG to produce on-site power.

Project Results

The RACT economic standard for NOx is $3,000 per ton (1994 dollars), $4,599 per ton (2007 dollars), and $4,966 per ton (2010 dollars (calculated)). Given the total NOx emissions of the Owl’s Head WPCP for years 2004-06, and the calculated tons reduced if SCR with activated carbon was implemented, the estimated cost of removal was $13,632 per ton under the current permit, and $8,156 per ton under the proposed 225 TPY NOx limit. Both far exceed the upper limit provided under NOx RACT guidance. Therefore, the study demonstrated that SCR with activated carbon was not RACT for the IC engines at Owls Head.


Malcolm Pirnie, Inc.
Accounts Receivable 23444 Network Place
Chicago, IL 60673

Principle Investigator

Kit Liang

Universities Involved


Project Type:

Research Study

Technologies Types:

Waste Management and Pollution Prevention
Water/Wastewater treatment systems

NYSERDA Contact Information

Kathleen O'Connor


R&D - Environment & Energy Res

Contract Details

Start Date: 1/11/2010
Project Status: Active
Contract Number: ST9402-1

Last Updated: 1/10/2011