The Herald‘s Jay Fitzgerald reports that exports from Massachusetts companies fell by 20 percent in the first half of 2009, “thanks to the global recession.” (Nationally, the drop in exports was about 24 percent.) Exports of our most popular items, “computers and electronic products,” were down by 22 percent.

The map below shows the biggest category of exports for each state, based on data from the US Department of Commerce’s TradeStats Express.

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In the cars vs. computers battle, Massachusetts (and New Hampshire and Vermont) is allied with most of the Western US, but “transportation equipment” still edges out the high-tech sector — $77 billion to $74 billion so far this year — as America’s best-selling category of export.

Rhode Island stands out as the only state where “waste and scrap” have bragging rights. The Federal Reserve Bank gave a good description of this economic sector, an outgrowth of the state’s jewelry industry, in 1999:

Yes, that’s right. Rhode Island has a $100 million annual income exporting scrap and waste. And it’s not all wrecked cars, newsprint, plastic, and rubber. In fact, the lion’s share comes from the reclamation of precious metals.

Metech International, based in Mapleville, Rhode Island, is a leader in the industry and one of several such companies in the state. It does a multimillion-dollar business recovering tiny amounts of gold, silver, and other metals mostly from used computers and other electronics products. Metech takes these products to its Rhode Island plant where it samples them to determine the metal content. The material is then shipped to smelters in countries such as Canada, Sweden, and Belgium where the metals are recovered and resold, eventually to find their way back into the manufacture of electronic goods.

Our second map shows the top recipient of exports for each state:

Canada obviously dominates here, but Mexico and China have gained toeholds in the West. And why is Massachusetts one of only two states with the United Kingdom as its leading customer? Fitzgerald explains that it’s mostly due to the “export of gold products tied to the jewelry sector.” The UK is likely to fall from the top of the list as the economy recovers in other countries and Massachusetts is able to sell more high-tech and biotech products.