One of the main selling points of ethanol from the outset of the modern ethanol boom has been its contribution to clean air. This “green” focus has mainly been on vehicle tailpipe emissions. Relative to conventional gasoline formulations, ethanol’s higher oxygen concentration causes it to burn more completely, and therefore emit fewer pollutants.
From the very start, however, the ethanol industry’s work to control emissions from the ethanol production plants themselves has achieved results. These efforts have developed a vibrant, growing domestic renewable energy industry without sacrificing air quality.
On the horizon, the question of how greenhouse gases will fit into the Clean Air Act, as well as a number of potential rule changes, mean emissions compliance will continue to be among the more challenging aspects of producing ethanol.
“The current level of emissions control regulations protect public health and safety, as well as the environment,” affirmed Bill Roddy, manager for environmental affairs at ICM, Inc. The Colwich, Kansas-based ethanol industry leader has provided process technology to 102 biorefineries across the United States and Canada, including a broad spectrum of emissions control technology.
“The recent reclassification of ethanol under federal rules was an appropriate move,” Roddy said. “For 20 years ethanol plants were misclassified as a chemical process plants, and now they are treated as fuel ethanol production plants using natural fermentation.”
This has proved to be a timely change for the ethanol industry, making the process to permit and expand existing ethanol plants quicker and easier. The reclassification has also allowed ethanol plants “more breathing room, but emissions have not risen dramatically,” Roddy added.
The Clean Air Act, under its Prevention of Significant Deterioration (PSD) permitting requirements, calls for the use of the “best available control technology” (BACT). Rather than setting an aggregate level for combined criteria pollutants – things like particulate matter (PM), volatile organic compounds (VOC), nitrous oxide (NOx), and others – PSD sets a trigger level for any pollutant. If an ethanol plant emits more than 250 tons per year (tpy) of any single one of these pollutants, regulation would require BACT to be put in place. That being said, nearly all existing ethanol plants in the U.S. already utilize BACT to stay under the PSD thresholds, and to avoid the permitting delays that a PSD review demands.
“Under the 250 tpy rule, you have a little more breathing room for change,” Roddy said. “For a 100 million gallon per year plant permitted under the 100 ton per year rule, it’s difficult to expand to meet market demand. After the increase to the 250 ton per year limit, the level of control technology remained consistent and the emissions are generally the same, so it’s more convenient for them to maintain compliance every hour of every day, which in turn allows for subsequent expansion. Before the 250 rule, the process to expand used to take anywhere from 12 to 18 months under PSD rules. A plant running at 95 tons per year of a particular pollutant – for example, one that wanted to expand from 100 million gallons to 120 or 130 million gallons per year – can expand without triggering time-consuming PSD rules. If you can’t precisely time your expansion to meet the demand, it can be a serious setback in this business.”
Experts note that not all industries have as many aspects of their processes and activities controlled under the Clean Air Act as the ethanol industry does. Ethanol plants must control everything from the particles generated by handling raw grain to the dust kicked up on the roads around the plant.
“The best plants are well-organized in their compliance activities and the records they keep of those activities. It makes a very good impression with inspectors when they come for an inspection and they find well-organized folders for the records keeping track of what the plant is doing to comply with permit requirements,” said Piyush Srivastav, whose company, Nebraska Air Quality Specialties LLC, provides consulting services to ethanol companies regarding Clean Air Act permitting and compliance. His background with Nebraska Department of Environmental Quality and a major electric utility give Srivastav critical insight into how to manage compliance.
In his time at DEQ, Srivastav wrote more air quality permits than the rest of his permitting section combined. Now in his eighth year as president of Nebraska Air Quality Specialties, Srivastav is a current winner of the Entrepreneurial Spirit Award from the Lincoln Chamber of Commerce.
“The other thing I consider a characteristic of the best model of emissions compliance is one in which ethanol companies are actively engaged in the permitting process – understanding the regulations, asking questions, and not simply accepting permit provisions,” Srivastav said. “Ask the questions so that you know exactly how the permit provisions will impact the company’s process, and make sure that the permit provisions will not result in unnecessary non-compliance due to poorly-written permit requirements that have no basis.”
Srivastav noted that most ethanol plants were permitted under the older 100 ton-per-year rule (required for chemical process plants), and a number of them may have not pursued the change in their permits that could benefit them.
Active engagement in the permitting process can result in permits that are appropriate and not unnecessarily stringent. Srivastav knows of cases where the regulators inadvertently required more than what is required by Clean Air Act and applicable state laws. The result of active engagement is limiting liability and increasing operational flexibility that can allow a plant to move forward with expansions or new projects more expeditiously. A well-written permit can save plants very large sums of money, in the form of reduced cost of operating the plant and reduced chances of permit non-compliance that can result in large penalties.
Keeping PSD at arms length: the universal use of best available control technology
“As a general rule, the emissions controls in place at ethanol plants are considered BACT,” said ICM’s Roddy. The point is to remain under the 250 tpy level, and so be classified as a “minor source of pollutants.” Exceeding that level means that “best available control technology” equipment is required and it narrows the choices and level of control technology a plant can make.
Asked to single out the most important emissions control equipment investments an ethanol plant makes, Srivastav said, “Because PSD regulations regulate multiple pollutants, exceeding the PSD threshold for any of those pollutants will make the plant a major PSD source. However, for ethanol plants, the primary PSD pollutants that are managed by control equipment are particulate matter (PM), PM less than or equal to 10 microns in diameter (PM10), and volatile organic compounds (VOCs). Typical control equipment used to control VOCs includes scrubbers and/or thermal oxidation. PM and PM10 are typically controlled by bag houses. In addition, nitrogen oxides (NOx), sulfur oxides (SOx) (if using coal boilers) and carbon monoxide (CO) emissions also have to be kept in mind.”
Here are the basics of “best available control technology” for an ethanol plant, according to Roddy:
1. Bag houses , essentially a vacuum that cleans particulate matter out of the air in the grain receiving and milling, dried distillers grains handling, and load-out facilities.
2. Scrubbers for fermentation emissions. Once the grain has gone through “the cook,” gases released by the fermentation are sent through a column of water, which removes volatile organic compounds and other hazardous pollutants, and releases pure carbon dioxide to the air.
3. Low-NOx burners and air/fuel ratio controls. Every ethanol plant has a source of combustion to create steam, either boilers or thermal oxidizers followed by heat recovery steam generators. These combustion controls limit the amount of VOCs, CO, and other pollutants that come from incomplete combustion.
4. Thermal oxidizers to combust the pollutants in the gases from the DDGS drying process.
5. Large storage tanks equipped with internal floating roofs for both ethanol and gasoline storage, a feature which decreases evaporation of organic compounds and release from the tanks.
6. Equipment for the flaring of gases in tankers or rail cars where ethanol is loaded, preventing the release of VOCs.
7. Leak detection and repair program. A typical ethanol plant has between 400 and 1,000 components – valves, flanges, and pumps – in its fermentation and distillation systems. Technology to “sniff out” VOC emissions and repair leaks is essential.
8. Controlling dust from the arrival and departure of trucks, through roads sweepers, paving, or other methods.
“ All of these things help keep a plant in compliance (with the Clean Air Act), and they also help the plants to be a good neighbor to others in the area ,” Srivastav said.
The history of the industry has many examples of ethanol plants cooperating with government agencies in order to limit or reduce pollution. One of the most significant examples was in 2002, according to Roddy, when the industry agreed to a wholesale adoption of the use of thermal oxidizer technology.
“At the time, our industry was drying DDGS without thermal oxidizers to clean up the emissions, and EPA basically said, ‘You guys are emitting a lot of air contaminants from dryers’,” Roddy recalled.
Under a consent decree between EPA, the State of Minnesota, the U.S. Department of Justice, and 12 ethanol plants in Minnesota, the plants – which produced 400 million gallons of ethanol per year at the time – agreed to install thermal oxidizers.
"These companies are to be commended for working cooperatively with state and federal officials to achieve compliance with the New Source Review requirements of the Clean Air Act," Tom Sansonetti commented after the adoption of the agreement, then the Assistant Attorney General for the Justice Department’s environment and natural resources division.
Since 2002, nearly all plants with an ethanol capacity greater than 20 million gallons per year utilize a thermal oxidizer to control and reduce emissions from the DDGS drying process. The only plants that don’t include this equipment are those located in close proximity to a cattle feedlot. With a nearby market for the distillers grain co-product, it does not need to be dried and can rather be sold and delivered “wet.”
Though equipment and state-of-the-art computer hardware and control applications are of primary importance, Srivastav underlines the importance of the human part of the equation as well.
“It’s a combination of the control technology that is designed to meet the BACT or any other emission limit, and proper operation and monitoring by a combination of monitoring equipment and plant personnel to ensure equipment is operated in compliance,” Srivastav said. “Typically the equipment vendor will provide some level of guidance for proper operation and maintenance of the equipment. In addition, plants also develop their own internal standard operating practices to implement the vendor guidance. The importance of the plant personnel being very familiar with the requirements of their permits cannot be over-emphasized. Plants need to be intimately familiar with the requirements of the permits. Lack of familiarity with the permit requirements and how they impact operational parameters can cause unnecessary non-compliance that can be avoided.”
Stay tuned – some emissions rules are still in flux
The U.S. Environmental Protection Agency has just issued a new National Ambient Air Quality Standard for nitrogen oxide. The main feature of this new NAAQS is that facilities emitting NOx must model their compliance hourly, according to Srivastav.
“Early indications are there are two problems,” Srivastav said. “One is that the states are struggling with how to implement that standard – there are technical issues around how to model compliance. The other is that even some small equipment, emergency generators, for instance, might not meet the standard. That is an unknown. It is a major concern because everyone has combustion sources.”
Another rule generated by the Clean Air Act, the National Emission Standards for Hazardous Air Pollutants for Chemical Manufacturing Area Sources – commonly referred to as Area Source MON – is in the midst of reinterpretation by EPA.
“EPA made an interpretation earlier this year, and the ethanol plants did the applicability analysis, and it was not applicable to any of the plants,” he noted.
Srivastav could not pinpoint a motive for the most recent reinterpretation, except to say that it did not appear to follow from any scientific finding.
“This is where it can be valuable to be engaged, to be asking questions of policy makers and elected officials,” Srivastav said. He noted that the Clean Air Act’s provisions are based on well-documented, well-founded scientific studies of health and environmental effects. But interpretations can take regulations beyond what the regulations were originally intended for.
Will GHGs become a trigger for Prevention of Significant Deterioration (PSD)?
Under the provisions of the Greenhouse Gas (GHG) Reporting Rule, ethanol plants must monitor and report the amount of GHG they generate through the combustion of fuels. This information will be combined with information from all U.S. industries, to eventually provide data for policy makers to develop rules such as carbon cap-and-trade or carbon taxing programs.
As far as deciding that carbon emissions can trigger a finding that a plant is a major source of pollution, for the moment, EPA has said it will wait upon Congress to make a law.
An EPA memo dated March 29, 2010 reads: “The U.S. Environmental Protection Agency (EPA) completed its reconsideration of a December 18, 2008 memorandum entitled ‘EPA’s Interpretation of Regulations that Determine Pollutants Covered by Federal Prevention of Significant Deterioration (PSD) Permit Program.’ After carefully reviewing comments on the proposal, EPA is taking the following actions:
· Affirming our existing position that PSD permitting is not triggered for a pollutant such as GHGs until a final nationwide rule requires actual control of emissions of the pollutant.
· Interpreting that PSD permitting requirements are triggered when the control requirement of the nationwide rule ‘takes effect’ – rather than at signature.”
Roddy notes that, by volume, a kernel of corn is one-third starch, one-third protein, and one-third carbon dioxide gas. Producing and using ethanol does give off carbon, but it is “neutral carbon,” he said. In other words, fermenting corn to produce ethanol and combusting that ethanol in a vehicle’s engine releases nearly the same amount of carbon that the corn plant absorbed out of the atmosphere during its growth phase – typically within a year or two of the time it is processed into ethanol. This is in stark contrast to fossil fuel combustion, which releases carbon that has been stored under the earth for millions of years.
It is hoped, though it is not certain, that whatever carbon accounting is selected, it will differentiate between neutral carbon and fossil-sourced carbon, Roddy said.
“Future regulation or legislation is expected to have major implications on permitting and managing the costs associated with GHG emissions requirements ,” Srivastav said. “Ethanol producers must be aware of their GHG footprint in order to assess future liabilities. They should consider investing in preparing a GHG Management Plan to strategically evaluate the opportunities and liabilities associated with the future cost of carbon and GHG emissions. Ethanol producers need to be closely monitoring the regulatory and legislative developments, technology developments, and GHG emissions reduction opportunities.”
Over the past two decades, the ethanol industry has proven itself conscientious in the pursuit of Clean Air Act compliance, and that is unlikely to change. Given the expense of the investment in these emissions controls and the operational and liability impacts that permitting can create, active engagement in the permitting and compliance process is going to remain an important component in the business models of successful ethanol companies.
