Using Microturbines to Turn Waste Gas into Energy

The Capstone Turbine Corp. based in Chatworth, Calif., the first U.S. company to market commercially viable microturbine energy products, which are gaining popularity across the globe.

Waste360 recently sat down with Darren Jamison, president and chief executive officer of the Capstone Turbine Corp., to discuss its microturbine energy technology.

Waste360: Tell me about how the microturbines burn waste gas to create power and heat.

Darren Jamison: Capstone microturbines are small combustion turbines approximately the size of a refrigerator. They are comprised of a compressor, combustor, turbine, alternator, recuperator—a device that captures waste heat to improve the efficiency of the compressor stage—and generator.

Fuel enters the combustion chamber; the turbine can run on natural gas, propane, biogas, diesel, biodiesel or kerosene—really almost anything with a BTU content that burns. The hot combustion gases expand and spin a turbine, which is connected to the shaft of an electrical generator. The exhaust transfers heat to incoming air via the recuperator.

Air passes through a compressor and is warmed by the exhaust gases before entering the combustion chamber, pre-heating the combustion process and increasing simple cycle efficiency to 33 percent.

Waste360: How many wastewater treatment plants, farm digesters, and landfills in North America use Capstone’s system?

Darren Jamison: Because Capstone does not sell directly but sells though a global distribution network—and because we sell into six different vertical markets—getting the exact number of units sold into wastewater treatment plants (WWTP), farm digesters and landfills in North America is difficult. Capstone has sold in excess of 8,500 units worldwide, so I would estimate the number in the biogas space in North America to be in the several hundred-range.

If you look on our website you will find video case studies of Sheboygan WWTP and York WWTP, along with several landfill sites like Sauk County in Wisconsin. One of our largest WWTP plant installations in the world is located in Brazil and our largest concentration landfill units are in France.

We are doing farm digesters across Latin America, Europe, Australia and most recently on a pig farm in South Africa. In addition, our distributors have recently installed biogas units at several breweries across Europe and two in North America breweries and food processors are finding unique ways to generate biogas from the organic material left over from the brewing or food processing.

Waste360: How does each application differ?

Darren Jamison:

Waste360: How much energy can the system create?

Darren Jamison: Capstone microturbines provide scalable solutions from 30 kW to 30 MW. They are simple to install lightweight, portable and require very little maintenance.

Waste360: How much waste can the system process?

Darren Jamison: Because Capstone microturbines can be set up in tandem at any given facility; they can process any amount of waste gases during a given period of time. The microturbine array can be expanded or tapered as methane production changes over time.

Waste360: What makes Capstone’s system different or unique from other anaerobic digesting systems?

Darren Jamison: Unlike reciprocating engines, Capstone microturbines can operate on biogas with methane content as low as 30 percent. And because of their streamlined design, the microturbines require much less maintenance than other systems. Microturbines have one moving part and require very little maintenance compared to a reciprocating engine that is a concert of moving parts and requires regular scheduled and unscheduled maintenance.

Waste360: What are the benefits of the system?

Darren Jamison: Capstone microturbines offer a wide range of benefits. The patented air bearing technology means no lubricants or coolants are needed. The fact that there is only one moving part means minimal maintenance is required. The system operates on a wide range of fuels and is an ultra-low emission product that provides highly reliable and flexible onsite energy generation. And thanks to advanced combustion controls, they produce one-tenth of the emissions of reciprocating engines with no exhaust after-treatment.