Creating Carbon Offsets

Gas turbines turn biogas into electricity
By Carroll McCormick  

Nickel Magazine, March 2008 -- Many airlines offer their customers a way to offset greenhouse gases produced by their flight. These so-called “carbon offsets” are small donations which are ultimately used to finance projects that will help reduce greenhouse gases in the world by an equivalent amount.

Virgin Atlantic Airways Ltd., for example, supports two projects with the money donated by customers. One is the reconstruction of a hydroelectric plant in Indonesia; the other, a project in India that generates electricity from biomass, such as sugarcane husks.

In fact, many of the small biogas projects registered by the Clean Development Mechanism (CDM) in India burn renewable, alternative fuels in gas turbines to generate electricity. These turbines require nickel alloys for their efficient operation.

The CDM, which is an arrangement under the Kyoto Protocol allowing industrialized countries with a greenhouse gas reduction commitment to invest in projects that reduce emissions in developing countries, has 935 registered projects, most of which are energy-related. Well over a third of all CDM’s projects are in India (more than in any other country).

Among the manufacturers of gas turbines used in these biogas projects is Capstone Turbine Corporation of Chatsworth, California, U.S.A. It manufactures four sizes of turbines that generate 30, 60, 65 and 200 kilowatts.

Nickel alloys are a critical enabler of turbine technology, providing strength and corrosion resistance at high operating temperatures. For example, nickel alloy N06002 is used in the combustion chamber of Capstone’s generators where corrosive gases burn at temperatures as high as 870°C. The spinning turbine is made of N07713, and the main rotor shaft is fabricated from N07718. The recuperator housing, which recycles hot gases to the combustion chamber, is made of austenitic stainless steels S30100 and S34700. Other components made from nickel-containing alloys include the rotor, turbine nozzle, recuperator, thrust shaft, heat shields and fuel injectors.

India’s participation in energy projects that reduce greenhouse gas emissions is a major development: According to the United States Agency for International Development, the country is the world’s fifth-largest (and second-fastest-growing) producer of greenhouse gases, and its power sector is the largest single contributor. USAID is helping India reduce its emissions with clean energy technologies and best practices. In 2003, the agency reported that biogas projects, along with other energy programs, helped prevent the production of 11.3 million tons of carbon dioxide. (Biogas is a mixture of methane and carbon dioxide produced by the bacterial degradation of organic matter and used as a fuel.)

Corporations in countries with emission targets can also buy carbon offsets from countries that earn them by implementing projects that cut greenhouse gas emissions. The CDM, under the guidance of the Conference of the Parties of the United Nations Framework Convention on Climate Change, evaluates and registers projects that reduce greenhouse gas emissions. The carbon offsets, or credits, are awarded for sale to countries to apply against their emissions targets.

As more projects are built to generate electricity from alternative fuel sources using gas turbines, fewer dirty conventional power sources will be required, reducing global greenhouse gases.

Carroll McCormick is a Montreal-based freelance writer.

Photos: Clean Development Mechanism and Capstone Turbine Corporation

Clean Development Mechanism Website: cdm.unfccc.int Capstone Turbine Corporation Corporate Headquarters 21211 Nordhoff Street Chatsworth, CA  91311 U.S.A. Phone: 1- 818-734-5300 Toll Free: 1- 866-4-CAPSTONE (22778663) Web site: www.capstoneturbine.com

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