What is the "clean tech" business sector and why have I been hearing that term so much lately?
-- Andrea Newell, Denver, Colo.

Cleantech is a loosely defined category of businesses dedicated to creating cutting edge technologies that address the world's environmental problems. These high flying companies -- most of which began small with the hope of ascending to publicly traded status -- are the new darlings of Wall Street, attracting billions in venture capital and public funding in what many financial analysts are calling the next big thing since the burst of the dot-com bubble.

Venture capitalists poured more than $3 billion into the cleantech sector in 2007 alone. Whether this cleantech boom will lead the rest of the economy down the green path for the long term -- or go bust in a couple of years like its dot-com predecessor -- remains to be seen.

In the thick of the movement is Cleantech Network LLC, a research firm and clearinghouse for cleantech companies and investors that also publishes the online information clearinghouse, Cleantech.com. The firm defines its budding industry as "new technology and related business models offering competitive returns for investors and customers while providing solutions to global challenges."

The firm interacts with a network of 8,000 investors, 6,000 companies and 3,500 professional organizations involved in alternative energy and energy efficient transportation, wastewater management technologies, air pollution control innovations, sustainable materials production and sourcing, environmentally responsible industrial and agricultural applications and waste recycling and management.

Some examples of the thousands of companies that consider themselves part of the cleantech movement include: Finavera Renewables, a firm that is developing underwater turbines and buoys to generate power from the ocean's tides and waves; 3TIER Group, which uses advanced computer modeling to help energy companies and utilities figure out where best to site wind, solar and hydro-electric projects; Avalence LLC, which is developing high-pressure hydrogen generation and storage equipment that will dispense hydrogen for use in transportation, home power and industrial applications; and, Infinia Corporation, which is developing a utility-scale system to harvest solar energy.

Over and above the cleantech sector's potential for addressing crucial environmental problems, analysts see it as a bright spot in the darkening picture of the recession-bound economy over the next few years.

Marketing research and consulting firm Fuji Keizai USA expects the global market for cleantech products and services to grow from the $284 billion is it is generating today to over $1.3 trillion within a decade. The value of the companies in the sector is also expected to grow from today's $104 billion to some $467 billion in the same 10-year time frame.

CONTACTS: Cleantech Network LLC, www.cleantech.com; Finavera Renewables, www.finavera.com; 3TIER Group, www.3tiergroup.com; Avalence LLC, www.avalence.com; Infinia Corporation, www.infiniacorp.com.

I'm planning a summer backpacking trip and was hoping to buy some of the latest green-friendly outdoor clothing. Where the best options out there today that wear as well as traditional items but without the environmental guilt?
-- Steve Nezhad, Boston, Mass.

Outdoor gear and clothing manufacturers are slowly but surely beginning to work materials crafted from recycled, reused or otherwise sustainable sources into their products.