The fund holds a narrow portfolio of all-cap, global clean energy companies, which it defines as those involved in the biofuels, ethanol, geothermal, hydroelectric, solar, and wind industries. Aside from holding the companies that produce energy through these means, ZCLN also includes companies that develop technology and equipment used in the process. To hone in on the clean energy theme, ZCLN takes large concentrated positions in about 30 companies, which are then weighted by market-cap and rebalanced on a quarterly basis.