In 2011, the sales value of greentech manufacturing, from manufacturing inputs like silicon through intermediate products like solar cells to end products like wind turbines and biofuels, came to 198 billion euros ($245.3 billion) -- twice what it was in 2008.

It grew 31 percent per year from 2008 to 2010, but only ten percent in the last year. Growth in 2011 was strongest in energy efficiency at 22 percent, with solar photovoltaic (PV) coming in second at eleven percent.

According to Clean Economy, Living Planet: The Race to the Top of Global Clean Energy Technology Manufacturing 2012, the third annual report from the World Wildlife Fund, was authored by Arnoud van der Slot and Ward van den Berg, the slowing in growth was due to the maturing of the sector, the world’s slowed economy, and the “significant cost declines in both solar and wind that reduced sales value.”

China, of course, leads the pack, with growth of 29 percent in sales -- growing from $16.1 billion to $70.6 billion last year.

The report concludes that China’s success was due to lower labor and capital costs, stable government policies, strong applied R&D, and a well-developed supply chain.

Sales in the U.S. grew 17 percent in 2011 but significantly less than in 2010, especially as a portion of the country's total economy. Sales in Europe as a whole dropped from the 2010 level, but Germany showed the world’s third biggest rate of growth, followed by South Korea, Taiwan, and India.

As a portion of GDP, Denmark is the world leader, principally because it is so small and is home to Vestas, the world’s biggest turbine manufacturer. China is second and closing in fast.

The report predicts the world’s greentech sales value will be between EUR 240 billion ($297.4 billion) and EUR 290 billion ($359.4 billion) by 2015, rivaling the oil and gas industry’s equipment market, if best practices are adopted on three levels: governments, R&D institutes and financial institutions must shape the right conditions; greentech customers must drive market demand; and the greentech industry must “develop into an efficient, innovative industry and optimize its supply chain.”