We've been hearing about how hot the Italian market for solar and wind is. But we 're only now beginning to realize how hot.

This week, an Italian renewable energy executive was arrested on charges that he used wind and solar projects to launder money for the mafia. Italian law enforcement seized 1.5 billion euros worth of assets, including 43 wind and solar energy companies, according to the BBC and the news agency AFP.

Officials say that the businessman, Vito Nicastri, was taking advantage of Italy's high feed-in tariffs and poor government management to create new companies and recycle cash. Land-owners who belonged to the mafia were also given preferential treatment when siting projects. Nicastri's nickname was, appropriately, the “Lord of the Wind.”

This is the part of the story where we joke about how renewables are supposed to be clean.

The problem of “dirty” wind and solar projects has been brewing for years in Italy and other EU countries. In November of 2009, the president of Italy's National Wind Energy Association was arrested for trying to embezzle tens of millions of euros designated for wind farms.

The high-profile arrest of Vito Nicastri – who set up dozens of installation and manufacturing companies to launder money – illustrates the depth of the illegal behavior in Italy's renewable energy sector.

No word on how the government crack-down may affect Italy's ability to meet European renewable energy targets. But if the problem is as serious as it seems, it could setback the industry as government officials freeze assets and re-evaluate incentives.