Caveat Emptor...

Some things to consider on green engineering/renewable energy: apparently, the source of > 90% of the rare earths for the job are ironically in China.

China announced earlier this month that export taxes on some rare earths would increase next year.

"You better watch out. You better not cry. Better not pout. I'm telling you why...":

Keith Bradsher, NY Times: U.S. Called Vulnerable to Rare Earth Shortages

US Department of Energy: Critical Materials Strategy report

In Physics Today, the summary as follows:

• Several clean energy technologies—including wind turbines, electric vehicles, photovoltaic cells and fluorescent lighting—use materials at risk of supply disruptions in the short term. Those risks will generally decrease in the medium and long term.
• Clean energy technologies currently constitute about 20 percent of global consumption of critical materials. As clean energy technologies are deployed more widely in the decades ahead, their share of global consumption of critical materials will likely grow.
• Of the materials analyzed, five rare earth metals (dysprosium, neodymium, terbium, europium and yttrium), as well as indium, are assessed as most critical in the short term. For this purpose, “criticality” is a measure that combines importance to the clean energy economy and risk of supply disruption.
• Sound policies and strategic investments can reduce the risk of supply disruptions, especially in the medium and long term.
• Data with respect to many of the issues considered in this report are sparse.