BOARD MEETING DATE: July 9, 2010
AGENDA NO. 25

PROPOSAL:

Interim Report on Technology Assessment for Biogas Engines Subject to Rule 1110.2 

SYNOPSIS:

The February 1, 2008 amendment of Rule 1110.2 substantially reduced emission limits for engines fueled by landfill or digester gas (biogas). The compliance date for these new limits was set at July 1, 2012. However, the rule and the adopting resolution called for a Technology Assessment by July 2010 to verify the feasibility of available control technologies. This interim report summarizes staff’s technology assessment and findings to date, including the status of three on-going demonstration projects, which experienced significant delays due to the permit moratorium in 2009, and will be followed by another report upon completion of the technology demonstration projects. While the on-going technology assessment points to encouraging evidence in support of the feasibility of the biogas engine limits of Rule 1110.2, the delay in implementing the demonstration projects will likely necessitate an adjustment to the July 1, 2012 compliance date of the rule.

COMMITTEE:

Stationary Source, June 18, 2010

RECOMMENDED ACTION:

Receive and file. 
 

Barry R. Wallerstein, D.Env.
Executive Officer

Background

Rule 1110.2 limits NOx, CO and VOC emissions from stationary, non-emergency gaseous- and liquid-fueled internal combustion (I.C.) engines. Engines regulated by this rule include approximately 850 natural gas-fueled engines, 30 diesel engines and approximately 66 engines fueled by landfill or digester gas (biogas). Emissions of NOx and VOC from all of these engines combined prior to amendment of the rule were approximately 4.60 tpd NOx and 1.25 tpd VOC. The biogas engines tend to be larger engines and comprise a disproportionately large fraction of the total emissions—approximately 0.93 tpd NOx and 0.44 tpd VOC.

Rule 1110.2 was amended February 1, 2008 primarily to (1) improve compliance with existing emission limits by requiring more stringent monitoring, recordkeeping and reporting and (2) lower the applicable emission limits for NOx and VOC on both natural gas and biogas engines to BACT and nearly to BACT for CO. The new limits for the natural gas engines phase in and will be in full effect by July 1, 2011. Biogas engines were given until July 1, 2012 to comply with the new limits. The expected emission reductions resulting from the rule amendment are 2.17 tpd NOx and 0.69 tpd VOC overall, with the lower limits on the biogas engines accounting for 0.69 tpd NOx and 0.16 tpd VOC of those reductions.

During the amendment process of Rule 1110.2, while there was little question regarding the feasibility of the control technologies to meet the new limits on existing natural gas engines, many biogas engine operators questioned the viability of controls on biogas engines. To address the concerns expressed, the rule and the adopting resolutions directed staff to conduct a technology assessment by July 2010 to verify the achievability of the July 1, 2012 limits. The technology assessment was to include feasibility, cost-effectiveness, and compliance schedule and to also address global warming gas impacts as well as any potential for increased biogas flaring. The Board also directed staff to form an Advisory Committee consisting of appropriate members from industry and public agencies to provide input to and to review and comment on the Technology Assessment.

Advisory Committee

An Advisory Committee comprised of individuals from industry and public agencies who had expressed interest in the Rule 1110.2 technology assessment for biogas engines was formed. The committee consists of 48 individuals from organizations that own biogas engines, engine manufacturers, technology vendors, consultants, the California Integrated Waste Management Board and the Southern California Gas Company. Four committee meetings have been held to date. A list of the committee members and the minutes of the meetings are in Attachment A. Staff greatly appreciates the productive discussions and helpful information that was gained from this committee.

Technology Assessment

A report on staff’s technology assessment to date is attached (Attachment B). The evidence collected to date demonstrates the potential feasibility of the July 1, 2012 emission limits for biogas engines in Rule 1110.2. Further, staff is working closely with three stakeholders who voluntarily opted to participate in three demonstration projects (partially funded by AQMD) in our basin. Unfortunately, due to the unforeseen delays caused by the permit moratorium in 2009, these projects are not expected to be completed until June 2011. Therefore, the attached report provides a summary of data gathered to date and will be followed by another report soon after the demonstration projects are completed. Staff views the information from the demonstration projects as a critical component of this technology assessment and valuable in quantifying the benefits and impacts of the various technologies for our stakeholders.

This unforeseen delay in executing the demonstration projects will likely necessitate an adjustment to the July 1, 2012 effective date for the biogas engines. Any such adjustment to the effective date will be handled through a formal rulemaking to be initiated in the second half of this year.

Technologies

Staff found two approaches that appear capable of achieving compliance with the future emission limits: (1) application of selective catalytic reduction of NOx (SCR) and catalytic oxidation of VOC and CO together with biogas treatment upstream of the engine to remove catalyst-fouling impurities and (2) application of a non-catalytic technology known as NOxTech that reduces NOx, VOC and CO.

Prior to the 2008 amendment of the rule, it had been commonly believed that SCR and oxidation catalysts could not be used downstream of a biogas combustion device because of the presence of impurities known as siloxanes in biogases, which were known to rapidly foul catalysts. However, more recently, technologies that remove siloxanes from the biogas upstream of the combustion device have become available, and application of catalysts downstream of biogas combustion devices is now practiced. It is well known from experience with natural gas engines that these catalytic technologies can meet the future limits in Rule 1110.2. Staff found eight applications where siloxane removal systems were successfully employed upstream of engines, gas turbines and boilers fueled partially or primarily with biogas with SCR and/or oxidation catalysts installed for the purpose of controlling emissions. While substantial evidence exists, engine owners remain concerned that a demonstration of SCR and oxidation catalyst together on an engine fueled primarily on biogas at levels required by the future effective limits of Rule 1110.2 and over extended periods of time has not yet occurred.

The technology offered by NOxTech consist of a non-catalytic reactor that is reftrofitted to the engine exhaust and uses a small fraction of the engine fuel together with an injected reactant to achieve reductions of NOx, VOC and CO. Application of this technology to biogas engines is a more recent development. A demonstration in 2007 on combined exhausts from engines fueled with biogas and diesel indicated that this technology can meet the future Rule 1110.2 limits, however only limited emissions data were acquired.

Demonstration Projects

A brief summary of the technology demonstration projects that are being voluntarily conducted by several of the stakeholders within AQMD is provided below.

Also, a demonstration of SCR and oxidation catalyst on a landfill gas engine using a regenerative siloxane removal system is underway in the BAAQMD. Staff believes that technical and cost information will be available soon from BAAQMD and the technology developer, GE-Jenbacher, who is a member of the Advisory Committee.

Cost Effectiveness

Cost information was provided by OCSD for their planned installation of SCR and oxidation catalysts with siloxane removal and by the vendor of the NOxTech technology. The cost effectiveness in terms of dollars per ton of combined NOx and VOC emission reduction was calculated for applying each technology to reduce emissions from the current Rule 1110.2 emission limits to the future limits. Cost effectiveness was found to be dependent mainly on engine size. The calculated ranges of cost effectiveness of the two technologies for the range of biogas engine sizes in AQMD are as follows:

These figures are within ranges that have been accepted in past rulemaking. Futhermore, the costs for the NOxTech technology are expected to come down in the future as more experience is gained in fabricating the units. It should be noted that the cost and cost effectiveness estimates above are preliminary and will be further refined as more real-world information from the demonstration projects becomes available. 

Attachments (EXE, 1.2m)

A. Advisory Committee – List of Members and Minutes of Meetings

B. Assessment of Available Technology for Control of NOx, CO and VOC Emissions from Biogas-Fueled Engines – Interim Report