Bryan Stirrat heads Tetra Tech’s Solid Waste Practice Group and has more than 35 years of experience in landfill planning, design, operation, and closure. A respected authority on innovative landfill gas management and landfill closure strategies, he has been Principal Engineer on projects at more than 250 landfills in North America and the Pacific. Mr. Stirrat has managed multidisciplinary teams of engineers, planners, environmental specialists, and construction personnel implementing large landfill master planning, landfill gas migration control, and landfill closure projects. He is a specialist in developing approaches to minimizing long-term landfill operation and maintenance costs. He is a member of the Solid Waste Management Association of North America’s Landfill Gas Committee, and served on the California Integrated Waste Management Board’s Advisory Committee on Landfill Closure and the California Governor’s Task Force on Solid Waste.


Why is landfill gas so important to our clients?

Our clients view landfill gas as both a potential hazard and a potential resource. As organic waste decomposes in a landfill it creates a gas mixture composed primarily of methane and carbon dioxide. The gas can also contain trace amounts of non-methane organic compounds such as hydrogen sulfide, benzene, toluene, and other potentially harmful compounds. Unless collected and treated, landfill gas can migrate through the surface and subsurface of a landfill.

Landfill gas must be controlled since it can be explosive and represents a health risk to communities adjacent to landfills. It can also convey contaminants such as vinyl chloride to groundwater.

Landfill gas is also a resource that can be used by internal combustion engines or gas turbines to make electricity. It can be converted into compressed natural gas or liquid natural gas, which can be used as an alternative fuel.

How does Tetra Tech help clients meet landfill gas challenges?

Tetra Tech is unique in the breadth of landfill gas services we provide. We can model the gas generation potential of a landfill and characterize where and how it is migrating. We can design complete landfill gas extraction and treatment systems using a variety of treatment technologies. Tetra Tech’s national team of construction crews specialize in the installation and start-up of landfill gas systems. And once we’ve designed and constructed the systems, we have the field staff and equipment to operate, maintain, and monitor the systems throughout the life of the landfill and the regulatory-mandated post-closure monitoring period.

How has the landfill gas market changed in recent years?

Since landfill gas is a greenhouse gas, the recent focus has been on improving surface emissions controls and using landfill gas as a fuel source in renewable energy programs. For example, in California, the state is considering moving landfills into the cap-and-trade program to develop revenue streams to fund and incentivize improvements in landfill gas controls. They’re also contemplating dramatically restricting the disposal of organic materials in landfills. Organic materials are critical to the generation of landfill gas. This realignment of regulatory policies and priorities will have a big impact on our clients. Our challenge is to continue to offer the full-service expertise and skill needed to meet the evolving regulatory guidelines.

How have you helped clients meet these challenges?

We’ve worked with energy developers to fine tune well fields and optimize the quantity and quality of landfill gas being used in energy development programs. On the emissions control side, we conducted a study that helped prove that the source of off-site gas migration noted by the regulators at one of our client’s sites was not their landfill, but a natural offsite source. We also developed an automated modeling tool to help one of our clients compile and analyze landfill gas monitoring data to determine when their sites would exceed new greenhouse gas reporting thresholds.

Tetra Tech is also providing technical and outreach support services to the U.S. Environmental Protection Agency’s Landfill Methane Outreach Program. This is an international program facilitating the reduction of methane emissions from landfills by encouraging the recovery and beneficial use of landfill gas as an energy resource.

What are some of the opportunities on the horizon for Tetra Tech's landfill gas practice?

The State of California recently relaxed restrictions on the injection of landfill gas into natural gas pipelines. Currently, landfill gas extracted from landfills that is not being used to generate power is either thermally combusted in flare stations or treated in granular activated carbon systems. Under the new laws in California, landfill owners can work with local power authorities to build systems to clean up gas quality so it can be injected directly into common carrier gas pipelines.

In Canada, the British Columbia Ministry of Environment has committed to reducing greenhouse gas emissions from landfills by at least 33 percent of current levels by 2020 (Greenhouse Gas Reduction Statutes Amendment Act). This legislation aims to maximize gas emissions control and to identify opportunities for increased gas recovery.

Tetra Tech’s leadership in landfill gas management and gas processing for the energy market are a natural fit to meet this opportunity. Our landfill gas practice has been built around developing sound designs that cost-effectively control emissions and protect public health and safety. Tetra Tech has the experience to help clients achieve these goals.